SEDL / STP / STP942-EB / STP24489S

A Model for Predicting Low Cycle Fatigue Life under Creep-Fatigue Interaction

Rie, K-T
Institut für Schweisstechnik und Werkstofftechnologie, TU Braunschweig, Braunschweig,

Schmidt, R-M
Institut für Schweisstechnik und Werkstofftechnologie, TU Braunschweig, Braunschweig,

Ilschner, B
Ecole Polytechnique Federale de Lausanne, Lausanne,

Nam, SW
Korea Advanced Institute of Science and Technology, Seoul,

Pages: 16    Published: Jan 1988

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Abstract

An attempt is made to predict fatigue life under high-temperature low-cycle fatigue conditions with superimposed hold times. It is well recognized that a reduction in life in this region is caused by the nucleation and growth of cavities along grain boundaries. The cavities can be formed by vacancy clustering, dislocation pileup, and grain boundary sliding. The subsequent growth leads to grain boundary cracking and intergranular fracture.

The possibility of unstable crack advance is given if the crack tip opening displacement becomes equal to a critical cavity configuration. To describe this configuration we postulate a power function for cavity growth.

Experimental data and the predicted values show excellent agreement, indicating the important role of creep cavitation for creep-fatigue life prediction.