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采用活性粉末混凝土和聚苯乙烯材料研制了具有与天然砂岩相似孔隙分布特征和物理力学性质的孔隙体模型,通过不同孔隙率模型的SHPB冲击实验和CT扫描实验观察和分析了孔隙体中应力波的传播特性以及传播过程中内部孔隙和固体介质的变化.研究表明:1)孔隙率显著影响应力波的传播特征.相同应变率时,孔隙率越大,反射波幅越大、波峰越多、透射波幅越小;孔隙率降至5%时反射波接近于单峰;应变率越高上述现象越明显;2)孔隙体的能量耗散率WJ/WI随孔隙率增加而线性增加,WJ/WI对应变率较敏感;3)应力波传播性质和能量耗散行为的差异与孔隙的演化机制有关.孔隙率低于10%时内部机制表现为固体介质破裂或形成新孔隙,应力波能量主要被消耗形成新开裂面或新孔隙,原有孔隙变形不大.此过程中应变率对改变孔隙形状的作用不明显;孔隙率高于15%时孔隙演化机制与应变率有关,低应变率时仍以固体介质开裂或形成新孔隙为主,但新增开裂面或新孔隙的数量相对较少;高应变率时内部结构变化同时存在固体介质开裂和孔隙变形两种机制,其中孔隙变形占较大比例,应力波能量大部分被消耗于孔隙变形,表明只有在高孔隙率和高应变率条件下内部孔隙才会发生明显的变形.孔隙离心率e可以较好地刻画应力波作用下孔隙的变形.
The pore model with similar pore distribution and physical and mechanical properties as natural sandstone was developed by using reactive powder concrete and polystyrene. The SHPB impact experiment and CT scanning experiment with different porosity model were used to observe and analyze the stress wave The propagation characteristics of the porous media and the changes of the internal porous media and the solid media in the process of propagation.The results show that: 1) the porosity significantly affects the propagation characteristics of the stress wave.When the same strain rate, the larger the porosity, the larger the reflection amplitude, the more peaks, The smaller the amplitude is, the smaller the amplitude is, the smaller the amplitude is. When the porosity decreases to 5%, the reflected wave is close to the single peak. The higher the strain rate, the more obvious the above phenomenon. 2) The energy dissipation rate WJ / WI increases linearly with porosity, Which is sensitive to strain rate.3) The difference between the propagation properties of stress waves and the energy dissipation behavior is related to the evolution mechanism of pores.If the porosity is less than 10%, the internal mechanism appears as the rupture of solid medium or the formation of new pores, and the energy of stress waves is mainly Consumption of the formation of a new crack surface or new pores, the original pore deformation is not large in this process, the rate of change on the pore shape of the role of strain is not obvious; porosity higher than 15% of the pore evolution mechanism and should However, the number of newly-added cracking planes or new pores is relatively small. In the case of high strain rates, there are both solid-state medium cracking and pore deformation. , The pore deformation accounts for a large proportion, and most of the stress wave energy is consumed in the pore deformation, which shows that the internal pore can deform obviously only under the conditions of high porosity and high strain rate. The porosity eccentricity e can be better Describe the deformation of pore under the effect of stress wave.