层状陶瓷材料多晶微结构模拟与力学响应

发布时间：2018-03-05 02:09

本文选题：层状陶瓷材料　切入点：多晶微结构　出处：《西北工业大学》2016年博士论文　论文类型：学位论文

【摘要】：由于层状陶瓷复合材料具有独特的叠层结构,研究者能从宏观结构的角度对其进行层内和层间设计,从而制备综合性能优异的新型陶瓷材料。层状陶瓷材料微观多晶结构和宏观多层结构共同决定了材料的性能。然而,在目前的数值模拟研究中,大部分仅对陶瓷块材多晶微结构进行模拟,缺乏从原子尺度、多晶微结构尺度和层状结构对层状陶瓷的“结构-力学响应”关系开展数值模拟,也尚无相关计算软件。本文针对层状陶瓷基复合材料,从材料的微观多晶和宏观多层结构出发,综合采用第一性原理、蒙特卡罗方法和有限元数值计算方法,分析具有多晶微结构的层状陶瓷材料的力学响应,发展层状结构陶瓷材料参数化设计软件,为制备新型层状陶瓷基复合材料提供指导依据。主要研究内容与结果如下:(1)采用蒙特卡罗方法模拟了多晶微结构演变,并采用有限元数值方法对多晶微结构进行了力学响应分析。研究结果表明:多晶微结构的平均晶粒随着模拟时间的增大而增大,平均应力大小与平均晶粒大小符合Hall-Petch关系。(2)在单层多晶结构的基础上,采用蒙特卡罗方法模拟层状材料多晶微结构演变,并进行了有限元力学响应分析,重点研究了层数,层厚比,模量比等材料参数对层状结构材料力学响应的影响规律。研究结果表明:(a)对于三层材料,当层厚比变化时,材料硬(软)层所占比例随之变化,相应微结构模型的平均应力也发生变化。当内外层模量比大于2时,平均应力随着内层材料厚度增大而增大,当模量比小于1时,平均应力随着内层材料的厚度增大而减小。(b)对于强晶界材料,不论材料的叠层顺序是外层为硬层还是为软层,材料平均应力均随着晶粒长大而减小。对于外层为硬层时,材料的平均应力随着材料层数增多而减小,而对于外层为软层时,材料平均应力随着材料层数增多而增大。(c)对于均匀材料,平均应力与模量比呈线性增长关系;对于非均匀材料,平均应力与模量比呈非线性增长关系。(3)计算了层状结构陶瓷复合材料的残余应力及表观断裂韧性,并研究了材料层数、层厚比、烧结温度以及模量比等参数对层状陶瓷材料残余应力及表观断裂韧性的影响规律。研究结果表明:(a)当奇偶层层厚比等于1时,随着层数增多,单层越薄,受压层应力增大,受拉层应力减小。当裂纹尖端处于外层受压层时,表观断裂韧性随材料层数的增多而增大。当内外层总厚度比等于1时,拉压层的应力大小相等,且不随层数的变化而改变。当层数增多时,在压/拉层界面处的表观断裂韧性降低,但在拉/压层界面处的表观断裂韧性增大。(b)当奇偶层层厚比增大时,压应力大小降低,而拉应力大小增大。当裂纹尖端处于受压层,表观断裂韧性随层厚比的增大而增大。(c)烧结温度越高,在压/拉界面处的表观断裂韧性越大,在拉/压界面处的表观断裂韧性越小,但二者变化幅度均不大,说明烧结温度影响较小。(d)在压/拉界面处,模量比越大,表观断裂韧性越小,而在拉/压界面处,模量比越大,表观断裂韧性也越大。(4)采用面向对象程序设计,在OMTDesk软件平台下开发了交互式图形用户界面软件PCLab(Partical Cloud Laboratory),软件集成MC和FEM模块,可进行多层多晶微结构演变模拟与力学响应分析,能快速有效的研究层状材料结构的力学性能等多物理场问题。(5)提出了综合第一性原理、蒙特卡罗及有限元模拟的层状结构复合材料宏微观设计思路,并从原子尺度、多晶微结构尺度和层状结构对所设计的HfC/BN、Zr B2/BN和SiC/BN三种层状材料的“结构-力学响应”关系进行了数值模拟,研究结果表明:相同多晶结构及晶粒界面效果作用下HfC/BN的承载能力最强,ZrB2/BN次之,SiC/BN最低;不同的多晶结构或不同的晶粒效果作用下,三种材料具有相同或相近的力学响应。
[Abstract]:Because of the laminated ceramic composite laminate with unique, researchers from the perspective of macro structure layer and layer design, and preparation of new ceramic materials with excellent properties. The layered ceramic material micro structure and macroscopic polycrystalline multilayer structure determines the properties of the material. However, in the study at present, the numerical simulation of ceramics, most only polycrystalline microstructure is simulated, the lack of the atomic scale, polycrystalline structure and layered structure of micro scale layered ceramics "structure mechanical response" to carry out numerical simulation, no related calculation software. According to the layered ceramic matrix composites, starting from the micro crystal the material and the macroscopic multilayer structure, the first principle calculation method, Monte Carlo method and the finite element numerical analysis of mechanical layered ceramic materials with polycrystalline microstructure of the ring The development of software design, layered structure parameters of ceramic materials, and provide guidance for the preparation of new layered ceramic matrix composites. The main research contents and results are as follows: (1) using Monte Carlo method to simulate the microstructure evolution of the polycrystalline, and by using the finite element numerical method of polycrystalline microstructures were studied. The mechanical response analysis the results showed that the average grain size of polycrystalline microstructure increases with the increase of simulation time, the average stress and average grain size is consistent with the Hall-Petch. (2) based on the polycrystalline structure of monolayer, using the Monte Carlo method to simulate the evolution of polycrystalline layered material micro structure, and the finite element analysis of mechanical response. Focus on the layer, the layer thickness ratio, modulus ratio and material parameters effect on the mechanical response of layered materials. The results show that: (a) for the three layer material, when the thickness ratio changes, material Hard (soft) layer proportion changes, the corresponding average micro structure model of stress is changed. When the inner and outer layer modulus ratio is greater than 2, the average stress increases with the inner layer thickness increases, when the modulus ratio is less than 1, the average stress decreases with the increase in the thickness of the inner material. (B for the strong grain boundary) materials, regardless of stacking sequence of materials is as hard as the outer layer or soft material layer, the average stress decreases with grain growth. The outer layer is a layer of hard material, the average stress decreases with the material layer increased, while the outer layer is a soft material layer, the average stress with increasing number of layers increased. (c) for a homogeneous material, the average stress and modulus ratio increases linearly; for nonhomogeneous materials, the average stress and modulus ratio increased in non-linear relationship. (3) the residual layer structure ceramic composite material and stress calculation table The concept of fracture toughness, and the number of layers, layer thickness ratio, sintering temperature and the modulus ratio on the residual stress of laminated ceramic materials and effect on the law of fracture toughness. The results show that: (a) when the parity layers thickness ratio is equal to 1, with the number of layers increases, single layer thinner, compression layer the tensile force increases, the stress decreases. When the crack tip in the outer layer of compression, the apparent fracture toughness increased with the number of layers increases. When the total thickness of the inner layer and the outer layer is equal to 1, the tensile and compressive stress layer of equal size, and does not change with the number of layers change. When the layer number increase. The concept of fracture toughness decrease in compressive or tensile layer at the interface of the table, but the tension / compression interface, the apparent fracture toughness increases. When the thickness of the layer (b) parity ratio increases, the compressive stress size decreases, and the magnitude of tensile stress increases. When the crack tip in compression layer, apparent fracture with the increase of the thickness ratio of toughness Large increases (c). The higher the sintering temperature, the fracture toughness values in the push / pull at the interface of the table, in the tension / compression at the interface of the apparent fracture toughness is small, but the two changes were not significant, indicating little influence of sintering temperature. (d) in the push / pull at the interface. Modulus ratio increases, the apparent fracture toughness is small, and the tension / compression interface, modulus ratio increases, the apparent fracture toughness is also greater. (4) using object oriented programming, interactive graphical user interface software developed in the PCLab OMTDesk software platform (Partical Cloud Laboratory), MC software integration and the FEM module, can be multi crystal microstructure evolution simulation and mechanics analysis of layered material structure effective mechanical properties of multi physics problems. (5) proposed a comprehensive first principle, Monte Carlo and layered structure of composite material of macro finite element simulation of the micro design ideas, and from the original Sub scale, polycrystalline microstructure scale and layered structure to design HfC/BN, Zr B2/BN and SiC/BN three kinds of layered materials "structure - mechanical response relationship was simulated, the results show that: the same interface effect of polycrystalline structure and the grain bearing capacity of the strongest HfC/BN, the lowest SiC/BN ZrB2/BN. The polycrystalline structure; different grain size effect under the action of three kinds of materials with the same or similar mechanical response.

【学位授予单位】：西北工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ174.1

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