Growth and coalescence of fatigue cracks at weld toes in steel

Abstract The early fatigue growth of cracks starting from defects at the toe of good-quality manual and automatic steel T-plate welds was investigated. Evolution of aspect ratios and growth rates were monitored, and linear elastic fracture mechanics models of fatigue propagation were developed. It was found that small-crack effects caused by crack closure, weld metal microstructure and notch plasticity, together with the uncertainty associated with random initiation and early coalescence of microcracks, made any deterministic linear elastic fracture mechanics modeling of cracks less than a i = 0·3 mm impossible. Fatigue cracks on automatic welds developed much smaller aspect ratios, and grew much faster, than cracks on manual welds. Models of the evolution of aspect ratios on both manual and automatic welds are presented and discussed, and life predictions are compared with experimental results.