Effects of Socket Weld Field Condition on Vibration Fatigue Behavior of Carbon Steel Piping

Fatigue failure caused by vibration of socket welds often occurs in a nuclear power plant. The purpose of this study is to evaluate the integrity of the nuclear power plant socket weld under vibration fatigue condition. The vibration fatigue tests were conducted considering the field condition of socket welds. The types of field condition such as the weld quality, slip-on gap condition, weld leg size, eccentricity, pipe diameter were considered. A testing methodology is described, in which the test specimens bolted to the shake table were shaken by adjusting the specimen natural frequency, shake table speed and input acceleration. The results are as follows: There is no tendency to crack originated at the toe and the root. Fatigue strength was greater for 2 × 1 leg length, small diameter and no slip-on gap. Based on these results, the effects of socket weld field condition are discussed for small diameter welded pipe joints in the present study.