SEDL / STP / STP942-EB / STP24485S

Life of Crack Initiation, Propagation, and Final Fracture under High-Temperature Creep, Fatigue, and Creep-Fatigue Multiplication Conditions

Yokobori, AT
Associate Professor, Tohoku University, Aoba, Sendai

Yokobori, T
Professor Emeritus and Graduate, Tohoku University, Aoba, Sendai

Kuriyama, T
Professor Emeritus and Graduate, Tohoku University, Aoba, Sendai

Pages: 21    Published: Jan 1988

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Abstract

Studies were carried out on the crack initiation and propagation laws under high-temperature creep, fatigue, and creep-fatigue multiplication conditions for notched specimens of SUS 304 stainless steel.

For crack initiation life, it was found that relative notch opening displacement (RNOD) can be used. Furthermore, the remaining part of crack initiation life can be predicted by RNOD criterion; that is, by recording RNOD with respect to the suitable time within the service term and extrapolating the data with a straight line until the line intersects the critical value of RNOD.

The crack propagation life was expressed by a thermally activated type equation in explicit terms of independent parameters such as applied stress and temperature. The equation was approximately expressed in terms of the time-temperature equivalent parameter T(ℓn tp + C), where T = absolute temperature, tp = crack propagation life, and C = a nearly constant numerical factor. The experimental data are well expressed by this parameter.