Study On Physical And Mechanical Properties And Microscopic Mechanism Of Soybean Granules Based On Discrete Element Method

The study of the physical and mechanical properties of grain pellets is of great significance for the construction of silos and the improvement and research and development of food processing machinery.In this paper,soybean was used as the research object,and the indoor direct shear test was carried out to calibrate the relevant mechanical parameters.The particle flow discrete unit software PFC2 D was used to establish a large direct shear test numerical model,based on the particle motion state and the force chain network distribution during the shearing process.The principal stress direction,etc.,analyze the macrophysical and mechanical properties of soybean and the mesoscopic deformation mechanism,in order to reveal the general rule of soybean shear strength change.The main research results are as follows:(1)Using the improved grain-specific direct shear instrument,the maximum vertical stress of the soybean grain pile at a depth of 30 m is calculated by the Janssen formula to be about 200 kPa,and the vertical loads of 50 kPa,100 kPa,150 kPa,and 200 kPa are selected.Soybean was subjected to direct shear test,and the stress-strain relationship,shear strength index,internal friction angle and volume deformation of the sample soybean were measured.According to the test results,it can be concluded that the deformation of the sample can be roughly divided into three stages: compaction(shearing)-local shear(dilatation)-shear failure(the sample volume no longer changes or decreases);(2)A simplified numerical model of soybean direct shear test was established,and the most suitable mesoscopic parameters were selected for calculation and analysis.The results show that the numerical analysis results are consistent with the indoor physical test results,and the feasibility of the discrete element program to simulate soybean direct shear test is verified.During the shearing process,the maximum principal stress direction inside the specimen is deflected,and the deflection angle is consistent with the deflection angle of the force chain network,which is about 30°;the shear deformation is mainly concentrated in a strip-shaped region in the middle of the specimen,and the width is(12-15)between d50;(3)The shear rate,wall material and sample moisture content were single variables,and other parameters were invariants.The effects of three variables on soybean mechanical parameters were studied.The direct shear test found that if the shear rate is within a certain range,It has little effect on the shear strength indexes such as cohesion and internal friction angle of soybean;the larger the friction coefficient of the wall material,the larger the internal friction angle of soybean,but the effect on the cohesion of soybean is small;the greater the moisture content of soybean,the stronger its shear resistance.