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

虽然拉伸断裂已经被理解了50多年，但剪切断裂仍然鲜为人知，尤其是在形核过程方面。微裂隙群体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裂作用的发现，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学在最细微的尺度上是不同的，但证据表明，在自组织和断层的尺度上，这两种机制的行为相似。对这两种机制的比较可以带来新的见解，其中一种机制可能被用来解决涉及另一种机制的未回答问题。特别是，微透镜中转化材料的诊断性外观使破译自组织过程的尝试比试图区分因“脆性”过程而产生的材料中的多代裂纹要简单得多。这项研究将研究在高于2.5 Gpa的压力(压力太高，无法参与“脆性”过程)下进行橄榄石尖晶石转变的镁GeO4的失效途径，以描绘从加载生成的微透镜到自组织过程到断层的微观结构演变。

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.