基于数字散斑相关法的紧凑拉伸试样断裂韧性实验研究

本文采用数字散斑相关方法对2A12T4铝合金紧凑拉伸试样的断裂韧性进行了实验研究。应用数字散斑相关方法计算了实验过程中试样的应变场、应力场以及位移场。针对实验所得的结果以及紧凑拉伸试样的裂纹特征,采用了矩形积分路径。选择沿裂纹方向和垂直裂纹方向的J积分路径,并且推导出各方向上J积分的数值计算公式。根据推导得到的公式选择不同的积分路径进行J积分的计算,得到了断裂韧性J0积分路径的合理选择范围,同时验证了J积分的路径守恒性。然后根据所得的路径选择标准,选择合理的积分路径,计算出2A12T4铝合金断裂韧性J0的值。将所得结果与国标计算的J0值对比,误差为1.22%,说明了此种方法的正确性。从而为数字散斑相关方法在紧凑拉伸试样断裂韧性的测试研究中提供参考。

Experimental Study of Compact Tension Specimen Fracture Toughness based on Digital Speckle Correlation Method

Adopting digital speckle correlation method (DSCM), an experimental study of fracture toughness of compact tension specimen made of 2A12T4 aluminium alloy was carried out. DSCM was applied to calculate the strain field, stress field and displacement field of specimen during the process of quasi-static tensile. Based on experimental results and crack characteristics of compact tension specimen, the rectangular integral path was adopted. Selecting the direction along crack and direction vertical to crack as J integral path respectively, numerical calculation formulas of J integral along both directions were deduced. Based on deduced formulas, calculation of J integral along different path was achieved, and a reasonable selection range of J⁰ integral path for fracture toughness was obtained. At the same time, the conservativeness of J integral path was validated. Then, the fracture toughness of 2A12T4 aluminium alloy was calculated based on above mentioned selection range and integral path. Comparing obtained result with international standard, the error is 1.22%, which indicates the validity of this method. Thus, the application of DSCM in the measurement of compact tension specimen fracture toughness is confirmed.