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From failure analysis to power transmission design

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Originally presented in October 2013 at the Romax European Summit 2013 by CETIM

Originally presented in October 2013 at the Romax European Summit 2013 by CETIM

Published in: Automotive, Technology, Business
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  • 1. Page 1 Romax european summit 13’ Romax Technology European Summit 2013 From failure analysis to power transmission design A. VADNAL, M. OCTRUE, C. PATTE, R. SHANDRO
  • 2. Page 2 Romax european summit 13’ CETIM in 2 words French technological institute of mechanics Pool of ressources and technical skills dedicated to mechanics 700 people over 3 main sites in France Turnover : 115 M€ 4 associated centers and 2 international subsidiaries
  • 3. Page 3 Romax european summit 13’ CETIM in 2 words Missions mutualized action Technology transfer from academic research to innovative products Support to SMEs (mutualized R&D, co-development, normalization) Consulting, expertise, for matters with high technicity Power transmissions at CETIM On-site instrumentation Failure analysis Test bench engineering and product testing Assistance in the design process up to the turn-key prototype
  • 4. Page 4 Romax european summit 13’ Using Romax at CETIM On-site instrumentation Failure analysis Test bench engineering and product testing For failure analysis Cross-checking Normalized calculations Simulation For test bench engineering Results interpretation Fatigue test correlation Vibration levels correlation NVH Assistance in the design process up to the turn-key prototype In the redesign process Concept study Optimization Multicriteria Bearing details Gear micro-geometry
  • 5. Page 5 Romax european summit 13’ Using Romax for failure analysis Confirming the cause of the failure by simulation Enlight the origin of the failure Build a more predictive model Propose modifications and improvements
  • 6. Page 6 Romax european summit 13’ Advantages of Romax Combining the global approach and the components details Accurate modelling of bearings Internal geometry, non-linearity, preload, clearance Precise gear mesh simulation Micro-geometry, shafts and supports deflections Impact on load distribution and misalignment Influence of the environnement Housing and supports stiffness Complex load cycles
  • 7. Page 7 Romax european summit 13’ Case study Scientific research vessel Just to get some ideas 2 main props Twin motor drive for each gearbox, total 4,000 kW per gearbox Rducer output torque : 270,000 N.m Prop ⌀ : 3.9 m Motor span : 2.2 m
  • 8. Page 8 Romax european summit 13’ Kinematic architecture Power Take-in (PTI) gearbox Output : 4 MW Intermediate 1 Input 1 Intermediate 2 Input 2
  • 9. Page 9 Romax european summit 13’ Observations under working conditions After 6 months of operation Alarming vibration levels : up to 17 mm/s RMS on some bearings (10 mm/s recommend for those applications) Prematured bearing damage Prematured tooth damage M1 M2
  • 10. Page 10 Romax european summit 13’ Visual inspection After 6 months of operation Spalling on outer raceways of intermediate shaft bearings Generalized micro-pitting and a fatigue fracture on one tooth at the extremity of input pinion
  • 11. Page 11 Romax european summit 13’ Goal of Romax model Getting a further understanding of operating conditions Influence of housing stiffness Influence of bearing preload and resulting bearing stiffness If possible, enlight the phenomena observed by means of calculations to validate the model Propose some modifications accordingly
  • 12. Page 12 Romax european summit 13’ Step 1: housing modelling Housing in several parts Complex assembly Bolt stiffness taken into account
  • 13. Page 13 Romax european summit 13’ Step 2: bearings Unknown internal geometry Use of the approximated internal geometry calculated by Romax Very useful when you cannot measure the internal geometry Parts not available or too much damage Influence of the housing stiffness Major influence on the calculation of tapered roller bearings Realistic bearing stiffnesses for the calculation of deflections
  • 14. Page 14 Romax european summit 13’ Step 3: gears Introduction of the gear micro-geometry Precise calculation of the load sharing between bearings Very low span between the centers of the tapered roller bearings Calculation of the load sharing on the tooth flank Gear micro-geometry Pinion right flank Gear micro-geometry Pinion left flank
  • 15. Page 15 Romax european summit 13’ Main results - bearings Calculation of contact presure Difference in damage Loads are theoretically identical Damage : 77 % influence of µ-geometry, housing stiffness Damage : 44 %
  • 16. Page 16 Romax european summit 13’ Main results - gears Introduction of the gear micro-geometry Precise calculation of the load sharing between bearings Very low span between the centers of the tapered roller bearings Calculation of the load distribution on the tooth flank
  • 17. Page 17 Romax european summit 13’ Correlation: Romax vs observations Comparison between calculated results and observed damages Calculation shows higher pressure in the area where the crack initiated Calculation predicts a higher load on the bearings of side #1
  • 18. Page 18 Romax european summit 13’ Multicriteria optimization Only slight modifications allowed: Gear micro-geometry (since gears had to be replaced) Helix angle modification, tip relief Objectives Optimize pressure distribution on teeth flanks Reduce vibration levels (TE)
  • 19. Page 19 Romax european summit 13’ Genetic optimization within Romax On each gear wheel: Tip relief height Tip relief length Helix angle modification
  • 20. Page 20 Romax european summit 13’ New micro-geometry proposed New gear micro-geometry New gear set installed, with micro-geometry proposed by CETIM More uniform contact patterns Gearbox shows more acceptable vibration levels (max 5 mm/s RMS) Lower than required standard Lower than original micro-geometry
  • 21. Page 21 Romax european summit 13’ Conclusion Failure analysis = combination of skills Method Observation Analysis Knowledge Experience Vision of the failure Advice CETIM Failure analysis
  • 22. Page 22 Romax european summit 13’ Conclusion From failure analysis to power transmission design Performance improvement Failure Expertise Test Implementation Modelling (Re)design
  • 23. Page 23 Romax european summit 13’ Thank you for your attention

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