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.

尽管人们对拉伸断裂已经了解了50多年，但对剪切断裂的了解仍然很少，特别是在形核过程方面。微裂纹群演化为局部断层的自组织过程的细节，以及控制断层走向的因素仍然知之甚少。随着高压相变断层的发现，目前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是不同的，但有证据表明，在自组织和断层的尺度上，这两种机制的行为是相似的。比较这两种机制可以产生新的见解，其中一种机制可以用来解决涉及另一种机制的未解决问题。特别是，微透镜中转化材料的诊断外观使得破译自组织过程的尝试比试图区分由“脆性”过程损坏的材料中的许多代裂缝要简单得多。本研究将研究Mg2GeO4在大于2.5 GPa的压力下发生橄榄石-尖晶石转变的失败方法（压力太高，“脆性”过程无法参与），以绘制从加载产生的微透镜，通过自组织过程到断裂的微观结构演变。