Effect of welding and weld repair on crack propagation behaviour in aluminium alloy 5083 plates

Aluminium alloy 5083 is used in the fabrication of lightweight, high-speed marine vessels. The high cyclic service stresses on such structures render welded joints in them fatigue-critical. This paper presents experimental investigations on fatigue crack behaviour of welded 5083-H321 aluminium alloy plates. Crack propagation in the heat-affected zone of welded specimens was determined from tests conducted on single edge-notched tension specimens. Three-dimensional finite-element analysis was employed to determine stress intensity factors for cracks in the weld line. The crack closure effects of weld residual stresses were evaluated. The residual stresses significantly influence the crack growth rates. Fatigue behaviour of weld repairs in cracked plates was also investigated. The weld-repair process significantly increases the grain size and the size of defects in the heat-affected zone. The results indicate that weld repair of cracks in welded joints provides little improvement in residual life.