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通过对尺寸成等比例的砂岩试样进行三点弯曲试验,研究了Ⅰ型断裂问题中试样尺寸对砂岩断裂参数的影响.结果表明:随着试样尺寸的增大,名义张拉强度减小,名义断裂韧度和破裂过程区长度增大,三者均为试样尺寸的函数.基于试验结果,引入有效破裂过程区长度cf,建立等效线弹性断裂力学尺寸效应模型,通过理论分析,发现其尺寸效应曲线介于理想脆性和理想塑性材料之间,体现出准脆性材料的尺寸效应特点,并计算得到了不同尺寸试样的破裂过程区长度等断裂参数.为验证该尺寸效应模型在砂岩中的正确性,采用数字图像匹配技术(DIC)测定相应尺寸砂岩试样的破裂过程区长度,测定结果和理论模型计算值相符.
The effect of sample size on the fracture parameters of sandstone in type Ⅰ fracture was studied by three-point bending test on sandstone specimens of equal size.The results show that with the increase of specimen size, the nominal tensile strength decreases The small, nominal fracture toughness and the length of the rupture zone increase as a function of the sample size.Based on the experimental results, the effective rupture zone length cf is introduced to establish the equivalent linear elastic fracture mechanics size effect model, through theoretical analysis And found that the size effect curve is between the ideal brittle and the ideal plastic material, which shows the size effect of the quasi-brittle material, and the fracture parameters such as the length of the cracked area of the different size samples are calculated.To verify the size effect model In the sandstone, the length of the rupture zone of the sandstone sample with the corresponding size was determined by Digital Image Matching (DIC). The measured results are consistent with the theoretical model.