Constitutive Equations for Process and Product Design of Lightweight HCP Metals

9610130 Anand 无论运输方式如何， 车辆的建造需要联合收割机-良好的结构 刚度高强度和韧性， 腐蚀，它们必须尽可能轻， 为了节省燃料。 铝合金长期以来一直被用于 用于飞机的蒙皮和框架。并开始成为 用于汽车工业。 两个重要的光 用于运输工业的金属是钛， 镁。 本文介绍了近年来在开发 多晶塑性的数学理论， 不仅预测了各向异性的宏观应力-应变 反应和形状的变化，但也演变 在变形过程中， 主要用于面心立方（fcc）材料 晶体这种类型的进展要少得多， 材料 与 六方密排 （hcp） 晶体 结构 与fcc材料相比， 表现出更复杂的塑性变形模式， 较低的对称性 非弹性变形抗力 不同的卡瓦系统在以下方面可以是显著不同的 与fcc铝合金不同， hcp钛和镁合金表现出变形 双胞胎 这会导致它们的显著各向异性， 宏观 变形 特性， 和 这些 各向 需要妥善处理 为 在 开发强大的计算能力， 1.工艺设计-变形加工，以及 2.产品设计-改善结构响应 的 部件， 由钛和镁制成。 特别重要的是，这些材料的非弹性变形行为的滑移和孪生的基本理解的发展，和精确的弹粘塑性本构方程描述这种变形行为的发展。 我们建议发展各向异性的弹塑性 本构方程和计算程序 非弹性变形的建模与仿真 hcp钛中的晶体滑移和孪生 和镁。 计算能力将是有用的 在模拟各向异性的发展， 晶体结构的演化 数学 我们建议开发的模型和程序应 适用于各种变形加工的设计 操作，以及结构组件的设计 性能 __

9610130 Anand Whatever the mode of' transportation, materials used in construction of vehicles need to combine -good structural stiffness. strength, and toughness with high resistance to corrosion, and they must be as lightweight as possible in order to save fuel. Aluminum alloys have long been used for skins and frames of aircraft. and are beginning to be used in the automotive industry. Two other important light metals for the transportation industry ire titanium and magnesium. The recent progress in the development of a mathematical theory of polycrystalline plasticity which predicts not only the anisotropic macroscopic stress-strain response and shape changes, but also the evolution of crystallographic texture during deformation, has occurred primarily for materials with face-centered-cubic (fcc) crystals. Much less progress of this type has occurred for materials with hexagonal-close-packed (hcp) crystal structure. Compared with fcc materials, the hcp materials exhibit more complex modes of plastic deformation due to their lower symmetry. Inelastic deformation resistances of different slip systems can be substantially different in the hcp materials, and unlike the fcc aluminum alloys, the hcp titanium and magnesium alloys exhibit deformation twinning. This causes pronounced anisotropies in their macroscopic deformation characteristics, and these anisotropies need to be properly accounted for in developing a robust computational capability for 1. Process Design - deformation processing, and 2. Product design - improved structural response of components, made from titanium and magnesium1. Of particular importance is the development of a fundamental understanding of the inelastic deformation behavior of these materials by slip and twinning, and the development of accurate elasto- viscoplastic constitutive equations which describe this deformation behavior. We propose to develop anisotropic, elasto-plastic constitutive equations and computational procedures for modeling and simulation of inelastic deformation due to both crystallographic slip ,and twinning in hcp titanium and magnesium. The computational capability will be useful in simulating the development of anisotropy due to the evolution of crystallographic texture. The mathematical models and procedures that we propose to develop should be useful in the design of a variety of deformation-processing operations, and the design of components for structural performance. _______________________________ 1 Although the majority of processing of magnesium allows is done by casting, magnesium is also wrought to form tubes, plates, and sheet.