Accession Number : AD0732493

Title :   Theory of Fatigue Crack Growth Based on a BCS Crack Theory with Work Hardening.

Descriptive Note : Technical rept.,

Corporate Author : NORTHWESTERN UNIV EVANSTON ILL DEPT OF MATERIALS SCIENCE

Personal Author(s) : Weertman,Johannes

Report Date : 01 NOV 1971

Pagination or Media Count : 25

Abstract : The author's theory of fatigue crack growth, which is based on the Bilby, Cottrell, and Swinden crack theory, is modified to take into account work hardening at fatigue crack tips. In this analysis stress rather than cumulative displacement or cumulative damage is the quantity whose critical value controls the crack growth. The material at the tip of a fatigue crack progressively work hardens until the stress there reaches a critical value. The material then tears apart and the crack advances until it reaches a region in which the stress is smaller than the critical value. An equation which describes the growth of fatigue cracks is derived; it is essentially the same as the crack growth equation found in the earlier analysis. The major change is the replacement of the yield stress term in the older equation with an ultimate stress term in the newer equation. The chief change is the substitution for the average yield stress in the older equation with the ultimate stress in the present equation. (Author)

Descriptors :   (*CRACK PROPAGATION, *FATIGUE(MECHANICS)), DISLOCATIONS, THEORY, HARDENING, CRACKS

Subject Categories : Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE