Shot Peening Analysis on Trip780 Steel Exhibiting Martensitic Transformation

Abstract

In the last years, due to increasing ecology and environmental constraints, a search for lightweight structures has been carried out, leading to the use of more complex geometries and new materials. In that context, TRIP (TRansformation Induced Plasticity) steels are of particular interest as the due to their good mechanical properties to weight ratio [1]. They are often used in the automotive industry for reinforcement parts of the vehicle (bumper, door beam…). To increase life duration,critical parts are shot peened. The specific mechanical behaviour of TRIP steels is due to their microstructure: they contain residual austenite that can transform into martensite when a stress is applied. This mechanism is responsible for hardening of the steels. The beneficial effect of shot peening on metastable austenitic steels was recently established by Fargas et al. [2], resulting in extensive austenite to martensite phase transformation. Numerous analytical models and numerical approaches based on finite element analysis have been developed to simulate the shot peening process. Reviews of the wide variety of numerical models can be found in Rouhaud et al. [3] and Sherafatnia et al. [4]. Only few experimental studies have been published up to now dealing with the impact of shot peening on metastable austenitic steels [5-7]. The first model taking into account the TRIP effect during peening was proposed very recently by Halilovic et al. [8]; it was developed for an austenitic steel AISI 304 peened steel with a single laser shot using a large strain formulation of transformation plasticity.