Reduction of pulsed-laser surface irradiation induced residual stress using ultrasonic vibration method

The ultrasonic vibration method was introduced to relieve the residual stress in the small AISI 1045 steel specimen subjected to the pulsed-laser surface irradiation. The ultrasonic vibration plasticity framework was developed based on the thermal activation theory and the dislocation glide kinetics theory in order to reveal the double dynamic stress effect and the time effect of the ultrasonic stress relief. To validate the proposed model, the ultrasonic stress relief experiments were carried out using the AISI 1045 steel specimens treated by the pulsed-laser surface irradiation based on the Nd:YAG pulsed-laser machine. The results show that the ultrasonic stress relief has good effects on eliminating residual stress. Furthermore, the residual stress relaxation due to the double dynamic stress effect can be improved by increasing the ultrasonic vibration power and the initial magnitude of residual stress. The residual stress decrease due to the time effect can be improved by increasing the ultrasonic vibration time. The unified ultrasonic vibration plasticity model can accurately account the double dynamic stress effect and the time effect. The findings confirm that the ultrasonic stress relief can be used to eliminate residual stress in small workpieces and provide a basis to understand the underlying mechanism of the ultrasonic stress relief.