Development Of Finite Element Simulation System For Vacuum Forming Of Auto Parts Based On GPU

Automobile parts are an important part of the whole vehicle.Howev er,with the diversified demands of users and the increasingly high requirements of automobile manufacturers on parts forming,the previous explicit finite element algorithm for sheet forming cannot meet the specific application scenarios such as soft mate rials and deep drawing,and defects such as penetration are easy to occur.At the same time,due to the limitations of traditional hardware equipment,the finite element calculation of large-scale problems has problems such as low efficiency and poor stabil ity,which has become a key bottleneck for automobile CAE analysis.However,in dealing with large-scale finite element problems,insufficient calculation accuracy,low calculation efficiency and poor robustness are still exposed.Shortcomings,so it is ve ry necessary and urgent to improve the calculation efficiency of finite element analysis and the calculation stability of large-scale problems.The main work of this paper is to apply GPU-based parallel computing technology to explicit finite element analy sis and calculations,and develop an efficient finite element simulation system that covers dynamic nonlinear calculations and vacuum forming calculations and supports visual operations.The specific work and results are as follows:(1)First,based on the numerical theory of sheet metal forming,and according to the GPU hardware architecture,a detailed analysis of the parallelism of each process of the sheet metal forming finite element algorithm is carried out.Then,the process of solving the node contact force,friction force,element internal force,time step size,and node physical quantity update,respectively,realized the fine-grained parallel calculation based on GPU.Finally,through the ellipsoid box model and different scale cupping models to verify the thin plate forming explicit finite element parallel calculation method proposed in this paper,the calculation results show that the sheet metal forming is uniform and the calculation process is stable;compared with the CPU serial calculation,GPU parallel computing can achieve a speedup of more than 5 times.(2)Secondly,the defensive node method is introduced into the vacuum forming finite element algorithm to efficiently calculate the sheet metal contact force.This method does not need to specify additional penalty factors or reduce the time step to ensure the stability of the calculation process.Compared with other contact force algorithms,it has great advantages.Then,the commercial LSDYNA software and the independent simulation system of this paper are used to compare and verify the same ellipsoid calculation example.The results show that when the thin plate is in the state of deep drawing and large deformation plastic deformation,the LSDYNA calculation result shows a partial penetration phenomenon.The forming condition of the thin plate calculated by the system is very stable,and the stress distribution is relatively uniform.In addition,because it is not affected by explicit iterative steps,the introduction of this method can achieve higher computational efficiency,with an absolute speedup of 2.4.(3)Then,the vacuum force is equivalent to the uniformly distributed load on the element and then dispersed to the nodes,and a complete explicit finite element calculation method for thin plate vacuum forming is proposed.Then,the cupping model was used for simulation calculation,and the influence of different vacuum negative pressure values on the sheet metal forming process was explored.The calculation results of the stamping and vacuum forming programs show that the vacuum forming calculation results have a lower stress distribution value at the bottom corner of the cupping model,and the probability of forming defects such as cracks is also lower.It shows that the explicit finite element calculation method of vacuum forming proposed in this paper has high calculation accuracy and stability.(4)Finally,the time step,the discretized node force,the update of node physical quantity and other calculation parts of the algorithm are discussed.The parallel strategy of FTTE(From Thread To Element),FTTN(From Thread To Node)and FTTD(From Thread To Degree)with one To one unit,Node and Degree of freedom of GPU Thread was adopted,respectively.Explicit fini te element parallel calculation of vacuum forming based on GPU is realized.Then,through vectorization of array pointers,vectorized memory aligned access is realized,which greatly reduces the cycle of reading and writing data.Then,based on the realization of the vacuum forming finite element serial program and parallel program,a visual operation interface of the vacuum forming finite element simulation system was develop ed.Its framework is divided into data and material module,vacuum control module,job submission module and result display The four parts of the interface greatly improve the ease of use of the system.Finally,a numerical example of cupping is used to te st the simulation system.The results show that compared with the CPU serial calculation,the GPU parallel calculation method proposed in this paper has almost zero accuracy loss and can achieve extremely high acceleration effects.The absolute speedup rat io reaches 6.5times.