加载速率对岩石动态断裂韧度影响的实验研究

Experimental research on effect of loading rate for dynamic fracture toughness of rock

为了获得岩石在高加载速率作用下的动态断裂韧度值并分析加载速率的影响,由分离式霍普金森压杆入射杆杆端附加劈尖及其基座对边切槽圆盘试样施加动态劈裂载荷。把应变片粘贴在裂纹尖端附近获得裂纹扩展时间;将劈裂载荷时间历程及裂纹扩展时间输入有限元计算模型,获得试样的起裂动态断裂韧度值。结果表明,在加载速率18.85×104MPa.m1/2s-1以下,大理岩的动态断裂韧度值随着加载速率的增大而上升,但上升趋势逐渐减弱。断裂韧度数值在高加载速率下呈现出明显的离散性。

In order to obtain dynamic fracture toughness of rock under high loading rates and to analyze the rate effect, an experimental procedure using edge-notched disc specimen was presented. Split Hopkinson Pressure Bar （SHPB） with a wedge and its holder appended to the end of the incident bar was used to exert dynamic split force at the edge notch of the specimen. The strain gauges were attached near the tip of the notch in order to detect the time of crack initiation; the splitting force history and the time of crack initiation were put into the finite element model to obtain the dynamic fracture toughness at crack initiation. The experimental results indicated that up to loading rate of 18.85×10^4MPa·m^1/2s^-1, the dynamic fracture toughness of marble increased remarkably with the raise of its loading rate, but the increasing trend gradually reduced. There was obvious scattering for the test results of dynamic fracture toughness under high loading rates.