基于SHPB试验的桦木压缩动力学特性  

Research on Dynamic Compression Characteristics of Birch Wood Based on SHPB Test

作　　者：许威[1] 花军[1] 张绍群[1] 陈光伟[1] 

机构地区：[1]东北林业大学机电工程学院,哈尔滨150040

出　　处：《林业科学》2015年第5期95-101,共7页Scientia Silvae Sinicae

基　　金：教育部高等学校博士学科点专项科研基金(博导类)课题(20130062110005)

摘　　要：【目的】利用木材动态压缩加载试验研究热磨机研磨解离破碎阶段木材原料受动态压缩载荷的动力学特性,并研究应变率、加载方向对木材原料动力学特性的影响,旨在深化木材原料研磨解离机制的研究,为热磨法纤维分离设备及磨片的齿形结构优化设计提供理论指导。【方法】利用Hopkinson杆试验装置对含水率为12.65%、密度为0.50 g·cm-3的桦木试件进行应变率约为400,800,1 200 s-1,加载方向为径向、弦向和轴向的动态压缩试验,获得桦木在不同应变率及方向上动态压缩加载的解离特征、动态应力-应变曲线及相应的力学特性。【结果】对比分析各组试验后试件的破坏形态发现:1)当应变率约为400 s-1时,径向、弦向和轴向加载的试件主要发生塑性变形;2)当应变率约为800 s-1时,径向加载试件被解离成几大块,并且有一些"火柴棍"状的小试件从大试件上剥离;弦向加载试件沿加载方向上产生更大的塑性变形,并且在试件上、下两端处沿加载方向产生贯穿性裂纹,试件被解离成三大块;轴向加载试件受载面边缘处的纤维大量产生压溃现象,在加载面上产生贯穿性裂纹且有片状小试件从大试件上剥离;3)当应变率约为1 200 s-1时,径向加载试件被解离成大量"火柴棍"状的小试件,并且小试件的尺寸明显小于应变率为800 s-1时;弦向加载试件沿加载方向上产生的塑性变形与应变率为800 s-1时相当,但是试件上端处被解离成许多片状的小试件,并且沿加载方向试件上产生了数条贯穿整个试件的大裂纹;轴向加载试件被解离成大量短粗状的小试件,并且小试件上带有明显的褶皱。对比分析各组试验试件的应力-应变曲线发现:1)动态压缩加载条件下桦木的应力-应变曲线可以由屈服点应变分为弹性阶段和屈服后弱线性强化阶段2部分;2)桦木沿径向加载应变率约为400,800,1 200 s-1时,其屈服强度和韧�[Objective]In the refiner grinding dissociation crushing stage,dynamic compression characteristics of wood raw materials were investigated by dynamic compression loading test. [Method]Dynamic compression experiments along radial,tangential and axial loading directions of birch wood （average moisture content and density was 12. 65% and 0. 50 g·cm^-3,respectively） were implemented by SHPB experimental device,and the strain rates were approximately 400, 800,1 200 s^-1 . The separation behavior during dynamic compression loading processes,dynamic stress-strain curves and the corresponding mechanical properties of wood were obtained in different loading directions and at different strain rates condition. [Result]The comparative analysis results of wood damage patterns indicated that：1） When the strain rate was 400 s^-1 ,plastic deformation mainly occurred in specimens,irrespective of radial,tangential or axial loading direction. 2） When the strain rate was 800 s^-1 ,radial-loading specimens were separated into several large pieces,and there were some small pieces,like“matchstick”,stripped out from the specimens. Severe plastic deformation was found along the loading direction in tangential-loading specimens. Furthermore,penetrating cracks along the top and bottom surfaces of the specimens were observed in tangential-loading specimens,which were dissociated into three large pieces. As for axial-loading specimens,crushing phenomenon and a large number of penetrating cracks occurred in loading surface,and some small pieces were stripped from the specimens. 3 ） When the strain rate was 1 200 s^-1 ,radial-loading specimens were dissociated into a large number of small“matchstick”pieces,and the size was obviously smaller than that at 800 s^-1 strain rate. As for the tangential-loading specimens,plastic deformation degree was similar to the situation when strain rate was 800 s^-1 . However,the top surfaces of the specimens were separated into several small sheet pieces,and some big cracks throughout the

关 键 词：分离式Hopkinson杆 桦木 压缩动力学特性 应变率 动态压缩屈服强度 动态压缩韧性模量 

分 类 号：S781.2[农业科学—木材科学与技术]