Analysis of Residual Stress Relaxation Under Mechanical Cyclic Loading of Shot-Peened Trip780 Steel Until Fatigue Lifetime

Author:  Clément Mauduit, Régis Kubler, Laurent Barrallier, Sophie Berveiller, Quentin Puydt, Martine Monin, Bastien Weber
Source:  ICSP-13
Doc ID:  2017062
Year of Publication:  2017
Abstract:  
Introduction and Objectives: TRIP aided steels are used in the automotive industry due to their high strength, ductility and toughness properties. Typical parts made of TRIP steels (as engine sub-frame for instance) are submitted to cyclic loading during their lifetime. Those parts could be also shot-peened to minimise the risk of fatigue failure. Studies have investigated the fatigue life of non-treated TRIP aided steels [1-3], the shot peening of TRIP steels [4-9] but very few [10] have investigated the mechanical residual stress stability after shot peening on TRIP steels and the impact on fatigue life. TRIP steels exhibit a multiphased microstructure of ferrite, bainite, residual austenite and martensite created after thermomechanical loading/straining. Shot peening on TRIP steel generates austenite to martensite phase transformation and a gradient of microstructure and residual stresses from the surface as characterized by Guiheux [9]. The aim of this study is to analyse the evolution of residual stresses (RS) generated by shot-peening during cycling and the effects of shot peening on fatigue life of a cold rolled TRIP780 steel. The stability of RS was assessed using X-ray diffraction techniques. Macroscopic finite element simulation of fatigue life.