Constitutive Equations for Process and Product Design of Lightweight HCP Metals

9610130阿南德无论采用何种运输方式，用于制造车辆的材料都需要具有良好的结构刚度。强度，韧性和高耐腐蚀性，他们必须尽可能轻，以节省燃料。铝合金长期以来一直用于飞机的外壳和框架。并开始在汽车工业中使用。交通运输行业的另外两种重要轻金属是钛和镁。多晶塑性数学理论的最新进展主要针对面心立方（fcc）晶体材料，该理论不仅预测了各向异性宏观应力应变响应和形状变化，而且还预测了变形过程中晶体织构的演变。这种类型的进展很少发生在具有六边形紧密排列（hcp）晶体结构的材料上。与fcc材料相比，hcp材料由于其较低的对称性而表现出更复杂的塑性变形模式。不同滑移体系的非弹性变形抗力在hcp材料中可能存在很大差异，并且与fcc铝合金不同，hcp钛合金和镁合金表现出变形孪晶。这导致其宏观变形特征具有明显的各向异性，并且在开发1的稳健计算能力时需要适当考虑这些各向异性。工艺设计-变形加工；产品设计-改进了部件的结构响应，由钛和镁制成。特别重要的是对这些材料的滑移和孪生的非弹性变形行为的基本理解的发展，以及描述这种变形行为的精确弹粘塑性本构方程的发展。我们建议建立各向异性弹塑性本构方程和计算程序，用于模拟和模拟hcp钛和镁中由于晶体滑移和孪晶引起的非弹性变形。计算能力将有助于模拟由于晶体织构的演变而引起的各向异性的发展。我们提出开发的数学模型和程序应该在各种变形处理操作的设计和结构性能组件的设计中有用。_______________________________ 1虽然镁的大部分加工是通过铸造完成的，但镁也可以锻造成管、板和板。

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.