Laser powder bed fusion (L-PBF) with layer-by-layer ultrasonic roller pressing (USRP) for residual stress relaxation and analysis

During the laser powder bed fusion (L-PBF) process, the high-speed movement of the laser heat source results in an inhomogeneous temperature and stress field, generating residual stresses. In this study, a novel method was proposed, which enhanced the L-PBF process by integrating mechanical loading with layer-by-layer ultrasonic roller pressing (USRP) to manage the residual stresses. The L-PBF-USRP method was developed to mitigate the internal residual stresses in the formed part on a layer-by-layer basis. The results showed that the L-PBF-USRP method reduced the residual stress in the X – Y plane by 50 MPa. In addition, a residual stress prediction model was formulated in this study to predict the USRP-induced residual stress by analyzing the mechanism of mechanical loading during layer-by-layer rolling. The effects of frequency, amplitude, and roller ball radius on the residual stress were analyzed using the residual stress prediction model.