Combined Finite-Discrete Element Methods And Its Application On Impact Fracture Mechanism Of Automobile Glass

The laminated glass is an indispensable part to automobile. A great number of traffic acci-dents have shown that the study on impact fracture mechanism of automobile laminated glass isof theoretical and practical importance in the field of pedestrian protection, passive safety andtraffic accident reconstruction. Due to the fact that the dynamic damage and failure processes ofautomobile glass in essence are the materials transferring from continuum to non-continuum,traditional numerical methods such as finite element method (FEM) and/or discrete elementmethod (DEM), as well as experimental study encountered sticky problems. In this disserta-tion, the combined finite element and discrete element methods in the context of automobilelaminated glass are studied systematically.Firstly, an algorithm combining three-dimensional (3D) particle-based discrete and finiteelement methods is proposed to analyze the dynamic mechanical behavior of laminated com-posite material like laminated glass. This new approach is conducted by decomposing the cal-culation domain into a finite element (FE) calculation domain and a particle based discreteelement (DE) calculation domain; the interaction between the two sub-domains is processed byusing a penalty function method. Comparing the results calculated by the present method withthat from FEM, the precision of the present method in the elastic range is proved. After that, theimpact fracture behavior of a laminated glass plate is simulated, and the numerical experimentsshow that the combined model could be used to predict some macroscopical physical quantities,such as the impact force of impactor.Secondly, the Single/Smeared crack model based on accurate approximation of experi-mental stress-strain curves, is extended into three-dimensional in the context of the combinedfinite-discrete element method (FEM/DEM). The crack model, in which the cracks are assumedto coincide with the element edges, is conducted by calculating the mechanics behaviors of ma-terial at different stages by using different methods, say, the finite element method in a standardway through the constitutive law is implemented at the strain hardening stage while the single-crack model is used at the strain softening stage. After extension, the Single/Smeared crackmodel, which is aimed at mode I loaded cracks and 2D plane stress problems only in its originalform, could be used to simulate the situations with both mode I and mode II loaded cracks in3D. After proving the validity of the model through several simple numerical examples, the impact fracture process of automobile laminated glass is simulated by 3D FEM/DEM, whichpreliminarily verifies the validation of the present method.Finally, a combined finite-discrete element method aiming to analyze the impact fractureprocess of shell structure, is projected. The developed method includes there aspects: (1) asimple and efficient solid-shell element, (2) the corresponding algorithm for contact interactionbased on a penalty function method, and (3) the corresponding crack model based on the Sin-gle/Smeared model. The accuracy of the proposed method in the field of larger deformation andsmall strain is verified through a large number of numerical tests. And then, the impact fracturebehavior of a glass plate is simulated, and the validation of the present method is preliminarilyverified through the comparison with experiment reported in references.All the above-mentioned methods are realized through numerical codes. Based on thealgorithm combining 3D particle-based discrete and finite element methods, a general purpose3D numerical analysis code CDFP is developed by using Fortran95 programming languageand the Object Oriented Analysis (OOA) method. All the relative work on FEM/DEM, i.e. 3DSingle/Smeared model and FEM/DEM method for shell fracture and fragmentation, has beenimplemented into the general purpose Y code.