Welding is widely used for joining materials. Residual stress remains near welded joints because of the high temperature attained during welding. Tensile residual stress on the surface of the material degrades its fatigue strength. Some methods of reducing residual stress such as heat treatment and shot peening can be used. These methods require special equipment and are time-consuming. On the other hand, ultrasonic vibration can be used to improve the precision of the machined surface and to cut hard metals. In this paper, we propose a new method of reducing residual stress using ultrasonic vibration during welding. The proposed method is applied to objects such as a car wheel. The transmission of ultrasonic vibration is an important factor in curved structures. An effective transmission device of ultrasonic vibration is developed. It is found that residual stress is reduced by about 20∼30% when ultrasonic vibration is used during welding. The effectiveness of the proposed method is demonstrated by an analytical method using a model considering elastoplastic characteristics.
