Experimental Investigation on Fatigue Crack Growth Law under Elastic, Elastic-Plastic and General Yield Conditions

Abstract

Fatigue crack growth tests of low-carbon steels were conducted under various experimental conditions including elastic, elastic-plastic and general yielding. The crack growth rate under the general yield condition was correlated to several mechanical parameters proposed previously, and it found that the J integral range ΔJ was the best parameter among them in expressing the growth rate. As far as plastic deformation of the specimen is reversible, the relation between the rate da/ dN and ΔJ was expressed as a unique power function for various experimental conditions. When ratcheting deformation took place, the rate became higher than that predicted from the relation. The limitation of the applicability of ΔJ under load controlled conditions due to ratcheting deformation was predictable from the limit load analysis and its limitation due to specimen size was also clarified.