【作者】 雷周；

【导师】 臧孟炎；

【作者基本信息】 华南理工大学 ， 车辆工程， 2011， 博士

【摘要】 汽车玻璃是汽车不可或缺的一个重要组成部分,汽车自生产之日起,就离不开车用玻璃。大量交通事故表明,汽车玻璃破坏机理的研究对行人保护、汽车被动安全和事故再现等方面有着十分重要的理论和实际意义。汽车玻璃冲击破坏过程本质上是材料由连续体向非连续体转化的一个复杂的力学过程,实验以及单纯使用有限元法或离散元法在研究这一问题中存在着一些困难和不足。本文系统地研究了适用于汽车玻璃冲击破坏分析的有限元与离散元耦合方法。首先,提出了一种颗粒离散元和有限元分区域耦合算法。该算法将待求区域划分为独立的离散元域和有限元域进行求解,使用罚函数法计算各求解区域耦合界面处的相互作用,实现了汽车夹层玻璃等层状复合材料的分区域耦合计算。通过与纯有限元法计算结果的比较,验证了该方法在弹性范围内的计算精度。在此基础上,对汽车夹层玻璃板冲击破坏过程进行了仿真分析。结果表明,耦合算法有望对冲击力等宏观量进行预测。然后,扩展了Single/Smeared破坏模型并将其应用于三维FEM/DEM方法。Single/Smeared破坏模型是基于试验应力-应变曲线的一种数值模型。该模型假设裂纹发生的位置与有限单元边界一致,针对材料不同阶段的力学行为,分别使用不同方法计算:应变硬化阶段使用标准的本构关系计算,应变软化阶段使用单一裂纹模型计算。Single/Smeared破坏模型最初只适用于二维I型破坏问题,扩展后可用于分析三维I型和II型破坏问题。在算例验证了该模型正确性的基础上,应用三维FEM/DEM方法模拟了汽车夹层玻璃冲击破坏过程,结合试验结果初步验证了该方法的有效性。最后,针对汽车玻璃结构,系统地提出了一种适合于板壳结构冲击破坏问题的FEM/DEM方法。基于板壳结构的受力特点,构造了一种简单高效的“solid-shell”板壳单元;基于势函数的罚函数法,发展了相应的接触算法用于处理板壳单元间接触力的计算;基于Single/Smeared模型,发展了相应的破坏模型用于破坏力学分析。通过对若干典型算例的计算,验证了该方法在大位移小应变条件下的板壳结构问题的求解精度。在此基础上,模拟了普通玻璃板的冲击破坏过程,通过与相关文献所介绍的试验研究的比较,初步验证了该方法的有效性。以上方法均通过软件实现。其中,基于颗粒离散元和有限元分区域耦合算法,使用Fortran 95语言和面向对象程序编制思想,开发了通用的三维求解系统CDFP。关于FEM/DEM方法的工作均应用于通用的求解程序Y。更多还原

【Abstract】 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.更多还原