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利用离散元数值计算方法,研究了圆盘试样径向加载时的空间应力分布及劈裂过程的裂隙扩展情况。结果表明:1)径向加载圆盘试样横截面上的应力分布规律与二维解析计算的结果相同,中轴线上的拉应力并不是常数,而是呈两端高、中间低分布,具有明显空间效应;2)不同高径比对拉应力的分布具有重要影响,试样两端最大拉应力随高径比增加而增大,中间拉应力随高径比增加而减小,当高径比大于1以后,最大和最小拉应力数值不再变化,因空间效应引起的拉应力增高程度最大为25%左右;3)由于拉应力分布不均,圆盘试样破坏裂隙首先在试样轴向两端产生,然后向试样内部延伸,试样宏观裂隙在中轴线贯通并不代表试样失去径向承载能力;4)由于空间效应影响,试样的最大径向承载应力随高径比增加而减少,由二维圆盘计算公式得到的巴西劈裂强度明显偏小,对于试验中常用的高径比为0.5的试样,建议使用系数k=1.25~1.30进行修正。
The discrete element numerical method was used to study the spatial stress distribution and the crack propagation in the radial direction of the disc specimen. The results show that: 1) The stress distribution in the cross-section of the sample loaded with the radial disk is the same as that calculated by two-dimensional analysis. The tensile stress in the central axis is not constant, but is high in both ends and low in the middle. Obvious spatial effect; 2) The different height-diameter ratio has an important influence on the distribution of tensile stress. The maximum tensile stress at both ends of the specimen increases with the increase of height-diameter ratio. The middle tensile stress decreases with the increase of height-diameter ratio. The maximum and minimum tensile stress no longer change when the ratio is greater than 1, and the maximum increase of tensile stress due to space effect is about 25%. 3) Due to the uneven distribution of tensile stress, To the two ends of the specimen, and then extend to the sample. The macroscopic fracture of the specimen passes through the central axis and does not represent the loss of radial load capacity of the specimen. 4) Due to the space effect, the maximum radial load stress of specimen increases with the ratio of height to diameter Increase and decrease, the Brazilian splitting strength obtained by the two-dimensional disc calculation formula is obviously smaller. For the sample with the height-diameter ratio of 0.5 which is commonly used in the experiment, the correction coefficient k = 1.25-1.30 is suggested.