Improvement Research Of The CAE Software Based On DEM And MBK Coupling

In practical industrial and agricultural production, granular materials exit widely such assoybean grain, corn grain, wheat grain and fertilizer granules in agricultural production, soilparticles, rock particles, mud particles and concrete particles in building materials, drugparticles in medical field etc. The exiting form of these particles is often not single or rare.Instead, they exist in our real world in a very large number. They are closely related to ourproduction and living. We usually adopt the discrete element method (DEM) to study themovement patterns and to implement mechanical analysis between these particles and othermedia. By using this method, the movement form of each particle can be calculated, andfinally the movement pattern of the entire particle system can be simulated.. As for the movement forms of objects, there are translational movement, rotationalmovement and compound movement of these two. These movement forms are all simple. Butin the real world, the movements are always more complicated that cannot be represented bysimple formula. The in-depth study on those objects or mechanical components with complexmovements helps us to understand the real world better. We cannot use simple physicalmovement rules and mathematical formulas to analyze these complex movements like whatwe do to simple translation or rotation movement. Instead, we abstract these mechanicalcomponents with complex movement modes into a multi-body system. Motion equations ofthe multi-body system are established by using the theory of multi-body kinematics (MBK).By solving these equations, we can get position, velocity, acceleration and other motioninformation of the rigid body at each time step. Therefore, the movement form of each rigidbody in the system can be analyzed.The software based on DEM and MBK coupling that our research team developed haveachieved the coupling calculation of three-dimensional discrete element method and multi-body kinematics. Yet, in early research, the software only achieved the simulation calculationbased on spherical particle for the purpose of the convenience for calculation. Theconsequences of such operation lead to a low software utility value and being out of the actualagricultural production, which will make a big error in the design of agricultural machinerycomponent. In order to be more close to the actual production, the variety of particle typeneeds to be further enriched. It is necessary to achieve the coupling of the DEM and MBKmethod on the basis of non-spherical particles such as ellipsoid, multi-ball and super ball, etc..In practical agriculture, the particles’ number in the process such as screening isextremely large. When we use computer technology to simulate the agricultural productionprocess, it will take a long computation time and the computing performance will be very low if we want to calculate massive number of particles. On the premise of the software functionsthat have been implemented, improving the computing performance is the top priority in theprocess of software development. The emergence of multi-core processors provides arelatively new method to solve this problem. Using the multi-core processor hardwarecondition to realize the parallel processing of applications is the primary means to improvethe computing speed and performance. In addition, the repeated work that brought about bythe realization of the same function is very common in the process of software development.At the same time, a lot of artificial unknown errors have been caused which lead to a greatdeal of manpower and resources waste. It is also complicated for late maintenance of thesoftware. The dynamic link library technology enables resources sharing. Multipleapplications can load and use the same dynamic link library at the same time to achieveindependent development of different functional modules which reduces the workload ofsoftware development, and avoids the artificial unknown error, thus the quality of thesoftware is improved.After simulating sphere particles by using the coupling software, it is not convincing to evaluate the performance of a mechanical component only by playing the work process, so different analysis standard is still needed, such as the quantitative analysis of porosity, particle flux, screening efficiency and so on. Therefore, it is necessary to add an analysis module into thesoftware. The result of performance analysis can be used to make sure whether the mechanical component is designed reasonably, and whether the working performance is well.The basic idea and theory of DEM are firstly introduced in this paper. The MBK principleand solving process are analyzed then. The basic theory of the coupling method of DEM andMBK based on non-spherical particles is discussed in detail and a specific implementationmethod is then given. As for the proposed multi-threaded and multi-core parallel algorithmsfor MBK calculation, the working principle and configuration method of OpenMP standardlibrary is introduced. Finally the specific implementation process for MBK calculationprocess parallel algorithm is given. This paper also introduces the method of creating andloading dynamic link library, and realizes the modular design for the calculation process ofDEM coupling with MBK method, which improves the flexibility and maintainability of thesoftware. In the aspect of improvement of computing performance and computing speed, thispaper also implements the application’s transplantation from32-bit computing platform to64-bit computing platform. Finally as for the process of particle screening, the module ofscreening statistic and analysis is added to fulfill the statistical analysis of the screeningperformance of the tagged mechanical components, the contacting and colliding performancebetween mechanical components and particles, and so on. Therefore, we can evaluate thatwhether the mechanical component accord with the requirement of real agriculturalproduction.In order to verify whether the improvement research of the software is reasonable or not,this paper operates some tests and gives example verifications for all the improvement functional modules. Test results show that the improved software canrealize the function ofcoupling DEM with MBK based on non-spherical particles which are much closer to realitycompared with the sphere particles. After the modular design for multi-body kinematics aswell as the calculation process of DEM coupling with MBK based on the dynamic link librarytechnology, the software can realize the reservation function which does not affect the use andmodify of other modules in it. This ensures the calculation results and improves the flexibilityand code encapsulation of the software. On the other hand, computing speed has beenimproved significantly when the quantity of calculating particles reaching a certain number.Computing speed and CPU utilization have achieved a certain improvement compared withthe traditional serial program after the parallel processing of multi-body kinematicscalculation is implemented. Furthermore, computing precision and computing performanceare increased after the coupling software transplants from32-bit computing platform to64-bitcomputing platform, so the full use of computer resources is realized. What’s more, thescreening statistic module fulfills the statistic analysis of different statistic magnitudes.Comparing the test result with the simulation process, it comes the conclusion that the modulegenerally accords with simulation requirements, and the screening performance of themechanical component can be evaluated according to the analysis result.