Research On Node Integral Dynamic Adaptive Algorithm And Its Application In Dynamic Large Deformation

Metal forming technology,from primary open forging and simple stamping,has developed into a large number of new engineering branches,such as extrusion,rolling,superplastic forming,etc.,providing strong technical support for the rapid development of the industry,becoming automotive,aerospace,Weapons,agricultural machinery and electrical and electronic components and other important processing methods.Taking a general view of the present state of the art in terms of modelling and computation of metal forming processes it appears that the finite element method is the most widespread numerical methodology for the analysis of complex industrial processes.However,as actual engineering problems become more and more complex,the discrete models needed to perform numerical simulations become increasingly large.Therefore,it is urgent to develop more efficient,accurate,higher-performance,and lower-cost modern numerical analysis techniques.Based on this requirement,this paper proposes a highly efficient adaptive scheme and applies it to metal forming numerical analysis.For the problem of mesh distortion in metal forming,a local mesh remapping algorithm is proposed.The main work and conclusions of this paper are summarized as follows:(1)The AFT algorithm theory,algorithm flow and program implementation are described in detail.Based on the AFT algorithm,the complex boundary problems and large differences in inner and outer boundary dimensions are proposed,and the algorithm is improved.The improved AFT algorithm can not only successfully solve the problem that the traditional AFT algorithm can’t be divided in the some cases,but also obtains higher-quality mesh,which provides the algorithm basis for adaptive analysis and grid re-meshing in the next step.(2)Developed a self-adaptive grid encryption analysis scheme based on N-SFEM,and constructed a basic structural framework and flow chart.The algorithm is divided into two parts: based on N-SFEM adaptive control strategy and multi-grid subdivision criteria.Firstly,the adaptive control strategy calculates the strain energy density of the node to find the high-strain region accurately,and divides the grid nodes into different encryption categories.Accurately located nodes that require mesh encryption.Then,based on the node classification,the multi-grid subdivision criterion is used to adaptively mesh the model.Through several examples,the excellent control strategy in the adaptive encryption algorithm can accurately locate the high-stress region.The appropriate multi-grid subdivision criteria can achieve fast mesh encryption.The results show that the algorithm can use fewer iterations,and get more accurate results.(3)The adaptive grid encryption algorithm is applied to the analysis of metal forming large deformation algorithms.The basic equations of the dynamic large deformation problem in metal forming process considering contact are given,and the contact algorithm and contact force calculation method are briefly introduced.At the same time,in order to solve the problem of grid distortion in large deformations,an adaptive grid re-draw algorithm is proposed,in which a new node physical quantity transfer method is designed.Through a series of case studies,the accuracy,stability and practicality of the algorithm proposed in this chapter are verified.The results show that the adaptive grid remapping algorithm solves the problem of grid distortion in metal forming.The new grid has a good network.And through the transfer of physical quantities,the new grid also has a complete physical quantity.After that,adaptive mesh encryption is performed to further improve the calculation accuracy of the algorithm.