Multiaxial Distortional-Hardening Plasticity to Advance Forming Process Modeling

板材成形工艺是最灵活、最节能的制造工艺之一，约占美国国内生产总值的7%。将板材转换成有用的部件通常分多个步骤进行，零件从一个成形模具转移到下一个成形模具，逐渐获得更复杂的形状。虽然这些多步骤工艺能够制造复杂的部件，但由于所需的模具和压力机的数量，它们也增加了成本。此外，从科学的角度来看，多个步骤会导致材料的重复加载和卸载，这对于以计算高效的方式进行建模非常具有挑战性。本研究旨在创建一种适用于重复装卸的材料模型，使工艺和模具设计科学化，最大限度地减少必要步骤，减少浪费，从而提高美国制造业的竞争力。由于汽车行业是多步板材成形的主要用户之一，这项研究还将使现代难以成形的钢和铝合金能够在汽车车身中使用，从而生产出更安全、更环保的汽车。这项工作将与两所韩国大学(其工作由韩国国家研究基金会资助)合作进行，这种合作将允许获得美国没有的设备和专业知识。研究生和本科生以及教师研究经验(RET)参与者和他们的学生将受益于该项目的工业重点以及其国际维度。为了向工业提供适用于包括重复加载和卸载在内的严重应变路径变化的稳健且计算高效的材料模型，本研究将：1)创建用于板材双向拉伸/压缩的独特机器并执行多轴塑性实验，2)使用该数据集来演化最近(2011)均匀各向异性硬化(HAH)塑性模型并创建扩展HAH模型，以捕捉实验，3)进行了多步成形实验，并用扩展的HAH模型对其进行了模拟，以进一步了解其演化过程，验证其性能。这项研究将研究两类材料，先进的高强度钢和铝合金，这两种材料都适用于各种重量敏感应用，但对严重的应变路径变化有很大的不同响应。除了这里研究的具体成形过程之外，建立一个稳健的、计算高效的材料模型来描述严重的应变路径变化，有望有助于对工业中所有的多步塑性变形过程以及低周疲劳和循环塑性进行建模。

Sheet metal forming processes are among the most flexible and energy-efficient manufacturing processes, corresponding to approximately 7 percent of the US Gross Domestic Product. Transformation of the sheet into a useful component typically occurs in multiple steps, with the part transferred from one forming die to the next, progressively obtaining a more complex shape. While these multi-step processes enable the creation of complex components, they also increase the cost due to the number of dies and presses needed. Also, from a scientific point of view, the multiple steps cause repeated loading and unloading of the materials, which is very challenging to model in a computationally-efficient way. This research aims to create a material model suitable for repeated loading and unloading, to enable science-based process and die design, minimize the number of necessary steps, reduce waste and thus enhance the competitiveness of American manufacturing. Since the automotive industry is one of the major users of multi-step sheet forming, this research will also enable the use of modern, difficult-to-form steels and aluminum alloys in auto-bodies, yielding safer and environmentally friendlier cars. The work will be performed in collaboration with 2 Korean universities (whose work is funded by the Korean National Research Foundation), and this collaboration will allow access to equipment and expertise not otherwise available in the US. Graduate and undergraduate students and Research Experience for Teachers (RET) participants and their students will benefit from the industrial focus of this project, as well as its international dimension.To provide industry with a robust and computationally-efficient material model suitable for severe strain-path changes, including repeated loading and unloading, this research will: 1) create a unique machine for biaxial tension/compression of sheets and perform multiaxial plasticity experiments, 2) use this dataset to evolve the recent (2011) Homogeneous Anisotropic Hardening (HAH) plasticity model and create the extended-HAH one, to capture the experiments, and 3) conduct multi-step forming experiments and simulate them with the extended-HAH model, to further inform its evolution and validate its performance. Two families of materials, advanced high strength steels and aluminum alloys, will be investigated in this research, both of which are of interest to various weight-sensitive applications, but have widely varying responses to severe strain-path changes. Beyond the specific forming processes studied here, the creation of a robust and computationally-efficient material model to describe severe strain-path changes is expected to benefit the modeling of all multi-step plastic deformation processes in industry, as well as low-cycle fatigue and cyclic plasticity.