Fatigue Behavior of HY-130 Steel Weldments Containing Fabrication Discontinuities

摘要

Fabrication discontinuities in weldments pose a serious engineering problem for structural applications involving cyclic loading. Often, the discovery of fabrication discontinuities through nondestructive inspection can pose a dilemma; if not properly repaired, failure can result from crack initiation and growth, however, if improperly repaired, post-repair discontinuities of even greater severity may result. Thus, a need exists for rational decision-making criteria to assess the mechanical severity of actual fabrication defects in weldments. This study was undertaken to explore the applicability of linear elastic fracture mechanics to characterize the fatigue behavior of high-strength steel weldments containing lack-of-penetration (LOP) and slag/lack-of-fusion (S/LOF) discontinuities. Full penetration, double-V butt welds with reinforcements removed were tested under zero-to-tension axial loading. Various filler metals and welding techniques were used. Both sound welds and welds containing discontinuities were cycled to failure. Whenever possible, cycles to crack initiation were estimated by strain gage measurements. The fracture mechanics approach was successful in correlating the fatigue lifetimes of specimens containing single LOP discontinuities of varying size. However, the fatigue behavior of specimens containing multiple S/LOF discontinuities proved to be much more complex and difficult to analyze.