Finite-element and XRD methods for the determination of the residual surface stress field and the elastic–plastic behaviour of duplex steels

Abstract

Duplex stainless steels have a complex microstructure with comparable volume fractions of austenite and ferrite. Due to differences in the mechanical properties, a heterogeneous distribution of stresses is generated in both phases. In this paper, a finite-element method and a thermo-mechanical model are described for determining the residual surface stress distribution on duplex steels. The stress distribution is calculated after various surface treatments and under straining conditions. The numerical calculations are then compared with the experimental results in order to verify the accuracy of the method. An original method based on successive XRD measurements is then proposed to study the elastic–plastic properties of both phases. The results are compared with those obtained from surface observations.

Acknowledgements

This work was supported by GDR No. 2557 (Reactivité et Ingenierie des Surfaces Métalliques (RISM)) from CNRS and GER Mécam (http://www.u-bourgogne.fr/REACTIVITE/GERMECAM). One of the authors (N.M.) would like to thank the Conseil Regional de Bourgogne (France) for financial support. The authors are grateful to Commissariat a© l’Energie Atomique-Direction des Réacteurs Nucléaires (CEA-DRN)/Departement de Mécanique de la Technologie (DMT)/SEMT (Saclay, France), who designed and developed the FE code Cast3M, and C. Lojewski (CRMC, Industeel) for stimulating discussions.