切口冷拨圆棒料的超低周疲劳断裂分析

借助于扫描电镜从细观和材料角度，研究了具有环状“Ｖ“型切口的冷拨圆棒料在超低周恒挠度下的断裂机理。同时指出，冷拨钢原材中存在轴向缺陷使得主裂纹在沿径向扩展的同时要发生轴向窜动，它是造成疲劳裂纹扩展区呈“馒头状”的原因之一，而冷拨钢特殊的组织形态决定了它的空洞形核必然受控于剪应力，这是造成疲劳裂纹扩展区呈“馒头状”的根本原因，另外，还发现冷拔铜在超低周疲劳条件下空洞形核主要有珠光体优先断裂形核、晶界形核、脆性颗粒断裂形核三种方式。

Analysis of Fatigue Fracture of Cold-dawn Bar With Notch Under Super-low Circling and Constant Deflecting

Fracture mechanism of cold-drawn bar with V-notch under super-low circlingand constant deflecting is investigated from the point of view of mesomechanics and materialsby means of scanning electronic microscopy,It is found that the axial defects in the bar makethe main crack scurry axially along with its radially propagation. This process is one of thecauses due to which the propagation range of fatigue crack becomes the form of the cupola.Further-more,the particular structure pattern in the cold-drawn bar makes the cavity nucle-ation be a shear-controlled one. And this is the main origin of the cupola-shape of the crackpropagatlon areas.