Final project report on UGC Minor Research Project entitled

FLOW FORMING BEHAVIOUR OF EXTRA DEEP

DRAWN AL6061 UNDER WARM DEEP DRAWING

UGC File No: MRP-6754/16(SERO/UGC) Dated: 30-6-2017

Submitted to

UNIVERSITY GRANTS COMMISSION

HYDERABAD– 500001

Submitted by

D.Swapna, Assistant Professor, M. E. Dept.,

DEPARTMENT OF MECHANICAL ENGINEERING

R.V.R. & J.C.COLLEGE OF ENGINEERING

(Autonomous) Chandramoulipuram :: Chowdavaram

GUNTUR - 522 019, ANDHRA PRADESH, INDIA. Email: rvrjcce@hotmail.com

APPENDIX-I

UNIVERSITY GRANTS COMMISSION

SOUTH EASTERN REGIONAL OFFICE

HYDERABAD – 500001.

FINAL REPORT OF THE WORK DONE ON THE

MINOR RESEARCH PROJECT

FLOW FORMING BEHAVIOUR OF EXTRA DEEP DRAWN AL6061 UNDER

WARM DEEP DRAWING

1. Name and address of the principal investigator

D. Swapna

Assistant Professor, M. E. Dept.,

Department of Mechanical Engineering,

R.V.R. & J.C. College of Engineering,

Chowdavarm,

Guntur-19

2. Name and address of the Institution

R.V.R. & J.C. College of Engineering,

Chowdavarm,

Guntur-19

3. UGC approval No. and date UGC File No: MRP-6754/16(SERO/UGC)

4. Date of implementation 30-6-2017

5. Tenure of the project 2 Years

6. Total grant allocated Rs. 3,15,000/-

7. Total grant received Rs. 2,85,000/-

8. Final expenditure Rs. 2,85,000/- + Rs. 3,261(Interest received)

+ Rs. 2,45,500/-(Matching grant from college)

+Rs.30,000/-(Advanced received from college)

= Rs.5,63,761/-(Total)

Enclosure-I

Objectives of the Project

Enclosure-I

Objectives of the Project:

In Automotive industries, compulsory of weight reduction and intricate panel shapes has

driven the need to improve the formability. While striving for the formability improvement, the

drawbacks such as high materials cost, low production rates and requirement of new forming

equipment has to be considered. Warm forming is considered as sheet forming process performed

at an elevated temperature that is lower than the recrystallization temperature of the material.

Mostly Al that support for warm forming are, firstly, warm working leads to the increased ductility

and formability of the sheet, and secondly, the yield point and forming force decrease at elevated

temperatures

This project used the Hydraulic Deep Drawing equipment to understand the basic

mechanism leading to problems in the utilization of warm temperature. The material behavior at

the elevated temperature is to be studied through experimental and numerical modeling using design

of experiments. The failure prediction while generating the components is to be performed.

Enclosure-II

Detailed Report of Work done

Enclosure-II

Detailed Report of Work done

In order to minimize the effect of failures on the experimental results, forming operation

was first performed on the work piece with Hydraulic Deep Drawing equipment. The twenty seven

experimental runs were performed based on the combinations with each experimental run, carried

three times to identify the most effecting parameter in forming and identify the failure occurrence

situation which can be reduced if identified.

1. Tensile Test:

The plastic flow behavior of Al-Mg-Si alloy was investigated by means of tensile tests. The

material was supplied in the form of 1, 1.5, 2 mm thick sheets. The thermo-mechanical behavior

was evaluated performing uniaxial tensile tests in a ADMET-UTM -200KN device as shown in Fig

1, which consists of spilt furnace of heating capacity 1200oC attached between bottom fixed plate

and to top movable jaw. The tensile tests were performed at RT (≈32), 150, and 300 °C, considering

an imposed cross head speed of 2mm/min. The heating time is fixed to 20 s in order to minimize

micro structural modifications while assuring that the required temperature in the specimen center

is achieved. A minimum of three tensile tests were performed for each test condition. The

reproducibility was confirmed by the average scatter of the true stress, which was less than ±1 MPa

for the same true strain value. Therefore, only one representative test is presented for each condition.

The tensile test results are presented as true stress – true strain plotted until the maximum load.

Specimens, with a gauge width of 10mm and length of 170 mm, were obtained by EDM of sizes

specified by ASTM B557[1] as shown in Fig 2& 3. Tensile tests with constant cross-head speeds

of 2mm/min at temperatures of room temperature (RT), 150 and 300 ◦C, were carried out to

determine the material properties as shown in Fig 4. After testing the samples were water quenched

in order to keep microstructure at room temperature.

Fig 1 Uniaxial Tensile Test Equipment

Fig 2. Samples for Uniaxial Tensile Test

Fig 3. Samples Generated through EDM

The stress–strain data were recorded and the mechanical properties yield strength (YS), ultimate tensile

strength (UTS) and total percentage elongation were determined. In the warm working temperature range,

flow stress of the alloy is influenced by both strain and strain rate. In case of most of the common alloys, the

flow stress equation which incorporates the effect of strain hardening and strain rate hardening is given by

σ = K εn έm (1)

Where K, n and m are strength coefficient, work hardening exponent and strain rate sensitivity index, obtained

from flow stress of true stress- true strain graph respectively. In order to determine the coefficients in the flow

stress equation, that is, strength coefficient (K), strain hardening exponent (n) and strain rate sensitivity (m),

using experimental true stress and true strain data in the strain rate range of 0.33/s.

2. Flow stress and ductility

Aluminum alloy is an anisotropic material that deserves attention. But Coër J and Bernard C

[2], while experimenting on aluminium alloys observed low variation in UTS in various directions

at elevated temperature of range 25-200oC. Even Keum et al [3] observed the same response at

300oC for Al5052. Garrett et al [4] work indicated that aluminium alloys though anisotropic, at

higher temperatures behave as isotropic. Byun T. S. et al. [5], studied the effect of specimen

thickness on tensile properties of SA508 Cl.3 steel with the thickness range of 0.2-2 mm specimens,

results show the thickness effect on the yield and ultimate tensile strength are nearly constant in the

thickness range of 0.2–2 mm. Therefore, at elevated temperature the sheets of thickness upto 2mm

exhibit constant mechanical properties.Hence, in this work the material is assumed to be isotropic

and experimentation of tensile test is performed for 2mm thickness sheet in single direction. The

test results are given in Table 1 obtained from Fig 4. The results obtained are shown in Fig 5-8

indicating the effect of elevated temperature on each parameter.

Fig: 4 The True stress-strain curves of aluminum alloy at elevated temperatures

Table 1. Calculated results of Aluminum 6061-T6 (2mm thick) samples for material properties of tensile testing specimen at Elevated

temperatures

TEMPRATURE E σy UTS DUCTILITY n K(Map) m

RT 5195.274 299 331 9.03% 0.2778 665 0.015

150˚ 3524.967 250 288 14% 0.1803 465 0.033

300˚ 3341 165 228 18% 0.0875 303 0.088

Fig 5 Temperature vs Strain Hardening Fig 6 Temperature vs Strength Co-efficient

Fig 7 Temperature vs Strain Rate Senstivity

050

100150200250300350400450

0 0.05 0.1 0.15 0.2

Tru

e s

tress

,Mp

a

True strain

RT150300

Fig 8 Specimens after Tensile Test

3. Hydraulic Deep Drawing Test:

In this study, the effects of forming parameters on the punch force and uniform thickness

distribution in the deep drawing of AA6XXX under non-isothermal condition were investigated.

Taguchi’s L27 array was used for conducting the experiments. For the determination of optimal

forming conditions (temperature, die speed, sheet thickness and lubrication) for minimum punch

force and minimum thickness variation, Taguchi’s signal-to-noise ratio was used. In addition, linear

and quadratic regression analyses were applied to predict the measured value. Finally, the reliability

of developed models was tested by the confirmation experiments.

The Deep Drawing experiments were carried out in non-isothermal conditions using a Hydraulic

Deep Drawing machine of 13 tonnage equipped with a maximum pressure of 115 bars, stroke of

main ram150mm and power pack 10 LPM max,120 bar pressure, 2kW drive motor. The

experimental setup for the forming tests is shown in Fig. 9. The work piece material used was

AL6061-T6 in the form of 105 mm diameter sheets of thickness 1, 1.5,2 mm. The chemical

composition of AL6061-T6 is given in Table 2. The forming tests were performed at three different

die speeds (0.4, 0.7, and 1m m/s), three temperatures (room temperature (RT), 150oC and 300 oC)

while the blank holder force was kept constant.

Table 2

Chemical composition of Al6061-T6 (wt. %).

Sheet Thickness Si Cu Fe Zn Mg Mn Cr Al Others

1 mm 0.57 0.181 0.279 0.048 1.199 0.067 0.179 97.30 0.17

1.5mm 0.64 0.186 0.36 0.043 1.049 0.119 0.181 97.27 0.146

2 mm 0.52 0.159 0.214 0.014 0.979 0.133 0.099 97.754 0.123

4. Forming tool - die design and lubrication:

The forming experiments were conducted using three types of die tool inserts: D1, D2, D3, are the

specified die materials given in Table 3 as shown in Fig 10. Die is made of Inconel steel with

constant punch diameter of 49.8 mm diameter placed with blank holder, which was supported by

three cushion pins. The tests were conducted at various lubrication conditions such as without

lubrication (WOL), Graphite (G) and Boric Acid (BA). The forming experiments were conducted

by heating the die and blank at specified temperatures by maintaining the punch at constant room

temperature (RT) to obtain better formability.

Table 3

Properties of forming die

Die Die Diameter Clearance

D1 52.3/52.6 mm 2.5/2.8

D2 53.5/53.6 mm 3.7/3.8

D3 54.3/54.6 mm 4.5/4.8

Fig 9 Experimental Setup Hydraulic Deep Drawing Equipment

Fig 10 Tool-Die Setup

5. The Taguchi method and design of experiments

Among various engineering analysis, Taguchi method is an influential design

which not only reduces the number of tests but also minimizes the effect of uncontrollable

factors.Forming temperature (T), die speed (V), sheet thickness (t) and lubrication

(µ) were selected as control factors and their levels were determined as shown in

Table 3. The most suitable orthogonal array L27 (3ˆ4) was selected to determine the

optimal forming parameters and to analyze the effects of manufacturing parameters

[6]. The L27 mixed orthogonal array shown in Table 4-5was used for conducting the

experiments shown in Fig 11.

Table 4

Forming parameters and their levels

Parameters Symbol Level 1 Level 2 Level 3

Blank Thickness (mm) A 1 1.5 2

Die and Blank Temperature B RT 150oC 300 oC

Die Speed (mm/s) C 0.4 0.7 1

Lubrication D WOL BA G

Taguchi method depends on the signal-noise (S/N) ratio to calculate the variation between

the experimental and the desired values [7, 8]. Generally, S/N ratio analysis uses three kinds of

quality features, such as the lower-the-better, the higher-the-better, and the nominal-the-best. For

each level of the process parameters, the S/N ratio is calculated based on the S/N analysis. The goal

of this study was to minimize punch force and thickness distribution. Therefore the lower-the-better

quality characteristic was used as shown in Eq

η= S/N ratio = -10 Log10 [ 1

n∑ y2] (2)

Table 5 Full factorial design with orthogonal array of Taguchi L27 (3^4)

Experiment no. Factor A Factor B Factor C Factor D

1 2 3 2 3

2 3 2 3 2

3 3 1 1 3

4 3 3 3 3

5 1 1 2 2

6 1 3 1 3

7 1 3 2 1

8 2 2 1 1

9 1 1 1 1

10 3 3 2 2

11 3 1 2 3

12 2 3 1 2

13 1 1 3 3

14 2 2 2 2

15 1 2 3 1

16 1 3 3 2

17 3 2 1 3

18 2 1 2 1

19 2 3 3 1

20 3 3 1 1

21 1 2 2 3

22 3 2 2 1

23 2 2 3 3

24 3 1 1 2

25 3 1 3 1

26 2 1 3 2

27 1 2 1 2

Table 6 The results of experiments and S/N ratios values.

Experiments

Control factors

Punch Force,

P

(KN)

S/N ratio for P

(dB)

Thickness

Variation, Th

(mm)

S/N ratio for Th

(dB)

A

Sheet

Thickness

(mm)

B

Die and Blank

Temperature

(oC)

C

Die Speed

(mm/s)

D

Lubrication

(µ)

1 1.5 300 0.7 G 39.4797 -31.9275 0.2125 13.4528

2 2 150 1 BA 66.6358 -36.4742 0.233521 12.6335

3 1.5 27 0.4 G 70.0294 -36.9056 0.117376 18.6084

4 2 300 1 G 73.7564 -37.3560 0.2786 11.1004

5 1 27 0.7 BA 50.2945 -34.0304 0.101652 19.8577

6 1 300 0.4 G 26.8453 -28.5774 0.145989 16.7136

7 1 300 0.7 WOL 25.9053 -28.2678 0.172466 15.2659

8 1.5 150 0.4 WOL 42.0087 -32.4668 0.175747 15.1022

9 1 27 0.4 WOL 54.2636 -34.6902 0.094252 20.5142

10 2 300 0.7 BA 44.8966 -33.0443 0.26804 11.436

11 2 27 0.7 G 92.4663 -39.3197 0.192625 14.3057

12 1.5 300 0.4 BA 21.8005 -26.7693 0.201206 13.9272

13 1 27 1 G 70.4265 -36.9547 0.110914 19.1003

14 1.5 150 0.7 BA 37.6288 -31.5104 0.203428 13.8318

15 1 150 1 WOL 32.2885 -30.1810 0.157349 16.0627

16 1 300 1 BA 32.8800 -30.3386 0.148733 16.5519

17 2 150 0.4 G 66.2397 -36.4224 0.2248 12.9641

18 1.5 27 0.7 WOL 55.5013 -34.8861 0.13448 17.4268

19 1.5 300 1 WOL 33.8566 -30.5929 0.24308 12.285

20 2 300 0.4 WOL 46.5978 -33.3673 0.274061 11.2431

21 1 150 0.7 G 48.7557 -33.7605 0.140068 17.0732

22 2 150 0.7 WOL 64.3460 -36.1704 0.236012 12.5413

23 1.5 150 1 G 67.7087 -36.6129 0.191699 14.3476

24 2 27 0.4 BA 84.4921 -38.5363 0.182839 14.7586

25 2 27 1 WOL 78.1531 -37.8589 0.178275 14.9782

26 1.5 27 1 BA 62.1216 -35.8649 0.133806 17.4705

27 1 150 0.4 BA 30.1380 -29.5823 0.127271 17.9054

Fig 11 Specimens obtained through Taguchi Method

5.1 Analysis of the signal-to-noise (S/N) ratio:

Punch Force (P) and thickness variation (Th) were measured via the experimental design

for each combination of the control factors by using Taguchi techniques, optimization of the

measured control factors were provided by signal-to-noise (S/N) ratios. The lowest values of punch

force and thickness distribution are very important for quality improvement of the product and

lowering production costs. For this reason, the ‘‘lower-the-better’’ equation was used for the

calculation of the S/N ratio. Table 6shows the values of the S/N ratios for observations of the punch

force and thickness variation. At the end of the forming tests, the average values of the punch force

and thickness variation were calculated to be 52.57 KN and 0.187 mm respectively. Similarly,

average values of S/N ratio for punch force and thickness variation were calculated to be -33.7951

and 15.23918889 respectively.Table7 and Table 8 indicate the S/N and Means effect of each

parameter in Figures12-19.

Table 7 S/N response table for P and Th factor.

Fig. 12. Effect of process parameters on average S/N ratio for P Fig. 13. Effect of process parameters on average S/N ratio for Th

Fig 14 Residual Plots of SN ratios of Punch Force (P) Fig 15 Residual plots for SN ratios of Thickness (Th)

Levels

Control factors

Punch Force (P) Thickness Variation (Th)

A B C D A B C D

Level 1 -31.82 -36.56 -33.04 -33.16 17.67 17.45 15.75 15.05

Level 2 -33.06 -33.69 -33.66 -32.91 15.16 14.72 15.02 15.37

Level 3 -36.51 -31.14 -34.69 -35.32 12.88 13.55 14.95 15.30

Delta 4.69 5.42 1.66 2.41 4.79 3.89 0.80 0.33

Rank 2 1 4 3 1 2 3 4

Table 8

Mean response table for P and Th factor

Levels

Control factors

Punch Force (P) Thickness Variation (Th)

A B C D A B C D

Level 1 41.31 68.64 49.16 48.10 0.1332 0.1385 0.1715 0.1851

Level 2 47.79 50.64 51.03 47.88 0.1793 0.1878 0.1846 0.1778

Level 3 68.62 38.45 57.54 61.75 0.2299 0.2161 0.1862 0.1794

Delta 27.31 30.19 8.38 13.87 0.0967 0.0776 0.0147 0.0072

Rank 2 1 4 3 1 2 3 4

Fig 16 Effect of process parameters on Means of Punch force ( P ) Fig 17 Effect of process parameters on Means of Thickness (Th)

Fig 18 Residual Plots for Means of Punch Force (P) Fig 19 Residual Plots for Means of Thickness (Th)

5.2 ANOVA method:

ANOVA is a statistical method which is used to determine the individual interactions of all

of the control factors in the test design. In this study, ANOVA was used to analyze the effects of

sheet thickness, temperature, die speed and lubrication on punch force and thickness variation along

the generated cup.The ANOVA results for the punch force and thickness variation are shown in

Table 9. This analysis was carried out a 5% significance level and a 95% confidence

level.According to Table 9, the percent contributions of the A, B,C and D factors on the punch force

were found to be 34.53%, 43.13%,4.11% and 10.25% respectively. Thus, the most important factor

affecting the punch force was temperature (factor B, 43.13%). According to the ANOVA results,

the percent contributions of the A, B, C and D factorson thickness variation were found to be

56.77%, 37.45% ,1.58% and 0.35% respectively. This showed that the most effective factor on

thickness variation was sheet thickness (factor A, 56.77%). The percent of error was considerably

low at 7.98% and 3.86% for P and Th respectively.

Table 9

Results of ANOVA for Punch Force and Thickness Variation.

Variance source Degree of freedom (DoF)

Sum of squares

(SS) Mean square (MS) F ratio Contribution rate (%)

P

A 2 106.08 53.041 38.92 34.53

B 2 132.49 66.246 48.61 43.13

C 2 12.62 6.309 4.63 4.11

D 2 31.49 15.747 11.56 10.25

Error 18 24.53 1.363 - 7.98

Total 26 307.21 - – 100

Th

A 2 0.042088 0.021044 132.48 56.77

B 2 0.027763 0.013882 87.39 37.45

C 2 0.001171 0.000585 3.69 1.58

D 2 0.000262 0.000131 0.82 0.35

Error 18 0.002859 0.000159 – 3.86

Total 26 0.074143 - – 100

5.3 Regression analysis of punch force and thickness variation:

Regression analyses are used for the modeling and analyzing of several variables where

there is relationship between a dependent variable and one or more independent variables [9]. In

this study, the dependent variables are punch force (P) and thickness variation (Th), whereas the

independent variables are sheet thickness (t), temperature (T) , die speed (V) and lubrication (µ).

The predictive equations which were obtained by the linear regression model of punch force

and thickness variation are given below.

Pl = 5.6078 + 27.3096t – 0.1095T + 13.9652 V+ 6.82148µ

R-Sq = 87.34% R-Sq(adj) = 85.04% (3)

Thl= -0.02037 + 0.09667t + 0.00028T + 0.02452V -0.002841µ

R-Sq = 94.02% R-Sq(adj) = 92.93% (4)

Here Pl and Thl show the predictive equations of punch force and thickness variation

respectively. R2 values of the equations which were obtained by linear regression model for P and

Th were found to be 87.34% and 94.02% respectively.

Fig. 20. Comparison of the linear regression model with experimental results for P and Th.

0

20

40

60

80

100

0 50 100

Actu

al-

P

Predicted -P

The predictive equations for the quadratic regression of punch force and sheet thickness are given below:

Pq= 121.93742 – 48.62591t – 0.184589T -76.75241V -28.57795 µ + 28.6912t2 – 0.039855tT + 1.95705tV -2.58555t µ + 0.000238T2 + 0.103006TV -0.008125T µ +25.73697V2 + 17.6861V µ + 7.0473 µ2

R-Sq = 99.49% R-Sq(adj) = 98.89% (5)

Thq = 0.00669 + 0.0417525t + 0.0004164T + 0.11773V – 0.02391 µ + 0.009071 t2+ 0.000128tT –

0.00552tV + 0.00555t µ - 7.76798e-7 + 5.92496e-6 – 3.7669e-5 – 0.06359V2 + 0.001582V µ + 0.00440 µ2

R-Sq = 98.11% R-Sq(adj) = 95.91% (6)

Here Pq and Thq show the predictive equations for punch force and thickness variation.The R2

values of the equations obtained by the quadratic regression model for P and Thwere found to be

99.49% and 98.11% respectively. Hence, more intensive predicted values were obtained by the

quadratic regression model as compared to the linear regression model.

Fig. 21 Comparison of the quadratic regression model with experimental results for P and Th.

5.4 Estimation of optimum punch force and thickness variation:

With the Taguchi optimization technique, a confirmation experiment was required to be conducted

for validating of the optimized condition [10]. In the estimation of optimum punch force and

thickness variation, Eqs. (7) and (8)were used respectively.

P opt = (A1-TP) + (B3-TP) + (C1-TP) + (D2-TP) + TP (7)

Th opt = (A1-TTh) + (B1- TTh) + (C1- TTh) + (D2-TP) + TTh (8)

0

0.05

0.1

0.15

0.2

0.25

0.3

0 0.1 0.2 0.3

Actu

al-

Th

Predicted-Th

Here, (A1, B3, C1, D2) and (A1, B1, C1, D2) represent the optimum level average values of

punch force (Popt) and thickness variation (Thopt) respectively (Table 4). TP and TTh state theaverage

of all of the P and Th values obtained from the experimental study (Table 8). As a result of the

calculations, it was estimated that Popt = 19.07594KN and Thopt = 0.07869 mm.

Whether the system had realized the optimization accurately enough needed to be

evaluated. For this purpose, the following equations were used in the specification of the confidence

interval (Cl) for estimated surface and flank wear [11]:

CIRa , Vb= √𝐹𝛼 ,1 ,𝐹𝑒 𝑉𝑒 [

1

𝑛𝑒𝑓𝑓+

1

𝑅] (9)

ηeff = N/ ( 1 + T dof ) (10)

Here, Fα,1,fe is the F ratio at a 95% confidence, α is the significance level, fe is the degrees-

of-freedom of error, Ve is error variance, ηeff is the effective number of replications, R is the number

of replications for confirmation experiments (Eq.(9)). N is the total number of experiments, and Tdof

is the total main factor degrees of freedom (Eq. (10)). F0. 5,2,18 = 3.5546 (from F test table), VeP =

1.363 and VeTh = 0.000159 (Table 7), R = 3 (Eq. (9)). N = 27, Tdof = 8 and neff = 3 (Eq. (10)). By

using the Eqs. (9) and (10) the confidence intervals were calculated as CIP = ± 1.797205 and CITh

= ± 0.019411 .The estimated average optimal punch force and thickness variation with the

confidence interval at 95% confidence is:

[Popt - CIP] < Pexp< [Popt + CIP], i.e.,

=[19.07594-1.797205] < 18.2 < [19.07594+1.797205]

= 17.27874< 18.2 <20.87315

[Thopt - CIP] < Thexp< [Thopt + CIP], i.e.,

=[0.07869 -0.019411] < 0.0832 < [0.07869 +0.019411]

= 0.059279 < 0.0832 <0.098101

The Pexp and Thexp values, obtained from the experimental study stayed within the

confidence interval limits. Thus, the system optimization for punch force and thickness variation

was achieved using the Taguchi method at a significance level of 0.05.

Table 10

Predicted values and confirmation test results by Taguchi method and regression equations.

Level For Taguchi method For linear regression equations For quadratic regression equations

Exp. Pred. Error (%) Exp. Pred.

Error

(%) Exp. Pred. Error (%)

P (KN)

A1B3C1 D2 (Optimum) 18.2 19.07594 4.78 18.2 19.28577 6 18.2 17.81311 2.17

A2B2C1 D2 (Random) 39.5 37.74594 4.44 39.5 41.72797 5.6404 39.5 38.01942 3.748

Th (mm)

A1B1C1 D2 (Optimum) 0.0832 0.07869 5.42 0.0832 0.088006 5.78 0.0832 0.086586 3.91

A2B3C1 D2 (Random) 0.2151 0.20239 6 0.2151 0.213008 1 0.2151 0.202112 6

5.5 Confirmation tests

Using Taguchi method and regression linear - quadratic equations, confirmation tests of the

control factors were conducted both for optimum and random levels. Table 9 indicates, the

comparison of experimental and the predicted values obtained from equations (Eqs.(3)-(6)),are

almost similar to each other.M.H. Cetin, suggested that, the error values must be below 20% for a

reliable statistical analyses [9]. Even though the calculated error percentages are higher in few

conditions, the results within acceptable limit, made the confirmation test as successful

optimization.

6. FORMING LIMIT DIAGRAM:-

The forming limit diagram was introduced by Keelar, an extensive work was done by

Goodwin and the evaluation of the FLD was made simple by Hecker. Strano and Colosimo

emphasised an approach to determine the forming limit curve based on experimental

results. Their work focused on the separation of safe strains and failure strains[12].Many

investigations have been reported on the sheet metal formability. However, a combined

study of the construction of a FLD, the prediction of a FLD using a model and influence of

parameters at different temperatures with different diameter blanks and with different

thickness has not yet been carried out.The present investigation has been undertaken with

the aim of establishing the forming limit diagram of three different thickness blanks 1mm,

1.5mm, 2mm with two different diameters 105mm & 110mm at three different

temperatures Room Temperature 32°C, 150°C, 300°C. This paper has attempted to

experimental evaluation of aluminium sheets at elevated temperature[13]. Also the Strains

along radial strain, hoops strain[14] is measured. Thickness variation measured along the

cup portions like Base, punch corner, wall, Die corner, Flange portion were measured. By

using experimental investigation forming limit diagram was plotted for all thickness blanks,

Safe zone for better forming was predicted.

The longest measurement of the circle is the major axis and the measurement

opposite to the major axis is called the minor axis. Estimation of major and minor axes of

extended circles is measured by using Tools makes microscope can see it in Fig.22. By

measuring the change in circle due to deep drawing i.e. Major and minor axis, figuring the

estimations of real strain and minor strains, plotted FLD OF AA6061-T6.A Tools maker

microscope (Computer operated) with an accuracy of 0.01 mm was used to measure

dimensions of the ellipses. The true major strain and the true minor strain were calculated

using the formulae as

True major strain = ln (Final D major/ original diameter)

True minor strain = ln (Final D minor/ original diameter)

The true major strain and the true minor strain were measured in the necked region, the

fractured region and the safe region. The forming limit diagram was drawn using the true

minor strain on abscissa and the true major strain on the ordinate. The safe region was

identified by drawing a curve using the strain values obtained in the necked region. The

strain states above the curve represent failure. The strain states below the curve represent

the safe region.

Fig 22 Tool Makers Microscope

A total of 27 experiments are performed and the results were plotted from Fig23 to Fig33.

Fig23Maximum draw load at various processing temperatures

Fig 24 Engineering thickness

0

10

20

30

40

50

60

70

80

30 150 300

MA

XIM

UM

DR

AW

ING

LO

AD

(KN

)

TEMPERATURE (°C)

DRAWING LOAD VS TEMPERATURE

-15-13-11

-9-7-5-3-113579

11

0 2 4 6 8 10 12 14 16 18 20 22 24

%En

gin

eeri

ng

thic

knes

s st

rain

Nodal distance from center of blank (mm)

Engineering thickness strain

ROOM TEMPERATURE 150 300

Fig 25 True thickness

Fig 26Engineering Radial strain

Fig 27 True Radial strain

-15

-10

-5

0

5

0 2 4 6 8 10 12 14 16 18 20 22 24%

Tru

e th

ickn

ess

stra

ni

Nodal distance from center of the blank (mm)

True thickness strain

Room temerature 150 300

0

2.43.8

20.2

16.2

12

9

4.6

0

23.6

18

9.8 108.2

2.4

01.82.4

16

6.8 6.6

4.4

2

0

5

10

15

20

25

0 5 10 15 20 25

% E

ngi

ne

eri

ng

rad

ial s

trai

n

Nodal distance from center of the blank (mm)

Engg. Radial strani vs Nodal distance

room temperature

150

300

0

2.3713.729

18.39

15.01

11.33

8.6177

4.49

0

1.980263.536

16.55

9.349 9.5317.8811

2.3716

01.78332.371

14.84

6.57 6.39

4.305

1.9802

0

2

4

6

8

10

12

14

16

18

20

0 5 10 15 20 25

%Tr

ue

rad

ial s

trai

n

Nodal distance from center of the blank (mm)

True radial radial strain vs nodal distance

room temperature

150

300

Fig 28 Engineering Hoops strain

Fig 29 True Hoops strain

0 -0.6

-10

-18

-20.2

-16

-11.6

0 -0.4

-8

-16 -16.8

-14.2

-8.2

0 -0.2

-6.4

-15-16.4

-11.4

-7.6

-25

-20

-15

-10

-5

0

5

0 2 4 6 8 10 12 14 16 18 20 22 24

% e

ngi

nee

rin

g h

oo

ps

stra

in

Nodal distane from center of blank (mm)

Engg. Hoops strain vs nodal distance

roomtemperature150

0 -0.6018

-10.536

-19.845

-22.5646

-17.435

-12.3298

0 -0.40008

-8.338

-17.435-18.392

-15.315

-8.555

0 -0.2002

-6.613

-16.2518-17.91266

-12.1038

-7.90432

-25

-20

-15

-10

-5

0

5

0 2 4 6 8 10 12 14 16 18 20 22 24

% T

ure

ho

op

s st

rain

Nodal distance from center of blank(mm)

True hoops strain vs nodal distance

room temperature

150

300

Forming Limit Diagrams for the different thickness and different diameters of blanks are

as follows.

Fig 30 FLD for 1mm Thick sheet

Fig 31 FLD for 1.5mm thick sheet

Fig 32 FLD for 2mm Thick sheet

Fig 33 Combined FLD

The chemical composition of the AA6061-T6 sheet metal reveals that high Mg

concentration and low Mn, Si and Fe concentrations, it results in better formability

compared to other series of aluminium alloys.

CONCLUSIONS

In this study, the effect of forming parameters and the optimal condition while drawing

of Al6061-T6 under gradient conditions was determined through Taguchi method.

ANOVA is used to evaluate the experimentation results. The following conclusions

may be drawn:

For minimizing the punch force and thickness variation, the optimum levels of the

control factors using S/N rates were determined. The most favorable conditions for

punch force is at A1B3C1D2 (i.e., sheet thickness = 1 mm, temperature = 300oC, die

speed = 0.4mm/s and lubrication = graphite) and for thickness variation at A1B1C1D2

(i.e., sheet thickness = 1 mm, temperature = RT, die speed = 0.4mm/s and lubrication

= boric acid) were observed.

Temperature and Sheet thickness are the main parameters that foretell the better

formability of Al6061-T6.

According to the outcome of statistical analyses, it was found that the temperature was

the most important factor for punch force with a percentage contribution of 43.13% and

that the sheet thickness was the most major parameter for thickness variation with a

percentage contribution of 56.77%.

The calculated and expected values of punch force and thickness variation shows

correlation coefficients (P = 0.988 and Th = 0.959) using quadratic regression models.

According to the confirmation test results, measured values were within the 95%

confidence interval.

All of these results showed that the Taguchi method was a reliable methodology for the

reduction of drawing time and forming costs in the non isothermal deep drawing of

Al6061-T6 alloy.

References

1. ASTM B557-02, ASTM Standard Test Methods of Tension Testing Wrought and

Cast Aluminum- and Magnesium-Alloy Products (2002).

2. Coër J, Bernard C, Laurent H, Andrade-Campos A, Thuillier S (2010) The effect of

temperature on anisotropy properties of an aluminium alloy. Exp Mech 51:1185–

1195. https://doi.org/10. 1007/s11340-010-9415-6.

3. Keum YT, Ghoo BY (2002) Anisotropy at high temperatures. J Ceram Process Res

3(3):178–181.

4. Garrett RP, Lin J, Dean TA (2005) An investigation of the effects of solution heat

treatment on mechanical properties for AA 6xxx alloys: experimentation and

modelling. Int J Plast 21:1640–1657. https://doi.org/10.1016/j.ijplas.2004.11.002

5. Byun T. S , Effect of specimen thickness on the tensile deformation properties of

SA5088 Cl.3 reactor pressure vessel, ASTM STP 1339, pg. 574-587,1998

6. Tushar Y. Badgujara, Vijay P. Wanib, 2018, Stamping Process Parameter

Optimization with Multiple Regression Analysis Approach, Materials Today:

Proceedings 5 , 4498–4507.

7. I. Asilturk, H. Akkus, 2011 ,Determining the effect of cutting parameters on surface

roughness in hard turning using the Taguchi method, Measurement 44 ,1697–1704.

8. O. Koksoy, Z.F. Muluk, 2004, Solution to the Taguchi’s problem with correlated

responses, gazi university, J. Sci. 17 (1) ,59–70.

9. M.H.Certin, B.Ozcelik, E.Kuram. E.Demirbas, 2011 , Evaluation of vegetable

based cutting fluids with extreme pressure and cutting parameters in turning of AISI

304L by Taguchi method, J.Cleaner Prod. 19,2049-2056.

10. N. Mandal, B. Doloi, B. Mondal, R. Das, 2011, Optimization of flank wear using

Zirconia Toughened Alumina (ZTA) cutting tool: taguch method and regression

analysis, Measurement 44 , 2149–2155.

11. A.Dvivedi, P.Kumar, 2007, Surface quality evaluation in ultrasonic drilling through

the Taguchi technique, Int.J.Adv.Technol,34, 131-140.

12. Kleemola, H.J.; Kumpalainen, J.O. (2013), Formability of aluminium and steel

sheets. Journal of Metals Technology, 159-162.

13. Ahmetoglu.M.; Broek. T.R.; Kinzel, G; Altan. T: Control of blank holder force to

eliminate wrinkling and fracture in deep-drawing rectangular parts. CIRP Ann.

Manuf. Technol. 44, 247–250 (1995).

14. Cunsheng Zhang, Xingrong Chu, Dominique Guines, Lionel Leotoing, Jie Ding,

―Effects of temperature and strain rate on the forming limit curves of AA5086

sheet, ‖ Procedia Engineering, vol.81, 2014, pp.772 – 778.

Enclosure-III

Achievements from the project

Enclosure-III

Achievements from the project

Ph. D.

D.Swapna,Prinicipal-Investigator is enrolled in Ph.D Programme at

Andhra university, Visakhapatnam, Andhra Pradesh.

Publication of results

D.Swapna, Ch.Srinivasa Rao, S.Radhika, “ Formability of lightweight materials-A

Review” , International Conference on "Advances in Materials and Manufacturing

Engineering (ICAMME- 2018)" during 24 & 25 January, 2018.(Scopus indexed)

D. SWAPNA, Ch. SRINIVASA RAO, D. Sameer KUMAR,S. RADHIKA, “AHP

AND TOPSIS BASED SELECTION OF ALUMINIUM ALLOY FOR

AUTOMOBILE PANELS”, Journal of Mechanical and Energy Engineering ISSN:

2544-0780 | e-ISSN: 2544-1671 Vol. 3(43) | No. 1 | April 2019 | pp. 43-50 DOI:

10.30464/jmee.2019.3.1.43.

Naveen. Y., Radhika.S and Swapna.D “EXPERIMENTAL ANALYSIS TO

PREDICT THE FORMABILITY OF ALUMINIUM AA6061-T6 SHEET METAL

AT ELEVATED TEMPERATURES”, International Journal of Recent Scientific

Research Vol. 10, Issue, 07(D), pp. 33555-33561, July, 2019, Available at

www.recentscientific.com

M. Gopi , K. Ravindra , Mrs. D. Swapna “Experimental and Simulation

Investigation of Non Isothermal Uniaxial and Biaxial Deep Drawing Tests for

AL6061-T6 Sheet”, International Journal for Research in Applied Science &

Engineering Technology (IJRASET) ISSN: 2321-9653; IC Value: 45.98; SJ Impact

Factor: 7.177 Volume 7 Issue VIII, Aug 2019- Available at www.ijraset.com.

Manpower trained

Our Department staff members and Non-teaching members were trained about the

Hydrualic Deep Drawing Equipment and how the reading has to be recorded while

doing the project work

Enclosure -IV

Summary of the findings

Enclosure –IV

Summary of the findings

Experimentation stage

a) A methodology was developed to study the influence of forming parameters on

hydraulic deep drawing machine in forming aluminium alloys such as Al6061-T6.

b) Four forming parameters (sheet thickness, temperature, speed and lubrication) were

considered with three levels for each forming parameter. The sheet thickness were 01,

1.5, 2 mm. The temperature were Room Temperature, 150oc and 300oc. The die speeds

of 0.4, 0.7 and 1 mm/s. The lubrication like without lubrication, graphite and boric

acid were considered.

c) The number of experimental runs and the combinations of each run was obtained by

using Taguchi’s orthogonal array. In order to minimise any effect of non-homogeneity

on the experimental results, forming operation was first performed on the work piece

with Hydraulic Deep Drawing machine. Each experimental run carried thrice.

d) Strain measurements for formed cups were carried out using high resolution Tool

maker’s microscope

e) This project used the Hydraulic Deep Drawing machine and Tool maker’s microscope

for identifying the optimized condition for minimum punch force and minimum sheet

thickness distribution and pre identification of cup fractures.

APPENDIX-II

Enclosure-V

Contribution to the society

Enclosure-V

Contribution to the society

i. Developed the optimised conditions to manufacture the intricate panels.

ii. Developed Forming Limit Diagrams to identify the failures of the component prior

to manufacturing process.

iii. In this work aluminium 6XXX alloys indicate better panel applications (both interior

and exterior) in near future.

Enclosure-VI

Publications out of the project

*Corresponding author: Naveen. Y Department of Mechanical Engineering, RVR&JC College of Engineering (Autonomous) Chowadavaram: Guntur-522019, AP, India

ISSN: 0976-3031

Research Article

EXPERIMENTAL ANALYSIS TO PREDICT THE FORMABILITY OF ALUMINIUM AA6061-T6 SHEET METAL AT ELEVATED TEMPERATURES

*Naveen. Y., Radhika.S and Swapna.D

Department of Mechanical Engineering, RVR&JC College of Engineering (Autonomous) Chowadavaram: Guntur-522019, AP, India

DOI: http://dx.doi.org/10.24327/ijrsr.2019.1007.3693

ARTICLE INFO ABSTRACT

Formability, it is the capacity of a material to be formed into a particular shape without failure, it is an important property of sheet metals to create complex sheet parts effectively. Prediction of Formability, Thickness distribution in deep drawing process will decrease the production cost and time of material to be formed. In this study, Experimental analysis is using to draw cylindrical cups at elevated temperatures i.e. Room temperature (32°C), 150°C, 300°C and with different thickness of blanks i.e. 1mm, 1.5mm, 2mm with 105mmm dia, 110 mm dia. Influence of forming temperature on maximum drawing load is measured. Influence of forming temperature on thickness strain, Influence of forming temperature on radial strain, Influence of forming temperature on Hoop strain were tabulated and experimentally analysed. Experimentally thickness distribution at various locations in half cut cup along with flange region is identified. Forming limit curves are plotted based on the experimental results predicted safe zone for sheet metal for different thickness of blanks.

INTRODUCTION

In automobile they test the formability of newly developed materials to introduce new models with better performance to get customer satisfaction or to select them for specific applications [1]. For that experimental analysis is needed number of experiments have to conduct to get good product. Theoretical analysis of deep drawing of cups was first reported by Hessenberg (HESSEBGERG, 1954), and Danckert (Danckert, 1995) studied the effect of residual stress in deep drawing of cylindrical cups by process modelling the die profile. The results of the parametic variation of the numerical simulation by Kobayashi and co-workers (Kobayashi and Alton, 1989; Kobayashi, 1978) compared reasonably well with experimental work of swift and chung (swift and chung, 1951), introduced plasticity matrices with elasto-plasto model for analysing cup drawing.D Swapna, S Radhika were reported a review on deep drawing (swapna and radhika, 146-149, 2018), Venkateswarlu. G and.; Davidson, M were (venkateswarlu, Davidson and Tagour, 2(11), 41–49 (2010).) worked on the influence of process parameters.A. C. Reddy, T. Kishen Kumar Reddy and M. VidyaSagar (vol.4, no.3, pp.53-62, 2012.) studied the characterization of warm deep drawing process. Yamuna, B., Reddy, A. C. Parametric (6(4), 2015, pp. 416-

424)) worked on influence of elevated temperatures on warm deep drawing process.

Table 1 Chemical composition of AA 6061-T6

Component Al Cr Cu Fe Mg Mn Si Ti Zn WT % 98.6 0.04 0.4 0.7 1.2 Max 0.15 0.8 Max0.15 Max 0.25

Table 2 Mechanical properties of AA6061

Property Metric English Hardness, Rockwell B 60 60

Hardness, Vickers 107 107 Ultimate Tensile Strength 310 MPa 45000 psi

Tensile Yield Strength 276 MPa 40000 psi Elongation at Break 12 % 12 %

Modulus of Elasticity 68.9 GPa 10000 ksi Poisson's Ratio 0.33 0.33

Fatigue Strength 96.5 MPa 14000 psi Fracture Toughness 29 MPa-m½ 26.4 ksi-in½

Shear Strength 207 MPa 30000 psi

The main tools used in deep drawing process are blank, punch, die and blank holder.Fig.1 will give the basic idea of deep drawing as follows.

Available Online at http://www.recentscientific.com International Journal of

Recent Scientific

Research International Journal of Recent Scientific Research Vol. 10, Issue, 07(D), pp. 33555-33561, July, 2019

Copyright © Naveen. Y., Radhika.S and Swapna.D, 2019, this is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited.

DOI: 10.24327/IJRSR

CODEN: IJRSFP (USA)

Article History: Received 15th April, 2019 Received in revised form 7th May, 2019 Accepted 13th June, 2019 Published online 28th July, 2019

Key Words:

AA6061-T6 sheets, Metal forming, Tools maker’s Micro scope, Forming limit diagram.

Naveen. Y et al., Experimental Analysis To Predict The Formability of Aluminium

Fig 1 Deep drawing of cylindrical cup formation

Aluminium alloys [4] are indispensable as an important material in sheet metal industry because of their superior properties such as acceptable cost, low density, good mechanical properties, structural integrity and simple fabrication prAluminium alloys are used in the production of railcars, marine hulls, military vehicles and aircraft. Sheet metal fabrication industries require materials that do not undergo necking, wrinkling and fracture during the forming process so that dimensional accuracy is maintained. The forming limit diagram was introduced by Keelar, an extensive work was done by Goodwin and the evaluation of the FLD was made simple by Hecker. Strano and Colosimo emphasised an approach to determine the forming limit curve based on experimental results. Their work focused on the separation of safe strains and failure strains[14].Many investigations have been reported on the sheet metal formability. However, a combined study of the construction of a FLD, the prediction of a FLD using a model and influence of parameters at different temperatures with different diameter blanks and with different thickness has not yet been carried out. The present investigation has been undertaken with the aim of establishing the forming ldiagram of Three different thickness blanks 1mm, 1.5mm, 2mm with two different diameters 105mm & 110mm at three different temperatures Room Temperature 32°C, 150°C, 300°C. This paper has attempted to experimental evaluation of aluminium sheets at elevated temperature. Also the Strains along radial strain, hoops strain [6] is measured. Thickness variation measured along the cup portions like Base, punch corner, wall, Die corner, Flange portion were measured. By using experimental investigation Forming lplotted for all thickness blanks, Safe zone fo0r better forming was predicted.

Experimental Procedure

In experimentation first aluminium sheets are cut into Blanks as per the requirement. The aluminium Blanks are set apart with line examples of circles by using electric discharge machining. Blank is clamped at movable blank holder. The starting operations directed at three distinct temperatures (Room temperature, 150°C, 300°C). At the point when sheet metal is formed, It is subjected to Different stresses. These stresses create non-uniform strains and many prompt wrinkling or crack in the formed specimen. forming procedure causes the line patterns to disfigure by a sum which relies upon the neighbourhood twisting experienced by the sheet metal. After the sheet metal is shaped, the circles will turn into an oval unless disfigurement is unadulterated biaxial stretching.

Experimental Analysis To Predict The Formability of Aluminium AA6061-T6 Sheet Metal At Elevated Temperatures

cup formation

are indispensable as an important material in sheet metal industry because of their superior properties such as acceptable cost, low density, good mechanical properties, structural integrity and simple fabrication process [5]. Aluminium alloys are used in the production of railcars, marine hulls, military vehicles and aircraft. Sheet metal fabrication industries require materials that do not undergo necking, wrinkling and fracture during the forming process so that dimensional accuracy is maintained. The forming limit diagram was introduced by Keelar, an extensive work was done by Goodwin and the evaluation of the FLD was made simple by Hecker. Strano and Colosimo emphasised an approach to

curve based on experimental results. Their work focused on the separation of safe strains and

.Many investigations have been reported on the sheet metal formability. However, a combined study of the

of a FLD using a model and influence of parameters at different temperatures with different diameter blanks and with different thickness has not yet been carried out. The present investigation has been undertaken with the aim of establishing the forming limit diagram of Three different thickness blanks 1mm, 1.5mm, 2mm with two different diameters 105mm & 110mm at three different temperatures Room Temperature 32°C, 150°C, 300°C. This paper has attempted to experimental evaluation of

ated temperature. Also the Strains is measured. Thickness

variation measured along the cup portions like Base, punch corner, wall, Die corner, Flange portion were measured. By using experimental investigation Forming limit diagram was plotted for all thickness blanks, Safe zone fo0r better forming

In experimentation first aluminium sheets are cut into Blanks as per the requirement. The aluminium Blanks are set apart with line examples of circles by using electric discharge machining. Blank is clamped at movable blank holder. The starting operations directed at three distinct temperatures (Room temperature, 150°C, 300°C). At the point when sheet metal is formed, It is subjected to

uniform strains and many prompt wrinkling or crack in the formed specimen. The forming procedure causes the line patterns to disfigure by a sum which relies upon the neighbourhood twisting experienced by the sheet metal. After the sheet metal is shaped, the circles will turn into an oval unless disfigurement is unadulterated

The longest measurement of the circle is the major axis and the measurement opposite to the major axis is called the minor axis. Estimation of major and minor axes of extended circles is measured by using Tools makes microscope can see iBy measuring the change in circle due to deep drawing i.e. Major and minor axis, figuring the estimations of real strain and minor strains, plotted FLD OF AA6061experimental setup shown in figure

Fig 2 Hydraulic deep drawing

Fig 3 Die with heater setup

T6 Sheet Metal At Elevated Temperatures

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The longest measurement of the circle is the major axis and the measurement opposite to the major axis is called the minor axis. Estimation of major and minor axes of extended circles is measured by using Tools makes microscope can see it in Fig.2. By measuring the change in circle due to deep drawing i.e. Major and minor axis, figuring the estimations of real strain and minor strains, plotted FLD OF AA6061-T6. The experimental setup shown in figure 2.

Hydraulic deep drawing machine

Die with heater setup

International Journal of Recent Scientif

Fig 4 Drawn cups with different thickness

RESULTS AND DISCUSSION

A total of 27 experiments are performed and the results were plotted from Graph 1 to Graph 11.

From graph 1 It can be observed that forming load is decreased at full draw when the processing temperature is increased. This is due to the flow stress decrees and ductility increases when the temperature is increased.

From graph 2 and graph 3. It can be observed that the maximum thinning occurs in the deep drawn cup at the punch corner radius region due to this region is subjected to biaxial tensile stress. The thickness variation at the bottom of the cup is negligible at all temperatures and it indicates no cold work is done at this region. The reduction of the thickness at the cup bottom decreases as the temperature is increasing. The effect of thinning increases at all temperatures and the temperature increases at 150°C, and subsequently, it decreases on increasing the temperature. This is due to flow stress is decreased as the temperature is increased.

From graph 4 and graph 5. It can be observed that the percentage of radial strain variation at the bottom of the cup is negligible at all temperatures it is due to no cold work done at this region. The radial strain increases as the temperature is increased and the maximum variation in radial strain is observed at the bottom of the cup. As the temperature increased the radial strain decreased at all temperatures and then subsequently, decreases on increasing the temperatures. This is due to the easy flow of metal as the temperature is increased.

From graph 6 and graph 7. It can be observed that the percentage of hoop strain variation at the bottom of the cup is negligible at all temperatures it is due to no cold work is done at this region. The hoop strain is decreased as the temperature increased. As the temperature is increased, the hoop strain decreases at all tempera150°C, and then decreases on increasing the temperatures. This is due to the easy flow of metal as the temperature is increased and also the required load to cause this flow is decreased.

From the above graph 8 to graph 11, FLD can be observed toa curve of the major and minor strains. The right side of forming limit diagram, which is indication for positive major and minor strains. The left side of forming limit diagram indicates pertinent for positive major and negative minor strains. From the graph 8 we can observe forming limit diagram for 1mm thickness with two different diameter specimens, in this we can clearly see that safe zone, neck zone and unsafe zone. As we increase the thickness of the test specimen it can observe that fld limit is increasing from 1mm sheet to 2mm sheet we can see this variation in graph 11. It can be seen that from the graph 10 to 11Forming limit diagrams that thickness of specimen impacts forming utmost curves of AA6061. Identified that the optimum forming thickneexperiment, the FLD curves are shifted up significantly along themajor strain axis. By increasing the thickness of the specimens the formability is increasing.

International Journal of Recent Scientific Research Vol. 10, Issue, 07(D), pp. 33555-33561

Drawn cups with different thickness

A total of 27 experiments are performed and the results were

From graph 1 It can be observed that the maximum forming load is decreased at full draw when the processing temperature is increased. This is due to the flow stress decrees and ductility increases when the

From graph 2 and graph 3. It can be observed that the maximum thinning occurs in the deep drawn cup at the punch corner radius region due to this region is subjected to biaxial tensile stress. The thickness variation at the

at all temperatures and it indicates no cold work is done at this region. The reduction of the thickness at the cup bottom decreases as the temperature is increasing. The effect of thinning increases at all temperatures and the temperature

0°C, and subsequently, it decreases on increasing the temperature. This is due to flow stress is decreased as the temperature is increased. From graph 4 and graph 5. It can be observed that the percentage of radial strain variation at the bottom of the

p is negligible at all temperatures it is due to no cold work done at this region. The radial strain increases as the temperature is increased and the maximum variation in radial strain is observed at the bottom of the cup. As the

radial strain decreased at all temperatures and then subsequently, decreases on increasing the temperatures. This is due to the easy flow of metal as the temperature is increased. From graph 6 and graph 7. It can be observed that the

rain variation at the bottom of the cup is negligible at all temperatures it is due to no cold work is done at this region. The hoop strain is decreased as the temperature increased. As the temperature is increased, the hoop strain decreases at all temperatures at 150°C, and then decreases on increasing the temperatures. This is due to the easy flow of metal as the temperature is increased and also the required load to

From the above graph 8 to graph 11, FLD can be observed to as a curve of the major and minor strains. The right side of forming limit diagram, which is indication for positive major and minor strains. The left side of forming limit diagram indicates pertinent for positive major and negative minor

e graph 8 we can observe forming limit diagram for 1mm thickness with two different diameter specimens, in this we can clearly see that safe zone, neck zone and unsafe zone. As we increase the thickness of the test

increasing from 1mm sheet to 2mm sheet we can see this variation in graph 11. It can be seen that from the graph 10 to 11Forming limit diagrams that thickness of specimen impacts forming utmost curves of AA6061. Identified that the optimum forming thickness for this experiment, the FLD curves are shifted up significantly along themajor strain axis. By increasing the thickness of the

Graph 1 Maximum draw load at various processing temperatures

Graph 2 Engineering thickness

Graph 3

0

10

20

30

40

50

60

70

80

30

MA

XIM

UM

DR

AW

ING

LO

AD

(K

N)

TEMPERATURE (

DRAWING LOAD VS TEMPERATURE

-15-13-11-9-7-5-3-113579

11

0 2 4 6 8%

En

gin

eeri

ng

thic

kn

ess

stra

in

Nodal distance from center of blank (mm)

Engineering thickness strain

ROOM TEMPERATURE

-13

-11

-9

-7

-5

-3

-1

1

3

5

0 2 4 6 8 10

% T

rue

thic

kn

ess

stra

ni

Nodal distance from center of the blank (mm)

True thickness strain

Room temerature

33561, July, 2019

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Maximum draw load at various processing temperatures

Engineering thickness

True thickness

150 300

TEMPERATURE (°C)

DRAWING LOAD VS TEMPERATURE

10 12 14 16 18 20 22 24

Nodal distance from center of blank (mm)

Engineering thickness strain

ROOM TEMPERATURE 150 300

10 12 14 16 18 20 22 24

Nodal distance from center of the blank (mm)

True thickness strain

Room temerature 150 300

Naveen. Y et al., Experimental Analysis To Predict The Formability of Aluminium AA6061-T6 Sheet Metal At Elevated Temperatures

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Graph 4 Engineering Radial strain

Graph 5 True Radial strain

Graph 6 Engineering Hoops strain

0

2.43.8

20.2

16.2

12

9

4.6

0

23.6

18

9.8 10

8.2

2.4

01.8

2.4

16

6.8 6.6

4.4

2

0

5

10

15

20

25

0 5 10 15 20 25

% E

ngi

nee

rin

g ra

dia

l st

rain

Nodal distance from center of the blank (mm)

Engg. Radial strani vs Nodal distance

room temperature

150

300

0

2.3713.729

18.39

15.01

11.33

8.6177

4.49

0

1.98026

3.536

16.55

9.349 9.531

7.8811

2.3716

0

1.7833 2.371

14.84

6.57 6.39

4.305

1.9802

0

2

4

6

8

10

12

14

16

18

20

0 5 10 15 20 25

%T

rue

rad

ial

stra

in

Nodal distance from center of the blank (mm)

True radial radial strain vs nodal distance

room temperature

150

300

0-0.6

-10

-18

-20.2

-16

-11.6

0 -0.4

-8

-16-16.8

-14.2

-8.2

0

-0.2

-6.4

-15-16.4

-11.4

-7.6

-25

-20

-15

-10

-5

0

5

0 2 4 6 8 10 12 14 16 18 20 22 24

% e

ngi

nee

rin

g h

oop

s st

rain

Nodal distane from center of blank (mm)

Engg. Hoops strain vs nodal distance

room temperature

150

300

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Forming Limit Diagram

Specimens were sheared from the aluminium sheet metal AA6061-T6 with a thickness of 1mm,1.5mm, and 2mm, with a diameter of 105mm and 110mm. All specimens were marked with circles by using electronic discharge machining, with circle of 5mm diameter. And were formed up to the point of fracture using the hydraulic press. Sheet specimens were subjected to different states of strain namely tension plane strain and tension-compression because of the varying width. During formation, the circles were distorted to ellipses. A Tools maker microscope (Computer operated) with an accuracy of 0.01 mm was used to measure dimensions of the ellipses. The true major strain and the true minor strain were calculated using the formulae as

True major strain = ln (Final D major/ original diameter) True minor strain = ln (Final D minor/ original diameter)

The true major strain and the true minor strain were measured in the necked region, the fractured region and the safe region. The forming limit diagram was drawn using the true minor strain on abscissa and the true major strain on the ordinate. The safe region was identified by drawing a curve using the strain values obtained in the necked region. The strain states above the curve represent failure. The strain states below the curve represent the safe region.

Forming Limit Diagrams for the different thickness and different diameters of blanks are as follows.

Graph 8 FLD for 1mm Thick sheet

Graph 9 FLD for 1.5mm thick sheet

Graph 10 FLD for 2mm Thick sheet

Graph 7 True Hoops strain

0 -0.6018

-10.536

-19.845

-22.5646

-17.435

-12.3298

0 -0.40008

-8.338

-17.435-18.392

-15.315

-8.555

0

-0.2002

-6.613

-16.2518 -17.91266

-12.1038

-7.90432

-25

-20

-15

-10

-5

0

5

0 2 4 6 8 10 12 14 16 18 20 22 24

% T

ure

hoo

ps

stra

in

Nodal distance from center of blank(mm)

True hoops strain vs nodal distance

room temperature

150

300

Naveen. Y et al., Experimental Analysis To Predict The Formability of Aluminium

Graph 11 Combined FLD

CONCLUSON

The chemical composition of the AA6061reveals that high Mg concentration and low Mn, Si and Fe concentrations, it results in better formability compared to other series of aluminium alloys. The results also shown that the 2mm thick AA6061 has the highest major limiting strain at a particular minor strain for the tension-tension, plane strain and tension compression strain states therefore, the workability range of this sheet metal is good. In forming of sheet metal, the AA6061-T6 sheets exhibited higher limit strains at 300the 1500C and room temperature. As the temperature increases we can observe good formability with low application of load. As thickness increases the level of FLD increases up to 2mm, identified that at the forming thickness1mm,1.5mm and 2mm, the FLD curves are shifted up significantly along the major strain axis. After experimentation on AA6061drawing, it can be concluded that the working temperatureworking thickness of AA606-T6 material is between 1503000C and 1.5mm to 2mm for producing quality products and smooth operations for AA6061-T6 materials.

Acknowledgmen

The authors would like to thank the University Grant Commission, India, as the present work is carried out as a part of UGC-MRP [MRP-6754/16 (SERO/UGC)].

References

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2. G. Palumbo, L. Tricario. Numerical and experimental investigations on the warm deep drawing process of circular aluminum alloy specimens. J. Mater. Process. Technol 184 (2007) 115-123.

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Experimental Analysis To Predict The Formability of Aluminium AA6061-T6 Sheet Metal At Elevated Temperatures

The chemical composition of the AA6061-T6 sheet metal reveals that high Mg concentration and low Mn, Si and Fe concentrations, it results in better formability compared to

alloys. The results also shown that the 2mm thick AA6061 has the highest major limiting strain at

tension, plane strain and tension compression strain states therefore, the workability

good. In forming of sheet metal, the T6 sheets exhibited higher limit strains at 3000C then

C and room temperature. As the temperature increases we can observe good formability with low application of load.

f FLD increases up to 2mm, identified that at the forming thickness1mm,1.5mm and 2mm, the FLD curves are shifted up significantly along the major strain axis. After experimentation on AA6061-T6 deep drawing, it can be concluded that the working temperature and

T6 material is between 1500C to C and 1.5mm to 2mm for producing quality products and

T6 materials.

The authors would like to thank the University Grant the present work is carried out as a part

6754/16 (SERO/UGC)].

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T6 Sheet Metal At Elevated Temperatures

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W. Miller, S. Zhuang, L. Bottema, J. Wittebrood, -Recent development in aluminium alloys for the automotive Industry, ‖ Materials Science and Engineering: A, vol. 280, no. 1, 2000, pp.37-49. Cunsheng Zhang, Xingrong Chu, Dominique Guines, Lionel Leotoing, Jie Ding,-Effects of temperature and strain rate on the forming limit curves of AA5086 sheet,

gineering, vol.81, 2014, pp.772-778. Ahmetoglu.M.; Broek. T.R.; Kinzel, G; Altan. T: Control of blank holder force to eliminate wrinkling and

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Eivani.AR.,Akbarzadeh.A.,2009. Experimental and analytical studies on the prediction of forming limit diagrams. Journal of Computational

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deep drawing process for EDD steel, International Journal of Multidisciplinary Research & Advances in Engineering, vol.4, no.3, pp.53-62, 2012. FahrettinOzturk, Murat Dilmec, MevlutTurkoz, Remzi E. Ece, Huseyin S. Halkaci,-Grid Marking and Measurement Methods for Sheet Metal Formability, ‖ Design and Production of Machines and DIES/MOLDS,

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FahrettinOzturk, Murat Dilmec, MevlutTurkoz, Remzi E. Ece, Huseyin S. Halkaci,-Grid Marking and Measurement Methods for Sheet Metal Formability, ‖ Design and Production of Machines and DIES/MOLDS,

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Profiles of EDD Steel at Elevated Temperatures, ‖ International Journal of Chemical, Molecular, Nuclear,

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International Journal of Recent Scientific Research Vol. 10, Issue, 07(D), pp. 33555-33561, July, 2019

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18. A. Chennakesava Reddy, “Evaluation of local thinning during cup drawing of gas cylinder steel using isotropic criteria,” International Journal of Engineering and Mate-rials Sciences, vol.5, pp.71-76, 2012.

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How to cite this article:

Naveen. Y et al., 2019, Experimental Analysis To Predict The Formability of Aluminium AA6061-T6 Sheet Metal At Elevated Temperatures. Int J Recent Sci Res. 10(07), pp. 33555-33561. DOI: http://dx.doi.org/10.24327/ijrsr.2019.1007.3693

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ICAMME-2018

Formability of lightweight materials-A Review

D. Swapnaa∗, Ch. Srinivasa Raob, S. Radhikaa,∗ aDepartment of Mechanical Engineering, RVR&JC College of Engineering (A), Chowdavaram, Guntur, AP 522019, India

bDepartment of Mechanical Engineering, AU College of Engineering, Andhra University , Visakhapatnam, AP 530003, India Abstract Aerospace entire body and fuselage wings are made of sheet metal forming which converts flat sheet without fracture and excessive thinning. Formability test is used to access major failures such as splitting, wrinkling and distorted shapes. Most of the formability tests such as Hydraulic Bulge test, Marciniak In-Plane Sheet torsion test, and Miyauchi shear tests indicate information about material properties. Sheet forming technology has emerged as the most advanced technique due to its capability of producing lightest structural parts that have been widely used in the automotive industry. Remarkable advantages such as low tooling cost, flexibility and ease of operation, low tool wear, better surface quality and capability to form complex shapes made sheet forming as most adaptable test for material properties. Many materials such as low carbon steel, copper, magnesium and aluminum alloys can be used in forming process. Predicting the input parameters which affect the product quality is an important issue in many industrial manufacturing processes. Most of the forming processes are enhanced by optimal process parameters such as blank holder force, cavity pressure, punch force and temperature. In the present paper, major experimental works reported in the literature about the effect of process parameters in different forming processes on drawing ratio and thickness reduction of formed part by many researchers have been reviewed.

Keywords: Drawing, Warm drawing, Process parameters, Limiting Drawing Ratio, Thinning, FLD.

1. INTRODUCTION

Modernised society requires, low load vehicles with less fuel consumption, which has been a challenging task, faced by most of the manufacturing industries. This demand for light weight has diverted the attention towards advanced high- strength steels, aluminium alloys, magnesium alloys and composites. Some materials have poor formability, which limit the application of materials to a certain extent. Especially, formability of aluminum alloys is onl y about two thirds of deep drawing steel grade with an elongation of about half[1].In particular, aluminum alloys have unusual combinations, such as high strength, formability,weldability, corrosion resistance, recyclability and low cost which make them as an counterpart to steel in the automotive industry. In spite of these advantages, aluminium alloys poor formability at room temperature has limited its application which can be overcome by performing the formability at elevated temperature. Since at higher temperature, improvement in formability is due to reduction in yield strength and increase in ductility. Lightweight materials, such as ultra-high-strength steel, titanium alloys and aluminum alloys are used extensively in aerospace and automobile industries leading to increasing demands for advanced forming technologies, as conventional forming methods lack the ability to meet the need for fabricating lightweight structures. Due to demand in lightweight aluminium alloys are extensively used in manufacturing as shown in Figure 1. Many application areas such as aircraft and gas turbine engines, (figure 2) where various lightweight materials are used.

Fig 1: Average use of aluminum [2]. Fig 2: Percentage of aluminum, titanium, and steel alloys and carbon

fiber reinforce plastic (CFRP) of the structural weight of modern large commercial aircraft and gas turbine engines [3].

D. Swapna et al. / Materials Today: Proceedings 18 (2019) 426–435 427

However, the growing demand for lightweight materials as given in Figure 3 has shifted the challenges from casting to sheet metal forming, thus giving weight reduction and simultaneously good surface finish leading to limiting environmental impact[4].

Fig 3. VW Strategy of sheet forming Technology development [4] 2. SHEET METAL FORMING PROCESS:- 2.1 Tensile Test:-

In sheet metal forming, there are two regimes of interest - elastic and plastic deformation. Forming a sheet to some shape obviously involves permanent ‘plastic’ flow and the strains in the sheet could be quite large. Whenever there is a stress on a sheet element, there will also be some elastic strain. To identify the material property some of the basic test such tensile test are performed. During this part of the test, the cross-sectional area of the strip decreases while the length increases; a point is reached when the strain-hardening effect is just balanced by the rate of decrease in area and the load reaches a maximum Pmax. From the load, extension diagram shown in Figure 4, the engineering stress strain curve is calculated as shown in Fig 5 which is widely used for identification of material properties

Fig 4: Load–extension diagram for a tensile test of a drawing quality sheet

Engineering stress, strain is defined as

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Fig 5: Engineering stress–strain curve for the test of drawing quality sheet

In this diagram, the initial yield stress is

(σf)0 = Py/A0 (2)

The maximum engineering stress is called the ultimate tensile strength or the tensile strength and is calculated as

T S = Pmax./A0 (3)

The elongation at maximum load is called the maximum uniform elongation, Eu.The strain at initial yield, ey, as mentioned, is very small, typically about 0.1%. The slope of the elastic part of the curve is the elastic modulus, also called Youngs modulus:

E = (σf)0/ey (4) In order to obtain the mechanical properties of the material, the tensile test is carried out by using universal tensile test machine and the yield strength, ultimate tensile strength, elongation, modulus of elasticity along with work hardening exponent and material constants will be extracted. The properties obtained from tensile test are used in simulation for further analysing the forming process. 2.2Deep Drawing Process:-

Using double acting hydraulic deep drawing machine show in Fig 6 consists of primary and secondary ram. Punch is attached to primary ram while blank holder is attached to secondary ram. Die is attached to press bed. Throughout the deformation process, load cell with LVDT which is used in capturing the load-displacement is attached at the top of the primary ram. Tooling temperatures are controlled and modified with the help of thermocouples and control panel. The forming process starts by heating the tooling, then placing the blank on the die, later the punch is moved downwards at a speed approximately 50mm/min and test was stopped as soon as necking /failure is observed through a mirror placed below the die.

Fig 6: Double-action hydraulic press with heating arrangements to conduct warm forming experiments

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3. PROCESS PARAMETERS:

In sheet hydroforming process, process parameters play a vital role, it is essential to find their influence on the deformation behavior of the sheet metal. In any forming, process parameters such as material, process and geometrical paramete rs play a vital role to improve the durability of the product.

3.1 BLANK HOLDER FORCE:- In Sheet Hydroforming process, the effects of process conditions such as temperature, hydraulic pressure, blank holder force and forming speed, play a major role in formability. Loading paths such as pressure and blank holder force (BHF) are the main driving force. Generally, BHF arises wrinkling whereas higher BHF results in fracture or extra thinning. An optimal BHF has to be implemented in order to get a product, free from failure domain. The next part reviews about few works carried out by researchers pertaining to loading paths. Design of loading path in simulation was developed by Rimkus et al [7]. A mechanical model for cylindrical cup hydroforming at room temperature to study the optimum blank-holder force was investigated by Zhao et al [8], but, the variation of flange thickness is ignored. A process control design algorithm was developed by Koyama et al [9] and applied it to adaptive control technique of BHF in a circular cup deep drawing process to achieve 2.4% improvement in the limiting drawing ratio (LDR). The LDR is an indicator of the formability in the forming processes which is defined as the ratio of formed cup by initial blank diameter. Computer –aided engineering (CAE) based on finite element analysis (FEA) has been adopted by Gantar et al [10]. Yoshihara et al [11] investigated the effect of blank holding force (BHF) on warm deep drawing of magnesium alloy at elevated temperature. Due to localized cooling of blank center, proper temperature distribution is suggested for improvement in LDR. By optimizing the BHF, Gharib et al [12] generated objective function to calculate the maximum punch force that would not cause tearing of the sheet. The BHF profiles obtained could decrease the maximum punch force by 6% and the maximum thinning by 22%. Yudieski Bernal [13] optimized the geometric parameters in deep drawing through which maximum drawing load and BHF are optimized from which a reduction of 16.9% forming load is obtained. Shulkin et al [14] studied viscous pressure forming process with a multipoint blank holder force control on aluminum 6061-0 to form a nozzle inner panel component with corrugations. Liu et al [15] proposed a multi-step BHF load path in which the maximum BHF was reached in five steps of constant force against the continuous rise in pressure. In another work of the same author [16], the effects of loading paths, during the hydroforming, on sheet thickness distribution was studied using numerical simulation. Ekrem et al [17] improved finite element analysis controlled by fuzzy control algorithm (FEA-FCA) approach to determine the optimal loading profile Figure5 through which LDR could be enhanced by 2.925.Similar BHF profile was sugge sted by Koyama et al [9]. Modi and Kumar [18] through experiments and simulations found that it is possible to achieve better formability in terms of minimum corner radius and thinning in case of the variable blank holder force technique when compared to that of constant BHF technique. Using artificial neural network Manabe et al [20] developed an adaptive control system for BHF which could reduce thinning at punch shoulder and thickening at the cup end in addition to uniform thinning. A feedback controlled adaptive simulation strategy was adopted by Sheng et al [21] to adjust the magnitude of variable BHF to obtain 9% increase in conical cup depth and 5% decrease in thickness reduction. Variation of constant and variable BHF techniques in obtaining thinning of 20% and 16 % in AA5182 alloy square cups for hydroforming of square cups with AA5182 alloy was shown by Modi and Kumar [18]. Based on fuzzy control algorithm Choi et al [22] developed a method to identify proper loading paths in SHF under warm conditions. Under isothermal warm sheet hydroforming process Lang et al [23] studied the forming pressure and some geometric parameters that effects thickness distribution and required forming force at room temperature. Intarakumthornchai et al [24] obtained feasible paths for P and BHF in hydro mechanical deep drawing of AISI 1008 parabolic cup by three methodologies showing maximum thinning of 29.43% with no wrinkles in the sheet metal blank. Chu Wang et al [25] investigated the HDD process of a composite conical part with double concave features through theoretical analysis, numerical simulation, and process experiment. But according to Sinh and Angihorti [26] optimal loading profiles do not change with the change in the co-efficient of friction. The work of Takayuki Hama et al [27] reported that as the position of the die surface changes, the lubrication condition is to be varied. Rizwan Zafar et al [28] proposed that HDD can be efficiently used to form three metallic blanks simultaneously. 3.2 CAVITY PRESSURE:- Cavity pressure is one of the significant process variables to control the forming quality of a piece under HDD process. Optimal pressure levels are to be attained for better formability. During forming, due to insufficient binding force overflow of material towards the cavity occurs. Higher radial and hoop stresses act on the walls resulting wrinkling, which cannot be mended by low cavity pressure. On the other hand if cavity pressure is increased beyond

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the optimal range fracture tendency increases due to less flow of material from the flange area towards the die center. The experimental studies reveal that blank holder force is less in Hydroforming compared to conventional deep drawing. The reason for lower blank holder force is due to optimal cavity pressure Figure6 which act uniformly at the outer surface of lower blank supports a balanced flow of metal during forming process. Based on the classical theory of plasticity Yossifon et al [29, 30] formulated the critical fluid pressure. Using FEA, Shim et al [19] developed a method for optimal pressure curve in SHF. Combination of FE simulations and optimization in order to optimize forming pressure versus time was proposed by Gelin et al [31]. Considering unified mechanics equilibrium equations Nurcheshmeh et al [32,33] studied relation between through thickness normal stress and fluid pressure, finally flange thickness was also analyzed in different regions of cylindrical cup.

Fig 7: Typical pressure path in experiment and FE simulation[34]

Hyunbo and Dong [19] proposed a liner pressure-BHF load path with the help of trial runs through FE simulations where pressure is proportional to the penetration volume by a punch in hydromechanical deep drawing process. In the work of Yaghoobi A [35] thickness distribution was optimized by proper pressure path in hydroforming process using artificial neural network and simulated annealing algorithm. The same author in his other study [36] proposed combination of ANFIS based on fuzzy c-means (FCM) and GA to optimize the maximum thinning in the critical region of copper cylindrical – spherical parts, which results 8.63% . Bin-jun-zhou et al [37] studied double layer sheet hydroforming and compared with single sheet hydroforming. Observations reveal that whenever double sheet hydroforming is used, even with lower hydraulic pressure, severe thinning shifts to bottom area which usually appears near the die corner in single sheet hydroforming. Similarly the thinning ratio reduces form 13.6% to 8.9% due to double sheet hydroforming. Chu et al [25] through his investigations on multistage HDD has drawn successfully stepped geometries by optimizing performing depth and pressure path. An LDR of 2.46 for aluminum 6061-T4 during HDD with radial pressure was obtained experimentally by Lang et al [38, 39]. Investigations of Meng et al [40] revealed that the proper control of cavity pressure is beneficial for improving the drawability of aluminum alloys through a process window of cavity pressure which was established based o n the primary stress method. 3.3 PUNCH LOAD:- Maximal punch load is an important parameter in sheet forming process. Working with presses of higher capacities may lead to many types of defects such as cracks and tearing. Selection of the machine pressing, tools and restrains in the formation of wrinkles are opted depending on punch load. In case of SHF process, formation of wrinkles can be avoided with a proper selection of punch load, which in-turn is related to the forming force and internal pressure. Hence it is evident that selection of press heavily depends on the punch load and this load can be calculated based on the theory of plasticity. Optimization of the maximal punch load to avoid wrinkling and fracture and the design parameter of the deep drawing mechanism was done by Abdalla S.Wifi et al [41]. Genetic algorithm was used by J.R.Marty-Delgado [42] for the optimization of working parameter and predicted 32.6% reduction in the forming load during deep drawing process and helped for proper press selection. While optimizing BHF an objective function is developed by Gharib et al [12] to identify the maximum thinning while using linear BHF. Lang et al [23] investigated forming force and thickness distribution by considering different temperature and punch speeds under isothermal warm forming. The work of Reza Teimouri and Hossein Ashrafi [43] is on optimal geometry and process parameters, in which response surface models of punch force and maximum thinning was developed. The authors conducted sensitivity analysis, which indicated the domination of fluid pressure effect over thinning, on punch force. It is also reported that geometrical parameters such as punch and die corner radius respond for both thinning and punch force variations. Sherbiny et al [44] experimentally observed that both thinning and residual stresses are affected by geometric parameters such as punch and die radius.

D. Swapna et al. / Materials Today: Proceedings 18 (2019) 426–435 431

Study on two thermoplastic metal composite laminates by Rajabi et al [45] shows that forming load is influenced by temperature, whereas wrinkling is affected by BHF. Investigation of non-isothermal model for warm deep drawing by Kim et al [46] says that thinning distribution is uniform under non uniform temperature distribution among geometric parameters rather than uniform temperature distribution. Moreover LDR decreases with increase in punch speed. Through finite element simulation and empirical observation Ethiraj and Kumar [47,48] studied a reduction of 40% in drawing load for St304 deep drawing process while raising the temperature. In tailor-welded blank Padmanabhan et al[49] observed that the punch force for deep drawing increases with anisotropy in the blank sheets. Takayuki Hama [27] proved that punch force effects the lubrication between the die and blank holder. A reduction of 16.9% in drawing load was observed in the work of Yudieski Bernal-Aguilar [13]. The author adopted intelligent controls for finding the optimal values of punch and die radius. Investigations of Venkateswarlu G[50] show that at room temperature, deformation is possible for high punch force due to high shear stresses caused by friction co-efficient. The effect of these parameters on LDR in various works adapting various techniques is seen in Table 1

3.4 TEMPERATURE:- Advanced research work towards improvement of formability is a prime requirement in present industrial scenario. Most of the steel materials are used for starter end covers, petrol tanks, kitchen ware, cooker, refrigerator panels etc. Deep drawing materials which require high tensile strength and better ductility in compression are facing serious difficulties during forming due to large amount of deformations and high flow stresses of the materials. Advanced ideas such as I) Innovative stamping process II) increase in working temperature, have been adopted to improve formability. Warm temperature formability of the material can be observed by conducting a series of laboratory scale tensile testing, stretch forming and deep drawing experiments. Li and Ghosh [59] performed uniaxial tensile test for three aluminum alloys as AA5182, AA5754 and AA6111-T4 in the temperature range of 200-350oC with varying strain rates of 0.015-1.5 s-1. It was observed that at higher temperatures lower strain rate enhances post-uniform elongation. Keeping the punch temperature lesser than die temperature the author [60] studied the biaxial deformation behavior for the same three alloys. All the formed cups show maximum thinning at cup corner portion specifically in non-isothermal process the reduced thinning is observed whereas 35% thinking is observed at upper wall. Most of the work in forming analyzed on thinning as given in table (2),showing the importance of uniform distribution of metal during forming process.

Table 1. Investigation done for improving Limiting

Drawing Ratiousing various approaches.

AUTHOR Input Parameter Methodology

Amino.H,et.al,(1990),Kasuga, Y(1958)et,al[51,52]

Groche P,et.al(2002)[53]

Friction-increasing effect, pre-bulging effect,and

fluid-lubrication effect

Coldand warm temp

Experimentation

Comparativestudybetweenwarm

LangLH,et.al

loaduniformpressure

conventional deep drawing and hydrodynamicdeepdrawing optimization

(2004)[23] LangL,et.al(2005)[39]

Blankholder gap,fluidpressure

Numerical and experimental

Khandeparkar T,et.al(2008)[54]

analysis DSHP

WeiL,et.al(2011)[15] VariableBHF,fluidpressure Two-step strategy proposed a Multi-stepBHFloadpath

Gorji,A.,et.al(2011)[55]

Meng B,et.al(2013)[40]

Pressurepath

proper control of cavitypressure

Simulation using FEM

Theprocesswindowbasedonthe

primarystress method.

HuseyinSH,et.al(2014)[56]

HashemiA,et.al(2015)[57]

Prebulging pressureanddimensions

of thedrawbead

Thickness,strength

Optimization

Numerical simulation to find

Yao Wang1,et.al(2016)[58]

Thinning andFracture

process window changing loading mode

Ekrem,et.al

(2016)[17]

RezaTeimouri,et.al(2017)[43]

Optimal loadingprofiles

optimal die geometryandfluid pressure

Rulebasedmatricesofthefuzzy

controlalgorithm(FCA) Responsesurfacemodels

432 D. Swapna et al. / Materials Today: Proceedings 18 (2019) 426–435

Fig 8: Thickness distribution in experimental deep drawn cups for Different die and punch temperature combinations with close view of Thinning

development [60]

Bolt et al [66] demonstrated that at elevated temperatures surface finish defects disappear. The uniaxial tensile test performed by Ozturk et al [67] on AA5754 showed an increase in total elongation without serration at cryogenic temperatures and warm conditions. The strain rate hardening effect causes its increase in formability at warm conditions while increased

Table2. Different parameters effecting the thinning of the formedcup bydifferentapproaches

Author Input Parameter Methodology

Wang ZJ,et.al(2004)[61] P ,BHF VPFfor corrugatedthin-walled

sheet parts

Zhao SD,ET.AL(2004)[8] Flangethickness,temperature Experimentation

Choi H,et.al(2007)[22] BHF, Hydraulicpressureandtemperature Fuzzycontrolalgorithm (aFEA-

FCA)

Wang ZJ,et.al(2008)[62] Pressure Double-sidedbulging

Choi H,et.al(2008)[63] Thinsheets,temperature Experimentation

SharmaAK,et,al(2009)[64] Frictioncoefficient Numericalstudy

IntarakumthornchaiT,et,al.(2011)[24] P and BHF Fuzzycontrolapproachusing

LSDYNA GorjiA,et,al(2011)[55] Pressurepath Experimentation

GreenDE,et.al(2011)[33] Fluid pressure. Unified mechanics equilibrium equations

NurcheshmehM,et.al(2012)[32] Fluid pressure. Unified mechanics equilibrium equations

ModiB,et.al(2013)[18] constantandvariableBHF Experimentation.

YaghoobiA,et.al(2013)[35] PRESSUREPATH Artificialneuralnetworkand

SimulatedAnnealing algorithm

Meng B,et.al(2013)[40] Cavitypressure Experimentation

Zhang F,et.al(2015)[65] Hydro-bulge Numerical simulation during

DSHP.

A.Yaghoobi1,et.al(2016)[36] Pressurepath CombinationofANFISbasedon fuzzyc-means (FCM) and GA

EhsanKhosrojerdi1,et,al(2016)[34] Temperature,Forming speed HDDRP Experimentation

ChuWang1,et.al(2016)[25] Initialpressure Theoretical analysis, numerical

simulation, and process

experiment

RezaTeimouri1,et.al(2017)[43] Optimal die geometry Numericalsimulation

D. Swapna et al. / Materials Today: Proceedings 18 (2019) 426–435 433

elongation at cryogenic temperature is associated with work-hardening phenomena. Tensile test to identify the influences of grain size and texture on the formability of Al 1050 was investigated by Bacroix et al [6 8]. The author found that re-crystallization

took place at the lowest investigated temperature of 280 oC and hence concluded that the macroscopic response of the tested materials strongly depended on their texture. Wang et al [69] and He et al [70], showed that the dome height increases with an increase in temperature before reaching the recrystallization. But after recrystallization, due to reduced ductility, the dome height decreases thus resulting in poor formability. The variation of yield locus with temperature for AA5083-O aluminum alloy was experimentally determined by Naka et al [71]. A

significant rise in limiting strain level was noticed at 300 oC condition with lowest deformation rate of 0.2 mm/min. The hydraulic bulge and tensile test results, indicate that flow stress curves from tensile test are limited to lower strain levels when compared to flow stress curves form bulge test. In 1946, Finch et al [72] investigated the development in the deformability at relatively

moderate temperature of about 150 oC for both rectangular and circular aluminium cups under warm deep drawing. Fukui et al [73], Lenz [74], Miyagawa [75] and Tozwa [76] experimentally shown improvement in cylindrical cup height and critical punch stroke with increased temperature. Necking site and forming limits were successfully predicted through simulation by Takuda et al [77]. Rajabi et al [45] reported that the deep drawing process of two thermoplastic metal forming load is effected by temperature. Yourui Tao [78] successfully showed that the packed layer hot drawing for spherical shape part of FVSO812 is an excellent forming method for high strength, low plasticity materials which effectively reduces the generation of wrinkling and fracture. On observation Kim et al [79] suggested that the effect of temperature gradient for deep drawn rectangular cup of AA5182 sheet at warm conditions can be measured by strain distribution and thickness distribution. The same author in his other study [46] revealed that the formability (cup height) can be improved in non-homogeneous tooling by concentrating on punch speeds and temperature effect. Ehsan Afshin [80] concentrated on Al 1050/St304 and Al 5052/St304 laminated sheets in warm deep drawing process. They studied the temperature effect on wrinkling, thinning and forming load. Deep draw ability of high strength materials such as AA7075 in warm conditions was investigated by Toros .S [81]. But the process is complicated for thin sheets, because of sever thinning, failure was observed by Choi H [63]. Replacement with hydroforming process allows such materials formability even at room temperature. But the production of complex components is still a challenging aspect which is fulfilled by innovative stamping process such as sheet hydroforming which combines with rapid tooling technique for the fast manufacturing of prototypes, thus shortening the product design process. Growing demand for weight r eduction in aerospace and automotive industries drives the usage of light materials such as aluminum, magnesium, and titanium alloys. Particularly aluminum alloys have been used to manufacture complex components with thinner profiles and improved mechanical strength in various industrial sectors. Mostly 40 to 60 % weight reduction in car manufacturing can be seen due to steel replacement with aluminum which leads to fuel effectiveness. Lightweight alloy materials are in low plastic deformation capacity and low elongation at room temperature (usually 5-20%). Formability is explained in terms of flow stress which is affected by temperature and strain rate. Generally aluminum alloys formability is improved as flow stress decreases with respect to increased temperature and reduced strain rate. An experimental study by Chang et al [82] shows that in isothermal hydrodynamic deep drawing, AZ31 magnesium alloy sheets experience failure

for temperature lower than 150 oC. The effect of rebounding temperature on total elongation and the elongation ratio for AZ31B alloy at elevated temperatures was investigated by Lin et al [83]. The minimum spring back for Ti-6242 under hot sheet metal forming is reported by Eva-Lis Odenberger et al [84]. Nitin Kotkunde [85], using FE simulation predicted blank diameter and optimized temperature for thickness distribution to understand failure phenomena. By calculating the stress and strain analytically, Cho et al [86] observed the effect of process parameters on flange and die corners. Under warm conditions, optimal loading profiles [87] were determined by using fuzzy logic. 4. CONCLUSIONS Tremendous changes from the past two decades are observed in sheet forming process due to demand of lightweight materials. Though various process parameters exist in sheet forming process, most effecting parameters like blank bolder force, cavity pressure, punch force and temperature are considered in this paper. Even minute variations in these parameters drastically affect the formability process. Formability of any material is effect by flow stresses, which in turn are affected by temperature and strain rate. Strain rate can be controlled by adjusting the loading paths and punch forces. Although, many researchers have adopted different techniques for studying the process parameters, still a lot of potential is left in warm hydro forming process. More focus has to be extended in this area so as to reach future advancements in automotive applications. References

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Experimental and Simulation Investigation of Non-Isothermal Uniaxial and Biaxial Deep Drawing

Tests for AL6061-T6 Sheet M. Gopi1, K. Ravindra2, Mrs. D. Swapna3

1, 2, 3Department of Mechanical Engineering, R.V.R. & J.C. College OF Engineering (Autonomous), (Accredited by NAAC with ‘A’ Grade)

Abstract: The process of Deep Drawing plays a vital role in the Production process of different parts in various process environments. Aluminum alloy sheets are increasingly used in automotive and aerospace industries. However, the aluminum alloy sheets are usually formed at elevated temperatures due to low formability at room temperature. The warm deep drawing process of aluminum 6061-T6 sheets are numerically studied by non-isothermal experimentation and simulation. To study the formability of AL6061 material, both uniaxial and biaxial tests are performed. The drawn depth and stress, strain distributions obtained from non-isothermal experimentation agreed well with up to 6% variation of simulation results. Keywords: deep drawing process, AL6061-T6 alloy, warm forming, and non-isothermal process.

I. INTRODUCTION The investigations and development of lightweight materials are very important issue in automotive and aerospace industries. Sheet metal parts are utilized in different industrial applications such as automobile and truck bodies, aircraft, railway cars, farm and construction equipment, beverage cans, kitchen utensils, etc. sheet metal forming processes are generally divided into three major categories that are cutting, bending and drawing. The product weight can be effectively reduced using lightweight materials such as aluminum alloys, which has excellent mechanical properties such as young’s modulus strain hardening(n), strain sensitivity(m), yield stress, ultimate tensile strength,ductility. The cylindrical shaped blank of aluminum alloy, which limits deformation at room temperature. Therefore, the aluminum alloy shows limited formability at room temperature. In general, the formability of aluminum alloy is effectively improved by increasing temperatures. Most studies investigated the formability of aluminum alloy sheets with cylindrical cup deep drawing in isothermal conditions .Non-isothermal forming has been introduced in which only die and blank are under heating condition, keeping punch at room temperature .Several papers on the warm forming of aluminum alloy was significantly improved at temperatures up to 300˚C, but work under non-isothermal condition at specified temperature has rare studies. Several research papers conducted FE simulation for the warm forming of aluminum alloy sheets. Using non- isothermal conditions with DEFORM, MARC. Although, few papers have been published on the FE simulations and experimentations for the warm forming of aluminum alloy sheets using non-isothermal conditions. Many researchers have experimented with the high strength low formability materials like aluminum or magnesium alloys to evaluate their forming characteristics. These materials nowadays replace the steel in automobile and electronic industries due to their excellent properties like lightweight, high specific strength. Takuda et al (2002), Wang and Lee (2006), Van Den Boogaard and Huétink (2006), Gavas and Izciler (2007), Palumbo and Tricarico (2007) are some of those who used aluminum or aluminum alloys in their research work. Magnesium or magnesium alloys are used as investigating materials by Shoichiro Yoshihara et al (2003), Qun- Feng Chang et al (2007) (i& ii), Lee et al (2007) (i& ii), Ren et al (2009), Heung-Kyu Kim and Woo-Jin Kim (2010), Aimei Zhang et al (2011), to name a few. Non-isothermal experimentation in deep drawing for AA5XXX alloys was conducted by Kaya et al[1], observed that the temperature improvement improves the limiting drawing ratio. Shehata F et al [2] conducted both uniaxial and biaxial test to study the formability of the material. Observations reveal that the elongation which improves due to increase in magnesium content, increase in temperature, and decrease in strain rate depends on the m-value. In biaxial test, the material less sensitive to temperature and strain rate compare to uniaxial tension. [3]S.Toros studies show that though aluminum alloys are excellent high strength to weight ratio, there formability increases only at elevated temperature such as 200 to 300 rather than room temperature. Uniaxial and Nakajima tests were conducted by Zhu Chen, Gang Fang, [4] to study the formability of 6061-T6 sheets using the FLD curves

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which predict the failure generated while drawing the sheets. It can be seen that increase in temperature and decrease in forming speed will give better drawing. Jacqueline Noder, [5]This paper examines non-isothermal warm forming experiments on AA7xxx-series channel sections at two different initial blank temperatures (187 and 253°C) with room temperature tooling.. Based on attached thermocouples during forming, thickness measurements and recorded force-stroke curves, the simulation model is validated. Kim, H. S, [6] this study examines the application of warm forming of aluminum alloys for automotive panels. Warm forming improved not only the deep-drawing formability of aluminum alloys but also their shape fix ability in hat-shaped bending. With increasing BHF, the shape fix ability improved further and was comparable to that of Steel. Finch, D. M., Wilson [7] studies shows interest in tailored welded blanks for weight reduction which is as challenging task in formability. The experiments performed above re crystallization temperature on 6061 and 7075 blanks using damage factor damage factor based on Cockcroft Latham algorithm was taken as the constraint for defect free product. Li, D., and Ghosh, A [8] Uniaxial tensile deformation behavior of three aluminum sheet alloys, Al 5182_/1% Mn, Al 5754 and Al 6111-T4, are studied in the warm forming temperature range of 200_/350 8C and in the strain rate range of 0.015_/1.5 s_1. The enhancement of strain rate sensitivity (m value) with increasing temperature accounts for the ductility improvement at elevated temperatures. The uniaxial tensile test is identified to serve as a screening test for ranking relative formability among different sheet alloys. Based on this criterion, the strain hardened 5xxx alloys (Al 5182_/Mn and Al 5754) have shown better formability’s than the precipitation hardened alloy (Al 6111-T4). In this study, the warm deep drawing processing under non-isothermal condition for aluminum alloy sheets has been studied experimentally and numerically. In order to verify the warm forming process, tensile tests and warm cylindrical cup deep drawing experiments were conducted. The drawn depth and stress, strain distributions of the sheet obtained in the experiments were compared with FE simulation results.

II. EXPERIMENTAL SETUP A. Uniaxial Tensile Test Understanding material mechanics is critical for engineering. The uniaxial tension tests provide a simple and effective way to characterize a material's response to loading. By subjecting a sample to a controlled tensile or compressive displacement along a single axis, the change in dimensions and resulting load can be recorded to calculate a stress-strain profile. From the obtained curve, elastic and plastic material properties can then be determined. Therefore, to investigate material mechanics and gain experience in uniaxial testing, we performed compressive and tensile tests on alloys, pure metals, and calculated their Young’s modulus, yield stress, ultimate tensile strength, and strain hardening exponent, strain sensitivity, strength coefficient. The Engineering and True Stress strain behavior of the aluminum sheet at elevated temperatures indicated increased elongation and decreased stress. The uniaxial tensile machine specifications are as follows: load cell capacity of 100KN, Strain rate of 0.33/s with cross head speed, and each piece took 5 minutes to complete the experiment. The uniaxial tensile machine is fixed with furnace and down jaw is fixed, up jaw is movable. The maximum furnace capacity is 1200˚C. The uniaxial tensile machine heaters are prepared by using silicon carbide materials, to avoided heat exposure to load cells, asbestos cloths are used and load cells are surrounded with water cooling circulation. The uniaxial tension machine as shown in Fig1.

Fig: 1 uniaxial tension machine.

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For uniaxial tests, the displacement is typically held at a constant rate, and displacement and resulting load are recorded. The load is measured by a series of strain gages, or “load cell,” while the displacement can be recorded as displacement of the crosshead, or the beam on which the specimen load frame is mounted. For more precise load measurements, strain gages or an extensometer can be directly fixed to the specimen. To make direct comparisons between materials, loading responses must be normalized against sample geometry. Therefore, the dimensions of each sample are noted to compute stress and strain from load and displacement, respectively. In tensile tests, specimens typically have two shoulders and a gauge section in between, the Sample to be created for the tensile test with dimensions, as shown in figure.2

Fig.2.Sample to be created for the Tensile test.

Table .1 Mechanical Properties OF AL6061-T6 1 Density 2.7 g/cc

2 Youngs modulus

68.9 GPa

3 Poisson’s ratio 0.33

4 Tensile Yield stress

276 MPa

5 Ultimate tensile strength

310 MPa

6 Shear Strength 207 MPa

For this section of the laboratory experiment, a metal and three metal alloys aluminum 6061 were subjected to uniaxial tension using the ADMT-UTM (USA) tension test specimen model. The samples standards ASTMB 557 structures to localize the point of failure to the centre of the samples during testing the initial sample dimensions (width and thickness) were measured, and then the samples were mounted into the fixed lower base of the ADMT-UTM (UASA) tension test specimen model. The gage length L between the fixed lower base and upper fixture was measured to determine the initial length of the sample undergoing uniaxial tension.

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To determine the mechanical properties, uniaxial tensile tests on AL6061 were conducted at temperatures ranging from room temperature to 300oC. AA6061-T6 aluminum alloy sheet specimens with a thickness of 2mm were prepared according to ADMT-UTM (USA) tension test specimen model.

Fig.3.Aluminium 6061-T6 (2mm) specimens for tensile testing at elevated temperatures.

Figure 3 shows the aluminum 6061-T6 with 2mm thickness specimens for tensile testing. Tensile specimen with specified dimensions which are shown in the above Fig.2 had a gauge length of 170 mm and width of 40 mm. The specimens were elongated at nominal strain rates of 0.33/s. The true stress-strain behavior of the AL6061 sheet at elevated temperatures indicated increased elongation and decreased stress. The stress strain relations of the aluminum at 32oC to 300oC along the rolling direction. The specified chemical composition of these sheets is shown in Table 2.

Table .2 Chemical Composition OF Al 6061-T6

Component Wt. % Component Wt. % Component Wt. %

Al

95.8 - 98.6

Mg

0.8 - 1.2

Si

0.4 - 0.8

Cr

0.04 - 0.35

Mn

Max 0.15 Ti

Max 0.15

Cu

0.15 - 0.4

Other, each

Max 0.05

Zn

Max 0.25

Fe

Max 0.7

Other, total

Max 0.15

B. Biaxial Cup Deep Drawing In the deep drawing technique, the flat piece obtained from a large sheet metal is named blank which is usually clamped on the top surface of the forming die by means of a rigid tool conventionally called blank-holder. In order to obtain a symmetric shape for a defects- free product, the centre point of the blank should coincide exactly with the centre of the die opening. Blank holder to catch the blank, punch force to form the blank into the die cavity, are the two main resources contribute in providing the force needed to form the sheet metal blank completely.

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The load capacity of machine is 13 Tones and maximum pressure is 115 bars. The stroke of main ram is 300mm and height of machine is 1500 mm. The formability of the AL6061-T6 sheets under deep drawing tests are conducted by using 13-ton hydraulic press at temperature ranging from room temperature to 300 ̊C. as shown in Fig.4.To increase the blank temperature, the blank is heated inside the preheated tool. In non-isothermal process, blank and die are heated, while punch is maintained at room temperature. The blanks are heated to the forming temperature using muffle furnace box. The main tool dimensions are as follows: punch diameter of 49.8mm, blank thickness of 2mm, die diameters for 2mm blank thickness, using 52.5/52.6mm, blank diameter of 105mm, and die travelling distance is 152mm, die profile radius 15mm. the blank holding force varied from 3 to 6 KN, Die force 67.1 KN and boric acid paste is used as a lubricant. The experiment is conducted on cylindrical blanks with Hydraulic Machine shown in above Fig.4

Fig: 4 deep drawing experimental machine.

III. EXPERIMENTAL PROCEDURE A. Uniaxial Tensile Test In order to investigate the effects of temperature on the mechanical properties and forming behavior of the aluminum alloy, the tensile test was performed on 2mm AL6061-T6 sheet at room temperature, 150˚C and 300˚C. The specimens were elongated at nominal strain rates of 0.33/s. The Hollomon’s constitutive equation is applied to analyze the material properties

σT= K€ n

Where, σT = true stress, €= true strain, n= strain hardening and k= strength coefficient. The stress–strain data were recorded and the mechanical properties yield strength (YS), ultimate tensile strength (UTS) and total percentage elongation were determined. In the warm working temperature range, flow stress of the alloy is influenced by both strain and strain rate. In case of most of the common alloys, the flow stress equation which incorporates the effect of strain hardening and strain rate hardening is given by

σ =K €n €.m From the above mentioned equation strain hardening, strength co-efficient, strain rate sensitivity were evaluated. The determined coefficients were used as input in FE simulations to define the flow curve of the material in the warm working temperature range.

Fig: 5 The Eng. stress strain relationship of AL6061-T6 at elevated temperatures.

0

100

200

300

400

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

Eng.

stre

ss,M

pa

Eng.strain

RT150300

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Fig: 6The True stress-strain curves of aluminum alloy at elevated temperatures.

The engineering and true stress-strain relationships obtained from the tensile tests at the three different directions of the AL6061-T6 sheets of 2mm in thickness used in this work are presented in Figure 5and Figure 6 respectively. Also, the mechanical properties acquired from these tests are listed in Table 3

Table 3 Calculated results of Aluminum 6061-T6 (2mm thick) samples for material properties of tensile testing specimen at Elevated

temperatures. TEMPRATURE E σy UTS DUCTILITY n K(Map) m

RT 5195.274 299 331 9.03% 0.2778 665 0.015 150˚ 3524.967 250 288 10.25% 0.1803 465 0.033 300˚ 3341 165 228 11.9% 0.0875 303 0.088

Fig 7: The results of the tensile testing of the AA6061-T6 sheets with different Temperatures- strain hardening, strength

coefficient, strain sensitivity.

0100200300400500

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16

True

stre

ss,M

pa

True strain

RT150300

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Tensile properties of AA6061-T6 sheets YS, UTS and total percentage elongation are determined from the stress–strain data at these conditions and these are summarized in Table 3. For a given strain rate, with an increase in the temperature, strength (both YS and UTS) decreased and ductility increased. Similarly, at a given temperature, as the strain rate increased, YS and UTS increased and ductility decreased. In this temperature range of testing, though softening is responsible for decrease in flow stress with temperature, strain hardening is also significant at 32˚C and 150˚C as indicated by increase in flow stress with strain. However, at 300˚C, strain hardening is lower and is almost negligible at the lowest strain rate. This is consistent with the decrease in n value with an increase in the temperature. Effect of strain rate is clearly visible on the flow stress, and it became more pronounced as the temperature increased. This is in accordance with an increase in the strain rate sensitivity index (m) with temperature. Higher m value also helps in achieving higher total elongations. The alloy exhibited more than 10% total elongation at 32˚C to300˚C and the maximum elongation of 11.9% has been obtained at the highest temperature and the lowest strain rate. The tensile properties and stress–strain data clearly indicate that both strain and strain rate have a strong influence on the flow stress in this temperature range. Hence, to define the flow curves of this alloy in FE simulations, it is important to use the constitutive equation which incorporates the effect of strain and strain rate on flow stress. The experimental true stress–true strain data at different strain rates and temperatures were used to fit a strain rate–dependent power hardening rule and the material coefficients were determined at each temperature. The values of strain hardening exponent (n), strain rate sensitivity index (m) and strength coefficient (k) in the constitutive equation with temperature are given in Table 3. The engineering and true stress– true strain curves predicted with the developed constitutive equations agreed well with the experimental curves as shown in Figures5 and 6. Figures6 and Table 3 show that both stress and strain characteristics of the specimens change with different temperatures. However, the dependency of the strain characteristics is stronger than that of rolling direction the stress characteristics. While the differences between the minimum and maximum values of the yield and tensile strengths of their average values, the difference between the minimum and maximum values of the strain at maximum stress and ultimate strain of their average values .It should be noted that the differences between the sheets with different temperatures are not all systematic differences and, for example, the batch scatter of the properties also plays a role. For AL6061-T6, the strain at maximum stress and ultimate strain increased as sheet temperature increased the strain at maximum stress again slightly decreases while the ultimate strain slightly increases. However, one can therefore conclude that temperatures increased from up to 300˚C, the strain limits of the specimens increase. B. Biaxial cup Deep Drawing Test The drawing operation begins when the punch moves down, pushing the blank into the die cavity. Through the operation, the blank experiences a complex sequence of stresses and strains continuously as it is formed into the required shape. The drawing process involves different forming stages, shown in Figure 8a. At the beginning, the forming force is transmitted to the blank through the die, resulting in a bending action in the metal over the punch and die corners. In this stage the metal is drawn slightly towards the opening of the forming die to produce an initial shallow cup as shown in Figure 8b. As the die is kept moving downwards, the metal bent previously just over the around corner of the punch is drawn into the clearance between the punch and the die, where it must be straightened to form the side wall of the final cup. At the same time, the bottom of the initial cup and the metal that was bent over the die corner move downwards correspondingly with the punch. In order to keep the metal at the die corner not stretched excessively at this stage more metal must be sent from the flange portion. Consequently, the outer portion of the blank is drawn continuously towards the die cavity to compensate the metal being used in forming the side wall, resulting in reducing perimeter diameter of the blank

Fig.8.Steps of Deep Drawing Process

Experiments were performed with a tool set schematically presented in Figure 8. The blanks were placed on top of cold punch which was slightly extended vertically from the blank holder .The blanks were lubricated with a water-based paste. The paste was applied on both sides of the blank before being placed on top of the punch. For drawing at warm temperature, the die and the blank holder were

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Fig: 9. Experimental Setup used for warm deep drawing.

Heated with internal heating blank and the punch were cooled with water through internal water circulating channels. Thermocouples were used to measure the temperatures of punch and the die. During the heating process, water of the lubricant evaporates leaving the lubricant on the blank, which still gave sufficient lubrication at 300˚C. The blank was heated up and reached the desired temperature soon after it came into contact with the die and blank holder. This is referred to as holding shown in Figure 8a. Drawing was performed by moving down the blank holder and the die, and the punch remained immobile as shown in Figure 8b. During drawing operation, the force exerted by the punch was recorded against the punch displacement. It was stopped when the desired depth was reached. The cups were water quenched after the drawing. For drawing at room temperature the sequence of operation remained exactly the same except the heating and cooling steps. It is clear now that the flange region and the side wall of the cup significantly experience the great portion of the deformation through drawing processes. In the flange region, the friction forces play a crucial role in the success of the drawing operation. Once the drawing force is applied to the flange portion conquers the friction between the blank and the surfaces of the blank holder and the die, and then the material starts moving towards the forming cavity by using sectional positions for warm deep drawing, as shown in Fig.10.

Fig.10.Sectional positions of warm cylindrical cup deep drawing.

Fig.11.Stroke length vs Pressure.

This is the variation graph which shows stroke length vs pressure at 32˚C, 150˚C, 300˚C and the appropriate values shows how the increase in temperature gives better formability.

010203040

0 5 10 15 20 25 30

32 Celsius

150

300

stroke lenth

Stroke lenth vs Pressure

pres

sure

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Fig.12: - Time vs. Stroke length.

This is the variation graph which shows time vs stroke length at 32˚C, 150˚C, 300˚C.

Table.4. Experimental values

Condition

Height(mm)

Thickness(T1,T2,T3,T4,T5)

Volumetric Stresses(MPa) Specimens

σ1

σ2

σ3

32˚C 16 1, 0.95, 0.92, 0.87 0.96

2500.38, 11557.97,14084.53,5741.

23,61.52

10197.88,1362.84,6442.15,28521.84,14688.10

6021.86,5486.50,5159.23,15638.02,7396.41

150˚C 18 0.99, 0.96, 0.94, 0.85, 0.95

2129.01,3061.91,536.73,9490.97,9121.67

4560.49,17922.95,4843.67,589.09,1508.22

895.01,7552.12,4045.11,11127.05,3982.42

300oC 24 1, 0.97, 0.94, 0.91, 0.90

4424.75,2345.69,2259.06,3758.7,2771.84

4922.21,10631.27,11952.08,2399.35,2359.82

942.55,-6782.51,-6637.13,11346.45,435.48

T1= FLANGE, T2= DIE CORNER, T3= WALL, T4= PUNCH CORNER, T5= BASE

IV. SIMULATION A. Simulation of Uniaxial Tensile Test The tensile test simulation is performed in ANSYS19.2 software; In Figures below shows the simulation of work piece model and deformations at elevated temperatures. The reference temperature for the three required temperature simulation is taken as 20˚C and geometric properties are given according to dimensions. Meshing is done in size controls, one end of the tensile work piece is constrained and other side a gradual stepped load of 30KN is applied and solved. The results are noted as follows. The figure 13 shows 3D model of the tensile test specimen. The initial condition of the sample at the time of the application of the load. The Fig14 shows Thermal conductivity Specimen at elevated temperatures. The final condition of the sample, i.e. the sample is broken into two pieces and the values of von misses stress that has obtained during the test. By conducting the tensile test, we obtained the stress-strain graph. The plotted graphs are shown in above Fig 5 and 6. Elastic deformation occurs in the initial portion of a stress-strain curve, where the stress-strain relationship is initially linear as shown in above fig 6. In this region, the stress is proportional to strain. Mechanical behavior in this region of stress-strain curve is defined by a basic physical property called the modulus of elasticity. The modulus of elasticity is the slope of the stress-strain line in this linear region, and it is a basic physical property of all materials. It essentially represents the spring constant of a material. The modulus of elasticity is also called Hooke's modulus or Young's modulus. The proportional limit is a point in the elastic region where the linear relationship between stress and strain begins to break down. At some point in the stress-strain curve, linearity ceases, and small increase in stress causes a proportionally larger increase in strain. This point is referred to as the proportional limit because up to this point, the stress and strain are proportional. If an applied force

010203040

0 5 10 15 20 25 30

32 Celsius

150

300

Time vs Stoke length

Time

Str

oke

leng

th

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below the PL point is removed, the trace of the stress and strain points returns along the original line. If the force is reapplied, the trace of the stress and strain points increases along the original line. The elastic limit is a very important property when performing a tension test. If the applied stresses are below the elastic limit, then the test can be stopped, the test piece unloaded, and the test restarted without damaging the test piece or adversely affecting the test results. For example, if it is observed that the extensometer is not recording, the force-elongation curve shows an increasing force, but no elongation. If the force has not exceeded the elastic limit, the test piece can be unloaded, adjustments made, and the test restarted without affecting the results of the test. However, if the test piece has been stressed above the EL, plastic deformation will have occurred, and there will be a permanent change in the stress-strain behavior of the test piece in subsequent tension tests.

Fig.13.3D model of the tensile test specimen.

Fig.14.Thermal conductivity Specimen at elevated temperatures.

Table.5. Simulation values for tensile specimens. Temperatures Deformation Vonmises

stress(MPa) Principle

stress(MPa) specimens

32˚C 2.341 179 176 0 2.341

150˚C 2.585 211 206 0 2.585

300˚C 2.78 251 234 0 2.78

The Tensile Test Analysis of AL6061-T6 using finite element method has been conducted using a computer Program called ANSYS 19.2. The results have been obtained. From the stress-strain graph it is understood that The Aluminum alloy follows the Hooke’s Law i.e., stress is directly proportional to strain. After the linear region in the graph, there occurs necking on the sample and finally it breaks.

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B. Simulation of Biaxial cup deep Drawing Non-isothermal simulation of cylindrical cup deep drawing of the aluminum alloy 6061 at elevated temperatures is performed using ANSYS 19.2 software. Commonly half of the geometries are modeled due to their symmetric boundary condition and meshed model as shown in Figures14 and 15. Tools are treated as rigid bodies with Non- isothermal and mechanical properties. The material properties of the AL-6061T6 Sheet obtained from the tensile test were used in simulation. The simulation parameters are as follows: punch velocity of 1mm/s, associated thermal conductivity of 32˚C to 300˚C, die travelling timing steps, and pressure in MPa, and punch strokes are depending on the applied pressures as per experimental procedure, the variations of the symmetrical cups at elevated temperatures and simulation values of the biaxial cups as shown below Table.6

Fig.14.Symmetric boundary. Fig.15. Simulation of meshed model.

Table.6.Simulation values for biaxial cups. Temperatures Deformation Stresses(MPa) Specimens

32˚C 15.96 5755.23,28524.88,15629.03

150˚C 17.85 9491.99,588.1,11122.35

300˚C 23.96 3758.9,23996.36,11346.5

Fig: 16. Experimental and simulation relationships between forming temperature and drawn depth.

Fig: 17. Experimental and Simulation drawn shape of the cylindrical cup at 300˚C.

05

101520

0 50 100 150 200 250 300 350

Dra

wn

dept

h,m

m

Temprature(̊C)

ExperimentSimulation

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Fig.18. Comparison of Experimental and Simulation thickness distribution at 300˚C.

The simulation drawn shape of cylindrical-cup deep drawing is shown in Fig.16, Which indicates that the drawn depth increases with increasing temperature for both the simulation and experiment. The cylindrical blank, indicates the non-isothermal condition simulation results using a flow stress curve at room temperature and 300˚C. The study assumed that the blank would be rupture when the tinning ratio exceeded at die corner position and flange positions of the cup. There is a considerable discrepancy of the drawn depth at the non-isothermal condition simulation at tool temperature of 300˚C.the deformation of the non-isothermal simulation agrees with the drawn depth of the non-isothermal experimental. The cup wall is cooled and constant by the punch in the non- isothermal simulation. The blank can be more easily drawn from a high temperature that is 300˚C. Figures 17 and 18 shows the drawn shapes and thickness distribution from the experiment and simulation at up to 300˚C, respectively. The simulation the thickness distribution agrees with the experimental results. The temperature was lower at the punch corner and increased towards die corner. A discrepancy between the experimental and simulation results was due to different grid sizes.

V. CONCLUSION The evaluation of the formability of aluminum alloy sheet 6061-T6 was studied using both experimental approaches and simulation modeling. The tensile tests are indicated that the both engineering and true stress-strain curves decreased with increasing temperature. With a stress- strain of 300˚C, and the mechanical properties of the aluminum tensile work piece specimens are indicated that when temperature increases with the decreasing young’s modulus. When E increases but yield stress or n decreases, similarly when E decreases but n or yield stress increases. The temperature increases with the ultimate tensile stress will be decreases, as well as ductility increases with also increasing the strain rate sensitivity with respect to temperatures. The temperature is an increase with strength coefficient is decreases. The warm cylindrical-cup deep drawing indicated that the cup height increased with increasing temperatures. The better formability is obtained from non-isothermal simulation agreed with the experimentation results. And finally we will conclude that the better formability of cylindrical cup will be agreed with higher temperature of 300˚C, in this experimentation and simulation results. Future work will focus on determining the process conditions of warm deep drawing, such as die corner radius, spring back effects, using non-isothermal simulations. Further work can be extended to analyses different thickness plates at different speeds, pressures and temperatures. This project extended to bending and crushing analysis for experimental results to validate the manual and simulation results.

VI. ACKNOWLEDGEMENT The authors would like to thank the University Grant Commission, India, as the present work is carried out as a part of UGC- MRP [MRP-6754/16 (SERO/UGC)].

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AHP and TOPSIS based selection of aluminium alloy for automobile panels

D. SWAPNA, Ch. SRINIVASA RAO, D. Sameer KUMAR, S. RADHIKA

DOI: 10.30464/jmee.2019.3.1.43 Cite this article as: Swapna D., Srinivasa Rao Ch., Kumar S., Radhika S. AHP and TOPSIS based selection of aluminium alloy for automobile panels. Journal of Mechanical and Energy Engineering, Vol. 3(43), No. 1, 2019, pp. 43-50.

Journal of Mechanical and Energy Engineering Website: jmee.tu.koszalin.pl ISSN (Print): 2544-0780 ISSN (Online): 2544-1671 Volume: 3(43) Number: 1 Year: 2019 Pages: 43-50 Article Info: Received 20 February 2019 Accepted 18 March 2019

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 (CC BY 4.0) International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

ISSN: 2544-0780 | e-ISSN: 2544-1671

Vol. 3(43) | No. 1 | April 2019 | pp. 43-50

DOI: 10.30464/jmee.2019.3.1.43

AHP AND TOPSIS BASED SELECTION OF

ALUMINIUM ALLOY FOR AUTOMOBILE PANELS

D. SWAPNA1*

, Ch. SRINIVASA RAO2, D. Sameer KUMAR1

,S. RADHIKA

1

1 Department of Mechanical Engineering, R.V.R. & J.C College of Engineering, Guntur, India,

e-mail: dswapna32@gmail.com 2 Department of Mechanical Engineering, College of Engineering, Andhra University, Visakhapatnam, India

(Received 20 February 2019, Accepted 18 March 2019)

Abstract:Automotive industry is a very attractive area for young researchers to do continuous

research and also it can be considered as an important thrust area as it is directly related to

passenger safety. New developments in automotive sector can be seen in many domains like

material selection, design, manufacturing etc. Since wrong selection directly leads to product

failure, among these, the proper selection of a particular material can be treat as utmost priority.

Hence, the present work discusses a methodology to select the best aluminium alloy for

automobile panels among various alternates serving the same purpose. Analytical Hierarchy

Process (AHP) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS)

methods with entropy weighting criteria are implemented for finding the best material and the

results are discussed.

Keywords:Material selection, MADM methods, AHP, TOPSIS, aluminium alloys

1. INTRODUCTION

Automotive designers are seeking for lightweight

materials with greater strengths. In modern vehicles,

many automotive parts made of steel are being

replaced with aluminium for weight reduction which

enhances the fuel economy and consequently reduces

the CO2 emissions [1]. Excellent properties of

aluminium alloy such as high strength, corrosion

resistance and weldability drives young researchers to

forward the research with aluminium as an alternate to

steel.

Further, keeping weight reduction as main

objective for most of the auto motor components

previously generated by casting and extrusion are

replaced by sheets parts as shown in Fig. 1.

The shape generated by steel sheet cannot be

developed by aluminum alloys without failures

because of its design shape limits and lower degree of

freedom in forming. General failures such as

wrinkling in steel are modified by improving the blank

holder force which cannot be applied for aluminum

alloys as it creates cracks leading to damage of

components. Compared to steel, aluminum has 1/3

modulus of elasticity, low anisotropy values which

tend to extensive local deformation. So the design of

automotive panels with Aluminum alloys is always

a challenging mission for the designers.

Fig. 1. Exploded view of Audi A8 space frame (a) and closures by weight (b)

However, a wide variety of aluminium alloys are

available for a particular application. The selection of

specific alloy by satisfying all the constraints without

derailing the functional failure is always a major task.

a)

b)

44 Swapna D. et al. | Journal of Mechanical and Energy Engineering, Vol. 3(43), No. 1, 2019, pp. 43-50

So far the manufacturers used Trial and error method

which is not valid every time.

Multi Attribute Decision Making (MADM)

methods are being more popular now a day to solve

the critical situations of decision making in

a systematic and logical way. These methods use

simple mathematical formulae in complex decision

making also. So far these methods are applied in many

fields like Staff Selection [3], Alloy wheel material

selection using magnesium alloys [4], Pharmacy

product selection [5] and in many more [6].

Therefore, this paper exposes an organized

approach for the selection of good material for

automobile panels by the application of some MADM

methods. Section 2 discuss the problem formulation

while the section 3 and 4 describe the methodology

and implementation of algorithms. Finally,

conclusions are presented.

2. PROBLEM STATEMENT

As mentioned in the earlier section, the weight of

an automobile can be reduced by replacing steel with

an alternate material namely Aluminium.Cantor et al.

[7] and Toroset al. [8] observed that depending on

different regions and different manufacturing

strategies wide range of aluminium alloys are applied

in body panels. Based on features such as strength and

formability, various alloys such as Heat treatable and

non-heat treatable alloys are used in panels, developed

from deep drawing process [9]. Further a survey is

conducted on the available literature [10-13] w.r.t.

Aluminium alloys and their necessary properties used

in the automotive industry in view of panel

applications. The researchers highlighted the prospects

of various alloys that are being currently used as well

as the research potentials of Al alloys in the near

future. It is further observed that there are various

alloys serving for the common application with each

alloy is having its own merits and demerits. The alloys

considered in the present study are tabulated in Table 1.

The problem is modelled to select the best alloy

among ten different materials satisfying seven

criterions. This problem is complex as the second

material posse’s good thermal conductivity while the

first material has good percentage of elongation. 6061

with T6 condition i.e. material 10 is a good choice in

view of good ultimate tensile strength and

hardness.The material for panel application must be

the fittest of all.Therefore, the problem is modelled to

identify and to select the best alloy among the

compared with MADM methods The problem

considered here is also a multi objective type as such it

has to satisfy all the constraints and must produce

a good quality solution.

3. METHODOLOGY

Multi Attribute Decision Making (MADM)

methods or Multi Criterion Decision Making

(MADM) methods are used when decision making is

critical. These methods works with simple

mathematical formulae and becoming more popular in

the recent years in view of applications in vide fields.

The generalised procedure of these MADM methods

are depicted in Fig. 2.

There are a sub class of methods like SAW, WPM,

AHP, TOPSIS, VIKOR, PROMETHEE, ELCTRE .etc

under the common name MADM or MCDM. Among

these SAW and WPM methods are simple and AHP

and TOPSIS are more popular in view of high

potentiality in various fields [14, 15].

Tab. 1. Decision Table for the selection of material

S.N

o Material

Density

(g/cm3)

Thermal

conductivity

(W/mK)

Percentage

of

Elongation

at break

Elasticm

odulus

(GPa)

UTS

(MPa)

YTS

(MPa)

Hardnes

s

(BHN)

1 AA6016-T4 2.7 190 27 69 200 110 55

2 AA6016-T6 2.7 210 11 69 280 210 80

3 AA5182-O 2.65 130 12 68 280 130 69

4 AA5754-O 2.67 130 19 68 210 90 52

5 AA5454-O 2.69 130 17 69 240 100 61

6 AA5052 2.68 140 22 68 190 79 47

7 AA5454 2.69 130 17 69 240 100 61

8 AA5154 2.66 130 20 68 240 94 58

9 AA 6061-T4 2.7 170 18 69 230 130 63

10 AA6061-T6 2.7 170 10 69 310 270 93

Swapna D. et al. | Journal of Mechanical and Energy Engineering, Vol. 3(43), No. 1, 2019, pp. 43-50 45

Fig. 2. Procedure involved in MADM Methods

3.1. AHP method

AHP Stands for Analytical Hierarchy Process

developed by T.L Sathy in 1980. It is one of the most

popular methods of MADM with many advantages.

The major distinctive of the AHP method is to use

pair-wise comparisons for comparing the alternatives

with respect to the various criteria. It is easy to use and

has lot of interdependence of parameters for better

output. The ability of to handle large size problems is

an another advantage of using this method [15, 16].

3.2. TOPSIS Method

Technique for Order of Preference by Similarity to

Ideal Solution (TOPSIS) is another method under the

category of MADM methods. In 1981, Ching-Lai

Hwang and Yoon developed this method. This method

is an approach to identify an alternative which is

closest to the ideal solution and farthest to the negative

ideal solution in a multi objective environment. After

the weights calculation and normalization of data,

identify the positive alternatives in and calculate the

separation measures of each alternate. Then evaluate

the relative closeness and rank. The detailed formulae

and examples in calculating performance is widely

available in web [3, 5]. The advantage of this method

is its ease in usage irrespective of problem size.

TOPSIS has been successfully implemented in both

Engineering, management and business and marketing

domains [15].

3.3. Entropy method

Entropy method uses the decision table to compute

the weights regardless operator’s choice. Entropy

methods have gain much importance in the recent

years as these methods reduces the decision makers

experiments as much as possible by implementing

mathematical computation for determining the

weights. A detailed procedure of entropy method is

given by Farhad Hosseinzadeh Lotfi et al. [17]. In

entropy method, the higher the difference in

performance values is considered for more weight age

and the materials with similar performance was given

with lower weightage.

Tab. 2. Normalized data of decision Table 1

S.No Material Density

(g/cm3)

Thermal

conductivity (W/mK)

Percentage of

Elongation at break

Elastic

modulus (GPa)

UTS

(MPa)

YTS

(MPa)

Hardness

(BHN)

1 AA6016-T4 0.98148 0.90476 1.00000 1.00000 0.64516 0.40741 0.59140

2 AA6016-T6 0.98148 1.00000 0.40741 1.00000 0.90323 0.77778 0.86022

3 AA5182-O 1.00000 0.61905 0.44444 0.98551 0.90323 0.48148 0.74194

4 AA5754-O 0.99251 0.61905 0.70370 0.98551 0.67742 0.33333 0.55914

5 AA5454-O 0.98513 0.61905 0.62963 1.00000 0.77419 0.37037 0.65591

6 AA5052 0.98881 0.66667 0.81481 0.98551 0.61290 0.29259 0.50538

7 AA5454 0.98513 0.61905 0.62963 1.00000 0.77419 0.37037 0.65591

8 AA5154 0.99624 0.61905 0.74074 0.98551 0.77419 0.34815 0.62366

9 AA 6061-T4 0.98148 0.80952 0.66667 1.00000 0.74194 0.48148 0.67742

10 AA6061-T6 0.98148 0.80952 0.37037 1.00000 1.00000 1.00000 1.00000

46 Swapna D. et al. | Journal of Mechanical and Energy Engineering, Vol. 3(43), No. 1, 2019, pp. 43-50

4. RESULTS AND DISCUSSIONS

The implementation of MADM methods uses

a sequence of steps as mentioned in Section 3. After

the preparation of decision table (Table 1), the next

step is preparing the Normalized Table based on

beneficiary and non-beneficiary variables. MATLAB

software is implemented to generate the data from the

equations. Normalized matrix for the problem

considered is shown in Table 2.

The weights were computed according to Entropy

method and are tabulated in Table 3. From Table 3, it

can be observed that the large difference in YTS

values of all the materials lead to higher weights while

the weightage factors of density and Elastic modulus

are very low. These values are corresponding to

almost similar performance behavior of all materials in

the decision table. It can also be understood that the

selection of best material does not much influenced by

these attributes.

4.1. AHP method As per the procedure of AHP method, pair wise

comparison of each alternate with other is prepared.

Sample of pair wise matrices for alternatives 1, 10 are

given in Table 4 (a) & (b).

After obtaining the pairwise comparison matrices,

the overall performance of alternatives i.e materials is

obtained by multiplying the relative weight of each

criterion with its consequent weight value of each

alternative and summing over the characteristic for

each alternative. The performance scores of each

material obtained from AHP are shown in Fig. 3.

Tab. 3. Entropy Weights for the attributes

Density

(g/cm3)

Thermal

conductivity

(W/mK)

Percentage of

Elongation at

break

Elastic modulus

(GPa)

UTS

(MPa)

YTS

(MPa)

Hardness

(BHN)

0.000121 0.094519 0.241070 0.000146 0.063899 0.48693 0.113311

Tab. 4. Pair Wise comparison matrices for each material

(a) Material 1

1 2 3 4 5 6 7 8 9 10

1 1.0000 1.0000 0.9818 0.9888 0.9963 0.9925 0.9963 0.9851 1.0000 1.0000

2 1.0000 1.0000 0.9818 0.9888 0.9963 0.9925 0.9963 0.9851 1.0000 1.0000

3 1.0188 1.0188 1.0000 1.0075 1.0150 1.0113 1.0150 1.0037 1.0188 1.0188

4 1.0112 1.0112 0.9925 1.0000 1.0074 1.0037 1.0074 0.9962 1.0112 1.0112

5 1.0037 1.0037 0.9851 0.9925 1.0000 0.9962 1.0000 0.9888 1.0037 1.0037

6 1.0074 1.0074 0.9888 0.9962 1.0037 1.0000 1.0037 0.9925 1.0074 1.0074

7 1.0037 1.0037 0.9854 0.9925 1.0000 0.9962 1.0000 0.9888 1.0037 1.0037

8 1.0150 1.0150 0.9962 1.0037 1.0112 1.0075 1.0112 1.0000 1.0150 1.0150

9 1.0000 1.0000 0.9814 0.9888 0.9963 0.9925 0.9963 0.9851 1.0000 1.0000

10 1.0000 1.0000 0.9814 0.9888 0.9963 0.9925 0.9963 0.9851 1.0000 1.0000

(b) Material 10

1 2 3 4 5 6 7 8 9 10

1 1.0000 0.6875 0.7971 1.0576 0.9016 1.1702 0.9016 0.9482 0.8730 0.5914

2 1.4545 1.0000 1.1594 1.5384 1.3111 1.7021 1.3111 1.3793 1.2698 0.8602

3 1.2545 0.8625 1.0000 1.3269 1.1311 1.4680 1.1311 1.1896 1.0952 0.7419

4 0.9454 0.6500 0.7536 1.0000 0.8524 1.1063 0.8524 0.8966 0.8254 0.5591

5 1.1090 0.7625 0.8840 1.1730 1.0000 1.2978 1.0000 1.0517 0.9682 0.6559

6 0.8545 0.5875 0.6811 0.9038 0.7704 1.0000 0.7704 0.8103 0.7460 0.5053

7 1.1090 0.7625 0.8840 1.1730 1.0000 1.2987 1.0000 1.0517 0.9682 0.6555

8 1.0545 0.7250 0.8405 1.1153 0.9508 1.2340 0.9508 1.0000 0.9206 0.6236

9 1.1454 0.7875 0.9130 1.2115 1.0327 1.3404 1.0327 1.0862 1.0000 0.6774

10 1.6909 1.1625 1.3478 1.7884 1.5245 1.9787 1.5245 1.6034 1.4761 1.0000

Swapna D. et al. | Journal of Mechanical and Energy Engineering, Vol. 3(43), No. 1, 2019, pp. 43-50 47

Fig. 3. Performance scores of each material according to AHP

It can be seen from Fig. 3.that the highest

performance is score is for AA6061 – T6 material and

the order of preference for the selection of materials

according to AHP is 10 - 2 - 1 - 9 - 3 - 8 - 7 - 5 - 4 - 6 .

4.2. TOPSIS method

With the normalized matrix and Weight matrix

Normal Decision matrix Rij and Weighted Normalized

matrix Vij are computed. From weighted normalized

matrix , the ideal best and worst solutions (V+ , V-) as

well as the separation measures (S+,S-) for each

alternate is calculated with the TOPSIS formulae are

shown below in Table 5 and 6.

Tab. 5. Ideal Best and Ideal Worst Solutions (V+ , V-)

Attributes V+ V-

1 0.00003 0.00003

2 0.04034 0.02497

3 0.11433 0.04234

4 0.00004 0.00004

5 0.02599 0.01568

6 0.28961 0.08473

7 0.05110 0.02582

Tab. 6. Separation measures of materials (S+, S-)

Materials S+ S-

1 0.1731 0.0802

2 0.0937 0.1427

3 0.1643 0.0571

4 0.1980 0.0400

5 0.1887 0.0382

6 0.2081 0.0508

7 0.1887 0.0382

8 0.1927 0.0458

9 0.1561 0.0654

10 0.0723 0.2068

By using the data of Table 6. The performance

scores of each material is calculated and is shown in

Fig. 4.

As seen from Fig. 4, AA 6061 – T6 has the highest

performance score than the other materials and the

order of preference for the selection of materials in

panel application according to TOPSIS is 10 - 2 - 1 - 9

- 3 - 6 - 8 - 7 - 5 - 4 .

Fig. 4. Performance scores of each material according to TOPSIS

48 Swapna D. et al. | Journal of Mechanical and Energy Engineering, Vol. 3(43), No. 1, 2019, pp. 43-50

4.3. Comparison of both methods

Based on the performance scores obtained from

AHP and TOPSIS, Ranking was given to each

material and Tabulated in Table 7.

Tab. 7. Ranking of Materials

S.No Material AHP

RANK

TOPSIS

RANK

1 AA6016-T4 3 3

2 AA6016-T6 2 2

3 AA5182-O 5 5

4 AA5754-O 9 10

5 AA5454-O 8 9

6 AA5052 10 6

7 AA5454 7 8

8 AA5154 6 7

9 AA 6061-T4 4 4

10 AA6061-T6 1 1

It can be observed that, the ranking of materials is

not uniform as each method has its own procedure to

rank the alternates. However, for this particular

problem both methods suggested AA 6061-T6 is the

best choice of material. So the usage of AA 6061 – T6

material will enhance the performance of automobile

panel as suggested by MADM methods.

5. CONCLUSIONS

In view of weight reduction strategies in

automotive industry, the replacement of steel with

aluminium is found to be the best option. As there are

number of Aluminium alloys for the same purpose and

to replace with the suitable alloy satisfying the

functional requirement is a challenging task. Ten

different alloys with seven attributes are considered in

the present study. The procedure involved for the

selection panel applications by the class of MADM

methods like AHP and TOPSIS is given in detail and

are successfully implemented. Entropy method was

adopted to find the weights and are incorporated to

find the solution quality. From the results, it is

observed that the material AA6061 with T6 condition

is the best alternate. Though the two methods AHP

and TOPSIS differ in the respective procedures but for

this particular problem the both methods suggested the

same material as the best choice. The present approach

tries to find the best material in a logical way, still

further research should be carried out for practical

application of the proposed material in the respective

field.

Acknowledgment

This work is carried out as a part of UGC-MRP

[MRP-6754/16 (SERO/UGC)]. On this occastion,

I would like to thank the University Grant

Commission, India.

Nomenclature

The following Nomenclature is used in the present

study

Symbols

V+ , V- – Ideal Best and Worst Solutions

S+ , S- – Separation Measures

T4 – Solution heat treated with natural aging

T6 – Solution heat treated with Artificial aging

O – Annealed

Acronyms

MADM – Multi Attribute Decision Making

AHP – Analytical Hierarchy Process

TOPSIS – Technique for Order of Preference by

Similarity to Ideal Solution

SAW – Simple Additive Method

WPM – Weighted Product Method

VIKOR – Vlse Kriterijumska Optimizacija

Kompromisno Resenje

PROMETHEE – Preference ranking organization

method for enrichment evaluation

ELECTRE – ELimination and Choice Expressing

REality

BHN – Brinell Hardness Number

UTS – Ultimate Tensile Strength

YTS – Yield Tensile Strength

AA – Aluminium Alloy

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Biographical notes

D. Swapna received her M.Tech

Degree in 2007 with specialization in

CAD/CAM. She is currently preparing

the research on Development of

Alumium panels for automitove

applications with the funding of

University Grants Commission (UGC),

New Delhi, India.

Ch. Srinivasa Rao is a professor in

Mechanical Engineering Department

of Andhra University College of

Engineering, Visakhapatnam. He

guided more than 8 research scholars

and several Post Graduate students in

various domains of Mechanical

Engineering. He published more than

150 national and International journals

with high eminence.

D. Sameer Kumar working as

assistant professor in the Department

of Mechanical Engineering, R.V.R. &

J.C. College of Engineering, Guntur.

His areas of interest include Material

selection using MADM methods as

well as Design and Development of

composites applied to automotive

industry.

S. Radhika received her Ph.D. from

Andhra University in 2015. She is

currently associate professor in the

Department of Mechanical Engineering,

R.V.R. & J.C. College of Engineering,

Guntur. Her areas of interest is to work

with Optimization principles applied to

manufacturing strategies.