Two-Phase Model of Damage, Shear Localization and Plate Boundary Formation

损伤、剪切局部化和板块边界形成的两相模型

• 批准号: 0105269
• 负责人: David Bercovici
• 金额: $ 31.04万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-01-01 至 2005-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0105269&HistoricalAwards=false
• 关键词: Two; Phase; Model; Damage; Shear

Bercovici, DavidEAR-0105269 The investigator proposes to study the process of lithospheric shear localization (focussing of deformation in solid materials due to nonlinear weakening mechanisms) and plate boundary formation through his newly developed two-phase damage theory. The theory states that a damaged material (i.e., with microcracks and voids) is, in its simplest form, a two phase material (a matrix phase representing solid host, and a fluid phase representing void-filling material such as water or air). It also states that the energy going into making microcracks is the surface energy of the crack wall, which in the two phase model is the surface energy of the interface between phases. Preliminary results show sharp localized weak zones under intense shear, and distributed damage with extreme shear (suggestive of processes such as crack-branching instabilities). The theory, however, is still in a very basic form and has only been tested for simple one-dimensional geometries. Thus, the proposed project entails further development and testing to 1) apply it to more mantle/lithosphere-relevant geometries and conditions; and 2) include further pertinent physics. The model will be applied to cases of uniaxial compression; compressive folding and tensile necking; gravity-driven flows (as in slope and continent stability); source-sink driven flows (to examine the excitation of toroidal motion from purely poloidal flow); and convectively driven motion. The new physics to be studied and incorporated includes healing and annealing processes; inter-phase reactions (e.g., hydration); anisotropy (to account for pore/microcrack alignment); thermomechanical effects (e.g., fluid thermal expansion which affects pore pressure, thermoviscous behavior of matrix material, and temperature sensitivity of interface surface tension); and partitioning of deformational work between irreversible dissipative heating and semi-reversible storage as interface surface energy. This project will further our understanding of the fundamental processes of lithospheric and other shear localization mechanisms, as well as the origin of tectonic plates and plate boundaries.

Bercovici, DavidEAR-0105269 研究人员建议通过他新开发的两相损伤理论来研究岩石圈剪切局部化（由于非线性弱化机制导致固体材料变形集中）和板块边界形成的过程。该理论指出，受损材料（即具有微裂纹和空隙）最简单的形式是两相材料（基体相代表固体主体，流体相代表填充空隙的材料，例如水或空气）。它还指出，产生微裂纹的能量是裂纹壁的表面能，在两相模型中是相间界面的表面能。初步结果显示，在强剪切作用下会出现明显的局部薄弱区，并且在极端剪切作用下会出现分布式损伤（暗示裂纹分支不稳定等过程）。然而，该理论仍处于非常基本的形式，并且仅针对简单的一维几何进行了测试。因此，拟议的项目需要进一步的开发和测试，以：1）将其应用于更多与地幔/岩石圈相关的几何形状和条件； 2) 包括进一步相关的物理学。该模型将应用于单轴压缩的情况；压缩折叠和拉伸缩颈；重力驱动的流动（如斜坡和大陆稳定性）；源汇驱动流（用于检查纯极向流对环形运动的激励）；和对流驱动的运动。需要研究和整合的新物理学包括愈合和退火过程；相间反应（例如水合）；各向异性（考虑孔隙/微裂纹排列）；热机械效应（例如影响孔隙压力的流体热膨胀、基体材料的热粘性行为以及界面表面张力的温度敏感性）；不可逆耗散加热和半可逆存储之间的变形功作为界面表面能的分配。该项目将进一步了解岩石圈和其他剪切定位机制的基本过程，以及构造板块和板块边界的起源。