冲击压缩载荷作用下杨木的力学性能研究

通过SHPB动态压缩实验，对杨木在高应变率条件下的力学特性进行了研究。基于一维应力波理论的分析表明，尽管杨木相比于金属压杆具有较低的波阻抗，其SHPB动态压缩实验中试样两端的应力均匀性条件仍可以得到满足，而不需要进行入射波整形。通过在透射杆上使用半导体应变片，可以获得具有较高信噪比的透射波信号。结合杨木的准静态实验结果发现，其应力-应变曲线具有多孔材料的典型特征。轴向试样具有Ⅱ型吸能结构特征，失效应力和平台应力都具有应变率敏感性，其平台应力的敏感性稍弱；弦向试样具有Ⅰ型吸能结构特征，没有明显的失效强度，其平台应力具有应变率敏感性，与通常的Ⅰ型吸能结构相比存在一定差异。通过对实验数据的拟合，发现应变率对杨木失效强度的影响符合对数率。

Response of a Chinese white poplar under impact compressive load: experiment and analysis

Dynamic response of the Chinese white poplar is investigated using modified Kolsky (split Hopkinson pressure) bars. Analysis based on the elementary one-dimensional wave theory indicates that the stress uniformity in specimens tested dynamically by the SHPB method can be achieved notwithstanding the lower mechanical impedance of woods, no additional incident-pulse shaping technique is required as usually proposed for soft materials. The dynamic data are discussed and compared to those of quasi-static experiments. Results show that the Chinese white poplar has typical properties of all cellular solids. Concerning the longitudinal samples, both the initial failure strength and the plateau (crushing) stress are sensitive to the strain rate, while the degree of the plateau stress enhancement is lower compared with the former. For the tangential samples have no distinct initial failure stress, the plateau stress is regarded as the initial failure stress. It is shown that the plateau stress is very sensitive to the loading rate. The effect of strain rate on the initial failure stress of Chinese poplar wood has the logarithm law exponent.