【作者】 张俊彦；

【导师】 张平；

【作者基本信息】 湘潭大学 ， 一般力学与力学基础， 2003， 博士

【摘要】 全文共分七章。第一章全面系统地综述了多孔材料的研究历史与现状。第二章对多孔材料的结构与力学性能进行了理论分析。第三章对多孔材料的结构与力学性能进行了实验研究。第四章建立了二维蜂窝材料的格构模型。第五章探讨了多孔材料的破坏过程。第六章通过理论分析和计算机模拟，讨论了缺陷对多孔材料力学性能的影响。第七章给出了结论与展望。 本文采用实验研究、理论分析和数值模拟相结合的方法，对多孔材料的力学性能和破坏进行了较深入的分析研究。主要研究内容和结论如下： 1．通过分析多孔材料的微观结构、变形机理，指出影响多孔材料力学性能的主要因素有孔壁材料的本征性质、孔洞的大小、形貌和相对密度。首次建立了蜂窝材料相对密度的统一公式，把Gibson、Ashby的结果作为特例包含在内。 2．研究了多孔材料代表单元各向异性性质，提出了表征胞元形状各向异性参数，建立了相应的理论模型，讨论了胞元形状各向异性对力学性能的影响，指出多数胞元通常呈各向异性，由其周期性排列构成的多孔材料宏观上也体现各向异性，只有当代表单元无序随机排列时，才在宏观上体现统计各向同性，很多形状规则的胞元只具有单轴或多轴对称性，而非各项同性。 3．把泡沫材料中的孔洞看成是一种夹杂，借助细观力学方法求出了多孔材料的等效弹模；得出相对密度对多孔材料力学性能影响的主要结果。 4．选用典型的弹塑性泡沫和典型的脆性泡沫材料进行了不同温度、不同应变率下的单轴拉压实验，进行了显微观察和在位观察。讨论了其本构关系，材料的各向异性，温度、应变率和相对密度的相依性，以及破坏形式。在本实验范围内(准静态)，变形速率对材料的力学性能没有显著影响，但应变率变化很大时(超出准静态)其影响不能忽略；在本实验范围内(20℃-330℃)，温度的变化会显著影响材料的力学性能，即泡沫材料的弹性模量、屈服极限、强度极限、断裂韧度等随之下降，理论预测与实验结果的趋势吻合较好；对力学性能影响最大的是材料的相对密度；实验同时显示，金属泡沫具有明显的各向异性，证实了第二章的理论分析。 5．将二维蜂窝材料最小代表单元抽象为多边形，将孔壁抽象为梁，定义了多孔材料的周期性拓扑网络结构，求出了代表单元的变形能，用均匀化方法求出了能量密度，更多还原

【Abstract】 This dissertation consists of six chapters. The first chapter presents a comprehensive study of the historical and current studies in cellular materials. In chapter 2 and chapter 3 the microstructures and mechanical properties of cellular materials are theoretical analysed and experimental studies respectively. The destruct process of materials are discussed in chapter 4. In chapter 5 effects of defects on mechanical properties of materials are argument by theoretical analyzing and computer simulating. Lastly, this dissertation presents the conclusion and prospects of studies in cellular materials.By combining experimental study, theoretical analysis and numerical simulation, mechanical properties and fracture damage are analyzed thoroughly. Major contents and results are followed by these:1. The microstructures and deformation mechanism of foams are studied, it is pointed out that the principal factors which affect the mechanical properties of cellular material include eigen nature of cell wall material, size and morphology of cell and relative density. For the first time, a uniform formula of the relative density of honeycomb is established, which include the results by Gibson and Ashby.2. Parameters of symptom of anisotropy of unit cell shapes are put forward, and corresponding theoretical model is established. It is pointed out that most of the unit cells are commonly anisotropic, and cellular material which is constituted by periodically arranged unit cells shows anisotropy in macroscopic, only when representative units are arranged randomly out of order inside the solid, it shows statistical isotropy in macroscopic. Many unit cells with regular shapes only shows axial symmetry or multi- axial symmetry but not isotropy. There are some error in 《Cellular solids:structure and properties》 by Gibson and Ashby.3. Considering the cells in cellular material as a kind of inclusion, the equivalent elastic modulus of cellular material is educed using micromechanics method. Major results of the relative density-dependence of mechanical properties of cellular materials are summarized, and a cellular model of honeycomb is raised.更多还原