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Tenue à la fatigue des culasses : modélisation du traitement thermique et développement de nouvelles méthodes numériques.

Abstract : TO OBTAIN THE OPTIMAL MATERIAL PROPERTIES, AUTOMOTIVE CYLINDER HEADS, MADE OF ALUMINIUM ALLOYS, ARE HEAT TREATED (QUENCHING - AGEAING). THIS THERMAL TREATMENT GENERATES RESIDUAL STRESSES AND HAS TO BE TAKEN INTO ACCOUNT IN THE NUMERICAL HIGH CYCLE FATIGUE DESIGN. SINCE THE RESIDUAL STRESSES ARE PRINCIPALLY DUE TO THE INHOMOGENEOUS QUENCHING COOLING, THE THERMAL EVOLUTION MUST BE CORRECTLY SIMULATED. HEAT TRANSFER COEFFICIENTS H(T), DEFINING THE HEAT EXCHANGES, ARE USED TO OBTAIN THE NUMERICAL COOLING. A SIMPLE ANALYTICAL FUNCTION IS PROPOSED WHOSE PARAMETERS ARE OPTIMISED TO FIT THE EXPERIMENTAL CURVES. THE REMAINNING RESIDUAL STRESSES FOLLOW FROM A SIMPLE MECHANICAL ANALYSIS. IT IS FOUND THAT THE STRESSES IN THE LOCAL CRACKING AREA ARE TENSILE AND THEREFORE STRONGLY UNFAVOURABLE FOR THE HIGH CYCLE FATIGUE ENDURANCE. IN ADDITION, TAKING INTO ACCOUNT THE RESIDUAL STRESSES IN THE FATIGUE DESIGN, AT THE END OF THE THERMAL TREATMENT, LEADS TO PREDICTIONS FOR THE RISK REGIONS THAT ARE CONSISTENT WITH EXPERIMENTAL OBSERVATIONS. MOREOVER, IN ORDER TO USE NUMERICAL SIMULATION IN THE OPTIMISATION OF THE DESIGN PROCESS, COMPUTATIONAL TIME MUST BE REDUCED IN THE RESOLUTION OF AN EVOLUTION PROBLEM OR THE SEARCH OF THE STABILIZED SOLUTION OF A STRUCTURE SUBMITTED TO A PERIODIC LOADING. THE METHOD IS BASED ON THE LARGE TIME INCREMENT METHOD AND THE DIRECT CYCLIC METHOD : THE GLOBAL EQUILIBRIUM, WRITTEN UNDER ITS RESIDUAL FORM, IS SOLVED ONTO A REDUCED WAVELET BASE. A SUPSTENSIAL REDUCTION OF COMPUTATIONAL TIME IS OBTAINED WHEN THE STABILISED SOLUTION IS SEARCHED.
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https://pastel.archives-ouvertes.fr/pastel-00002588
Contributor : Ecole Polytechnique <>
Submitted on : Wednesday, July 21, 2010 - 10:43:18 AM
Last modification on : Wednesday, October 14, 2020 - 3:52:12 AM
Long-term archiving on: : Friday, October 22, 2010 - 3:42:03 PM

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  • HAL Id : pastel-00002588, version 1

Citation

François Comte. Tenue à la fatigue des culasses : modélisation du traitement thermique et développement de nouvelles méthodes numériques.. Mécanique des matériaux [physics.class-ph]. Ecole Polytechnique X, 2006. Français. ⟨pastel-00002588⟩

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