Multi-objective optimization of the subsurface residual stress field of TC4 alloy in machine hammer peening

Abstract

Machine hammer peening (MHP) is a surface strengthening process by introducing residual compressive stress at the part's surface. Many indicators of residual stress, such as the surface residual compressive stress and depth of residual compressive stress, significantly impact the fatigue performance of parts and thus need to be optimized. The present study focuses on two main problems in multi-objective optimization of the subsurface residual stress field induced by MHP: the relationship between a specific residual stress field and a combination of impact velocity and indentation distribution and how to implement the MHP process that could produce such a combination. The latter problem was first addressed by a kinematic model of the MHP device, which can optimize the MHP device input parameters to achieve the target axial impact velocity. For the former problem, a finite element model was first established to simulate the residual stress field induced by MHP. Then, the response surface method was used to optimize the simulated residual stress field with multiple objectives. Based on the above two models, we can obtain the appropriate MHP parameters to induce a target subsurface residual stress field. A verification experiment was carried out, and the residual stress field obtained was relatively close to the theoretical one, with a deviation of 1.7 % for the depth of residual compressive stress and 13.8 % for the surface residual compressive stress.