Finite element analysis and optimization of spherical motion burnishing of low-alloy steel

Abstract

A reliable finite element modelling (FEM) approach to the spherical motion burnishing (SMB) process is developed with a view to gaining a fundamental understanding of the process and its optimization. SMB is a patented method for mechanical surface treatment of external cylindrical faces aimed at the enhancement of the fatigue life of the metallic component as well as its roughness, micro-hardness, depth hardening, wear, and corrosion resistance. A special feature of SMB is its kinematics: the tool motion is a superposition of a spherical movement and a rectilinear translation with respect to the workpiece. In order to decrease the FEM problem size, an approximated kinematic theory for the SMB is developed. In accordance with this theory the tool motion is approximated with a series of planar movements. As a result, a plane strain SMB FEM model is developed. The initial roughness is modelled in order to to achieve a more realistic representation of the workpiece geometry. To establish the flow stress and sliding friction coefficient, a combined approach is developed which contains mechanical tests, sensitivity FEM analysis, and inverse FE analysis of the corresponding pushing process. A planned numerical experiment is carried out on the basis of the created SMB FEM model. Six regression models of the treated layer characteristics are obtained and analysed on the basis of the FEM simulations. The FEM results are evaluated and compared to the experimental ones and their validity is proved. Finally, the regression models are used as objective functions in a multi-objective optimization problem formulation of the SMB process. As a result, the optimal combination of the governing SMB parameters is established.