正交异性材料平台巴西圆盘试样的位移公式及其应用

A Displacement Formula for Flattened Brazilian Disc Specimen of Orthotropic Material and Its Application

巴西圆盘试样广泛用于地质材料的力学性能测试。改进后的平台巴西圆盘克服了集中力产生应力集中的缺点,正交异性材料则是对各向同性材料的推广,在这样的背景下提出正交异性巴西圆盘试样的压缩位移公式。用有限元分析软件ANSYS模拟正交异性岩石的巴西圆盘试样的对径压缩实验;利用有限元分析结果对正交异性平台位移压缩公式进行精度检验,并用半经验半解析的方法,对该公式进行局部的修改,修改后的公式在岩石材料的正交异性指数的整个范围的总体评价上,误差小于6%,具有更好的计算精度。最后,描述了平台巴西圆盘位移公式的应用,通过对正交异性岩石平台巴西圆盘试样进行两个正交方向的两种加载角的对径压缩试验,记录载荷-位移曲线,可由初始直线段的斜率倒数来确定正交异性材料的各个弹性参数,包括杨氏模量、泊松比和剪切弹性模量。

Brazilian disc specimen is widely used in mechanical testing for geomaterials Modified Brazilian disc specimen overcomes the shortcoming of stress concentration caused by concentrated loading. Orthotropic material is a generalization of isotropic material. It is in this background that the displacement formula of flattened Brazilian disc for orthotropic material is proposed. Then the finite element software ANSYS is used to simulate the orthotropic flattened Brazilian disc specimen subjected to diametrical compression, the accuracy of the approximate formula of compression displacement is checked. The formula is further modified with a semi-empirical and semi-analytical approach ,and it is shown to have better accuracy than the original formula covering the whole range of orthotropic anisotropic index of rock, the error is less than 6%. Finally, the application of this displacement formula is introduced with an example, that is by recording the load-displacement plots of flattened Brazilian disc specimens loaded in two orthotropic directions and in two loading angles, respectively, the elastic constants, including two Young＇ s modulus, two Poisson＇ s ratios and the shear modulus, of an orthotropic material can be determined by the inverse slope of the straight line of the plots.