Collaborative Research: Micromechanics-based Framework for Modeling Fracture of Weldments in Structural Steel

由钢建造的民用基础设施在很大程度上依赖于焊接来连接不同的部件(如梁和柱)。焊接节点往往是这些结构的薄弱环节，容易发生断裂，在地震等荷载作用下会导致灾难性的破坏或坍塌。预测和模拟这类断裂对这些结构的安全评估和设计是必不可少的。然而，这种类型的失效在计算机模型中模拟是具有挑战性的，因为目前的方法不能正确地表示焊接过程引起的材料性能的变化以及这些变化是如何削弱结构的。该奖项将支持基础研究，以了解焊接如何在这些连接中的非常小的尺寸上改变材料特性，然后将创建一种方法，在计算机模拟中使用这些特性来预测焊接连接的故障。这项研究的成果和软件技术将提高建筑和其他基础设施的安全性和弹性，有利于国家的社会和经济。代表人数不足的群体的参与、对具有新知识的学生的教育以及向实践者转让技术将产生广泛的影响。该奖项将为国家科学基金会在国家减少地震灾害计划(NEHRP)中的作用做出贡献。由于焊接件中形成的复杂而复杂的微结构，以及与这些微结构相互作用的陡峭的应力和应变梯度，焊接钢连接经常在极端载荷下失效。目前用于模拟焊接件的方法不能模拟这些微结构的机械性能或它们与施加载荷的相互作用。当这些连接遭受大规模屈服或超低循环疲劳断裂(通常发生在极端载荷下，如地震)时，情况尤其如此。这项研究将通过对热机械产生的样品进行实验室实验，加深对焊接组织及其力学性能的基本理解。然后，研究将通过多尺度模拟的创新框架将这些发现提升到结构尺度。这一知识和框架将被实施，以便在各种受研究人员和结构工程师欢迎的数字平台(开源和商业平台)中进行方便的集成。这一方法(包括其实施)将通过广泛的实验室测试和有限元模拟得到了解和验证，并向目标受众和用户群体广泛传播。这项研究产生的数据将存档在自然灾害工程研究基础设施(https://www.DesignSafe-ci.org).This)数据仓库中(NSF的裁决反映了国家科学基金会的法定使命，并已通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Civil infrastructure constructed from steel relies heavily on welding to connect various parts (such as beams and columns) to each other. Welded connections are often the weak points in these structures and are prone to fracture, leading to catastrophic failure or collapse under loads such as during earthquakes. Predicting and simulating such fracture are essential for safety assessment and design of these structures. However, this type of failure is challenging to simulate in computer models, because current methods cannot properly represent the changes in material properties caused by welding processes and how these changes weaken the structure. This award will support fundamental research to understand how welding changes material properties over very small dimensions in these connections, and then will create a method to use these properties within computer simulations to predict the failure of welded connections. The findings and software technology from this research will enhance the safety and resilience of buildings and other infrastructure, benefiting the nation’s society and economy. The involvement of underrepresented groups, education of students with new knowledge, and technology transfer to practitioners will result in broad impacts. This award will contribute to the National Science Foundation role in the National Earthquake Hazards Reduction Program (NEHRP). Welded steel connections often fail under extreme loads due to the complex and multiple microstructures that are formed in weldments, and the steep stress and strain gradients that interact with these microstructures. Current methods for simulating weldments cannot simulate the mechanical properties of these microstructures or their interactions with applied loads. This is especially true when these connections are subjected to large-scale yielding or Ultra Low Cycle Fatigue fracture (which occur commonly under extreme loads such as earthquakes). This research will develop fundamental understanding of weld microstructures and their mechanical properties through laboratory experiments on thermomechanically generated samples. Then, the research will upscale these findings to the structural scale through an innovative framework of multi-scale simulation. This knowledge and framework will be implemented for convenient integration within various numerical platforms (open source as well as commercial) that are popular with researchers and structural engineers. This approach (including its implementation) will be informed and validated by extensive laboratory testing and finite element simulation, and broadly disseminated to target audiences and user groups. Data generated by this research will be archived in the Natural Hazards Engineering Research Infrastructure (NHERI) Data Depot (https://www.DesignSafe-ci.org).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.