The objective of this study is the prediction of damage and residual stresses induced by hot processing which leads to phase transformation in martensitic stainless steel. This study firstly concerns the modelling of the damage of material induced by a complex history of thermoelastoplastic multiphase in heat-affected-zone (HAZ) of welding. In this work, a two-scale mode of elastoplastic damage multiphase was developed in the framework of thermodynamatics of irreversible process. The constitutive equations are coupling with ductile damage, elastoplasticity, phase transformation, and transformation plasticity. Besides, a damage equation was proposed based on Lemaitre''s damage model in the framework of continuum damage mechanics. The experiments of 15-5PH were implemented for the identification of phase transformation, transformation plasticity and damage models. Tensile tests of round specimens were used to identify the parameters of the damage model as well as mechanical behaviours at various temperatures. Tests of flat notched specimens were designed to provide the validation of the damage model and strain localization using three-dimensional image correlation technologies. In addition, microscopic analysis was performed to provide microstructure characterization of 15-5PH and to discover the damage mechanism. Finally the numerical simulation was performed in the code CAST3M?of CEA. On the one hand, numerical verification of the flat notched plates was implemented and compared with experimental results. On the other hand, we used the two-scale model including phase transformation, transformation plasticity and damage to simulate the level of residual stresses of a disk made of 15-5PH metal heated by laser. The internal variables, such as strain, stress, damage, were successfully traced in the simulation of two-scale model. The simulation results showed the transformation plasticity changes the level of residual stresses and should not be negligible; damage decreases about 8 percent of the peak value of residual stresses on upper surface of disk.
Abstract
Contents
Nomenclature
Chapter 1 Introduction
Chapter 2 Martensitic Stainless Steel and Solid-state Phase Transformation
Chapter 3 Damage Mechanics and Welding Damage
Chapter 4 Evolution Damage Multiphase Modelling
Chapter 5 Experimental Study and Identification of Damage and Phase Transformation Models
Chapter 6 Numerical Simulation and Implementation of Constitutive Equations
Chapter 7 Conclusions and Perspectives
Bibliography
Appendix A Experimental Devices
Appendix B Experimental Results of 15-5PH in Details
Appendix C Example of Multiphase Program in CAST3M
List of figures
List of tables
