SEDL / STP / STP1122-EB / STP24164S

Small Crack Growth in Multiaxial Fatigue

Reddy, SC
Associate Engineer, EASI Engineering, Auburn Hills, MI

Fatemi, A
Associate Professor, The University of Toledo, Toledo, OH

Pages: 23    Published: Jan 1992

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Abstract

The small crack problem in multiaxial fatigue is studied using available crack growth data from thin-walled tubular specimens made of Inconel 718 and 1045 HR steels. The loadings consist of axial, torsional, proportional and nonproportional axial-torsional with or without mean stress, and biaxial tension tests. An equivalent strain based intensity factor range based on Irwin's energy release rate, as well as a proposed strain based intensity factor range formulation based on the critical plane approach, are used to correlate the crack growth data obtained from different loading conditions. The proposed formulation is an attempt to present a unified approach to crack initiation as well as crack propagation, based on the physical mechanisms of the multiaxial fatigue damage process. Crack growth rate correlations and small crack effects with respect to the microstructure and different loading paths are discussed.