摘要:
对于实际金属材料,裂纹前端总是存在一个或大或小的塑性区.对于小范围屈服,线弹性断裂力学分析仍适用,但必须对塑性区的影响作修正.传统的修正方法(以下简称lrwin法)[1,2],是引入有效裂纹长度的概念,即认为由于塑性区的存在,实际裂纹长度必有所增加,如取裂纹长度等于有效裂纹长度2(a+ry),其中2a为裂纹的原长,2ry为裂纹的增长量,则可不必考虑塑性区的存在,仍按线弹性断裂力学处理.本文则认为:由于塑性区的存在,实际的裂纹长度和外加应力均会增大.即是说,应力强度因子中的两个参量a及σ1(外加应力)值均将改变.文中指出,按本文方法确定的应力强度因子式(3.2),较通用公式(3.4)更接近于Duffy[4]的符合实验结果的经验公式(3.6).
Abstract:
For the practical metallic material, preceding the fracture, there always exist the domains of plasticity. For the plasticity limited in scope, the linear elastic mechanics is still applicable, but it is neccesary to correct the influence of the domain of plasticity. The traditional method of correction (Irwin's method) is to introduce the conception of the effective fracture length, namely, owing to the existence of the domain of plasticity, the practical length of the fracture increases. If we take the length of the fracture to be equal to the effective fracture length 2(a+ry), where 2a is the original length of the fracture and 2ry is the added length, we may not regard the existence of the domain of plasticity and still use the linear elastic fracture mechanics to deal with.In this paper, we regard that owing to the existence of the domain of plasticity, the practical fracture length and the extremal applied stress both increase, i.e., the value of the two parameters a and σ1 (external applied stress) both change.In this paper, it is pointed out that the stress intensity factor being determined by the method in this paper eq. (3.2) is closer to Duffy's experimental eq. (3.6) coinciding with experiment than the commonly used eq. (3.4).
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