SYMPOSIA PAPER Published: 01 January 1989
STP18839S

Fatigue Crack Growth Under Combined Mode I and Mode II Loading

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The influence of static Mode I and static Mode II loading on Mode I fatigue crack growth has been studied with 12 weight % chromium steel.

Static Mode I was superimposed as a tensile load on fatigue-loading with mean stress equal to zero, thus resulting in R-values of - 1, - 0.33, 0, +0.25, and +0.5. For these values, fatigue-crack growth curves were determined in the threshold regime with crack growth rates typically between 3 × 10-13 and 5 × 10-9 m/cycle.

In addition, a constant static Mode II load was superimposed on the same above-mentioned Mode I load. The resulting crack growth rates were found to vary systematically with crack length and load ratio. For R-ratios ⩽ 0 enhanced fatigue crack growth rates were observed at crack lengths up to a defined value. After a certain crack length was attained, slightly reduced crack growth rates were detected. For high R-ratios, long as well as short fatigue cracks grew slower than under pure Mode I fatigue loading. The results are discussed in light of the crack closure phenomenon and the fracture morphology, which was studied in a scanning electron microscope (SEM).

In the Appendix, a basic procedure for determining stress-intensity values for high-frequency (21 kHz) fatigue loading is given in comparison with conventional loading.

Author Information

Stanzl, ES
Institute for Meteorology and Physics, Vienna, Austria
Czegley, M
Technical University of Vienna, Austria, Institute for Technical and Applied Physics, Vienna, Austria
Mayer, HR
Institute for Meteorology and Physics, Vienna, Austria
Tschegg, EK
Technical University of Vienna, Austria, Institute for Technical and Applied Physics, Vienna, Austria
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Details
Developed by Committee: E08
Pages: 479–496
DOI: 10.1520/STP18839S
ISBN-EB: 978-0-8031-5081-2
ISBN-13: 978-0-8031-1250-6