基于数字图像相关方法的端羟基聚丁二烯推进剂复合型裂纹J积分测量

为实现复合型裂纹尖端变形场及J积分测量，对预制含中心贯穿复合型裂纹的端羟基聚丁二烯(HTPB)推进剂试件进行了拉伸观察试验，获得了复合型裂纹试件的变形图片序列。采用数字图像相关(DIC)方法得到试件表面的位移和应变场，运用J积分理论和DIC方法得到的变形场计算复合型裂纹尖端的J积分。将DIC方法得到的变形场结果以及运用J积分理论和DIC方法计算得到的J积分结果与有限元结果进行了对比分析。分析结果表明：DIC方法获得的变形场分布特点与有限元结果吻合较好；不同积分路径下的J积分具有守恒性，验证了DIC方法可以有效地计算J积分；相同拉伸位移和复合型裂纹下J积分随角度的增大呈下降趋势，裂纹从0°Symbol~A@45°时J积分值 变化较小，裂纹从45°Symbol~A@67.5°时J积分值有较明显的下降。

J-integral Measurement of Mixed Mode Cracks of HTPB Propellant Based on Digital Image Correlation Method

In order to realize the deformation field and J-integral measurement of mixed mode crack tip, the hydroxyl-terminated polybutadiene (HTPB) propellant specimens with center-through mixed mode cracks were prefabricated, and the stretching of propellant specimens was tested. The deformation picture sequences of specimens with different angle cracks were obtained. The digital image correlation method (DIC) is used to obtain the displacement and strain field of specimen surface. The J-integral of the mixed mode crack tip is calculated using the J-integral theory and the deformation field obtained by DIC. The results are compared with the finite element results. The results show that the distribution characteristics of deformation field obtained by DIC are consistent with the results obtained by the finite element method. The J-integrals under different integral paths are conserved, which verifies that the digital image correlation method can be used to effectively calculate J-integrals. For the same tensile displacement, the J-integral of mixed mode cracks decreases with the increase in angle. The J-integral value changes little when the crack angle changes from 0° to 45°, and the J-integral value decreases obviously when the crack angle changes from 45° to 67.5°.