Stress State, Strain History and Microstructural Effects in Ductile Fracture

延性断裂是金属和某些聚合物中普遍存在的一种破坏模式，其主要作用是承载。材料失效预测在许多工程应用中都是必不可少的，包括交通、能源和制造领域。目前对延性断裂的理解是基于微孔增长理论，该理论无法合理解释在各种制造或渗透过程中观察到的失效类型，或者具有重要技术价值的轻质材料的断裂。该奖项支持基础研究，以提供所需的知识，以开发或强大的模型和模拟工具的结构材料在加载条件下的延性断裂尚未有满意的解决方案。作为一个潜在的好处，研究成果将有助于开发交通工具中坚固耐用的轻质材料，最终将导致更少的燃料消耗和减少排放，并对环境产生积极影响。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和国际研究环境。此外，开发的模拟软件将通过GNU许可程序向研究人员和工程师提供。材料力学目前面临的最具挑战性的问题之一是对先进金属材料失效的预测，特别是在低应力三轴条件下，第三应力不变量似乎有重要影响。到目前为止，社区通过制定经验失败标准或对现有的空洞增长模型进行特别扩展来应对这一挑战。同时考虑了洛德参数(L)和应力三轴性。本研究将有助于回答如下重要问题：(I)Lode效应的起源是什么？(Ii)如何在空穴形核、长大和合并之间分配Lode参数(L)的本征效应？(3)如何量化L对塑性失稳发生的外在(或表观)影响？答案将使用微观机械建模方法，这是真实的物理断裂现象在管理的长度尺度。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来检验模型预测。

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.