Fatigue Simulation in a Yamaha Race Car Engine

1. Fatigue Simulation in a Yamaha Race Car Engine Klaudio Bari and Andrew Rolfe Advanced Material Conference Edinburgh 07th September 2017

2. Contents • Failure of connecting rod in our race car • Calculations at RPM 8000 and RPM11000 • Simulation Procedure • Dynamic Loading Results and Analysis • Fatigue Results and Analysis • Evaluation and Conclusion

3. Failure of Connecting Rod

4. Acting Stresses in Connecting Rod • Connecting rods translate reciprocating force from piston to rotational torque in crankshaft. • Total force on connecting rod combines piston (pressure) force and force of the reciprocating mass’s own inertia (inertia force). • Stress is force over area, for complex geometries the stress distribution is complex. • Repeating stresses can cause fatigue failure.

5. History of the Engine RPM during Failure • EDR Data From RaceTechnologyV8.5

6. Engine Data 8000 RPM

7. Calculation the compression force • Calculated Pressure From Engine Analyzer Pro

8. Calculations of tension force

9. Connecting Rod axial force

10. 2 Calculations

11. 4 Simulation Procedure SolidWorks Connecting Rod Original Connecting Rod • 3D Scanned • Modified

12. 4 Dynamic Simulation Method

13. 4 Mesh Construction Mesh Control Applied

14. 5 Dynamic Loading Results • Maximum stress at 8,000 RPM: 117 MPa (FOS > 5) • Occurs at TDC • Maximum stress at 11,000 RPM: 263 MPa (FOS > 2) • Occurs at TDC

15. 5 Dynamic Loading at 8000 RPM

16. Maximum Stress 117 MPa Rear View > < Data Readout

17. Dynamic Loading at 11000 RPM

18. 5 Dynamic Loading Analysis • Connecting rod will definitely survive a single loading at either speed • Minimum FOS of 5.6 under average engine running speed • Stress concentrated around oil ‘spurt-hole’

19. 4 Fatigue Simulation Method • Fatigue simulated from dynamic FEA using S-N curve below at 1x106 Cycles:

20. 6 Fatigue Results

21. 6 Fatigue Results • No fatigue in connecting rod at 8,000 rpm • Small amount of fatigue at 11,000 rpm around oil ‘spurt-hole’ • Minimum life of 492,700 cycles x 2 = 985,400 engine revolutions (one 720o cycle is two revolutions)

22. 6 Fatigue Analysis • Very small amount failed • This would take 1½ hours to fail in fatigue at 11,000 rpm. • This is still considered high cycle fatigue

23. 7 Evaluation • Force calculations were validated N • Normalised data from calculations • Connecting rod force graph from Piedrahita & Riaza

24. 7 Evaluation • Normal forces as well as axial should have been considered • Dynamic Analysis Program (DAP) should have been used • Should consider assembly of rod and cap incorporating bolt torques • Should consider forces at big and small ends simultaneously • Fatigue simulation could virtually ignore compressive stress • Simulation cannot predict material anisotropy, inclusions or pores.

25. 7 Conclusion of Findings • Connecting rod should not fail on single loading, nor should it buckle • Stress is concentrated around oil ‘spurt-hole’ • It will take 1½ hours of continual use at maximum rpm to fatigue fail connecting rod • Original engine design limit was 12500 so 1½ hours isn’t that long for 11,000 rpm • Revving engine at limit typically causes rapid engine failure • Engine only touches 11,000 rpm for a few seconds at a time • Does not consider material imperfections however

26. 7 Recommendations • Manufacture the component by forging rather than casting • Change geometry of oil ‘spurt-hole’ • Ensure bolts and bearings are in good condition too • Prevent formation of pores and inclusions during manufacture