Study on the Thermal Shock Fracture Mechanism of Ceramics Based on the Dynamic Characterization of Thermal Stress and Microfracture Process

基于热应力动态表征和微断裂过程的陶瓷热震断裂机理研究

基本信息

批准号：
15360349
负责人：
WAKAYAMA Shuichi
金额：
$ 9.73万
依托单位：
TOKYO METROPOLITAN UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

Ceramic materials used at elevated temperatures are usually subjected to damage due to thermal shock fracture. One of the most popular thermal shock tests is the water quench test, in which the critical temperature difference, where samples are subjected to severe damage, is used as a measure of the thermal shock resistance. However the characterization of microfracture process under thermal shock as well as transient thermal stress field is indispensable, since thermal shock fracture is caused by the accumulation of microscopic damages such as microcrackings under thermal stress. In this project, a new experimental technique for the investigation of thermal shock fracture behavior, Disc-on-Rod test, is proposed. The temperature fields in the specimen were measured and used to calculate the 2 dimensional thermal stress field. Furthermore, microfracture process was characterized by AE measurement. In the present project, followings have been achieved.1. Experimental system of Disc-on-Rod test was significantly developed. The in-situ observation of crack initiation and propagation behavior under thermal shock was enabled by digital video camera unit. Furthermore, the 3D-analysis of thermal stress was enabled by introducing full-version FEM code (ANSYS).2. The crack propagation behavior under thermal shock was characterized dynamically. The dependence of crack stability on the length of pre-crack was understood quantitatively, which showed good agreement of theoretical prediction by Hasselman's unified theory. In addition, the crack growth behavior of toughened ceramic composites was characterized successfully.3. Non-destructive evaluation technique of microfracture process in ceramics under mechanical loading was drastically developed and applied to bioceramics. The assessment technique of long-term reliability of ceramics was developed and will be applied to thermal shock fracture.

在高温下使用的陶瓷材料通常会因热冲击断裂而受到损坏。最流行的热冲击试验之一是水淬试验，其中样品遭受严重损坏的临界温差被用作耐热冲击性的衡量标准。然而，热冲击和瞬态热应力场下的微断裂过程的表征是必不可少的，因为热冲击断裂是由热应力下微裂纹等微观损伤的积累引起的。在该项目中，提出了一种研究热冲击断裂行为的新实验技术，即圆盘棒试验。测量样本中的温度场并用于计算二维热应力场。此外，通过AE测量对微断裂过程进行了表征。本项目主要取得了以下成果： 1．圆盘棒试验系统得到显着发展。通过数码摄像机装置可以现场观察热冲击下裂纹的萌生和扩展行为。此外，通过引入完整版本的 FEM 代码 (ANSYS)，可以实现热应力的 3D 分析。2。动态表征了热冲击下的裂纹扩展行为。定量地理解了裂纹稳定性对预裂纹长度的依赖性，这与哈塞尔曼统一理论的理论预测吻合良好。此外，还成功地表征了增韧陶瓷复合材料的裂纹扩展行为。 3．机械载荷下陶瓷微断裂过程的无损评价技术得到大力发展，并应用于生物陶瓷。开发了陶瓷长期可靠性评估技术，并将应用于热冲击断裂。