d3219 technical report 091116

TECHNICAL REPORT No: 091116

TITLE: FATIGUE STRENGTH EVALUATION OF

YIELD IMPROVED CRANKSHAFT

TEST: FULLY REVERSED BENDING & TORSION FATIGUE

TESTING LOAD RATIO R = -1

PART: DAG OM457 12.8L CRANKSHAFT

(BFL DIE NO: 3219)

DATE: 16 NOV 2009

Prepared by: Approved by: Rajesh Mane Shyam Takale Manager (FTL CDFD Engg) Sr. Vice President (CDFD Engg)

*******

BHARAT FORGE LTD Mundhwa, Pune, Maharashtra State, INDIA

******* This document may not, in whole or in part, be copied, photocopied, reproduced, translated, or reduced to any electronic medium or machine-readable form without prior consent, in writing, from an authorized representative of Company. This document is for internal use only and may not, in whole or in part, be provided to anyone outside of Company, including customer, clients, or prospects.

CONFIDENTIAL - FOR INTERNAL CIRCULATION ONLY

TECHNICAL REPORT NO: 091116

CONFIDENTIAL - FOR INTERNAL CIRCULATION ONLY PAGE: 2 OF 18

CONTENTS

------------------------------------------------------------------------------------------------------------ SR DESCRIPTION PAGE ------------------------------------------------------------------------------------------------------------ 1. Objective 3 2. Background 3 3. Details of test 4 3.1 Crankshaft Bending Fatigue Test setup 4 3.2 Crankshaft Torsion Fatigue Test setup 4 3.3 Test Methodology 5 3.4 General details 6 3.5 Strain measurement & analysis Bending test 7-8 3.6 Strain measurement & analysis Torsion test 9 3.7 Calculations 9 4. Bending test results in staircase format 10 5. Torsion test results in staircase format 11 6. Design Modification Details: Trim Line Pictures 12 7. Design Modification Details: RR + Blocker + Finisher + Flash 13 8. Failure Pictures: Bending Samples 14-16 9. Failure Pictures: Torsion Samples 17 10. Tabulated test results 18 11. Conclusion 18 12. Further actions 18



1. OBJECTIVE: To evaluate bending & torsion fatigue strength of DAG OM457, 12.8L 6-Cyl Yield Improved crankshaft (BFL D3219) by fully reversed (R = -1) fatigue test methodology

2. BACKGROUND: As a part of continuous process improvement & VAVE program, DAG

OM457, 12.8L crankshaft (BFL D3219) was optimized for yield improvement. Details are given below.

With optimized design, cut weight was reduced from 197.7 kg to 168.9 kg

resulting 14% improvement in yield on an average & around 29kg (14.5%) material saving in cut weight & 3.5kg in net weight per crankshaft.

New crankshaft batch with 7.. (Sink code & Run code) with optimized design was tested to evaluate fatigue strength.

Validation is done by conducting fully reversed bending & torsion fatigue tests on 6 samples as per BFL test standard.

The tests were carried out in Fatigue Testing Laboratory (FTL) of Bharat Forge Limited, Pune, INDIA (BFL).

From this run onwards the modification of P2 & P5 bevel thickness is also incorporated in design for better balancing as discussed with MCD-II.

INITIAL MODIFIED

Stock Size (mm) RCS 165 x 931 mm DIA 170 x 939 mm

Cut Weight (kg) 197.7 168.9

Net Weight (kg) 146.3 142.6

Yield (%) 74.00% 84.43%



3. DETAILS OF TEST: 3.1 CRANKSHAFT BENDING FATIGUE TEST SETUP

3.2 CRANKSHAFT TORSION FATIGUE TEST SETUP



3.3 TEST METHODOLOGY The crankshaft bending & torsion fatigue test was run using the resonant dwell test methodology as per BFL Bending test procedure (BFL-TP-001) & Torsion test procedure (BFL-TP-002). The procedure in short is as follows: The Resonant test procedure involves fastening 2 large mass inertia plates on to the specimen throw in order to provide a resonating arrangement. This structure is then subjected to a high frequency vibrating load via a mechanical connection with an electro magnetic shaker until the system is in resonance (normally between 50 & 120 Hz). The specimen is subjected to specified number of cycles at a fixed load (R=-1). If a crack develops during this period it changes the resonant response of the structure (drop in resonance frequency). The control system monitors the frequency change and when this exceeds 3 Hz change from the original then the test is stopped & specimen is classified as FAIL. If no frequency drop is occurred beyond 3 Hz, the part is classified as a PASS. A fixed number of specimens are tested at differing loads. The resulting data is analyzed by staircase to produce mean fatigue strength at specified cycles. The applied force is determined by calibration of the bending setup in static & dynamic loading in order to relate applied acceleration to applied stress in pin fillet and center of pin diameter. Calibration is carried out using two strain gauges glued in the pin fillet & one on the pin diameter center at BDC on the specimen. For torsion setup, calibration is done only in dynamic condition with two strain gauges glued in half bridge configuration at 45 degree & 225 Degree with respect to TDC of Pin, on center of pin diameter along the pin circumference.



3.4 GENERAL DETAILS Bending: Start of Test : 22 Sept 2009 End of Test : 22 Oct 2009 Number of samples tested : 6 samples Resonance (Test) frequency : 111-112 cycles per second. Customer specification : Pin fillet micro strain = 3200 for R= -0.2 Load ratio which is equivalent to 4000 micro strain for load ratio R = -1 Cycles specification : 5 Million. Failure criteria : Frequency drop beyond 3 Hz or crack in MPI after test. Bending Moment to Micro strain relation : 6500 N-m = 806.9 ue in pin center g Level relation to Micro strain relation : 90 g = 723.3 ue in pin center Crankshaft Material : 38MnVS6 (Micro alloy Steel) Torsion: Start of Test : 14 Oct 2009 End of Test : 06 Nov 2009 Number of samples tested : 6 samples Resonance (Test) frequency : 54-55 cycles per second. Customer specification : 95 MPa / 10 M cycles. Failure criteria : Frequency drop beyond 3 Hz or crack in MPI. Acceleration to Shear stress relation : 39.96 g = 110.36 MPa shear stress Crankshaft Material : 38MnVS6 (Micro alloy Steel)



3.5 STRAIN MEASUREMENT & ANALYSIS FOR BENDING FATIGUE TEST: A. Static calibration B. Static Graph: Micro strain vs. Bending Moment

CALIBRATION CHART - STATIC

y = 0.1241x + 0.2451

0

20

40

60

80

100

120

140

160

180

200

0 200 400 600 800 1000 1200 1400 1600

Bending Moment (N-m)

Mic

rostr

ain

Load Bending moment PIN CENTER

(KN) (N-m) Microstrain

0 0 0

1 300 38

2 600 74

3 900 111

4 1200 150

5 1500 186



C. Dynamic calibration: D. Dynamic Graph: Micro strain vs. Acceleration (g Level)

CALIBRATION CHART - DYNAMIC

y = 8.0584x - 1.9103

0

200

400

600

800

1000

1200

1400

1600

0 20 40 60 80 100 120 140 160 180 200

Acceleration (g Level)

Mic

rostr

ain

Baseline data: 6,500 N-m = 4,151 micro strain in fillet = 91.07 g level Refer calibration of Job No 047/5 done on 10 Nov 2008.

PIN CENTER

Microstrain

5 47

10 91

15 138

20 183

25 228

g Level



3.6 STRAIN MEASUREMENT & ANALYSIS FOR TORSION FATIGUE TEST: A. Dynamic calibration:

g LEVEL

Micro-strain

CH1 CH2 AVG

2 32 39 35

4 61 76 68

6 92 113 103

8 122 151 137

10 153 188 171

B. Graph:

Calibration Charty = 16.94x + 1.0405

0

20

40

60

80

100

120

140

160

180

0 2 4 6 8 10 12

g level

Mic

ro-s

trai

n

3.7 CALCULATIONS 1. Stress = Youngs Modulus * Strain / (1 - Poisons Ratio ^2) 2. Bending Moment = Force * Arm length 3. Torque = (Pi / 8) * Shear Modulus * Cube of Diameter * Strain



4. BENDING TEST RESULTS IN STAIRCASE FORMAT:

Test number 2 3 4 1 5 6

Job No. 563/6 563/4 725/5 563/2 725/1 725/3

Sr. Number 9S0055 9S0055 9S0725 9S0055 9S0725 9S0725

Heat Code BK BK HK BK HK HK

Failure

locationNo Failure Pin collar FE

Multiple

cracks on

Journal Fillet

Flange End

No Failure

Multiple

cracks on

Journal Fillet

& Pin Fillet

Gear End

Multiple

cracks on

Journal Fillet

& Collar on

Flange End

Date 26-Sep-2009 27-Sep-2009 3-Oct-2009 25-Sep-2009 14-Oct-2009 23-Oct-2009

5000

6000

5500

7000

6500 5M

BM, N-m

7500

5M

1.30M

5M

5M

5M



5. TORSION TEST RESULTS IN STAIRCASE FORMAT: 1 2 3 4 5 6

747/4,5 747/1,2 717/5,6 717/2,3 409/5,6 409/1,2

4,5 1,2 5,6 2,3 5,6 1,2

No failure No failure

P6 near oil

hole

extended to

w12.

No failure

Failed in P6

BDC along

diameter

No failure

22-Oct-09 26-Oct-09 26-Oct-09 31-Oct-09 3-Nov-09 6-Nov-09

9S0747

HK

9T0409

I I

9S0717

HG

19 116.5

10M

16 10M

Date

Serial No.

Failure Location

HEAT

Pin No.

80

Job No.

15 92

14

104

86

17

98

13

18 4.5M110

Test No.

Stress

(MPa)

10M

2.7 M

10M

Torque

(kNm)



6. DESIGN MODIFICATION DETAILS: TRIM LINE PICTURES



7. DESIGN MODIFICATION DETAILS: RR + BLOCKER + FINISHER + FLASH

REDUCE ROLL BLOCKER

FLASH FINISHER

Flash Thickness Tail J4 Flange Tail J4 Flange

Design 5 5 5 6.5 6.5 6.5

Actual 4.5 6.5 5 5.8 8 6.2

Blocker Finisher

FLASH THICKNESS



8. FAILURE PICTURES: BENDING

Sample#3, Job NO: 563_4 Tested at 7000 Nm Location: Pin Collar Flange End

Sample#4, Job No: 725_5 Tested at 6500 Nm Location: Journal Fillet Flange End



8. FAILURE PICTURES: BENDING (continued)

Sample#5, Job No: 725_1 Tested at 6500 Nm Location: Journal Fillet Gear End

Sample#5, Job No: 725_1 Tested at 6500 Nm Location: Pin Fillet Gear End



8. FAILURE PICTURES: BENDING (continued)

Sample#6, Job No: 725/5 Tested at 6000 Nm Location: Journal Fillet Flange End



9. FAILURE PICTURES: TORSION

Sample No: 3 Job No: 717_6 Tested at 18,000 Nm Location: Pin Fillet-Oil Hole

Sample No: 5 Job No: 409_6 Tested at 18,000 Nm Location: BDC



10. TABULATED TEST RESULTS: Test results are summarized below in tabular format.

TEST BENDING TORSION

B50 Specification

3200 micro strain in pin fillet at R = -0.2

(Equivalent to 4000 micro strain in pin fillet

at R = -1)

95 MPa (Equivalent to 15.5 kN-m

torque on 94mm pin diameter)

Cycles 5 million 10 million

B50 Fatigue Strength 4151 micro strain in pin

fillet at R = -1 107 MPa (Equivalent to

17.5 kN-m)

11. CONCLUSION: Yield improved crankshaft satisfy minimum Bending & Torsion fatigue strength requirement as specified by the customer. Multiple crack initiation from side wall as observed on samples tested for bending in general comes from grinder burn. All three samples from crankshaft with serial number 9S0725 have shown this type of failure mode.

12. FURTHER ACTIONS: Acid etching to be done on three samples from crankshaft having serial number 9S0725 to confirm presence of grinder burn.

END OF TECHNICAL REPORT # 091116

d3219 technical report 091116

Documents

details of test

fatigue test methodology

torsion test results

bfl test standard

bending torsion fatigue

tabulated test results

torsion samples

bending samples