热-力载荷下陶瓷材料体应力及裂纹演化机制研究

The ceramic materials will be subject to the effect of heat and external force under fabrication and service process. The damage of ceramic materials such as stress concentration, crack propagation and etc. caused by heat-force loading may eventually results in performance degradation, failure and rupture of materials and component. The body stress state analysis and crack evolution mechanisms in the ceramic materials under heat-force loading have become one of the urgent problems to be solved in the research and development of nuclear ceramic materials. At present, there is no nondestructive and non-contact measurement method for body stress and micro crack measurement for ceramic material under heat-force loading, which is a key issue in the research of ceramic characterization. This project proposes to establish the body stress characterization method for ceramic materials, based on the in-situ observation method of crack propagation and DIC measurement of total field strain/stress, which is combined finite element method. The method will be applied to measure the body stress and evolution of crack propagation for lithium hydride and magnesium oxide under heat-force loading. Effect of temperature and loading on stress state evolution and initiation and propagation rate of crack will be analyzed. Performance and lifetime under different temperature loading will be also explored. All results will be contributed to provide experiment basis and theoretical guideline to the fabrication and service of nuclear ceramic materials.

陶瓷材料生产和服役中难以避免会受到热和外力作共同作用而产生应力集中和裂纹萌生/扩展等损伤，最终使得材料及部件性能下降、失效和破裂，热-力载荷下材料体应力状态分析和裂纹演化机制也成为核陶瓷材料研发和服役中迫切需要解决的问题之一，适用于陶瓷材料的热-力载荷下体应力/裂纹的无损测量方法研究是陶瓷材料表征研究的前沿课题和难点。本项目拟针对氢化锂和氧化镁等粉末冶金陶瓷材料，发展可适用陶瓷材料的热-力载荷下裂纹扩展原位观察和全场应变/应力测量的DIC测量方法，结合弹性力学理论和有限元数值模拟，建立陶瓷材料热-力载荷下体应力表征方法以研究体应力及裂纹的演化机制，分析温度和力载荷大小/类型对陶瓷材料应力状态和裂纹萌生/扩展速率的影响，研究陶瓷材料残余应力产生机理及对裂纹萌生/扩展的影响，探索改善热-力载荷下陶瓷材料部件应力状态以减少裂纹萌生和阻止扩展的方法，为陶瓷材料研发和应用提供实验依据和理论指导。

氢化锂陶瓷材料在生产和服役中易受到热/力作用而产生内应力集中和裂纹萌生/扩展等损伤，热-力载荷下材料体应力状态分析和裂纹演化机制是陶瓷材料研发应用的前沿课题，其中迫切需要解决的难点是研发热-力载荷下陶瓷材料体应力及裂纹的无损检测及表征方法。项目研制了氢化锂陶瓷材料的高温力学实验及光学DIC测量原位实验平台，完成了氢化锂陶瓷在室温/高温下的板材拉伸断裂强度测试和三点弯曲动态疲劳测试及其全场应变DIC表征和有限元模拟验证，建立了基于DIC和有限元的氢化锂陶瓷体应力表征及裂纹原位观测方法，同步测量和分析氢化锂陶瓷在热-力载荷下的应力及裂纹的演化机理，系统研究温度（200-550℃）、加载速率（0.001-2mm/min）、力载荷（<500N）、材料样品尺寸（厚度3-12.5mm）及缺口（切口深度1mm）对氢化锂陶瓷的高温力学行为、应力分布和裂纹萌生及扩展的影响，首次获得了氢化锂陶瓷的高温拉伸/弯曲断裂强度、体应力分布及演化机理、裂纹萌生及扩展机制、动态疲劳/蠕变损伤规律的系统性和创新性成果。此外，项目研制了氢化锂陶瓷材料的X-CT原位恒载拉伸实验台，完成氢化锂陶瓷在恒力载荷下和受热后的内部缺陷的X-CT原位测量实验，探索研究并成功建立了基于DVC方法的氢化锂陶瓷体应力及三维裂纹的直接表征方法，首次获得氢化锂陶瓷的孔隙/夹杂和体应力分布的直接测量结果及恒力载荷（10-130N）和温度（<400℃）的影响。项目为氢化锂陶瓷材料的制备加工、储存、运输和服役应用提供了关键的材料强度、应力状态及失效评价等重要数据，并探索了优化氢化锂陶瓷内部应力分布以减小裂纹萌生和演化扩展的方法，为改善氢化锂陶瓷材料的内部缺陷及服役环境以提高部件强度及服役寿命提供了实验依据和理论指导。