Research On Numerical Simulation Of Penetrometer Based On Discrete Element

Although penetration instrument has been widely used in geotechnical engineering and geological engineering,there is a lack of systematic research on the influencing factors and mechanism of penetration instrument.At present,penetration problem is affected by the change of particle size distribution,particle packing density,penetration instrument from different angles and other factors in the actual application process,which will cause different changes of particles in the penetration process.In order to deepen the understanding of the characteristics of penetration apparatus in granular materials,the change of displacement,stress,heat and energy of penetration apparatus with the change of particle size was analyzed.In this paper,the discrete element MatDEM software is used to simulate the penetration process of glass beads with different particle sizes with different Angle penetration instruments.Firstly,based on the discrete element correlation theory,the mechanical properties of the three-dimensional compact packing model are introduced,including the deformation,young’s modulus,tensile strength,Poisson’s ratio,compressive strength and discrete element numerical simulation methods.Secondly,code was written to establish penetration instruments at different angles of 30°,45°,60° and 180°,as well as cylindrical sample containers.Then,5mm,10 mm and 20 mm block samples were generated to be cut into cylindrical samples and put into cylindrical sample containers.Then the sample material training,balance model and load setting,including automatic testing,iterative calculation,standard balance,strong cementation balance,model parameter initialization,etc.Finally,all structures are imported into the simulation box for discrete element numerical simulation.In combination with the sample analysis of different particle sizes,the interaction between particles and the variation of gravitational potential energy,elastic potential energy,kinetic energy and total energy were analyzed.The numerical results show that with the penetration depth increasing,the displacement,stress and heat of glass beads closer to the penetration instrument are greater than that of glass beads farther away from the penetration instrument.In addition,the particle displacement of 30°,45° and 60° penetrator is mainly on its two sides,showing a triangular shape.The particle displacement at the bottom of the cone tip is very small,while the stress is mainly vertically and horizontally squeezed out.The force of the glass beads above the end is small,and the force is concentrated on the cone tip,and there is an obvious force chain.However,there is a displacement at the end of the 180° penetration instrument,which presents a horizontal direction and is close to both sides of the penetration instrument,and the end position is shifted perpendicular to the penetration instrument.The main stress is vertical compression.The elastic potential energy,kinetic energy and total energy first increase and decrease,and the continuous vibration of the curve gradually tends to be stable,and finally becomes horizontal.In addition,according to the numerical simulation results of discrete element,the smaller the particle size,the finer the display results.By establishing a numerical model,this paper studies the complicated motion process of penetration instrument in particles,reveals the change rule of penetration instrument in particles from different angles,and provides a reasonable guidance for the later experimental research.