Abstract
Welding is widely used in construction of many structures. Residual stress is generated near the bead because of locally given heat. Tensile residual stress degrades fatigue strength. Some methods for reduction of residual stress are proposed. Heat treatment and shot peening are practically used. However, these methods require special equipment and time consuming. The authors have proposed a new method for reduction of residual stress. In this method, vibration is applied during welding. In this paper, ultrasonic vibration is used during welding. Some specimens are welded without vibration for comparison. It is well known that residual stress has statistical distribution. Under same condition, some specimens are welded and residual stresses are measured. The normal distribution is assumed for distribution of residual stresses. Comparing residual stresses of specimen applying vibration with those without vibration, probability of reduction of residual stresses is estimated. The condition for reduction of residual stress is examined from view point of statistical evaluation.
