弯曲载荷下含半椭圆表面裂纹平板疲劳裂纹扩展试验方法研究  

Method to Evaluate Fatigue Crack Growth Rate of Semi-elliptical Surface Cracked Plates Under Bending

作　　者：杜开开 包陈[1] 何广伟[1] DU Kaikai;BAO Chen;HE Guangwei(Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province,Southwest Jiaotong University,Chengdu 610031)

机构地区：[1]西南交通大学应用力学与结构安全四川省重点实验室,成都610031

出　　处：《机械工程学报》2024年第24期153-162,共10页Journal of Mechanical Engineering

基　　金：国家自然科学基金资助项目(12072294)。

摘　　要：基于能量密度等效方法提出了含半椭圆表面裂纹平板三点弯曲试样的等效应力强度因子半解析模型,结合有限元分析获得了裂纹前缘不同位置的应力强度因子分布。通过假设半椭圆表面裂纹的疲劳裂纹扩展路径,由柔度技术建立了预测表面裂纹形貌尺寸的方法,在疲劳裂纹扩展试验中通过改变应力比勾勒裂纹前缘验证了柔度法的精度。采用SA-508钢完成了不同初始形貌的半椭圆表面裂纹疲劳扩展速率试验,结果表明,疲劳弯曲下的半椭圆表面裂纹倾向于沿路径a/t=1−a/c扩展,即表面裂纹的形状在疲劳扩展中呈现固定的演化趋势,且该特性不受初始裂纹形貌和尺寸的影响。前缘上不同位置的裂纹扩展速率有明显差异,表面点的扩展速率最大,最深点最小,在优先疲劳扩展路径上,裂纹形貌差异对半椭圆表面裂纹的疲劳裂纹扩展速率影响较小,相同位置处的裂纹扩展速率近似相同。Based on the energy density equivalent method,a semi-analytical model of equivalent stress intensity factor for semi-elliptical surface cracked plate under bending was proposed,and the stress intensity factor distributions at different positions on the crack front were obtained by finite element analysis.By assuming the fatigue crack propagation path of semi-elliptic surface crack,a method for predicting surface crack shape was established by the compliance technique.The accuracy of the compliance method was verified by changing the loading ratio to outline the crack front in the fatigue crack propagation test.SA-508 steel was used to test the fatigue growth rate of semi-elliptic surface crack with different initial crack geometric configurations.The results show that the semi-elliptic surface crack shape tends to evolve along a preferred path under fatigue bending load and the path is a/t=1−a/c,the shape of the surface crack shows a fixed evolution trend as crack grows and is not affected by the initial crack size and shape.The crack growth rate at different positions of the surface crack front is significantly different,the growth rate at the surface point is greater than that at the deepest point.When the crack propagates along the preferred path,the difference of initial crack shape and size has little effect on the fatigue crack growth rate of semi-elliptical surface crack,the crack growth rate at the same position is approximately the same.

关 键 词：半椭圆表面裂纹 疲劳裂纹扩展 应力强度因子 能量密度等效方法 柔度法 

分 类 号：O346[理学—固体力学]