Short Crack Growth and Coalescence Along the Toe of a Manual Fillet Weld

Abstract

An 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 pm. 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.

The influence of surface geometry and topography on the fatigue cracking behaviour of laser hybrid welded eccentric fillet joints

“…12(c) is separated by a ratchet line. Details for ratchet line formation at this state are discussed in [40]. When ratchet lines disappear after crack growth across the weld, the individual cracks coalesce and form a single crack plane.…”

Coupling of X‐ray computed tomography and surface in situ analysis combined with digital image correlation method to study low cycle fatigue damage micromechanisms in lost foam casting A319 alloy

“…Although the river patterns marked in Figure 8G revealed the direction of cracks originated from the cleavage of a Si particle in a local area, one cannot obtain more information about crack propagation in a larger area. However, the ‘ridge’ line (Figure 8G), which formed during the coalescence of cracks from two different planes, 39 was observed between initiation site C and Pore A (Figure 8C). This implies that crack initiation C may be due to coalescence of two cracks.…”

Coupling of X-ray CT and surface in-situ analysis combined with DIC method to study low cycle fatigue damage micromechanisms in lost foam casting A319 alloy

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