Fatigue crack propagation in residual stress fields of welded plates

This paper presents some recent results of a research programme on the evaluation of the fracture mechanics properties, principally the crack propagation rate, of plasma welded aluminium joints, 2219-T851. Crack propagation tests were carried out on large centre cracked tension (CCT) specimens and on small compact tension (CT) specimens. The main difference between the two typs of specimens concerned the residual stresses, which were not present in the CT specimens, due to their reduced dimensions. The residual stresses were measured in cracked and uncracked plates, by means of strain gauges. The results of the crack propagation tests carried out on the two types of specimens were fully comparable in the case of a crack which propagates along the weld bead, in the heat-affected zone, as the residual stress effect was quite low, while the crack propagation rate measured in the CT specimens was lower than that in the CCT specimens in the case of a crack which propagates perpendicularly to the weld bead. Residual stress measurements allowed the evaluation of the residual stress effects on the crack propagation rate and close agreement was found between the results of the two set of tests. Copyright (C) 1997 Elsevier Science Limited.