Probabilistic Evaluation of a Method for Reduction of Residual Stress in Welded Structure Using Vibration

Abstract

Reliability of structures is sometimes statistically evaluated since strengths of structures, inner and external forces in structures are statistically distributed. Inspection planning of structures, which plays important roll in health management, is also determined in a probabilistic manner in those cases. In this paper, residual stresses in welded structures are focused on as welding is widely used for construction of many structures. Residual stress is generated near the bead because of locally given heat. Tensile residual stress on the surface of metal degrades fatigue strength and related to reliability of welded structures. Reduction probabilities of tensile residual stresses are examined. The authors have proposed a method for reduction of residual stress using vibration during welding and have shown the effectiveness of the method. Residual stresses are statistically distributed. The effectiveness of the proposed method is examined in a probabilistic manner. Thick plates are used as specimens and ultrasonic vibration and low frequency vibration are applied. Some specimens of same size and material are welded using vibration during welding under the same conditions of amplitudes or frequencies. Reduction probabilities of residual stress are obtained from the expected values and the standard deviations of residual stresses assuming the normal distribution.