FCP Report No. 6

Estimation of Fatigue Crack Propagation Life in Butt Weldments


F. V. Lawrence
P. C. Mainali
A. Y. C. Wong
Department of Civil Engineering


A method for calculating the fatigue crack propagation portion of the fatigue life of welds initiating fatigue failure at the toe of the weld is presented. The method can be applied to arbitrarily shaped and loaded members having external fatigue cracks of an assumed initial size. The results indicate that estimates using this procedure can provide reasonable estimates of the fatigue life of mild constructional steels. In the higher strength quenched and tempered steels, however, the initiation period which is neglected in this analysis may constitute the major portion of the fatigue life. The analytical model does allow the relative influence of weld geometry on the crack propagation portion of the fatigue life to be assessed.

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