SEDL / STP / STP1280-EB / STP16217S

Crack Initiation Life Behavior Under Biaxial Loading Conditions: Experimental Behavior and Prediction

Nowack, H
Professor and scientist, Gerhard Mercator University Duisburg, Duisburg,

Hanschmann, D
Senior research engineer, Porsche AG, Weissach,

Ott, W
Professor, Fachhochschule Niederrhein, Krefeld,

Trautmann, K-H
Senior research engineer, German Aerospace Research Establishment (DLR), Cologne,

Maldfeld, E
Professor and scientist, Gerhard Mercator University Duisburg, Duisburg,

Pages: 25    Published: Jan 1997

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Abstract

An experimental program with proportional and nonproportional loading histories was performed with cruciform aluminum specimens on a biaxial testing machine. FEMFAT, a crack initiation life prediction method as originally proposed by Ott, which includes an elastic-plastic stress-strain analysis based on the finite element method (FEM) in combination with a Mróz-type material model and an event independent continuous damage (EVICD) evaluation approach on the basis of incremental plastic work was applied to predict the crack initiation life behavior as observed in the experiments. The predictions were partially extremely conservative.

Two new fatigue evaluation approaches, EVICD-J1 and EVICD-N, were developed on the basis of the original EVICD approach to account for the effect of mean stresses. They led to significant improvements in the predictions.

The new approaches do not need cycle counting and are applicable to arbitrary multiaxial loading histories in the low-cycle fatigue (LCF) and in the high-cycle fatigue (HCF) range.