Multiaxial Distortional-Hardening Plasticity to Advance Forming Process Modeling

钣金成形工艺是最灵活、最节能的制造工艺之一，约占美国国内生产总值的7%。将板材转化为有用的部件通常需要多个步骤，零件从一个成型模具转移到下一个成型模具，逐步获得更复杂的形状。虽然这些多步骤过程能够创建复杂的部件，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反复加载和卸载，这对以计算效率高的方式建模是非常具有挑战性的。本研究旨在创建适合重复装卸的材料模型，实现科学的工艺和模具设计，减少必要步骤的数量，减少浪费，从而提高美国制造业的竞争力。由于汽车工业是多步板材成形的主要用户之一，这项研究也将使在车身上使用现代的、难以成形的钢和铝合金成为可能，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合作进行（其工作由韩国国家研究基金会资助），这种合作将使美国能够获得在其他方面无法获得的设备和专业知识。研究生和本科生以及教师研究经验（RET）参与者及其学生将受益于该项目的产业重点及其国际维度。为了向工业界提供一个适用于剧烈应变路径变化（包括反复加载和卸载）的鲁棒且计算效率高的材料模型，本研究将：1)创建独特的板材双向拉伸/压缩机器并进行多轴塑性实验；2)使用该数据集对最近（2011）的均质各向异性硬化（HAH）塑性模型进行演化并创建扩展HAH模型，以捕获实验结果；3)使用扩展HAH模型进行多步成形实验并进行模拟，进一步了解其演变并验证其性能。两类材料，先进的高强度钢和铝合金，将在本研究中进行研究，这两种材料都对各种重量敏感应用感兴趣，但对严重的应变路径变化有广泛不同的响应。除了本文研究的具体成形过程之外，创建一个鲁棒且计算效率高的材料模型来描述严重的应变路径变化，预计将有利于工业中所有多步骤塑性变形过程的建模，以及低周疲劳和循环塑性。

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.