Study On Numerical Simulation Methods For The Mechanical Field And Magneto-mechanical Coupling In Electromagnetic Riveting

As a new riveting process,electromagnetic riveting has the characteristics of high loading rate,high strain rate and microsecond forming.Numerical simulation has become an important research method for electromagnetic riveting.However,due to the interaction of multiple physical fields and complex dynamic large deformation process,the current numerical simulation methods mainly rely on the structural mesh to realize the electromagnetic riveting process.However,the high cost of pre-processing and calculation of the structural mesh,poor adaptability in complex models,difficult to realize automation and other problems limit the realization of the efficient numerical simulation scheme of the electromagnetic riveting process.The preprocessing and calculation of unstructured mesh are simple and suitable for complex problems,but it has the defects of poor stability and low accuracy.How to use the advantages of unstructured mesh to construct a numerical algorithm with high precision,low computational cost and high stability becomes the key to solve this kind of problem.Based on this,this paper studies electromagnetic riveting based on unstructured mesh,proposes a node-smooth finite element method for selfregulating integration points in structural fields,and proposes a coupling scheme of quasiparticle method for electromagnetic riveting applications.Specific work:Based on linear unstructured mesh,a node-smooth finite element method with selfadjusting integral points is proposed for dynamic large deformation analysis of complex problems.In the explicit dynamic large deformation analysis,the node smooth finite element method has fewer integration points,high efficiency,but poor stability.Stable node integration algorithm can effectively improve the stability by increasing the integration points,but its computing cost is also significantly increased.In this paper,combining the characteristics of the two methods,by introducing reasonable judgment indexes,the stable node integral algorithm is adopted in the high-stress and distortion-prone area of the structure to ensure the calculation accuracy and stability,and the node smooth finite element method is adopted in the low-stress area to improve the calculation efficiency,so that the advantages of the two methods can be retained.The computational efficiency and stability of the proposed method are verified by a series of examples.A magneto-mechanical coupling scheme based on particle type method is proposed.Focusing on the magnetic-force coupling problem of electromagnetic forming,after the calculation of the time step of the structure field,random sampling in the region near the workpiece is completed,and the sampled particles are taken as new nodes.Based on these nodes,interpolation and discrete equations are constructed to solve the electromagnetic field of the next time step.This method is not limited by mesh,and it is more applicable and convenient.Its practical effect has been verified by an example of electromagnetic forming.Based on the coupling scheme,a numerical simulation scheme of electromagnetic riveting process was constructed,and an electromagnetic riveting analysis system with the coupling of electromagnetic,structure-temperature field was built by code compiling.