SEDL / STP / STP1343-EB / STP15769S

Synergetic Effects of Fatigue Crack Closure Mechanisms

Zuidema, J
Assistant professor, research engineer, and assistant professor, Laboratory of Materials Science, Delft University of Technology, Delft,

van Soest, TM
Assistant professor, research engineer, and assistant professor, Laboratory of Materials Science, Delft University of Technology, Delft,

Janssen, M
Assistant professor, research engineer, and assistant professor, Laboratory of Materials Science, Delft University of Technology, Delft,

Pages: 11    Published: Jan 1999

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Abstract

Results are presented relating to the relative effect of two closure mechanisms. Two different crack closure mechanisms, closure due to surface roughness induced by shear lips and conventional plasticity-induced closure, are investigated and compared by performing fatigue crack growth tests on aluminum 2024 and technically pure aluminum. Constant ΔK tests using a sudden change in ΔK are used in order to measure both closure effects separately and also the combined effects of both mechanisms. It is found that in the case of a combined application of closure mechanisms the retardation result after a load transition is sometimes greater than the sum of the retardations of the separate mechanisms. Under the test conditions used the combined effect may be 2.4 times greater than the sum of the separate effects.