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为了考察不同方法确定的动态载荷对测试岩石动态断裂韧度的影响,在SHPB压杆系统上动态冲击直径80 mm的大理岩圆孔裂缝平台巴西圆盘,获得了弹性压杆上的应力波形,间接计算得到3种不同的作用在圆盘端部的动态载荷。将载荷输入ANSYS动态有限元模型中,求得了相应的动态应力强度因子,并根据试验-数值分析方法确定了岩石的动态断裂韧度测试值。结果表明,在加载速率约为4.0×104MPa·m1/2/s的条件下,采用三波法确定的大理岩的平均动态断裂韧度为3.92 MPa·m1/2,采用一波法比三波法计算的结果偏低11.22%,采用二波法比三波法计算的结果偏高20.15%,3种方法得到的结果差异较大。应力波在传播过程中,通过圆盘表面和预制裂缝面发生散射,部分能量不断发生释放是造成圆盘试件两端加载载荷不相等的主要原因。三波法是3种方法中比较理想的动态载荷确定方法,但需要考察试件的动态应力平衡性。
In order to investigate the influence of dynamic load determined by different methods on the dynamic fracture toughness of rock under test, the dynamic pressure wave on the elastic pressure bar was obtained by dynamically impacting the Brazilian circular disk with a diameter of 80 mm on the SHPB pressure bar system, Indirect calculation results in three different dynamic loads acting at the disk ends. The load was input into ANSYS dynamic finite element model, and the corresponding dynamic stress intensity factor was obtained. The dynamic fracture toughness test value of rock was determined according to the test - numerical analysis method. The results show that the average dynamic fracture toughness of the marble determined by the three-wave method is 3.92 MPa · m1 / 2 at a loading rate of about 4.0 × 104 MPa · m1 / 2 / s, 11.22% lower than the result of the two wave method than the three wave method calculated 20.15% higher, the results obtained by the three methods vary greatly. Stress wave propagates through the disk surface and prefabricated crack surface scattering, part of the continuous release of energy is caused by the two ends of the disc specimen loading load is not equal to the main reason. The three wave method is an ideal dynamic load determination method among the three methods, but the dynamic stress balance of the specimen needs to be investigated.