计及使役环境的高温陶瓷材料抗热震性能及表征方法研究

发布时间：2018-05-22 15:21

本文选题：高温陶瓷 + 抗热震性能　；参考：《重庆大学》2015年博士论文

【摘要】：高温陶瓷材料以其具有的良好化学和物理稳定性,在高温环境有氧气氛等苛刻环境条件下仍能照常使用,是高温领域最有前途的材料之一。作为热防护材料的高温陶瓷材料由于其使役环境的复杂性,整个使役历程温度变化幅度大,不同区域热环境差异较大,且作为结构的一部分受到结构其它部分的约束作用,致使其在使役历程中表现出的抗热震性能不再是单纯的材料本身的抗热震性能,而已有抗热震性能评价体系往往忽略了热环境、外界约束、热/力损伤等因素的耦合影响,因此迫切需要建立计及使役环境且可以更好揭示影响高温陶瓷材料抗热震性能机理的表征方法。本文采用理论分析、有限元模拟和实验相结合的方法,对不同使役环境下高温陶瓷材料及其结构的热冲击破坏行为及其表征方法开展了以下研究:①基于高温陶瓷材料的热物理性能参数对温度的敏感性及其服役热环境的复杂性,建立了适用于降温、升温以及主动冷却等不同热冲击服役环境的可考虑损伤及其演化等因素影响的抗热震性能热-损伤表征模型,研究了不同热冲击环境、损伤及其演化对其抗热震性能的影响,并从材料微结构设计角度提出了提高陶瓷材料抗热震性能的方法。考虑到高温陶瓷热防护材料的复杂使役环境,其抗热震性能是材料本身力学、热学性能在各种受热及其外界约束条件的综合表现,建立了可考虑外界约束以及热环境共同影响的高温陶瓷热防护材料抗热震性能理论与数值模拟模型,系统研究了外界约束、热环境等因素对材料抗热震性能的影响,进而从结构设计方面提出了可改善陶瓷热防护材料抗热震性能的措施。此外,采用实验与数值模拟相结合的方法首次研究了淬火剩余强度实验过程中试件进入冷却介质姿势对陶瓷材料热冲击行为以及表征结果的影响。②以氧化铝陶瓷材料为例,通过不同温度下的三点弯强度实验,研究了热震损伤在不同温度下对其断裂行为的影响,分析了材料强度对热震损伤敏感性随温度演化的内在机理及其对表征不同使役环境下材料抗热震性能的影响。进一步系统研究了不同损伤形式(表面裂纹、划痕等)在不同温度下对脆性材料(氧化锆(ZrO2)、钠钙玻璃)断裂行为的影响,分析了不同温度下损伤对材料破坏行为的影响规律,为更合理表征不同使役环境下材料的抗热震性能打下了基础,同时也为不同温度下含缺陷的高温陶瓷构件的可靠性评价提供了更合理途径。③基于能量法推导了含有微裂纹损伤的高温陶瓷材料温度相关性本构关系,根据材料温度相关性强度模型以及断裂能量平衡准则推导了裂纹扩展的温度相关性临界能量释放率。利用所得的本构关系、温度相关性临界能量释放率采用有限元数值模拟的方法,对Al2O3陶瓷以及ZrB2基高温陶瓷在不同初始温度下的热冲击行为进行了模拟,明确了裂纹扩展判据的温度相关性对陶瓷材料热冲击行为的评价以及数值模拟结果合理性的重要影响,且首次在数值模拟中考虑了热冲击过程中裂纹的演化与材料传热性能间的相互作用。基于Mori-Tanaka方法,针对高温陶瓷材料Si C耗尽层建立了考虑氧化、微裂纹损伤等影响的温度相关性本构模型,并采用UMAT子程序将之应用于有限元数值模拟;进一步研究了氧化损伤对高温陶瓷材料抗热冲击行为及强度的影响。
[Abstract]:High temperature ceramic materials are still one of the most promising materials in the field of high temperature because of their good chemical and physical stability. It is one of the most promising materials in the high temperature field. The regional thermal environment is different, and as part of the structure is constrained by other parts of the structure, the thermal shock resistance shown in the course of its causation is no longer the thermal shock resistance of the pure material itself, but the thermal shock resistance evaluation system often neglects the thermal environment, external constraints, thermal / force damage and other factors. As a result of coupling effect, it is urgent to establish an active environment and better reveal the mechanism of the thermal shock resistance of high temperature ceramic materials. In this paper, a combination of theoretical analysis, finite element simulation and experiment is applied to the thermal shock damage behavior and characterization of high temperature ceramic materials and their structures under different causation conditions. The following studies are carried out: (1) based on the sensitivity of thermo physical properties of high temperature ceramic materials to the temperature sensitivity and the complexity of their service thermal environment, the thermal shock resistance model of thermal shock resistance, which can consider the effects of damage and evolution, is established, which is suitable for different thermal shock environments such as cooling, heating and active cooling. The influence of different thermal shock environment, damage and its evolution on its thermal shock resistance, and the method to improve the thermal shock resistance of ceramic materials are proposed from the angle of material microstructure design. Considering the complex causation environment of the thermal protection material of high temperature ceramic, the thermal shock resistance of the material is the mechanics of the material itself and the thermal properties of the materials are in various heat and the outside world. The theory and numerical simulation model of thermal shock resistance of high temperature ceramic thermal protection materials, which can consider external constraints and the common influence of thermal environment, are established. The influence of external constraints and thermal environment on the thermal shock resistance of materials is studied systematically, and the thermal protection of ceramics can be improved from the structure design. In addition, the effect of the experimental and numerical simulation on the thermal shock behavior and characterization of the ceramic material during the quenching residual strength experiment was studied by the method of experiment and numerical simulation. (2) the experiment of three point bending strength at different temperatures was carried out with alumina ceramics as an example. The effect of thermal shock damage on its fracture behavior at different temperatures is studied. The intrinsic mechanism of the sensitivity of material strength to thermal shock damage with temperature evolution and its effect on the thermal shock resistance of materials under different causative environments are analyzed. The different damage forms (surface cracks, scratches, etc.) are further studied at different temperatures. The effect of the fracture behavior of zirconium oxide (ZrO2) and sodium calcium glass is analyzed. The effect of damage on the damage behavior of materials at different temperatures is analyzed, which lays a foundation for the more reasonable characterization of the thermal shock resistance of materials under different environmental conditions, and also provides a more suitable evaluation for the reliability evaluation of high temperature ceramic components with defects at different temperatures. Based on the energy method, the temperature dependence constitutive relation of high temperature ceramic materials with micro crack damage is derived. The temperature dependent critical energy release rate of the crack propagation is derived based on the temperature correlation strength model of the material and the fracture energy balance criterion, and the critical energy of temperature dependence is released by the constitutive relationship. The thermal shock behavior of Al2O3 ceramics and ZrB2 based high temperature ceramics at different initial temperatures was simulated by the finite element method. The evaluation of the temperature dependence of the crack propagation criterion on the thermal shock behavior of the ceramic materials and the important influence of the rationality of the numerical simulation results were made clear. The interaction between the crack evolution and the material heat transfer performance during the thermal shock process is considered. Based on the Mori-Tanaka method, a temperature correlation constitutive model is established for the Si C depletion layer of high temperature ceramic materials, which consider the effects of oxidation and micro crack damage. The UMAT subprogram is applied to the finite element numerical simulation. Further research is made. Effects of oxidative damage on thermal shock resistance and strength of high temperature ceramics.
【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ174.1

【相似文献】