Study of the influence of non-abrasive ultrasonic finishing on residual stresses in a titanium workpiece using finite element computer modeling

Abstract

The magnitude and sign of surface residual stresses are among the key factors influencing the fatigue resistance of metal and alloy parts, especially those operating under active cyclic loads. The creation of compressive residual stresses on the surface of a part, for example, through the method of non-abrasive ultrasonic finishing (NAUF), contributes to increased fatigue resistance. This work is dedicated to the study of the stress-strain state (SSS) of the deformation zone of a VT6 titanium alloy workpiece subjected to NAUF. The SSS analysis was carried out using finite element computer modeling in an elastoplastic task setting after a single impact of the deforming indenter followed by unloading. The study examined the effect of the amplitude of the indenter's oscillations and its geometric characteristics on axial residual stresses, their penetration depth, average normal stress, and strain intensity. The analysis of the modeling results shows that the strain intensity (e) increases with the increasing indenter radius. The distribution pattern of the parameter e is gradient, with values decreasing from the surface to the center of the workpiece. It has been shown that the axial residual stresses in the deformation zone during NAUF are predominantly compressive, which contributes to the increased fatigue resistance of the finished product. The analysis of the obtained data indicates that with increasing indenter's oscillation amplitude, the values of compressive axial residual stresses increase, reaching maximum values of 1300 MPa at an amplitude of 100 μm and an indenter radius of R1. The penetration depth of these stresses reaches 0.5 mm.