含缺陷功能梯度材料圆柱壳的弹塑性屈曲研究

发布时间：2018-03-12 21:54

本文选题：功能梯度材料　切入点：圆柱壳　出处：《华南理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：功能梯度材料(functionally graded materials,FGM)是一种两相材料共同混合的新型复合材料。此材料一般由陶瓷和金属复合组成,在宏观尺度上各组分材料的体积含量沿材料厚度方向连续变化,因此宏观物性也呈现连续变化的特征;这在很大程度上避免或降低了传统叠层复合材料因物性不连续在界面产生的应力集中现象,因此功能梯度材料的力学性能具有力学特性上的优越性,有非常高的应用潜力。由于功能梯度材料的金属相材料在屈曲过程中往往会表现出一些韧性,因此,采用弹塑性的本构模型描述功能梯度材料,有着重要的意义。本文首先对功能梯度材料当前常用的研究模型进行了对比分析,指出了现有研究的一些不足之处,再将弹塑性本构理论,层叠复合板理论相结合,针对功能梯度材料的弹塑性本构模型提出了一个完整的架构并在ABAQUS软件中进行了UMAT定义。在UMAT模块中定义了材料的多个属性并得出了弹塑性雅克比矩阵,并验证了该做法的实用性。本文采用了上述的分析方法为基础,建立了有限元分析模型,通过计算结果的模态等进行了分析,验证了分析模型的可用性。本文还通过上述的有限元分析模型,引入关于模态的初始缺陷,对含缺陷的功能梯度材料圆柱壳进行了数值计算,探讨了缺陷、径厚比、梯度参数,计算单元等因素对计算结果的影响,阐述了缺陷与极限屈曲载荷之间的联系,揭示了各因素和屈曲荷载间的相关关系。在本文的内容的最后,利用了ABAQUS软件中的显式动力有限元方法,建立了功能梯度材料圆柱壳的动态屈曲模型,对模型进行了计算分析,并对模型的网格密度等因素影响进行了比较。研究结果表明,上述的各项参数对功能梯度材料圆柱壳的动态屈曲有重要的影响。
[Abstract]:Functionally graded material materials (FGM) is a new type of composite material, which is composed of ceramic and metal composites, and the volume content of each component varies continuously with the thickness of the material at macroscopic scale. Therefore, the macroscopic physical properties also show the characteristics of continuous variation, which to a great extent avoids or reduces the stress concentration in the interface of traditional laminated composites due to the discontinuity of physical properties. Therefore, the mechanical properties of functionally graded materials have the advantages of mechanical properties and have a high potential for application. As the metal phase materials of functionally graded materials often exhibit some toughness during buckling, It is of great significance to describe functionally graded materials with elastoplastic constitutive models. In this paper, the current research models of functionally graded materials are compared and analyzed, and some shortcomings of the existing researches are pointed out. Then the elastic-plastic constitutive theory and the laminated composite plate theory are combined. This paper presents a complete framework for the elastoplastic constitutive model of functionally graded materials and defines the UMAT in ABAQUS software. In the UMAT module, several properties of the material are defined and the elastic-plastic Jacobian matrix is obtained. The practicability of the method is verified. Based on the above analysis method, the finite element analysis model is established, and the modal of the calculated results is analyzed. Through the above finite element analysis model, the initial defects of the modal are introduced, and the defect, diameter to thickness ratio, gradient parameters of functionally graded material cylindrical shells with defects are numerically calculated. The influence of calculation elements on the calculation results is discussed. The relationship between defects and ultimate buckling loads is expounded, and the correlation between each factor and buckling load is revealed. At the end of this paper, Using explicit dynamic finite element method in ABAQUS software, the dynamic buckling model of functionally graded cylindrical shells is established. The model is calculated and analyzed, and the effects of factors such as mesh density on the model are compared. The above parameters have an important effect on the dynamic buckling of functionally graded cylindrical shells.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB34

【参考文献】