Studies in Fracture - and Materials-Mechanics

本研究旨在研究微力学与陶瓷增韧机理之间的关系。在复合材料、层状电子器件和保护涂层等方面，已经尝试了许多技术来改善不同材料之间的结合。研究将对沿界面断裂的许多方面进行研究，包括控制脆性粘附层韧性的参数，组合模式加载对剥离的作用，以及粘附层内偏转裂纹轨迹的粘结增韧。将开展微裂纹和裂纹桥接这两种基本机制的理论工作，这两种机制原则上可以通过微结构加工来操纵，以提高多晶陶瓷的韧性。这项工作的目的是量化机制，以便可靠的韧性预测可以基于微观结构表征。本文将对三轴应力作用下塑性变形固体中的空化现象进行基础研究。将寻求发生“爆炸性”空隙生长的应力水平。这些应力状态代表了材料固有的稳定性极限，在最近的实验中，在高度受限的流动下似乎已经达到了这种极限。

This research is funded to study the relationship of micro- mechanics and the toughening mechanism of ceramics. Many techniques have been tried to improve bonding between dissimilar materials with applications to composite materials, layered electronic devices, and protective coatings. Research will be conducted to study a number of aspects of fracture along interfaces including the parameters controlling toughness of a brittle adherent layer, the role of combined mode loading on debonding, and bond toughening by deflected crack trajectories within an adhesive layer. Theoretical work will be carried out on micro-cracking and crack- bridging, two basic mechanisms which can in principle be manipulated by micro-structural processing to improve the toughness of polycrystalline ceramics. The objective of this work is to quantify the mechanisms so that reliable toughness predictions can be made based on microstructural characterizations. A basic study of cavitation in plastically deforming solids under triaxial stressing will be conducted. Stress levels at which "explosive" void growth occurs will be sought. These stress states represent intrinsic material stability limits which appear to have been attained in recent experiments under highly constrained flow.