Thermal shock damage caused by ceramic material parameter and configuration changes with phase field simulation

航空航天领域的许多构件是在高温和高转速等极端环境下进行长期的服役，受到复杂的热力耦合作用。而陶瓷及陶瓷基材料具有耐高温及抗氧化等优异的性能逐渐替代金属和合金，成为新一代高温材料的首选；但是陶瓷材料脆性较大，在冷热冲击下极易产生裂纹进而导致灾难性的破坏。 陶瓷材料的热震开裂行为是多场耦合的结果，断裂失效机理是十分复杂的，因此提高陶瓷材料热震损伤数值模拟的准确性和扩展应用范围具有重要的研究意义。本文通过水淬实验和相场理论下的数值模拟研究了陶瓷材料不同参数和不同构型下的热震损伤，分析了参数和构型改变对热震性能和裂纹扩展速度的影响。 实验上，确定了氧化锆和氧化铝陶瓷矩形板的临界热震温差并进行了380 ℃和480 ℃温差下的热震试验，对裂纹的长度和数目做了统计，其中包括了圆盘形氧化铝陶瓷的热震试验。 数值模拟上，基于相场理论建立了不同构型陶瓷材料的数值模型，利用ABAQUS进行模拟，重现了热震裂纹的扩展过程。通过临界热震温差、裂纹形貌、裂纹长度和裂纹数目的比对，验证了数值模拟的准确性并确定了本文中数值模型对于不同构型陶瓷材料的适用性。在上述基础上进行了不同材料参数（热导率、比热、密度、热膨胀系数、弹性模量和断裂韧性）的数值模拟，确定了材料参数对热震性能和裂纹扩展速度的影响，与经典的热震理论进行比较吻合较好；最后进行了双相材料热震损伤的数值模拟并对结果进行了分析。 本文完成了氧化铝和氧化锆陶瓷特定温差下的水淬实验，验证了相场理论适用于模拟出氧化铝之外其他陶瓷材料的热震损伤，并且证明了相场理论也适用于不同材料参数对热震裂纹扩展的影响，极大地扩展了相场理论的应用范围。</p

Effect of material parameters on thermal shock crack of ceramics calculated by phase-field method

Based on alumina ceramics, we employ the phase-field method to study the effects of thermal conductivity, specific heat, density, thermal expansion coefficient, Young's modulus, and fracture toughness on thermal shock cracks. The results show that increasing thermal conductivity and fracture toughness will reduce thermal shock damage. That is, the long crack length becomes shorter, or the crack density becomes smaller. However, increasing the thermal expansion coefficient and Young's modulus will increase thermal shock damage. It is consistent with the previous thermal shock theory. The effect of material parameters on crack propagation speed was also considered. In addition, we carried out a thermal shock test of the zirconia. The results of the phase-field calculation are the same as the thermal shock results of the zirconia. This paper verifies that the phase-field method is suitable for simulating thermal shock cracks in other ceramics

Measurement of ceramics cracking during water quenching by digital image correlation

Measuring the thermal shock crack growth process is crucial for revealing ceramic materials and structures' thermal shock failure mechanisms and evaluating their reliability. We used a self made water quenching system to conduct thermal shock tests on alumina and zirconia ceramics. The thermal shock process was recorded by high speed digital image correlation (DIC) during the test. The process of thermal shock crack initiation and propagation in two kinds of ceramics was determined by analyzing the speckle image change on the sample's surface. It is found that the crack growth rate of alumina is faster than that of zirconia, which is caused by different material parameters. This paper presents an in situ measurement method for the initiation and prop agation of thermal shock cracking in ceramic materials. It can provide a measurement method to identify and predict the thermal shock damage of ceramic components