Stress State, Strain History and Microstructural Effects in Ductile Fracture

韧性断裂是一种普遍存在于金属和某些聚合物中的失效模式，其主要功能是承载。预测材料失效对许多工程应用至关重要，包括交通、能源和制造业。目前对韧性断裂的理解是基于微孔生长理论，该理论无法合理化在各种制造或渗透过程中观察到的失效类型，或技术上重要的轻质材料的断裂。该奖项支持基础研究，为开发或强大的模型和模拟工具提供所需的知识，这些模型和工具是在加载条件下结构材料中韧性断裂的，但还没有令人满意的解决方案。作为一个潜在的好处，研究成果将有助于在运输车辆中开发坚固坚韧轻质材料，这将最终导致更少的燃料消耗和减少的排放，对环境产生积极的影响。外联活动将通过与法国和卡塔尔实验室的互动，为本科生和研究生创造一个跨学科的国际研究环境。此外，开发的模拟软件将通过GNU许可程序提供给研究人员和工程师。PI计划将结果记录在关于该主题的专著中。材料力学界目前面临的最具挑战性的问题之一是预测先进金属材料的失效，特别是在低应力三轴度下，第三应力不变量的重要影响已经被注意到。到目前为止，社区已经通过开发经验失效标准或现有空隙增长模型的临时扩展来应对这一挑战。同时考虑了矿脉参数L和应力三轴度。目前的研究将有助于回答一些重要的问题，如：（i）什么是起源的矿脉效应？(ii)如何分配矿脉参数（L）在孔洞成核、生长和聚结中的内在影响？(iii)如何量化L对塑性失稳发生的外在（或表观）影响？答案将提供使用微观力学建模方法，是真正的断裂现象的物理在管理长度尺度。将进行模型的计算实施，并将根据现有的和新获得的实验数据对模型预测进行测试。

Ductile fracture is a ubiquitous mode of failure in metals and some polymers whose main function is load bearing. Predicting material failure is essential to many engineering applications, including those in transportation, energy and manufacturing. Current understanding of ductile fracture is based on a theory of microvoid growth which is unable to rationalize the type of failures observed in various manufacturing or penetration processes, or the fracture of technologically important, lightweight materials. This award supports fundamental research to provide needed knowledge for the development or robust models and simulation tools of ductile fracture in structural materials under loading conditions for which yet no satisfactory solution exists. As one potential benefit, the research outcomes will aid in the development of strong and tough lightweight materials in transportation vehicles, which will ultimately lead to less fuel consumption and reduced emissions with a positive impact on the environment. The outreach activities will create an interdisciplinary and international research environment for both undergraduate and graduate students through interactions with French and Qatari laboratories. In addition, the developed simulation software will be made available to researchers and engineers through a GNU licensing process. The PI plans to document the results in a monograph on the subject matter.One of the most challenging problems the mechanics of materials community presently faces is the prediction of failure in advanced metallic materials, particularly at low stress triaxiality where seemingly important effects of the third stress invariant have been noticed. So far, the community has responded to this challenge by developing empirical failure criteria or ad hoc extensions of existing void growth models. The Lode parameter (L) and the stress triaxiality both are considered. The present research will help answer important questions such as: (i) What is the origin of the Lode effect? (ii) How to apportion the intrinsic effects of the Lode parameter (L) among void nucleation, growth and coalescence? (iii) How to quantify the extrinsic (or apparent) effect of L on the occurrence of plastic instabilities? Answers will be provided using a micromechanical modeling approach that is true to the physics of the fracture phenomena at the governing length scales. A computational implementation of the model will be conducted and the model prediction will be tested against available and newly acquired experimental data.