基于纤维解离高应变率加载对木材动力学特性影响分析

The Influence of High Strain Rate Loading on Wood Dynamic Characteristics Based on Fiber Dissociation

为解决纤维解离应变率对木材动力学特性的影响问题,以环孔材水曲柳和散孔材桦木为试材,应变率为0.001、400、700、1000 s^(-1),含水率为全饱和,加载方向为径向、弦向和轴向,测试2种试材的动力学特性,分析应变率对木材动力学特性的影响。研究结果表明,应变率和试材的解离程度呈正相关关系;环孔材水曲柳解离后呈细长状,散孔材桦木解离后呈短粗状;环孔材水曲柳弦向最易解离,散孔材桦木径向最易解离;高应变率加载时,环孔材水曲柳和散孔材桦木的应力-应变曲线由屈服点应变分为弹性阶段和屈服后弱线性强化阶段,环孔材水曲柳内部结构的不均匀性大于散孔材桦木;2种试材的抗压强度均随应变率的增大而增大。研究结果发现环孔材水曲柳和散孔材桦木的动力学特性均具有较强的应变率敏感性,环孔材水曲柳和散孔材桦木均是应变率敏感材料。

In order to solve the problem of the influence of fiber dissociation strain rate on the dynamic properties of wood,the ring-porous Fraxinus mandshurica and diffuse-porous birch were used as test materials,with the strain rates of 0.001,400,700,and 1000 s^(-1),under fully saturated conditions and with loading directions of radial,tangential,and axial directions.The dynamic mechanical properties of the two test materials were tested,and the effect of strain rate on the dynamic characteristics of wood was analyzed.The research results showed that there was a positive correlation between strain rate and wood dissociation degree.After dissociation,Fraxinus mandshurica of ring-porous wood appeared slender while birch of diffuse-porous wood appeared short and thick.Radial direction in Fraxinus mandshurica of ring-porous wood was most easily dissociated,while tangential direction in birch of diffuse-porous wood was most susceptible.Under high strain rate loading,both Fraxinus mandshurica of ring-porous and birch of diffuse-porous woods'stress-strain curves were divided into the elastic stage and the stage of weak linear strengthening after yielding,with the non-uniformity of internal structure greater in Fraxinus mandshurica of ring-porous wood than in birch of diffuse-porous wood.The compressive strength of the two specimens increased with the increase of strain rate.The results found that the dynamic properties of Fraxinus mandshurica of ring-porous wood and birch of diffuse-porous wood had strong strain rate sensitivity,and they were both strain rate sensitive materials.