Study on Zigzag Path of Low Cycle Fatigue Surface Crack Propagation under Cantilever Bend Loading
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摘要: 通过悬臂弯曲加载方式,采用逐级递增的六级名义应变水平作为控制模式,完成了四件试样10CrNiMo钢的低周疲劳表面裂纹扩展速率(SCPR)试验。试验发现,在每级名义应变水平控制下,SCPR整体上趋于某一稳定值,但局部裂纹扩展出现时快时慢现象,在低名义应变水平控制下尤为明显。对上述现象进行了分析,结果表明:出现局部裂纹扩展不稳定的原因是由于表面裂纹扩展的路径呈现转折和分叉的曲折性特征,转折和分叉通常会降低表面裂纹的扩展速率,但有时也会加速表面裂纹的扩展。Abstract: Low cycle fatigue surface crack propagation rate(SCPR) test of 10CrNiMo steel with four pieces of specimens were carried out,adopting six-grade nominal strain increased gradually as control parameters under cantilever bend loading.It was found that under the control of every-grade nominal strain,SCPR tends to a certain stable value,but local crack propagates sometimes fast and sometimes slow and it is particularly obvious under the control of low nominal strain.Analysis indicated that surface crack propagation presented a zigzag path of transition and bifurcation,which brought on local cracks unstable growth.Usually,transition and bifurcation will decrease surface crack propagation rate,but sometimes also accelerate surface crack propagation.
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