Design And Implementation Of Simulation Software Based On MBD And DEM Coupling

With the progress of human society,machinery is widely used in industrial production and processing,agricultural fertilization and seeding activities.And a well-designed machine usually has good working performance,which is conducive to the improvement of production efficiency and the reduction of energy and material loss,so it can produce greater economic benefits.In the field of agricultural production,the objects of mechanical operation are mostly granular materials,such as cultivated soil,corn,soybean and other crop seeds.In some realistic scenarios,mechanical operations have all come into contact with large-scale particle groups,such as tractor driving on the soft road,dump truck unloading goods(bulk materials),subsoiler loosening soil,seeder ditching in the field,etc.At this time,it is divorced from the reality to discuss the mechanical movement in isolation.It is necessary to analyze the working condition and evaluate the mechanical properties in combination with the contact effect with granular materials.The traditional design of agricultural machinery is realized through repeated manufacturing and field test of the physical prototype.The impact of the contact between the mechanical components of these complex motion modes and the granular materials cannot be accurately measured.Due to the development of computer technology and the improvement of various numerical analysis methods,the design and evaluation of modern mechanical products has changed from the original physical prototype experiments to CAE-driven design and virtual experiments.In this paper,the multi-rigid body dynamics method used to simulate the complex motion behavior of mechanical equipment and the discrete element method for discontinuous body behavior in particle dynamics are coupled.On the basis of the three-dimensional discrete element analysis software AgriCAE,which is independently developed by the research group,a coupling simulation software is designed and implemented to show the working state of mechanical components and the movement track of granular materials,providing a new reference for the analysis and optimization design of the working process of seeder,subsoiler,bulldozer,excavator,etc.Firstly,this paper studies the model and method of multi-rigid body dynamics based on Cartesian coordinates,implements the MBD solver program,adds the inverse dynamics calculation function,and dynamically loads it into the AgriCAE main program.Secondly,the realization of coupled simulation software is completed from three aspects of boundary modeling,simulation calculation and post-processing.On the basis of the original boundary modeling,the complex rigid body definition was added,several constraints were added and the corresponding constraint equations were established,and external forces and force elements required for dynamics were also added;In the simulation calculation module,when particles contact with rigid body,the contact forces are calculated by the data interaction of software DEM and MBD module,so as to refresh the movement of particles and rigid body.It provides the constraint reaction force curve analysis and data export functions for the coupled calculation results or the separate calculation results of dynamics.The other functional modules of the AgriCAE software are improved next.For STL boundary modeling,the function of saving and importing multi-body model parameters is added,which simplifies the modeling steps of using the same mechanism for many times;the contact determination algorithm of ball particle and virtual circle boundary and contact mechanics model of wet particles are improved.The function of setting display mode is provided for the dynamic demonstration of calculation results.In the screening performance analysis module,the function of static statistics area is realized,and the statistical area is drawn on the interface.Finally,the function test and example analysis of the software are carried out.Through the modeling and calculation of the multi-body system such as seeder,and the coupling simulation examples,the feasibility of the software developed in this paper and the reasonable effectiveness of the coupling method are verified,which has a certain practical application value.Other improved functions are tested to meet the design requirements and expected results.