Weld Strength and Crack Growth Ductility from the Lazy-L Test

摘要

Fully plastic fracture of fillet welded T-joints is characterized by the limitmoment, slip line displacement to crack initiation, and crack growth ductility, defined as the slip lin displacement per unit crack advance. A novel fillet weld fracture experiment, the Lazy-L Test, is developed as a simple, inexpensive method of measuring data used to calculate these parameters. Fully plastic fracture mechanics provides an extrapolation of Lazy-L Test results to other fillet weld failure modes observed in ship grounding, including peeling of the shell plating. The Lazy-L Test is introduced as an alternative to more costly and difficult experimental and computer methods, and suggested for consideration as a standard test in the design and qualification of fillet welds for service. The Lazy-L is used to test single fillets in predominant bending (opening from the root of the weld), single fillets in predominant transverse shear, and double fillets in predominant bending. The plastic flow field for each configuration is modeled by single arcs of sliding in the fillet selected to yield a least upper bound to the limit moment. Load displacement data for each configuration determine an experimental limit moment, displacement to initiation and crack growth per unit slip line displacement. The results are generalized for other weld loadings when expressed in terms of the mean normal stress across the crack tip. Twelve experiments are presented for 6mm and 9mm weld sizes produced using GMAW with the combination of LR-EH36 steel plate and E7O16 stick electrode. (MM).