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对循环载荷作用下 15MnVN钢的显微组织变形、微观裂纹的萌生和短裂纹扩展过程进行了研究。结果表明 ,在孔边应力集中处 ,显微组织的变形是不均匀的 ,其主要集中在铁素体晶粒内。在循环载荷作用下 ,晶内滑移带与晶界相互作用 ,形成晶界微裂纹。微裂纹合并形成短裂纹。裂纹尖端塑性区内晶粒同样经历裂纹的萌生和扩展过程。在短裂纹范围内 ,裂纹的扩展过程有很大的随机性。分析结果表明 ,短裂纹的扩展过程符合对数正态分布。
The microstructure deformation, microscopic crack initiation and short crack propagation of 15MnVN steel under cyclic loading were studied. The results show that the stress in the hole edge, the deformation of the microstructure is not uniform, mainly in the ferrite grains. Under cyclic loading, the intragranular slip band interacts with grain boundaries to form grain boundary micro-cracks. Microcracks merge to form short cracks. The grain in the plastic zone of the crack tip also undergoes the initiation and propagation of cracks. In the short crack range, the crack propagation process has a lot of randomness. The analysis results show that the expansion process of short cracks accords with lognormal distribution.