Accession Number : ADA134767

Title :   Entropy Production during Fatigue as a Criterion for Failure. The Critical Entropy Threshold: A Mathematical Model for Fatigue.

Descriptive Note : Annual rept. no. 1, 15 Aug 82-14 Aug 83,


Personal Author(s) : Whaley,P W

PDF Url : ADA134767

Report Date : 15 Aug 1983

Pagination or Media Count : 106

Abstract : A mathematical model of fatigue crack nucleation is described using the irreversible thermodynamics to quantify the damage caused by plastic straining. The model is based on the hypothesis that the entropy gain which results from dynamic irreversible plastic straining is a material constant. A random model of internal friction is used to calculate the irreversible part of the hysteresis energy dissipation rate, enabling the quantification of uncertainty through the variance of the dynamic plastic strain. In this manner, the mathematical model for fatigue crack nucleation provides an estimate for longevity including confidence intervals under arbitrary temperature, environment, and loading history. The model explains the existence of an endurance limit. Although this analysis was conducted for an uncracked material leading to time estimates for crack nucleation, the theory can easily be extended to the case of crack propagation using the methods of fracture mechanics. (Author)

Descriptors :   *Fatigue(Mechanics), *Nucleation, *Entropy, Crack propagation, Strain(Mechanics), Plastic properties, Failure(Mechanics), Thermodynamics, Mathematical models

Subject Categories : Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE