基于DIC的爆炸加载下脆性材料裂纹扩展规律的试验研究

通过数字图像相关法（DIC），应用PMMA对爆炸加载条件下脆性材料的裂纹扩展规律进行了试验研究。基于对称性试验模型，实现了裂纹尖端位置和应变场信息的同步记录。以此为基础，通过对比分析获知，主应变场应变值最大点不能作为裂纹尖端的判断依据。并以动态裂纹扩展速度为参量，应用断裂动力学和最小二乘牛顿迭代法，计算出了考虑惯性效应的Ⅰ-Ⅱ混合型裂纹的应力强度因子:K_Ⅰ和K_Ⅱ值会随着裂纹扩展方向改变而发生突变；K_Ⅰ最大值为2.63 MPa·m1/2，最小值为0.89 MPa·m1/2；其整体变化趋势表明，爆炸加载条件下脆性材料裂纹扩展随能量积聚和释放呈循环阶梯式递减发展。

Experimental study on crack propagation of brittle materials based on DIC under explosive loading

In this paper, the digital image correlation method is used to test the tip position of the brittle material in the explosion loading strip, the stress intensity factor calculation considering the inertia effect and the crack propagation law. Firstly, the symmetry experimental model is used to realize the intuitive positioning of the crack tip, and the more accurate full-field strain and displacement information is recorded. By analyzing the main strain field at the crack tip, the maximum strain point cannot be used as the crack tip. Judgments based. Secondly, based on the fracture dynamics, the crack propagation length, the crack propagation velocity and the displacement information of the data points in a certain area of the tip are obtained according to the crack tip position. The differential principle and the least squares Newton iteration method are used to calculate the inertial effect. The stress intensity factor of the I-II hybrid crack, wherein the K_I maximum is 2.63 MPa·m1/2 and the minimum value is 0.89 MPa·m1/2. The overall trend of K_II has remained basically the same, but due to the complexity of the late stage of the model, the crack propagation direction changes and the mutation occurs; Then, the overall trend of the stress intensity factor shows that the crack propagation of the brittle material develops in a cyclically decreasing manner with the energy accumulation and release under explosive loading conditions, but the variation range is relatively large when crack initiation and crack arrest occur, and in the test. The late expansion crack is an I-II hybrid type. Finally, the crack propagation length and stress intensity factor change trend are compared with the actual test results. The two are basically the same, which indicates that the test method and the theoretical calculation result can be well matched, and the experimental precision is high, which is feasible.