Experimental Study On Stress Transfer Of Alfalfa During Compression Under Assistive Vibration Force Field

Alfalfa has the reputation of "King of Forage".It not only has high yield,good quality and rich nutrition,but also improves the soil and protects the environment.Compressing it into grass blocks can solve the storage and transportation difficulties caused by the looseness and disorder of alfalfa itself,and retain the nutrients of pasture to a large extent.However,the current compression molding equipments at home and abroad generally suffer from serious wear of key components and high energy consumption in the production process,which seriously hinders the popularization of molding equipment.In order to solve these problems,the research group used the principles of vibration to reduce friction and deformation resistance,and vibration compaction,and introduced the vibration force field into the alfalfa compression process to explore new ways to save energy and improve quality.In this thesis,the effects of vibration frequency and amplitude on the stress transfer of Alfalfa during compression were studied by using the method of experiment and discrete element simulation on the self-developed biomass compression experimental system.The results are as follows.(1)Vibration parameters had obvious effects on the maximum pressure and internal stress during alfalfa compression.Compared with non-vibration compression,vibration reduced the maximum pressure,and the maximum pressure changed with the vibration parameters;to achieve the same compression density,the stress in the material was small during vibration compression,which verified that vibration can reduce or homogenize the internal stress of the compressed material,thus reducing the maximum force.(2)The stress transfer test showed that the stress in the upper layer was greater than that in the lower layer,which made the alfalfa particles in the upper layer move and be compacted faster,while the compaction degree of the lower layer was less than that in the upper layer,resulting in the uneven density of Alfalfa briquettes.The stress difference between the upper and lower layers in non vibration compression was much larger than that in vibration compression,which indicated that vibration compression can improve the quality of products.(3)Different vibration parameters resulted in different stress transfer.When the alfalfa compression test was carried out under the vibration force field with frequency of15 Hz and amplitude of 1.0 mm,the internal stress transfer rate of the material was the lowest.It showed that this vibration parameter was more conducive to the stress transfer in the compression process of alfalfa,so that the energy consumption in the compression process was reduced and the product quality was improved.(4)The discrete element EDEM software was used to simulate the compression process of Alfalfa under the combined action of compression piston and vibration force field.The results showed that the vibration force field was beneficial to the stress transfer in the material.Under the action of vibration force field,the stress transfer law was that the upper and lower power sources were respectively transferred to the middle material layer.