改进圆盘试验方法分析与抗拉强度公式的修正

Analysis of Improved Disk Test Methods and Modification of Tensile Strength Formulas

测定岩石、混凝土等脆性材料抗拉强度时最常用的方法是改进巴西圆盘试验,但存在几种不同的改进圆盘试验方法,各试验结果是否准确、相互之间有何差异需要明确。考虑不同的加载面圆心角,通过数值模拟的方法对比分析了3种改进圆盘试验之间的差异,并与理论结果进行了对比。结果显示,相同的加载面圆心角,采用弧形集中加载模式时试样劈裂面上的拉应力区分布范围最大,其次是弧形均布加载模式,最后是平台加载模式。当加载面圆心角在20°~40°范围内时,试样满足中心起裂的要求,且试样中心点处压应力与拉应力的比值较小,因此建议采用该范围内的加载面圆心角进行试验。根据脆性材料格里菲斯破坏准则,引入了修正系数k,对改进圆盘试验抗拉强度公式进行了修正。

The most common method for determining the tensile strength of brittle materials such as rock and concrete is improved disk test. The accuracy of each test result and any differences between them need to be clarified due to the existence of several different improved disk test methods. Considering different central angles of loading surface, the differences between the three improved disc tests were compared and analyzed combined with theoretical results by numerical simulation. The results show that when the central angle is the same, the distribution range of the tensile stress area on the splitting surface of the specimen is the largest under the curved concentrated loading mode, followed by the curved uniform loading mode, and finally the flattened loading mode. When the central angle of the loading surface is in the range of 20° ~ 40°, the disk meets the requirements of center cracking, and the ratio of compressive stress to tensile stress in the center of the disk is relatively small. Therefore, it is recommended to use the central angle in this range for testing. According to the Griffith criterion of brittle materials, a correction factor k is introduced to modify the tensile strength formulas of improved disk test.