霍普金森杆冲击加载煤样巴西圆盘劈裂试验研究

Dynamic split tensile test of Brazilian disc of coal with split Hopkinson pressure bar loading

为研究煤样动态拉伸变形破坏特征,利用分离式霍普金森杆冲击加载系统,对煤样进行冲击条件下巴西圆盘劈裂试验,探讨了冲击速度和煤样中层理倾角对煤样动态抗拉强度、破坏应变及应变率的影响;并通过高速相机和数字散斑图像分析方法,对样品的动态劈裂及表面应变场变化过程进行了初步分析。研究表明:冲击速度和层理倾角对煤样动态拉伸破坏特征有明显影响。冲击速度越大,煤样动态抗拉强度则越大,但其随冲击速度增加的幅度逐渐减小;样品破坏应变在冲击速度为3.5 m/s时出现最大值。在冲击速度相近的情况下,层理与加载方向夹角相垂直时,样品的破坏应变相对较大,而应变率则最小。抗拉强度随层理倾角波动变化。在层理倾角与加载方向平行或非垂直时,煤样主要表现为拉伸破坏;在层理与加载方向非平行或非垂直时,样品表现出基质的拉伸和层理的剪切破坏相伴生。

In order to study the tensile failure characterization of coal under impact loading, the split Hopkinson pres- sure bar was applied in the test of dynamic Brazilian disc split tension test of coals. The effects of impact velocity and bedding plane in the coals on the dynamic failure parameters, such as tensile strength, failure strain and strain rate, were discussed. A high speed camera and the Digital Speckle Correlation Method were used to analyze the dynamic failure process of coal samples. It is found that there are great effects of impacting speed and bedding plane of coal on the dynamic tensile failure features. With the increase of impacting speed, the dynamic tensile strength raises, but the rate of increase reduces. The failure strain reaches the maximum value as the impacting speed equal to 3.5 m/s. More- over, at the almost same impacting speed and as the bedding plane of coal vertical to the loading direction, the failure strain is almost the maximum ,but the strain rate reaches the minimum value. However, the dynamic tensile strength- fluctuates with the change of bedding plane. The split tensile failure dominate the failure process of coal as the bedding plane in coals vertical or parallel to the impact direction. In other directions of bedding plane ,the tension-shear failure model was observed.