基于大直径霍普金森压杆数值试验的非均匀介质动态破坏过程分析

基于细观损伤力学基础而开发的动态岩石破裂过程分析系统RFPA2D代替大直径SHPB试验技术对非均匀介质的动态破坏过程和动态性能进行数值模拟，分析了加载波形和介质的非均匀性对数值试样的动态性能，如应力-时间曲线、应变-时间曲线、应力-应变曲线和应变率-时间曲线的影响。分析表明，大直径SHPB弥散效应对试验结果的影响较大，选择合适的加载波形可以减小SHPB装置中应力波的弥散效应，得到较准确的试验结果，其中三角形波加载可以有效降低大直径SHPB动态测试中的应力波弥散，是岩石等非均匀材料SHPB动态测试的较理想加载波形；在相同加载条件下，岩石的非均匀性对波的弥散效应影响不大，但非均匀岩石的试验曲线比均匀岩石的曲线在波峰后都出现较大的振荡，这主要是由于不同均质度的岩石其单元具有不同的破坏分布造成的，不是波形弥散造成的。

Numerical analysis of dynamic failure process of inhomogeneous medium based on large diameter SHPB test

Based on mesoscopic damage mechanics, dynamic numerical code RFPA2D is developed to simulate the dynamic failure process and dynamic properties of inhomogeneous medium in large diameter split Hopkinson pressure bar (SHPB); the influence of waveform loaded to incidence bar and inhomogeneous medium on test results including stress-time curve, strain-time curve, stress-strain curve and strain rate-time are analyzed. The results of numerical analysis indicate that, when the diameter of SHPB is large, the geometric dispersion effects due to radial inertia become very important; and when the appropriate waveform is loaded, the dispersion effects in wave propagation can be reduced so that the more exact results is obtained; for example, triangle wave which may reduce dispersion effects is the appropriate loading waveform in dynamic test of inhomogeneous medium such as rock by using SHPB. Moreover, the influence of inhomogeneity of medium on dispersion is not obvious; and the change of test curve of inhomogeneous medium is larger than that of homogeneous medium after wave crest; it is caused by different distributions of failure unit in inhomogeneous medium, not dispersion of wave.