Numerical simulations of impacts during Surface Mechanical Attrition Treatment using crystal plasticity model in finite element method
Résumé
Surface Mechanical Attrition Treatment (SMAT) is a process, which transforms the top surface layer of materials from coarse grains to nano-sized grains by severe plastic deformation. SMAT is based on multidirectional mechanical impacts between shot and the surface of material. As the strain rate is high and the accumulated plastic strain is large, a great number of defects such as dislocations and deformation twins can be generated at the top surface, which progressively lead to the formation of a nanostructured layer. Simultaneously, high compressive residual stresses may be introduced in the SMAT affected layer. This nanostructured layer coupled with compressive residual stresses induced by SMAT allow to significantly improve the mechanical properties of materials. Due to excellent mechanical properties of SMATed materials, it is necessary and useful to investigate the SMAT process both experimentally and numerically in order to obtain a better understanding and a better control of the process. Experimental studies, extensively performed previously and recorded in the literature, have shown that the mechanical properties of SMATed materials are highly influenced by the microstructure such as grain size and work hardening. From a modeling perspective, it would be highly beneficial to establish accurate numerical models of SMAT in order to consider the influence of the different parameters of this process at the different scales. In this work, a crystal plasticity model introduced in finite element analysis, taking into account the microstructure, was used to investigate the plastic activity due to the impacts between shot and the surface of material. To do this, the shape-controllable 3D Voronoï geometries as well as meshes were first generated using Neper software. A phenomenological crystal plasticity model implemented through user-defined ABAQUS subroutines was used in this work to perform numerical simulations. A number of parameters are studied such as shot size, impact velocity, incident angle, etc. The influences of these different parameters on slip systems and stress fields were analyzed. The first results demonstrated the interests of numerical simulations for this specific process.
Origine : Fichiers éditeurs autorisés sur une archive ouverte