苜蓿振动压缩成型过程中的力链演变  

Evolution of force chain in vibration compression of alfalfa

作　　者：杜海君 雷霆 张永安[1] 武佩[1] 马彦华[1] 布库[2] Du Haijun;Lei Ting;Zhang Yong’an;Wu Pei;Ma Yanhua;Bu Ku(College of Mechanical&Electrical Engineering,Inner Mongolia Engineering Research Center for Intelligent Facilities in Prataculture and Livestock Breeding,Inner Mongolia Agricultural University,Hohhot 010018,China;Grassland Research Institute,Chinese Academy of Agricultural Sciences,Hohhot 010010,China)

机构地区：[1]内蒙古农业大学机电工程学院,内蒙古自治区草业与养殖业智能装备工程技术研究中心,呼和浩特010018 [2]中国农业科学院草原研究所,呼和浩特010010

出　　处：《农业工程学报》2022年第2期33-40,共8页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家自然科学基金项目(32060771,31860666);内蒙古自治区科技重大专项项目(2020ZD0002)。

摘　　要：为分析生物质在压缩过程中的力学行为,揭示振动压缩成型机理,基于离散元仿真分析方法对揉碎苜蓿振动压缩过程中应力传递,力链结构及演变过程进行研究。参照实际压缩成型试验,建立了揉碎苜蓿压缩系统的离散元仿真模型,利用物理试验对模型有效性进行了验证。基于建立的离散元仿真模型,进行了压缩过程中力链结构及演变的仿真分析,研究结果表明揉碎苜蓿无振动与振动压缩时力链分布及演变过程有所不同,无振动压缩轴向力链从上至下传递,强力链分布密度亦从上到下逐层递减;振动压缩在压缩初期轴向力链由下向上传递,后期则是上下同时向中间传递,压缩结束时成型块内强力链分布较为均匀。径向方向随着压缩行程的增加,强力链出现在心部周围,并且逐渐增强向外传递;在相同时刻,振动压缩时物料内产生强力链的分布密度及强度均小于无振动压缩时产生的强力链。对压缩行程末期的孔隙率研究发现,无振动压缩时上、下层物料孔隙率较小,中下层孔隙率较大,疏密两层孔隙率差值为3.65个百分点;振动压缩时模具内各层物料的孔隙率基本保持由上向下的递减趋势,疏密两层孔隙率差值为2.71个百分点,说明振动有利于均化物料的成型密度。该研究从细观尺度分析了生物质在振动压缩过程中的力学特性,可为探究振动压缩成型机理提供一种新途径。Natural forage has been widely compressed into the blocks ideal for long-term food storage in modern agriculture.The mechanical behavior of forage during compression can be directly related to the density of blocks and the compression energy consumption.In this study,a systematic investigation was made on the stress transfer,force chain structure,and evolution of crushed alfalfa in the process of vibration compression using a discrete element method(DEM),in order to clarify the mechanical behavior of forage and the mechanism of vibration compression.A DEM model of crushed alfalfa was also established to determine the stress change during compression.A physical experiment was conducted to verify the DEM model.It was found that the variation trend of compressive force after simulation was consistent with the experimental data.There was no significant difference between the simulated and experimental data at the significance level ofα=0.05.A simulation analysis was performed on the force chain structure and evolution during compression using the DEM model.The research results were as follows.The distribution and evolution of the force chain in compressed alfalfa were different in the process of compression with/without vibration.Once alfalfa was compressed without vibration,the axial force chain was transmitted from the top to the bottom,and the distribution density of the strong chain decreased layer by layer as well.The number of strong contact points was 39258 in alfalfa block.Once alfalfa was compressed by vibration,the axial force chain was transmitted from the bottom to the top in the early stage of compression,and the upper and lower ends were transmitted to the middle layer at the later stage.At the end of compression,the force chain in the block was distributed evenly,where the number of strong contact points was 38079.The more strong the contact points were,the greater the compression force was,and the more difficult the material was to be compressed.Once the crushed alfalfa was compressed whether with or

关 键 词：振动 离散元 苜蓿 力链 孔隙率 

分 类 号：S216.2[农业科学—农业机械化工程]