一种确定岩石类材料真实应变率效应的数值方法

摘要

It has been found recently that the dynamic compressive strength of rock-like materials testing on split Hopkinson pressure bar(SHPB) is increased with the increase of testing strain-rate. The dynamic compressive strength increasing is attributed to the combined action of material strain-rate effect,lateral inertial effect and end friction effect,and in actual SHPB tests they are coupled together and could not be separated from each other. To determine the material strain-rate effect of the rock-like materials in SHPB tests,it needed to remove the dynamic compressive strength increment caused respectively by lateral inertial effect and end friction effect. In this study, the numerical simulation method is employed to simulate the SHPB tests for rock-like materials. The effect of material strain-rate,lateral inertia and end friction is assumed to be uncoupled. In numerical SHPB tests,when the effect of material strain-rate and lateral inertia is not considered,the predicted dynamic compressive strength increment of rock-like materials induced only by the lateral inertia effect is obtained. Similarly,when the effect of material strain-rate and end friction is not considered,the dynamic compressive strength increment of rock-like materials obtained from numerical SHPB tests caused only by the end friction effect is determined. Then removing the dynamic compressive strength increment caused respectively by the lateral inertial effect and end friction effect from the dynamic compressive strength data obtained from actual SHPB tests,the material strain-rate effect of the rock-like materials in SHPB tests is determined. Finally,the assumption proposed in this study is verified by comparing the results with other research.%研究表明，分离式霍普金森压杆(SHPB)试验获得的岩石类材料动态压缩强度随着应变率的增加而提高实际上是由材料本身的应变率效应(称为真实应变率效应)、横向惯性效应和端面摩擦效应共同作用的结果，且这3种效应互相耦合。为了确定岩石类材料在SHPB试验中的真实应变率效应，需要消除横向惯性效应和端面摩擦效应作用引起的动态压缩强度增量。采用数值模拟的方法分析岩石类材料的SHPB试验，并假定材料的真实应变率效应、横向惯性效应和端面摩擦效应三者不相关。当不考虑材料的真实应变率效应和端面摩擦效应时，由数值SHPB试验获得的动态压缩强度随应变率的提高而增大便是仅由岩石试样的横向惯性效应引起的；同样的，当不考虑材料的真实应变率效应和横向惯性效应时，由数值SHPB试验获得的动态压缩强度增加便是仅由岩石试样的端面摩擦效应引起的。在此基础上，从SHPB试验中得到的动态压缩强度数据减去分别由横向惯性效应和端面摩擦效应引起的动态压缩强度增强量，即可获得岩石类材料在SHPB试验中的真实应变率效应。通过与已有研究结果比较验证了本文假设的有效性。