An ultrasonic vibration stress relief system and a method for eliminating residual stress using the same

Ultrasonic stress relief apparatus comprises an ultrasonic impact gun, a pressure sensor module and a control box. The pressure sensor module is fixed on the lower surface of a workpiece support platform, the ultrasonic impact gun is located above the workpiece support platform and is slidable along a guide which is fixed to a support platform. Residual stress can be removed from a welded workpiece by measuring the amount of residual stress removed from the workpiece by application of different pressing forces to the workpiece by the gun having a fixed gun current and vibration time. Using this data to obtain the pressing force required to remove all the residual stress from the workpiece, and then moving the gun along the weld while applying this pressing force thereby removing the residual stress.