中文摘要：

采用室内试验和数值模拟相结合的方法分析半边对称加载法和四点剪切加载法的联系与区别。首先对不同参数的半边对称加载试件和四点剪切梁分别进行断裂过程试验,以研究其裂缝扩展形态和断裂韧度;然后通过扩展有限元方法对裂缝尖端应力情况进行分析。结果表明：半边对称加载试件裂缝尖端剪切应力比垂直于预制缝的张拉应力大得多,裂缝沿着原预制缝方向扩展,断裂韧度与初始缝长无关,但随着试件长度的增加和高度的减小而增大;四点剪切梁试件裂缝尖端存在大小相当的剪切应力和最大主应力,裂缝起于预制缝尖端,扩展到近加载点位置附近,断裂韧度与试件的几何尺寸无关,随着初始缝长的增大和近加载点与预制缝截面距离减小而增大。

英文摘要：

The connection and difference between symmetrically single-edge notched loading method and four-point shear loading method were analyzed based on lab tests and numerical simulations.Tests were carried out for two different types of specimens to study crack propagation pattern and fracture toughness.Then,the extended finite element method was employed to study the stress distribution near the crack tip.Results show that for symmetrically single-edge notched specimens,shear stress near crack tip is much larger than tension stress perpendicular to the predefined notch.Crack propagates along the direction of original predefined notch,and fracture toughness is independent of initial length of notch,but it may increase with the increase of specimen length and the decrease of specimen height.Near the crack tip of four-point shear loading beam specimens,the magnitude of shear stress is similar to that of the maximum principal stress.Near the loading points,fracture toughness is independent of beam size,but it may increase with the increase of initial crack length and the shortening of distance between predefined crack and near-end loading point.