【作者】 钟志文；

【导师】 孙雨果；

【作者基本信息】 哈尔滨工业大学 ， 工程力学， 2009， 硕士

【摘要】 功能梯度材料具有良好的高温热稳定性和抗腐蚀性能,特别是它能有效地缓解热应力和残余应力,从而被广泛的应用于各种高温环境。由于材料设计,生产工艺及工作环境等方面的原因,功能梯度材料会产生大量的微裂纹,而这些微裂纹的扩展及合并会进一步产生一些主裂纹从而导致材料破坏。因此,研究功能梯度材料在热机载荷作用下的断裂力学行为对于功能梯度材料的安全使用及其结构的设计,优化有着非常重要的意义。然而功能梯度材料材料的非均匀特性使得热力学行为非常复杂,通常的解析解只能依靠模型的一再简化和边界条件的理想化,对于复杂的问题还需要借助于数值方法。本文主要尝试着利用数值方法对功能梯度材料在非定常热边界条件和定常的力边界条件作用下的断裂力学性能进行分析,主要研究内容如下:(1)研究了含有半椭圆表面裂纹的氧化锆/镍铬合金功能梯度材料板条在热冲击载荷作用下的裂纹问题。分析了热边界条件,裂纹纵横比以及裂纹深度对裂纹前沿分布的应力强度因子的影响。(2)研究了含有半椭圆表面裂纹的氧化锆/镍铬合金功能梯度材料板条在热冲击载荷和机械载荷共同作用下裂纹问题分析。(3)通过对材料属性变化的研究,分析了不同的材料属性对热力相互作用下的应力强度因子的影响,对高抗热震的梯度材料设计提出了一些建议。论文的第一章介绍了功能梯度材料的发展历程及热机械力学行为的研究现状。第二章介绍了热弹性力学的数值解法和非均匀梯度材料断裂力学的基本概念。第三章研究了含有表面半椭圆裂纹的功能梯度材料板条在热冲击载荷作用下的断裂问题分析。第四章进一步研究了在热力共同作用下的梯度材料板的断裂问题分析。第五章研究了材料属性变化对应力强度因子的影响。更多还原

【Abstract】 Functionally Graded Materials (FGMs) have been widely used in the high temperature environments to alleviate the thermal stresses and residual stresses effectively because of its high temperature structural and excellent corrosion-resistant properties. Due to the reasons from the design, manufacture, service environment, etc., all kinds of cracks or defects may cause the failure of FGMs. Therefore, it is very important to investigate the fracture behaviors for the FGMs under thermo-mechanical loads for the design, optimization and application. However, it is very complex to analysis the thermo-mechanical behavior owing to its non-uniform characteristics. Until now, various types of simplified mathematic models and idealized boundary conditions for FGMs can be theoretically solved. However, the numerical methods are further effectively to investigate the fracture behavior of FGMs especially for the more complicated models or boundaries. In this paper, Finite Element Method (FEM) was used to analyse the fracture mechanical performance of FGMs subjected to mechanical loads and thermal loads. The major researches as follows:(1) The surface fracture was studied for Zirconia / Ni-Cr alloy FGMs strip with a semi-elliptical surface crack subjected to the thermal shock load, and studied the influence of crack depth, aspect ratios and thermal boundary conditions on the normalized stress-intensity factors along a crack-front.(2) Studied on the semi-elliptical surface crack problems with Zirconia / Ni-Cr alloy FGMs strip subjected to thermal shock loads and mechanical loads.(3) Changed the material properties, looking for effects with the different properties of materials under thermo-mechanical loading on the stress intensity factors, and propose some recommendations to design the FGMs with higher thermal shock resistance.The fracture problems of FGMs were reviewed in Chapter One, including the advances of theoretical analysis, numerical simulation and experimental researches. In Chapter Two, numerical solution of thermo-elasticity and the basic concepts of fracture mechanics on non-uniform gradient material were introduced. In Chapter Three , a fracture issue which contained a semi-elliptical surface cracks in functionally graded material strip under thermal shock loading was Investigated. In Chapter four, this fracture issue was discussed while FGMs subjected to thermal shock loading and mechanical loading. In Chapter five, the impact to the stress intensity factor was investigated with the variational material properties.更多还原