Bending fatigue tests on defective circumferential welded pipe joints.

Abstract

While research work concerning fatigue strengths of welded joints containing defects is being extensively conducted in Japan, researchers are, in many cases, using plane plate specimens or small size test pieces. However, in consideration of the fact that piping joints are subject to complex changes in configuration and restrictive conditions in the Circumferential direction, it is believed that it is problematical to evaluate the defects based on the above-mentioned test results.Therefore, bending fatigue tests were conducted using actual pipe welds containing incomplete penetration, and the fatigue crack growth and correlation between defect and fatigue life were investigated.As a result, it was found that the crack growth behavior in a pipe under cyclic bending is similar to that under cyclic tensile load, and the number of loading cycles until a fatigue crack propagates throughout the wall thickness can be reasonably estimated from the stress intensity factor for the initial defect.