SHORT CRACK GROWTH AND COALESCENCE ALONG THE TOE OF A MANUAL FILLET WELD

Abstract

AbstractAn experimental study was undertaken on the early development of fatigue cracking along the wavy toe of a manual fillet weld between structural steel plates. Stress relieved and as‐welded cruciform specimens were tested under fully reversed loading at two stress amplitudes. Miniature strain gages installed along the toe were used to monitor the crack depth and crack opening level from a crack depth of 10‐20 μ. A calibration of gage response versus crack depth from a 2D finite element analysis is shown to be acceptable. The analysis of the gage responses and of the fracture surfaces including beach marks of short cracks has revealed that discontinuous straight‐fronted cracks rapidly form along the edge of the successive weld ripples. Their aspect ratio increases until some coalescence results from a progressive bridging between the adjacent crack planes. As the step of the ridge line decreases, the cracks fully coalesce into one uniform through‐crack. Faster growth rates associated with negative opening levels are recorded in as‐welded specimens. The welding residual stress distribution makes initiation and early crack propagation concentrate at the center of the specimen which results in a long semi‐elliptical crack.