The GPU Based DEM-FEM And Its Application On Travel Performance Analysis Of Off-road Tires On Granular Sand

Interactions between tires and sand have direct effects on travel performance of off-road vehicles.Therefore,it is of prime importance to investigate the interactions between the two parts,so as to improve the trafficability,dynamic property and ride performance of off-road vehicles.Up to now,the approaches used for the investigation of tire-sand interaction can be summarized as three groups,i.e.the theoretical analyses,experimental methods and numerical approaches.On the base of the previous work of our laboratory,a Graphics Processing Unit based(GPU-based)Discrete-finite element method(DEM-FEM)is developed and applied to the travel performance analysis of off-road tires on granular sand.Firstly,in view of the complicated tread patterns of the tire and the various contact types between the tires and the particles,a linear discrete and finite contact algorithm named DZCell is proposed for interactions between complicated structures and particles.The proposed DZCell algorithm includes two parts,global phase and local phase.In the global phase,potential segments rather than the nearest node for discrete elements are directly found as contact counterparts,which improves the efficiency and robustness.In the local phase,all the contact types between the particles and the tire are considered,which improves the accuracy of the algorithm.Numerical tests are performed to demonstrate the effectiveness of the proposed contact algorithm.Afterwards,in view of the countless sand and timing cost,a GPU-based DEM-FEM is proposed by using the FORTRAN 90/95 programming language and the CUDA FORTRAN programming model.Most of the computing is performed parallelly on the GPU,which improves the computational efficiency.On the base of these methods,a paralleled simulation system is achieved for the travel performance analysis of pneumatic tire on granular sand,and an explicit GPU-based DEM-FEM solver(coded in double precision),which is named as PDFP-OVS,is developed.The PDFP-OVS includes the discrete element method,the finite element method,the combined discrete and finite element method and the PID loading method.All of these methods can be performed on the CPU or the CPU/GPU system.Finally,a three dimensional discrete-finite element model of the pneumatic tire and granular sand is established,where the spherical discrete element is used for the sand,the linear hexahedral element is used for the tire and the discrete and finite contact algorithm is applied for the interactions between the tire and the sand.Then the travel performance of the tire on granular sand is investigated by using the PDFP-OVS and travel parameters under different slip conditions such as the normal force,the gross tractive effort,the drawbar pull and the sinkage are recorded.The simulation results are found to be in good agreement with the experiment results and the parallel computing is found to be more efficient than the CPU computing,which validates the capacity of the GPU-based simulation system in the travel performance analysis of the tire on granular sand.