冲击荷载下颗粒物质缓冲性能的试验研究

Experiments on shock-absorbing capacity of granular matter under impact load

颗粒物质是一种复杂的能量耗散体系.颗粒间的摩擦和黏滞作用可使冲击荷载引起的能量有效衰减,颗粒间的力链结构又可将瞬时局部冲击荷载进行空间扩展和时间延长,达到良好的缓冲效果.为研究颗粒物质对冲击荷载的缓冲性能,本文采用重力作用下球体冲击简内颗粒物质的试验系统,研究了简体底部作用力在颗粒材料、颗粒厚度等因素影响下的变化规律.试验结果表明:非规则颗粒具有更加良好的缓冲性能,粗颗粒的缓冲性能略高于细颗粒.颗粒厚度H是影响缓冲性能的重要因素,并存在一个临界厚度H_c.当H<H_c时,缓冲性能随H的增加而增强;当H>H_c时,H对缓冲效果的影响不再显著.以上研究是在同一冲击能量下进行的,而对于不同冲击能量下的H_c还需要深入开展.通过颗粒物质对冲击荷载缓冲性能的试验研究,可揭示颗粒材料的基本物理力学行为,为其在缓冲减振领域中的应用提供依据.

Granular matter is a complex energy dissipation system. The friction and the viscous contacts among particles can dissipate effectively the system energy caused by external impact load. The force chain structure in granular system can extend the local impact in spatial dimension and expand the instantaneous impact in temporal dimension, thus to obtain the effective shock-absorbing effect. To investigate the absorbing capacity of granular matter under an impact load, in the present study, we develop an experimental system, in which a rock ball impacts granular matter in a cylinder under gravity, and the impact force on the cylinder bottom is measured with three load cells. The influences of particle size, material propery, thickness of granular matter on shock-absorbing capacity are discussed. The results show that irregular particles have more shock absorbing capacity, while the large-size particles have a slightly higher shock absorbing capability than the small-size particles. The thickness of granular matter, H, is a key parameter to affect the shock-absorbing. Critical thickness, He, is obtained in the experiments. The shock-absorbing capacity of granular matter is enhanced with H increasing when H 〈 He, while H has little influence on shock-absorbing when H 〉/arc. The resutls above are obtained with constant impact energy. Critical thickness Hc should be a function of impact energy and will be determined in the next study. With the experiments on shock-absorbing capacity of granular matter, it can reveal basic mechanical behaviors of granular materials and be applied in mechanical vibration absorptions.