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利用硬度计在光滑沙漏状车轴钢疲劳试样上制造压痕,同时利用电火花在试样上加工缺陷,通过疲劳试验研究两种缺陷尺寸与试样疲劳极限之间的关系.将两类试样的测试结果和基于材料硬度、缺陷投影面积的Murakami模型计算结果进行对比.利用扫描电镜观察试样疲劳断口.结果表明,与计算结果相比较,压痕局部塑性变形导致的加工硬化和残余应力对试样的疲劳强度没有影响,裂纹依然从应力集中最大的压痕底部起裂.电火花缺陷表面粗糙度较大引起二次缺口效应,表面硬脆的重铸白层上还有微孔和微裂纹存在,导致此类试样疲劳强度低于模型计算结果,裂纹从电火花缺口底部多处萌生.
Using the hardness tester to make the indentation on the smooth hourglass-shaped axle steel fatigue test specimen, at the same time using EDM to process the defect on the test specimen, and through the fatigue test to study the relationship between the two defect sizes and the fatigue limit of the test specimen. The results of the test are compared with those of the Murakami model based on the hardness of the material and the projected area of the defect.The scanning electron microscopy (SEM) is used to observe the fatigue fracture of the specimen.The results show that compared with the calculation results, the work hardening and the residual stress caused by the local plastic deformation of the indentation The fatigue strength of the sample has no effect, the crack is still from the stress concentration at the bottom of the indentation rupture EDM defects caused by a larger surface roughness secondary notch effect, the surface of the brittle re-cast white layer there are micropores and The existence of micro-cracks, resulting in the fatigue strength of such samples is lower than the model calculation results, cracks from the bottom of the spark gap at many initiation.