A Study on Behavior of Mixed Mode Fatigue Crack Growth of Spiral Welding Part Under Bending Load

Abstract

Manufacturing of large scale steel pipes in a nuclear power plant, offshore structures and a petroleum chemical plant, etc., a spiral welding method is mainly used. Such a welding part generally has several types of defect such as an undercut, a pit and a crack and in many cases, it finally reaches the failure by crack growth from these. The linear elastic fracture mechanics has been applied to a study on fatigue crack growth of welding parts, that is, as the weld, the heat affected zone (HAZ) and the base metal part in a large scale steel pipe by several reachers. However, since such studies are mainly the results by a standard specimen under uniaxial tensile load, they are different from the fatigue crack growth of a real large scale steel pipe under multiaxial load. In this study, we performed the evaluation for the characteristics of the mixed mode fatigue crack growth behavior of a spiral welding part in a real large scale steel pipe under bending load.