Study On Stress Transfer Law Of Alfalfa Straw During Vibration Compression Based On Discrete Element Method

Due to rich nutritional value,Alfalfa is a kind of forage that livestock like to eat.In particular,the compressed Alfalfa block feed can not only increase the density,facilitate the storage and transportation,but also greatly improve the palatability of livestock and increase the intake.Therefore,Alfalfa block feed has a broad market prospect.In the process of compression,the friction between the crushed alfalfa straw and the deformation of the material make the stress distribution in the compressed material different along the compression direction,which will affect the microstructure,compression energy consumption and the quality of the block.In order to study the stress transfer law of Alfalfa straw in the compression process under vibration force field,the discrete element method is used to simulate the compression process.The specific research contents and results are as follows:1.Six groups of physical tests were designed,and the contact parameters between Alfalfa straw,Alfalfa straw and die were obtained by Friction coefficient tester and High-speed camera.The test results were:the collision recovery coefficient,static friction coefficient and rolling friction coefficient of Alfalfa straw and Alfalfa straw surface were 0.110,0.457 and 0.218 respectively;the collision recovery coefficient and static friction coefficient of Alfalfa straw and die surface were 0.163,0.598 and 0.240 respectively.2.The physical accumulation angle experiment of crushed Alfalfa straw was designed.The average accumulation angle was 38.88 ° by using the repose analyzer and image processing function of origin 2018 software.3.In EDEM In 2018 software,the crushed Alfalfa straw discrete element model was established,and the simulation parameters of Alfalfa straw were calibrated through Plackett-Burman test,steepest climbing test,Box Behnken test and T test,and the optimal combination of significant parameters was obtained:the static friction coefficient of Alfalfa straw-alfalfa straw was 0.45,the rolling friction coefficient of Alfalfa straw-alfalfa straw was 0.08,and the static friction coefficient of Alfalfa straw-die was 0.54.4.The numerical simulation analysis of Alfalfa straw compression process under vibration force field was carried out.Five geometry bin were placed at the axial position of compressed material from top to bottom by using the powerful post-processing module of EDEM 2018 software,The simulation results were:when Alfalfa straw was compressed without vibration,the stress transfer between material layers was layer by layer;when Alfalfa straw was compressed with vibration,the stress transfer between material layers was gradually transferred to the longitudinal depth at the stress point;when the vibration frequency was 15Hz,the maximum forming pressure was the smallest and the transfer effect was the best.