The Simulation Of Impact Fracture Process Of Automobile Glass Based On Combined DE/FE Method Research

The laminated glass is an import part to automobile and important component of vehiclesafety system. It is directly related to the safety of the life and property of drivers, passengersand pedestrians. So, the study on impact fracture property of automobile laminated glass is oftheoretical and practical importance in the field of passive safety, pedestrian protection andtraffic accident reconstruction.At present, scholars study the impact fracture problems of the automobile glass by usingexperiment, finite element method and discrete element method. However, traditionalnumerical methods such as finite element method (FEM) and/or discrete element method(DEM), as well as experimental study are encountered sticky problems. Therefore, in thisdissertation the combined discrete/finite element methods and corresponding problems arestudied systematically to better research the impact fracture problems of automobilelaminated glass.Firstly, the centrally combined and freely combined discrete/finite element algorithmsare developed based on the method combining the DE and the corresponding node of FE. Thefreely combined method makes the meshes of the FEs break the constraint of the sizes andarrangement of the DEs. The glass layer of laminated glass can be decomposed into DE andFE calculating domain by employing the two combined method. The validity and accuracy ofthe freely combined method is tested by using two examples. Moreover, in order to achievethe combined methods, the cubic arranged DE model is presented by using principle ofenergy equivalence.After that, a contact algorithm in the context of the combined discrete/finite element(DE/FE) method is proposed. The algorithm, which is based on the node-to-surface methodused in finite element method, treats each spherical discrete element as a slave node and thesurfaces of the finite element domain as the master surfaces. The contact algorithm consists ofglobal search stage, local search state and the contact force calculating stage. The validity andaccuracy of the algorithm is tested by employing examples.Finally, in order to simulate the fracture process of laminated glass a fracture model suitable to3D spherical discrete element method (DEM) is proposed based on the concept ofthe cohesive model commonly used in finite element method (FEM). In this fracture model,there are three types of interaction between discrete elements, namely connection, cohesionand contact. When fraction criterion is met, the type of interaction between the correspondingdiscrete elements translates from connection to cohesion. The cohesive traction is obtainedfrom the opening displacement of the corresponding elements according to the cohesivemodel. The model is applied to simulate the fracture process of automobile laminated glassbeam subjected to impact. By comparing the results with those obtained by experiment ofcorresponding paper, it is found that the fracture modes agree with each other very well. Itshows that the fracture model and simulation method can be used to investigate the fracture ofautomobile laminated glass.The algorithms discussed above are implemented into the in-house developed code,named CDFP.