An Experimental Approach to Understanding Self-Organization of Mode I Defects and Nucleation of Shear Fracture

理解 I 型缺陷自组织和剪切断裂成核的实验方法

• 批准号: 9805368
• 负责人: Harry Green
• 金额: $ 11万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-09-01 至 2001-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9805368&HistoricalAwards=false
• 关键词: Experimental; Approach; Understanding; Self; Organization

9805368Green, IIAlthough tensile fracture has been well understood for more than 50 years, shear fracture remains poorly understood, especially in terms of the nucleation process. The details of the self-organization process by which a population of microcracks evolves into a localized fault, and the factors controlling fault orientation remain poorly understood. With the discovery of high-pressure phase-transformation-induced faulting, there are now two mechanisms of shear failure available for study. Although the fundamental physics of the two mechanisms is different on the finest scale, the evidence suggests that on the scale of self-organization and faulting, the mechanisms behave similarly. Comparison of these two mechanisms can lead to new insights and potentially one can be used to resolve unanswered questions involving the other. In particular, the diagnostic appearance of the transformed material in microlenses makes the attempt to decipher the self-organization process much simpler than attempting to distinguish cracks of many generations in material faulted by "brittle" processes. This study will examine the approach to failure in Mg2GeO4 undergoing the olivine« spinel transformation at pressures greater than 2.5 GPa (pressures too high for "brittle" processes to participate) to map out the microstructural evolution from loading-generated microlenses, through the self-organization process, to faulting.

9805368Green，II 尽管 50 多年来，拉伸断裂已被人们充分理解，但剪切断裂仍然知之甚少，特别是在成核过程方面。 微裂纹群演化为局部断层的自组织过程的细节以及控制断层方向的因素仍然知之甚少。 随着高压相变诱发断层的发现，现在有两种剪切破坏机制可供研究。 尽管这两种机制的基本物理原理在最精细的尺度上有所不同，但证据表明，在自组织和故障的尺度上，这些机制的行为相似。 这两种机制的比较可以带来新的见解，并且有可能使用其中一种机制来解决涉及另一种机制的未解答的问题。 特别是，微透镜中转变材料的诊断外观使得破译自组织过程的尝试比试图区分因“脆性”过程而导致的材料中许多代的裂纹要简单得多。 本研究将研究 Mg2GeO4 在大于 2.5 GPa 的压力下（对于“脆性”过程来说太高，无法参与）经历橄榄石尖晶石转变的失效方法，以绘制从加载生成的微透镜到自组织过程到断层的微观结构演化。