US-Turkey Cooperative Research: Three-Dimensional Effects in the Fracture of Functionally Graded Materials

0322271 Lambros描述：该项目支持John M. Lambros，航空航天系，伊利诺伊大学，伊利诺伊州厄巴纳和Gunay Anlas博士，机械工程系，博阿齐奇大学，伊斯坦布尔，土耳其。 功能梯度材料（FGM）是具有连续空间变化的性质的材料，并且通常由金属/陶瓷组合组成，其中它们的相对体积分数连续变化。 FGM是同时提供结构支撑和热、冲击或磨损保护的候选材料。 它们的广泛使用迄今尚未实现，部分原因是缺乏对这种连续不均匀材料的力学，特别是其断裂响应的理解。 虽然一些分析和数值结果存在于文献中，这些主要是二维的，最经常涉及对称（即模式I）的条件。 实验研究少得多，但理论和实验之间的关系充其量是脆弱的，因为理论结果的有效性，通常是渐进的性质，在实验情况下是不清楚的。 重点将放在三个较少研究的方面的FGM的断裂：（一）在FGM的裂纹尖端的三维应力的发展依赖于属性梯度，（二）在实际情况下的裂纹FGM的渐近场的有效性程度，以及（iii）近尖端混合模式条件（无论是从加载或材料梯度不对称性）对上述两个的影响。 将对开裂梯度板的物理相关几何形状（三点和四点弯曲、边缘裂纹、紧凑拉伸）进行二维（2D）和三维（3D）有限元模拟。 结果将揭示通过厚度应力的尖端前的发展，并将提供一个渐近理论的有效性区域的内边界。 结果将通过与Lambros博士开发的基于聚合物的模型FGM的实验进行比较来验证。 这项研究将有助于扩展基本的理解的过程中涉及的FGM的断裂，特别是在三维应力发展，优势的渐近场和混合模式的尖端附近的条件。适用范围： Alnas博士的专长是复合材料、界面和梯度材料断裂的理论和数值分析。 大多数2D和3D模拟将在土耳其使用ABAQUS作为主要平台进行。 其他实验以及与之直接相关的一些模拟将在UIUC进行。 一个短期的规划之旅和每年至少两次会议将轮流在美国和土耳其举行。 Lambros和Anlas博士将由他们各自的研究生陪同。 博阿齐奇大学的研究生将有机会与UIUC的实验装置一起工作。 将在土耳其和UIUC开发涉及功能性性别平等的高级课程。 UIUC的美国研究人员和研究生将有机会与土耳其合作伙伴合作。

0322271 LambrosDescription: This project supports a cooperative research between Dr. John M. Lambros, Department of Aeronautics and Astronautics, University of Illinois, Urbana, Illinois and Dr. Gunay Anlas, Department of Mechanical Engineering, Bogazici University, Istanbul, Turkey. Functionally Graded Materials (FGMs) are materials possessing a continuous spatial variation of properties and typically are composed of a metal/ceramic combination in which their relative volume fractions are continuously varied. FGMs are candidate materials for simultaneously providing both structural support and thermal, impact or wear protection. Their widespread use has not materialized thus far, partially because of a lack of understanding of the mechanics of such continuously inhomogeneous materials, and in particular their fracture response. Although several analytical and numerical results exist in the literature, these are primarily two-dimensional and most often involve symmetric (i.e. mode I) conditions. Far fewer experimental studies exist, but the relation between theory and experiment is tenuous at best since the validity of theoretical results, usually asymptotic in nature, in experimental situations is not clear. Emphasis will be placed on three less studied aspects of the fracture of FGMs: (i) the development of three dimensional stresses at a crack tip in an FGM as dependent on the property gradient, (ii) the extent of validity of asymptotic fields in actual situations of cracked FGMs, and (iii) the influence of near tip mixed mode conditions (whether from loading or material gradient asymmetry) on both of the above. Two (2D) and three (3D) dimensional finite element simulations will be performed on physically relevant geometries (three and four point bend, edge crack, compact tension) of cracked graded plates. The results will shed light on the development of through thickness stresses ahead of the tip and will provide an inner boundary for the region of validity of the asymptotic theory. The results will be verified by comparison with experiments on the polymer-based model FGM that Dr. Lambros has developed. The research will help extend fundamental understanding of the processes involved in the fracture of FGMs, especially in regard to three dimensional stress development, dominance of asymptotic fields and mixed mode near tip conditions. Scope: Dr. Alnas' expertise is in the areas of theoretical and numerical analysis of fracture of composites, interfaces and graded materials. Most of the 2D and 3D simulations will be performed in Turkey using ABAQUS as the main platform. Additional experiments, as well as some simulations directly linked to them, will be performed at UIUC. A short planning trip and at least two meetings a year will be held alternately in the United States and Turkey. Drs. Lambros and Anlas will be accompanied by their respective graduate students. Bogazici University graduate students will have the opportunity to work with the experimental set-ups at UIUC. Advanced courses involving FGMs will be developed in Turkey and UIUC. American researchers and graduate students at UIUC will have a chance to cooperate with their Turkish partners.