基于数字散斑相关方法测定Ⅰ型裂纹应力强度因子

提出了一种通过数字散斑相关方法测定金属材料Ⅰ型裂纹尖端位置和应力强度因子的实验方法.实验采用疲劳试验机对含Ⅰ型缺口的Cr12MoV钢试件预制裂纹,通过数字散斑相关方法测试试件在三点弯曲加载条件下裂纹的扩展过程及裂尖区域的位移场.将位移场数据代入裂尖位移场方程组,采用牛顿-拉普森方法求解含未知参量的裂尖非线性位移场方程组,计算裂尖位置和应力强度因子.实验结果表明,采用该方法可以准确地测定金属材料Ⅰ型裂纹应力强度因子、裂尖位置及裂纹扩展长度,解决了以往研究中因不能准确测定裂纹尖端位置,而无法准确计算Ⅰ型裂纹裂尖断裂参数的难题,揭示了金属材料裂纹扩展过程中应力强度因子演化特征.

Determination of Mode I Stress Intensity Factors by Digital Speckle Correlation Method

An experimental method for determining mode I stress intensity factors and crack tip position of metal specimen by digital speckle correlation method is proposed in this paper. Before test, a precrack was made in front of the notch on a Cr12MoV specimen by fatigue testing machine, the crack growth process and the displacement contour map around crack tip of specimen were measured by digital speckle correlation method under three-point bending load condition. Then the displacement data were substituted into the non-linear crack tip displacement equations, and the equations were solved by Newton-Simpson method, the crack tip position and stress intensity factor were calculated. Experimental results show that the mode I stress intensity factor, the crack tip position and crack growth length of a metal specimen can be evaluated accurately from the displacement components by the proposed method, and the stress intensity factor's evolution features during crack growth process were also revealed.