Improvement On The Solver Of The Software AgriDEM Based On 3D DEM

China is a large grain production country,where 600 million tons of grains are produced and hundreds of billions of tons of soil are plowed every year.Therefore,the improvement of the working performance of related mechanical parts can bring huge economic and social benefits.In the digital design of agricultural machinery,the discrete element method can be used for the computer simulation of the working process of agricultural machinery in terms of the physical prototype modelling.This not only provides good data support for developers to optimize the design,but also shortens the development cycle of mechanical manufacture.As a result,the discrete element method is widely used in the simulation of agricultural production.However,the particle generation takes up a lot of simulation time because of the large magnitude of the crop particles in the simulation process.In addition,as the large amount of crop particles in the real world and the diversity of the particles' material properties,many kinds of particles need to be modelled in the simulation process,and the difference in particle property among different kinds of particles needs to be considered in the calculation of contact forces between particles.This increases the difficulty and time in the particle simulations.On the basis of the above issues,by the thorough analysis of the AgriDEM1.0,our research team developed previously,its solver is redesigned and implemented by means of the generation of multi-particle model,the proximity search of mixed particle model,and the calculation of the contact force of mixed particle model.The newly designed solver is renamed as AgriDEM2.0.Firstly,based on the original simulation software AgriDEM1.0 of our research team,the calculation part of the novel simulation software AgriDEM2.0 is redesigned and implemented using the Object-Oriented Programming.The particle modelling is improved.The spherical particle is considered as a special kind of combined spheres to be modelled.The concept of particle generation type is proposed.The general inlet and the domain-grid-based particle generation method are improved.The generation of mixed particle model is implemented.The grid-based proximity search algorithm is improved to support the neighbor search of mixed particle model.Five contact models that support multi-physical properties are designed and implemented.Based on the above work,the simulation of mixed particle model can be carried out.Secondly,the material test module is designed and implemented to perform the simulations of tensile test,compression test,shear test,and bending test.The test sample is modelled by the spherical spheres with a connection relationship.A variety of test samples can be generated by this method.The coupling calculation of bonding model with contact model is designed and implemented.For the spheres in the test samples,the bonding force between the particles with a connection relationship is calculated using the bonding model,while the contact force between the particles without a connection relationship is calculated using the contact model.The data analysis module of the material test is designed and implemented.The force-displacement diagram of mechanical parts is drawn by the data stored in the simulations.Finally,the test and analysis of the above implemented functions are carried out in this paper.The test results show that those functions implemented in this paper meet the requirements of simulation.And the improvements made in the AgriDEM2.0 make the simulations close to the actual tests.It means that the AgriDEM2.0 can be more widely applied in a variety of agricultural production simulations.Additionally,a lot of interfaces are provided in the calculation part of the AgriDEM2.0.It is the material test module that is implemented by these interfaces in this paper.For successive developers,these interfaces can help them to implement some specific functions.