岩石动态劈裂试验中能量变化的有限元分析

利用有限元软件ANSYS/LS-DYNA,对岩石平台巴西圆盘试件进行了SHPB动态劈裂试验的数值模拟,系统地分析了岩石试件劈裂破坏过程中的能量变化,并将本文所定义的能量参数,与学者lundberg的研究进行比较分析。结果表明:随着弹速的增大,试件的反向震塌现象加剧,但总体破坏程度却先增后减;应力波穿过试件所需的时间随着弹速增大而缩短,但透射杆增加的速度却呈减小趋势,这说明在一定范围内,冲击速度越大,试件的能量吸收率也越大;以入射杆、试件与透射杆三者构成的系统为分析对象,在6种弹速等级下,其内能均于1.15 ms左右急剧下降至最低值,据此推断1.15 ms为试件的破坏时刻t;本文中定义的试件破碎能W_b与弹速的关系和学者lundberg的研究定义的试件耗散能W_D相比,总体趋势相似,经归一化处理后更加接近,验证了该参数的有效性。

Finite Element Analysis on Energy Variation of Rock Dynamic Splitting Tests

The rock flattened Brazilian disc specimens were tested for the numerical simulation of dynamic splitting SHPB tests, using the finite element analysis software ANSYS/LS-DYNA. Based on the simulation results, the energy variation during the process of rock specimens’ splitting failure was systematically analyzed, while the energy parameter defined in this paper was compared with that from Lundberg’s researches. The simulation results show that: with the increase of projectile velocity, the reverse shock collapse phenomenon of the specimens intensifies, however the overall extent of the damage is growing up firstly then drops; The time required for the stress wave to pass through a specimen is getting shorter as the projectile velocity increases, nevertheless, the increased velocity of the transmission bar is actually showing a decreasing trend, indicating that in a certain range, the larger the impact velocity, the greater the energy absorption rate of the specimen is; Taking the system composed of the incident bar, specimen and transmission bar as an analysis object, through a range of six projectile velocity grades, the internal energy all sharply decline to the lowest value around 1.15 ms, so we infer 1.15 ms as the specimen destruction time t; The relation between the specimen broken energy (defined as W_b herein) and the projectile velocity is similar compared to the specimen dissipation energy W_D proposed in Lundberg’s researches, which is getting closer after normalization. So the effectiveness of W_b is verified.