Numerical evaluation of energy transfer during surface mechanical attrition treatment

Experiments showed that Surface Mechanical Attrition Treatment (SMAT) is one of the most effective ways to optimize the surface structure of metals and alloys, and therefore to enhance the global behaviors of a material and its service lifetime. However, there is still a lack of clear relationships between desired surface structures/properties and controlling parameters in SMAT process. The relationship between impact ball parameters and the indent coverage on a sample surface has been obtained from the previous work by coupling a global random impact model and a local impact frequency model. In this work, a more realistic SMAT model is built according to the previous investigation. The cyclic deformation process during SMAT always leads to change in the temperature of deformed material. Thus, the thermodynamic framework of the mechanical constitutive model allows the partition of the plastic work into the dissipated energy (usually, dissipated as heat) and the energy stored in the material due to increasing the grain boundary area (grain refinement) and introducing dislocations. The computational model of random flying balls with three different ranges of oblique angle is defined and the components of impinging and rebounding velocity during SMAT are monitored in this study. The stored energy and the fraction of plastic work converted into heat (β) are numerically evaluated.