圆杆和螺纹及板表面裂纹的扩展形态与SIF实验解分析

ANALYSIS OF EXPERIMETAL RESULTS OF SURFACE CRACK PROPAGATION SHAPE AND SIF OF ROUND ROD, THREAD ROOT AND PLATE

在对圆杆、圆杆表面多环形槽和螺纹根部表面裂纹应力强度因子(SIF)进行了实验研究的基础上,分析了3种SIF实验解相互间的差异和共性,在3种试件中,表面裂纹SIF值无论在裂纹最深点还是表面点,均以螺纹联接时最高,圆杆表面多环形槽次之,圆杆的值为最低,同时,还讨论了在以上3种情况下其表面裂纹前缘的扩展形态,并相现有的平面板在拉伸、弯曲疲劳载荷作用下,其表面裂纹的扩展前缘进行了比较,指出:它们虽然都是椭圆曲线的一部分,有相同的裂纹形状比a/C随裂纹深度比a/R增大而减小的变化规律,但圆杆与拉抻板的断口形态接近,而圆杆表面多环形槽和螺纹根部的断口形态则处于板的拉伸与弯曲之间。

Based on the experimental results of stress intensity factor (SIF) of the surface crack of round rod multi-circular notches on the surface of round rod, and thread root[2.3], the difference and identity of the rusults is analysed. The SIF value of thread is highest at the deepest point and the surface point of surface crack, and that of the round rod lowest. At the same time, their,crack propagation shape is also discussed, and a comparative study is made with the crack shape of plates under tension loading and bend loading. That indicates all crack shapes are a part of ellips curve, and there is same regularity of the a/c decrease with the crack a/R increase. But the crack shape of round rod is similar to that of a plate under tension loading, and the other two crack shapes are between tension and bend of plate.