Accession Number:

ADA052881

Title:

Characterization of Fatigue Crack Tip Deformation.

Descriptive Note:

Final rept. 1 Jan 75-31 Dec 77,

Corporate Author:

SOUTHWEST RESEARCH INST SAN ANTONIO TEX DEPT OF MATERIALS SCIENCES

Report Date:

1978-02-01

Pagination or Media Count:

21.0

Abstract:

During the past three years, fatigue crack tip plasticity and overload induced fatigue crack retardation have been studied using several complementary techniques, especially selected area electron channeling and high resolution SEM observation of crack tips under various stages of loading. It is found that while some materials exhibit plastic yielding behavior in agreement with existing theory, some materials, especially aluminum alloys, diverge widely both from one another and from theory. In particular, for equivalent stress intensities, overload ratios, and pre-overload crack growth rates, the retardation period in cycles for 2024-T3 significantly exceeds that for 6061-T6 and 7075-T6. This behavior is intimately related to the size and shape of the overload plastic zone, variations in which probably are controlled by the plastic flow rules for the alloys.

Subject Categories:

  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE