Final Report Low Cycle Fatigue of HY-130 (T) Butt Welds

A preliminary evaluation of the axial fatigue behavior of plates and transverse butt-welded joints in HY-130(T) steel is presented. The weldments were prepared using each of two experimental "second-generation" GMA welding wires and a coated electrode. Fatigue tests were conducted using both sound weldments and weldments containing various internal defects, including porosity, slag, lack of fusion, and lack of penetration. Radiographic and ultrasonic testing techniques were used to study the initiation and propagation of fatigue cracks originating at internal weld flaws. The fatigue studies have indicated that although the highest standards of quality may be used in the fabrication of HY-130(T) welded joints, it has not been possible to guarantee the elimination of all defects which have proven to be critical sites for internal fatigue crack nucleation under axial loading. Internal failures were as likely to occur in specimens rated as sound weldments under radiographic inspection as in weldments having regions containing readily detected flaws. Fatigue cracks originating at internal defects were found to initiate at approximately twenty to eighty percent of the total cyclic life-time of butt-welded joint, for tests conducted at a stress cycle of zero-to-tension. Within the normal limits of scatter for fatigue data, however, the number of cycles of crack propagation to failure beyond the point of internal initiation was found to be reasonably consistent at a specific test stress level, for weldments containing various types and percentages of weld defect area.Contract N00024-68-C-5125; Project Serial No. SF020-01-01, Task 72