Fatigue crack growth testing at negative stress ratios: discussion on the comparability of testing results
Fatigue crack growth testing at negative stress ratios: discussion on the comparability of testing results
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DOI：
10.1111/ffe.12082
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发表时间：
2014-01-01
影响因子：
3.7
通讯作者：
Sander, M.
中科院分区：
文献类型：
--
作者：
Benz, C.;Sander, M.
压缩载荷对疲劳裂纹扩展的贡献是疲劳界公认的事实。证据范围从完全压缩载荷下的疲劳裂纹扩展到负应力比载荷下的压缩欠载效应。由于裂纹在压缩下闭合，并且裂纹侧面传递压缩应力，因此加载情况与拉伸加载完全不同。本文讨论了负应力比下裂纹扩展试验方法的可比性。结果表明，当最大应力强度因子Kmax和负应力比R相等时，不同试样裂纹尖端的压缩载荷不同。此外，裂纹长度可以显着影响拉压载荷在裂纹尖端的加载条件。根据试样类型和裂纹长度，负力比可能会导致裂纹尖端应力的代数符号的变化或没有。因此，无法确保R0检测的可用文献结果的可比性。提出了提高拉压裂纹扩展试验可比性的建议。
It is an accepted fact in fatigue community that compressive loads contribute to fatigue crack growth. Evidences range from fatigue crack growth under fully compressive loads to effects of compressive underloads to negative stress ratio loading. Because the crack closes under compression and the crack flanks transmit compressive stresses, the loading situation is completely different to those of tensile loading. The present paper addresses the comparability of crack growth testing procedures at negative stress ratios. It reveals that compressive loading at the crack tip differs in different specimens for an equal maximum stress intensity factor K-max and negative stress ratio R. Furthermore, the crack length can significantly influence the loading conditions at the crack tip for tension-compression loading. Depending on the specimen type and crack length, a negative force ratio may lead to a change of algebraic sign of the stresses at the crack tip or not. As a consequence, the comparability of available literature results for R0 tests is not ensured. Proposals to improve the comparability of tension-compression crack growth testing will be given.