Cracks in functionally graded materials
Cracks in functionally graded materials
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DOI：
10.1016/s0921-5093(03)00582-3
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发表时间：
2003-12
期刊：
影响因子：
6.4
通讯作者：
H. Bahr;H. Balke;T. Fett;I. Hofinger;G. Kirchhoff;D. Munz;A. Neubrand;A. Semenov;H. Weiss;Y. Y. Yang-Y.
中科院分区：
文献类型：
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作者：
H. Bahr;H. Balke;T. Fett;I. Hofinger;G. Kirchhoff;D. Munz;A. Neubrand;A. Semenov;H. Weiss;Y. Y. Yang-Y.
介绍了分析功能梯度材料，特别是具有上升型裂纹扩展阻力曲线的材料裂纹扩展行为的权函数法。此外，梯度热障涂层（TBCs）下的循环表面加热激光辐照的断裂力学的基础上建模。梯度和非梯度热障涂层的损伤均经历了垂直开裂→分层→起泡→剥落的不同阶段。这一顺序可以理解为在热循环过程中由于烧结和高温蠕变而导致的渐进收缩的效果，这增加了随后变成分层裂纹的垂直裂纹的能量释放率。考虑TBC破坏机理的有限元模拟结果与实验数据吻合较好。在四点弯曲试验中测量了由于分级而导致的界面断裂韧性的增加和由于时效而导致的界面断裂韧性的减少。在循环加热中观察到的损伤的相关性进行了讨论。它是解释以何种方式分级是能够减少损害。
The weight function method is described to analyze the crack growth behavior in functionally graded materials and in particular materials with a rising crack growth resistance curve. Further, failure of graded thermal barrier coatings (TBCs) under cyclic surface heating by laser irradiation is modeled on the basis of fracture mechanics. The damage of both graded and non-graded TBCs is found to develop in several distinct stages: vertical cracking → delamination → blistering → spalling . This sequence can be understood as an effect of progressive shrinkage due to sintering and high-temperature creep during thermal cycling, which increases the energy-release rate for vertical cracks which subsequently turn into delamination cracks. The results of finite element modeling, taking into account the TBC damage mechanisms, are compatible with experimental data. An increase of interface fracture toughness due to grading and a decrease due to ageing have been measured in a four-point bending test modified by a stiffening layer. Correlation with the damage observed in cyclic heating is discussed. It is explained in which way grading is able to reduce the damage.