Exploration of Key Process Parameters and Properties of 40Cr Steel in Ultrasonic Surface Rolling Process

Abstract

Ultrasonic surface rolling (USRP) is an effective process to improve a workpiece’s fatigue property, in which ultrasonic vibration and static force are applied on the workpiece’s surface. In order to clarify the ultrasonic rolling strengthening mechanism of critical components and optimize the USRP parameters, a theoretical model of ultrasonic rolling was established. Based on the stress-strain curve of 40Cr steel, the USRP parameters were formulated. The compressive residual stress field of single point impact was analyzed by finite element simulation, and the simulation results were validated by conducting an experimental research. In addition, the changes in the surface properties of specimens under different USRP parameters were studied experimentally. The results show that with the increase in depth, the compressive residual stress on the external surface increases firstly and then decreases, and the maximum compressive residual stress is −338 MPa. As the amplitude is 12 μm and the frequency is 20 kHz, the static force of 600 N is optimal for the ultrasonic rolling of 40Cr steel. This study could provide a guide for the key parameters’ selection in USRP.