investigation into the influence of surface …

e-ISSN: 2582-5208 International Research Journal of Modernization in Engineering Technology and Science

Volume:03/Issue:05/May-2021 Impact Factor- 5.354 www.irjmets.com

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INVESTIGATION INTO THE INFLUENCE OF SURFACE TOPOGRAPHY

(ROUGHNESS / WAVINESS) ON THE ADHESION OF ENGINEERING

MATERIALS

Mohd Faizi*1

*1Student, Department Of Mechanical Engineering, National Institute Of Technology Calicut,

Calicut, Kerala, India.

ABSTRACT

The adhesion based joining technology offers many advantages compared to other methods of joining and its

usage is increasing for manufacturing and assembly. Surface roughness is believed to be one important

parameter that controls the state of adhesion strength. This work aims to investigate the influence of

roughness, and waviness on the adhesive joint of two engineering materials, aluminium, low carbon steel using

stylus instrument. Influence of roughness and waviness is investigated by 2D roughness parameters measured

from a specimen of with using aluminium and low carbon steel. Several specimens with different surface

topographies were prepared by means of the different manufacturing process such as polishing, milling, and

surface grinding, for the investigation. Shear strength of adhesive joint, as adhesive strength indicators, is

measured by means of the tensile testing machine. Epoxy-based structural adhesive (Araldite) is applied in

uniform thickness on the specimens with different surface topographies. The experiments are conducted as per

ASTM D 1002 standard meant for performance studies of adhesive joint. The experiments indicate that the

shear strength of adhesive joints increases with an increase in roughness of specimen. A rougher surface has

better adhesion because the area between substrate and coating is increased. The work presents optimal values

of surface topographies parameter for a better adhesive joint based on experimental evidence.

Keywords: Adhesive Thickness, Lap Shear Strength, Surface Roughness, Waviness, Mild Steel, Aluminium.

I. INTRODUCTION

The importance of adhesive material joining technology is increasing in the field of design and manufacturing

because it has several advantages compared with other methods, like rivet joint and welded joint compare to

these types of joint adhesive lap joints is better because of less joint weight. During failure in rivet and welded

joint whole workpiece will be scrape, but in the adhesive joint, if a failure occurs only adhesives will get affected

and adherent can again use. It has been said that surface treatment or surface finish of joining parts is very

important for achieving good adhesion since surface roughness and waviness are important parameters that

control the state of adhesion. For, obtaining these advantages requires a specific adhesive joint design that

improves its functional performance. Uehara et al. [1] investigated the influence of the surface roughness on the

bonding strength of adhesive joints based on a curve that shows the relationship between surface roughness

and bonding strength. They found that there exists an optimum value of the surface roughness with respect to

the strength of the adhesion and the variation of shear strength was less with a change in roughness. Moreover,

the influence of roughness on bonding strength was a combined effect of adhesive strength, surface area effect

and notch effect due to surface roughness. Surface roughness is one of the most relevant parameters that affect

bonding strength, the cost of achieving better surface finish adds to the total cost of joining method, which

should be comparable with alternative methods of joining. Reina et al. [2] investigated the effect of horizontal

and vertical roughness parameters on the mechanical performance of adhesive joints furthermore they applied

value analysis technique to figure out the cost associated with each process to obtain surface finish. The

concluded that even though the highest bond strength was achieved with rough machining, polishing was

preferred when economic and environmental factors are taken into consideration. A.M. Pereira et al. [3]

conducted an experimental and numerical investigation into the effect of geometrical and manufacturing

parameters on strength of high strength epoxy adhesive joints of aluminium alloy. Effects of surface roughness

induced by various surface preparation methods applied compressive pressure, adherent thickness, overlap

length on bond strength were analyzed and a numerical model was also developed. Boutar et al. [4] conducted

an experimental study to quantify the variables that affect the strength of single laps joint, such as surface




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preparation and adhesive thickness. Aluminium joints were fabricated and tested to assess the adhesive

performance. Shear strength of the joints was found to be lower with higher surface roughness. The results

showed that rougher surface roughness has less wettability which is coherent with the shear strength test.

However, increasing the adhesive thickness reduced the shear strength of joints Ghumatkar et al. [5] in this

work, investigated the effect of adherent surface roughness on adhesive bond strength. Different adherents (i.e.

low carbon steel and aluminium) with single lap joints were tested. They reported an optimum surface

roughness for maximum strength in both aluminium and low carbon steel adherent joints. Examination on the

fractured surface (SEM) after testing showed evidence of adhesive deformation for joints at higher failure load.

From the literature survey, it is found that both surface roughness and waviness have significant effects on

strength of adhesive joints, but the effect of waviness is not much more investigated. Not many of the works

have focussed on the comparison of the effect of both roughness and waviness parameters on shear strength of

epoxy-based adhesive joints. In this work, the influence of surface roughness (Ra, Rz) parameters and waviness

(Wa, Wz) parameters on shear strength of single lap joints in adherent materials like aluminium and low carbon

steel material were investigated. The surfaces of adherents were prepared by different machining processes

like polishing, end milling, and surface grinding. Optimum values of roughness and waviness parameters are

suggested based on their performance in shear testing.

II. MATERIALS AND METHODS Aluminium and low carbon steel were used as adherent in this study. Aluminium and low carbon steel plates

were cut by shearing machine in the required dimension of 150×25×12.5 mm according to ASTM D 1002. A bi-

component of structural epoxy-based adhesive Araldite ® 2016 (Huntsman International (India) private

limited) was used for this study. For performing experimental relationship for shear strength and surface

roughness parameter (Ra, Rz) and waviness parameter (Wa, Wz), In this process two types of material

(adherent) Aluminium and low carbon steel selected. For every material, three types of manufacturing process

polishing, end milling, and surface grinding process were performed. Aluminium adherents surface was

prepared by mechanical abrasion method using abrasive paper of different grades. Five different grade of

emery paper P80, P120, P220, P320, and P400 were used for polishing to achieve the different roughness and

waviness levels on the adherent surface. End milling is done in vertical machining machine (Make: Bharat Fritz

Werner). The attachment of workpiece is as shown in Figure 1. CNC vertical milling machine is used for

processing aluminum and low carbon steel specimen with varying parameters of feed and depth of cut to

achieve different roughness and waviness parameter.

Fig 1 Specimen in end milling process

2.1 Surface grinding

Similarly, the surface grinding process was done with the help of magnetic flux surface grinder for aluminum

and low carbon steel specimen with varying parameters of feed and depth of cut for the five sample-specimen

to obtained different surface roughness and waviness parameter. And obtained roughness and waviness value

are evaluated with the help of stylus profilometer as shown Figure 2.




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Fig 2 Specimen in surface grinding process

2.2 Roughness measurement

After the processing, the surfaces were cleaned using acetone to eliminate any residual particles remaining on

the surface. Surface roughness and waviness values were measured using stylus profilometer (Mitutoyo SJ410,

Japan) as shown Figure 3. A cut of length (Lc) of 0.8mm was chosen for roughness measurements and for

waviness the cut off length (Lf=Lcx3) was selected 2.4mm. The measuring range of the profilometer was 0.01-

10.0 µm. Roughness parameters, namely average roughness (Ra) and maximum roughness (Rz) and their

waviness counterparts were used to evaluate the surface quality of the specimen. Surface roughness and

waviness measurement were done in the longitudinal direction. The measurement speed was set to 0.50 mm/s.

The measurements were done according to ISO 4287: 1997

Fig 3 Stylus profilometer (Mitutoyo, Japan, model SJ410)

The measured roughness and waviness data for polished, milled and ground specimens are given in Table 1 and

Table 2.

Table 1: Surface roughness/waviness values of polished aluminum specimens

Polishing

grade

P400 P320 P220 P120 P80

Ra (µm) 0.95 1.29 2.01 3.13 3.89

Rz (µm) 6.15 7.31 8.76 16.31 19.75

Wa (µm) 0.31 0.37 0.49 0.81 0.97

Wz (µm) 1.01 1.97 2.81 4.53 5.37




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Table 2: Surface roughness/waviness values of polished low carbon steel specimens

Polishing

grade

P400 P320 P220 P120 P80

Ra (µm) 0.89 1.05 2.08 3.13 3.56

Rz (µm) 5.61 6.45 7.47 18.60 19.98

Wa (µm) 0.22 0.37 0.41 0.71 0.87

Wz (µm) 0.89 1.73 2.52 3.82 5.31

And obtained roughness and waviness value are calculated with the help of stylus profilometer, and measured

values are given in Table 3 and Table 4

Table 3: Surface roughness/waviness values of milled aluminum specimens

Process no. 1 2 3 4 5

Ra (µm) 0.87 2.31 3.17 4.03 4.17

Rz (µm) 6.11 7.17 9.67 14.01 19.32

Wa (µm) 0.29 0.34 0.41 0.76 1.01

Wz (µm) 0.87 1.69 2.73 2.96 3.15

Table 4: Surface roughness/waviness values of milled low carbon steel specimens


Ra (µm) 0.87 2.31 3.17 4.03 4.17

Rz (µm) 6.11 7.17 9.67 14.01 19.32

Wa (µm) 0.29 0.34 0.41 0.76 1.01

Wz (µm) 0.87 1.69 2.73 2.96 3.15

Similarly, surface grinding is done with the help of magnetic flux surface grinder for aluminum and low carbon

steel specimen with varying parameters of feed and depth of cut for the five sample specimen. And obtained

roughness and waviness value are calculated with the help of stylus profilometer, and measured values are

given in Table 5 and Table 6 below

Table 5: Surface roughness/waviness values of surface ground aluminum specimens


Ra (µm) 1.04 2.56 3.61 4.54 4.89

Rz (µm) 4.98 6.72 7.98 10.67 17.65

Wa (µm) 0.32 0.44 0.59 0.83 1.03

Wz (µm) 0.98 1.76 2.73 3.14 4.21

Table 6: Surface roughness/waviness values of surface ground low carbon steel specimens


Ra (µm) 0.96 2.03 2.98 3.76 4.67

Rz (µm) 6.23 8.41 10.28 12.67 16.45

Wa (µm) 0.38 0.49 0.64 0.87 1.16

Wz (µm) 1.01 1.68 2.87 3.28 4.09

III. EXPERIMENTAL SETUP

Structural adhesive single lap joint configuration was selected. The set up includes a single lap joint of

Aluminium / low carbon steel with Araldite adhesive. The materials were so selected as they are mainly used in




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aeronautical and automobile sector where light weight and high strength structures are required. The SLJs

were made in dimensions according to ASTMD 1002 dimensions for single lap joint is (150mm x 25mm x

12.5mm), Fig 4 shows dimensions and geometry of SLJs.

Fig 4 SLJ dimensions according to ASTMD 1002

Fig 5 Single lap joints of milled (a) aluminum and (b) low carbon steel specimens

3.1 Sample preparation

A single lap joint geometry was used for the experiment as shown in Fig 6. Before the application of adhesive,

the bonding surface region was cleaned with acetone. The adhesive was applied on the adherent surface and

spread over to the entire bonding area of the specimen. The adherent was bonded by applying constant weight

on specimen up to 24 hrs. The curing temperature was set to 22° temperature. Adhesive thickness was

0.5±0.05 mm.

Fig 6 Lap shear joint specimen preparation

3.2 Test Method

Single lap joint specimens were tested using a universal testing machine (Shimadzhu UTM AGX Plus 10 KN)

under monotonic loading with a crosshead speed of 0.5mm/min. Five specimens were tested for every

machining process at room temperature. The fasten length was 25 mm at both ends, while the fasten width was

over the entire width of specimens. During testing, load-displacement data were recorded.




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Fig 7 Experimental set-up for SLJs

Table 7: Shear strength value for aluminum and low carbon steel lap joint

The shear strength value of polished, end milled, and surface grinding SLJs in (N/mm2)

Polishing Milling Surface grinding

S.N. Aluminium

Low

carbon

steel

Aluminium

Low

carbon

steel

Aluminium

Low

carbon

steel

1 2.63 3.04 2.46 2.68 2.19 2.37

2 2.98 3.46 2.76 3.19 2.61 2.98

3 3.03 3.98 3.89 4.13 3.84 4.07

4 4.97 5.36 4.91 5.62 4.62 5.17

5 4.45 4.87 4.17 4.03 4.36 4.21

IV. RESULTS AND DISCUSSION 4.1 Polishing process (Aluminium material)

The shear strength values of bonded specimens with different roughness and waviness values were obtained

and the plotted correspondingly. Separate plots for Ra, Rz, and Wa, Wz were plotted and they are shown below.

Figure 8 (a) & (b) shows that shear strength with respect to surface roughness parameter Ra and Rz for

aluminium material in the polishing process. It is clearly seen that the shear strength values are slightly

increased in roughness parameter Ra from 0.89µm to 2.2µm and then the shear strength is increased much

more in the range of roughness parameter Ra from 2.2 µm to 3.8µm and then the shear strength is decreasing

fast rate after the roughness parameter Ra 3.8 µm, and for Rz parameter the value is from 6µm to 10µm and Rz

10µm to 17µm are increasing shear strength value and Rz value after 17µm the shear strength value is

decreasing rapidly. And from Figure 9 (a) & (b) the shear strength value for waviness value Wa in the range of

0.3µm to 0.8µm and then waviness value after 0.8µm shear strength value is decreasing, and for waviness

parameter, Wz from 0.8 µm to 3.8µm shear strength is increasing and after 3.8µm shear strength is decreasing.

Specimen




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(a) (b)

Fig 8 Effect of roughness parameters (a) Ra and (b) Rz of polished aluminium adherent on shear strength

(a) (b)

Fig 9 Effect of waviness parameters (a) Wa and (b) Wz of polished aluminium adherent on shear strength

4.2 Polishing process (Low carbon steel)

Figure 10 (a) & (b) shows that shear strength with respect to surface roughness parameter Ra and Rz for low

carbon steel in the polishing process. It is clearly seen that the shear strength is slightly increased in roughness

parameter Ra from 0.89µm to 2.2µm and then the shear strength is increased much more in the range of

roughness parameter Ra from 2.2 µm to 3.8µm and then the shear strength is decreasing fast rate after the

roughness parameter Ra 3.8 µm, and for Rz parameter the value is from 6µm to 10µm and Rz 10µm to 17µm

are increasing shear strength value and Rz value after 17µm the shear strength value is decreasing rapidly. And

from Figure 11 (a) & (b) the shear strength value for waviness value Wa in the range of 0.3µm to 0.8µm and

then waviness value after 0.8µm shear strength value is decreasing, and for waviness parameter, Wz from 0.8

µm to 3.8µm shear strength is increasing and after 3.8µm shear strength is decreasing.

(a) (b)

Fig 10 Effect of roughness parameters (a) Ra and (b) Rz of polished low carbon steel adherent on shear

strength




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(a) (a) (b)

Fig 11 Effect of waviness parameters (a) Wa and (b) Wz of polishe low carbon steel adherent on shear strength

4.3 Milling Process (Aluminium )


aluminium material in the end milling process. It is clearly seen that the shear strength is slightly increased in

roughness parameter Ra from 0.89µm to 2.4µm and then the shear strength is increased much more in the

range of roughness parameter Ra from 2.4 µm to 4µm and then the shear strength is decreasing faster rate after

the roughness parameter Ra 4 µm, and for Rz parameter the value is from 6µm to 15µm, are increasing the

shear strength value and Rz value after 15µm the shear strength value is decreasing rapidly. And from Figure

13 (a) & (b) the shear strength value for waviness value Wa in the range of 0.3µm to 0.8µm and then waviness

value after 0.8µm shear strength value is decreasing, and for waviness parameter, Wz from 0.8 µm to 3.0µm

shear strength is increasing and after 3.0µm shear strength is decreasing.

(a) (b)

Fig 12 Effect of roughness parameters (a) Ra and (b) Rz of milled aluminium adherent on shear strength

(a) (b)

Fig 13 Effect of waviness parameters (a) Wa and (b) Wz of milled aluminium adherent on shear strength




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4.4 Milling Process (Low carbon steel)

Figure 14 (a) & (b) shows that shear strength with respect to surface roughness parameter Ra and Rz for low

carbon steel material in the milling process. It is clearly seen that the shear strength is slightly increased in


range of roughness parameter Ra from 2.4 µm to 4µm and then the shear strength is decreasing fast rate after

the roughness parameter Ra 4µm, and for Rz parameter the value is from 6µm to 15µm, increasing the shear

strength value and Rz value after 15µm the shear strength value is decreasing rapidly. And from Figure 15 (a) &

(b) the shear strength value for waviness value Wa in the range of 0.3µm to 0.81µm and then waviness value

after 0.81µm shear strength value are decreasing, and for waviness parameter, Wz from 0.8 µm to 4.5µm shear

strength is increasing and after 4.5µm shear strength is decreasing.

(a) (a) (b)

Fig 14 Effect of roughness parameters (a) Ra and (b) Rz of milled low carbon steel on shear strength

(a) (b)

Fig 15 Effect of waviness parameters (a) Wa and (b) Wz of milled low carbon steel adherent on shear strength

4.5 Surface Grinding Method (Aluminium)


aluminium material in the surface grinding process. It is clearly seen that the shear strength is slightly

increased in roughness parameter Ra from 0.89µm to 2.5µm and then the shear strength is increased much

more in the range of roughness parameter Ra from 2.5 µm to 4.2µm and then the shear strength is decreasing

fast rate after the roughness parameter Ra 4.2 µm, and for Rz parameter the value is from 5µm to 13µm are

increasing shear strength value and Rz value after 13µm the shear strength value is decreasing rapidly. And

from Figure 17 (a) & (b) the shear strength value for waviness value Wa in the range of 0.3µm to 0.86µm and




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then waviness value after 0.86µm shear strength value are decreasing, and for waviness parameter, Wz from

0.8 µm to 3.3µm shear strength is increasing and after 3.3µm shear strength is decreasing.

(a) (b)

Fig 16 Effect of roughness parameters (a) Ra and (b) Rz of surface ground aluminium on shear strength

(a) (b)

Fig 17 Effect of waviness parameters (a) Wa and (b) Wz of surface ground aluminium adherent on shear

strength

4.6 Surface Grinding Method (Low carbon steel)


aluminium material in the polishing process. It is clearly seen that the shear strength is slightly increased in


range of roughness parameter Ra from 2.2 µm to 3.7µm and then the shear strength is decreasing fast rate after

the roughness parameter Ra 3.7 µm, and for Rz parameter the value is from 6µm to 14µm and Rz 10µm to

17µm and Rz value after 17µm the shear strength value is decreasing rapidly. And from Figure 19 (a) & (b) the

shear strength value for waviness value Wa in the range of 0.35µm to 0.85µm and then waviness value after

0.85µm shear strength value is decreasing, and for waviness parameter, Wz from 0.8 µm to 3.5µm shear

strength is increasing and after 3.5µm shear strength is decreasing.




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Fig 18 Effect of roughness parameters (a) Ra and (b) Rz of surface ground low carbon steel on shear strength

Fig 19 Effect of waviness parameters (a) Ra and (b) Rz of surface ground low carbon steel on shear strength

V. CONCLUSION

In this work effect of surface waviness and roughness on polished, end milled, and surface ground adherents on

adhesive bond strength were investigated. Single lap joints with different adherent material (aluminium and

low carbon steel) were tested using epoxy-based Araldite adhesive. The following conclusion can be drawn.

1. There are optimum values for roughness and waviness which could be observed from maximum shear

strength vs roughness/waviness parameter plots for both aluminium and low carbon steel joints.

2. The strength variation with respect to surface roughness follow the same trend (initially increasing and

then decreasing) as with waviness for a different process like polishing, milling, surface grinding.

3. Shear strength varies slowly between the Ra value 0.5 to 2 µm and then from 2µm to 4µm shear strength

increases at a faster rate. For the waviness parameter, it is observed that shear strength increased between

the waviness (Wa) value (0.2 µm to 0.8 µm) and after 0.8 µm shear strength value is observed to be

decreasing.

4. The optimum value of Ra for polished, milled and surface ground aluminium adherents was found to be 3.8

µm, 4 µm, and 4.2 µm respectively. Similarly, the optimum Rz values were 17 µm, 15 µm, and 13 µm

respectively.

5. The optimum value of Ra for polished, milled and surface ground low carbon steel adherents was found to be

3.8 µm, 4 µm, and 3.7 µm respectively. Similarly, the optimum Rz values were 17 µm, 15 µm, and 17 µm

respectively.

6. The optimum value of Wa for polished, milled and surface ground aluminium adherents was found to be 0.8

µm, 0.8 µm, and 0.86 µm respectively. Similarly, the optimum Wz values were 3.7 µm, 3 µm, and 3.5 µm

respectively.

(a) (b)

(a)

(b)




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7. The optimum value of Wa for polished, milled and surface ground low carbon steel adherent was found to be

0.8 µm,0.81 µm, and 0.85 µm respectively. Similarly, the optimum Wz values were 3.8 µm, 4.5 µm, and 3.5

µm respectively.

The effect of roughness and waviness profile parameters on shear strength of single lap joints was investigated

in this work. Profile parameters such as Ra, Rz and their waviness counterparts were taken into consideration.

For different materials and surface preparation methods, the optimum values of parameters and the trend of

the variation of shear strength with parameters could be analysed. At present, the work takes into

consideration profile parameters only. This investigation could be extended to areal roughness parameters

which are statistically more significant especially for surfaces with deterministic patterns. Moreover, areal

hybrid parameters such as root mean square surface slope Sdq and developed interfacial area ratio Sdr affects

the degree of wetting of the adherent surface by adhesive. A functional surface with optimum values of areal

surface roughness and waviness parameters can develop a high strength adhesive bonding. In addition to Al

and low carbon steel, other engineering metallic specimens also could be explored to establish the influence of

roughness and waviness on adhesion strength.

VI. REFERENCES

[1] Uehara K, and Sakurai, M. Bonding strength of adhesives and surface roughness of joined parts. Journal of

Material Processing Technology. 2002;127:7801-9.

[2] Reina JM, Prieto, J. J. N., and Garcia, C. A. Influence of the surface finish on the shear strength of structural

Adhesive Joints and Application. The Journal of Adhesion. 2009;85:324-40.

[3] Pereira AM, Ferreira, J. M., and Antunes F. V. Analysis of manufacturing parameters on the Shear strength

of Aluminium adhesive single-lap joints. J Mater Process Technology. 2002;61:610-7.

[4] Yasmina Boutar SN, Salah Mezlini, Lucas F. M. da Silva, Mohamed Hamdaoui & Moez Ben Sik Al. Effect of

adhesive thickness and surface roughness on the shear strength of aluminium one-component

polyurethane adhesive single-lap joints for automotive applications. Journal of Adhesion Science and

Technology. 2016;30:1913-29.

[5] Ghumatkar A, Sekhar, R., Banea, and Barros, S. de. Influence of Adherent Surface Roughness on the

Adhesive Bond Strength. Latin American Journal of Solids and Structure. 2016;13:2356-70.

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