OS1507 The study on the fatigue crack propagation behavior of the structures with fillet weld for load transmission type.(Second report)

Hydraulic excavators have a lot of welded joints. Performing fillet weld is easy and economical. However fillet welded structures have unwelded area which is to be origin of fatigue crack initiation. Although the groove and fillet weld is performed to decrease unwelded area, it is difficult to perform fillet weld on both side for attachment with box structure. And also the structure with groove does not match machine costs. Because of that, high accurate evaluation method is needed. Up to date, evaluation for unwelded area has been studied in many papers and there are many standard evaluations method for crack propagation of unwelded area. However almost the all papers investigated cross fillet weld, and there is few fillet welded investigation. Moreover it is uncertain that crack propagation evaluation for actual machine condition is match or not, because many actual machines have unwelded fillet weld, and influence of weld defect for crack propagation behavior is not clear. In this study, fatigue crack growth tests were carried out on fillet welded test pieces. A test piece is modeled as to the actual machine. As the results, there was little crack initiation life. Almost the all lifetime is crack propagation. And weld defect have an effect on the direction of crack propagation.