基于广义最大周向应变准则的断裂特性研究

裂纹尖端应力场的非奇异性常数项（T应力）对脆性或准脆性材料的断裂特性及裂尖塑性区的形状和大小都有显著的影响。为了探究T应力对脆性或准脆性材料I~II复合型断裂特性的影响规律，基于先前研究中提出的计及T应力影响的广义最大周向应变准则进一步讨论了T应力、裂纹尖端的临界距离r₀和泊松比ν对中心裂纹圆盘试件的裂纹扩展路径以及临界应力强度因子的影响规律，并利用该准则对基于中心裂纹圆盘试件的断裂试验结果进行了有效评估。结果表明：与传统的最大周向应变准则相比，中心裂纹圆盘试件中由于负T应力的存在，会使得裂纹开裂角的绝对值减小，同时使得临界应力强度因子（断裂韧度）的值增加。考虑了T应力影响的广义最大周向应变准则能很好的对试验结果进行预测；并且在纯II型时，基于广义最大周向应变准则的理论预测值比基于广义最大周向应力准则的理论预测值更接近试验值。

A Study on the Fracture Characteristics Analysis Based on the Generalized Maximum Tangential Strain Criterion

The non-singular constant stress term (T-stress) around the crack tip remarkably affects the fracture characteristics of brittle or quasi-brittle materials, and it is also closely related to the shape and size of the plastic zone near the crack tip. In order to explore the influence of T-stress on the I~II mixed mode fracture characteristics of brittle or quasi-brittle materials, the generalized maximum tangential strain (GMTSN) criterion, which considers the effect of T-stress, has been proposed in our previous research. In this paper, the further study on the effects of T-stress, critical distance r₀ and Poisson's ratio ν on the crack propagation path and the fracture resistance for central cracked Brazilian disc (CCBD) specimens have been carried out according to the GMTSN criterion. Moreover, the GMTSN criterion is used to predict the test results obtained with CCBD specimens. The results indicate that the T-stress and Poisson's ratio have a remarkable influence on the mixed mode fracture resistance based on the GMTSN criterion. When compared with the traditional maximum tangential strain (MTSN) criterion, a negative T-stress in a CCBD specimen always decreases the absolute value of the fracture initiation angle; however, the value of critical stress intensity factor is increased for negative values of T-stress. Theoretical values based on the GMTSN criterion, which considers the effect of T-stress, are in very good agreement with the test results. Moreover, the GMTSN criterion provides a better prediction for pure mode II when compared with the generalized maximum tangential stress (GMTS) criterion.