Deformation Processing: Crystallographic Texture Evolution and Shear Band Formation

可加工性通常被定义为在特定的变形加工操作中能够无故障地实现的变形程度。失效可能是与材料有关的开裂或断裂的基本现象，但也可能是任何其他不希望出现的情况，例如缺少模具填充或表面光洁度差。影响材料可加工性的主要因素是：(1)外部过程变量，如应力、温度、应变、应变率、摩擦和热传递边界条件及其演化；(2)内部微观结构变量，如气孔率、晶体织构、变形局部化及其演化，最终导致延性破坏。虽然人们非常重视发展预测变形加工过程中与孔隙率增长有关的缺陷的能力，但在将其他重要微观结构特征的演变纳入宏观数学模型方面仍有许多工作要做。具体地说，需要结合由于晶体织构和变形、局部化和失效而产生的影响。该项目旨在建立精确的各向异性热弹粘塑性本构方程和计算程序，用于模拟和模拟面心立方和六方封闭堆积合金中由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产生的各向异性的发展，以及在低和高相应温度下的大变形下与局域剪切带有关的材料加工缺陷的发展。这些数学模型对于各种冷变形和热变形加工操作的设计和分析应该是有用的。这样的模型将允许更快、更准确地设计成形金属零件的工具和程序。

Workability is often defined as the degree of deformation that can be achieved in a particular deformation processing operation without failure. Failure may be the basic material related phenomena of cracking or fracture, but it could also be any other undesirable condition, for example lack of die fill or poor surface finish. The major factors which influence the workability of a material are: (1) the external process variables of stress, temperature, strain, strain rate, frictional and heat transfer boundary conditions, and their evolution; and (2) the internal microstructural variables, for example porosity, crystallographic texture, deformation localization and their evolution culminating in ductile failure. While considerable attention has been paid to developing a capability for predicting defects associated with the growth of porosity in deformation processing operations, much remains to be done with regard to incorporating the evolution of other important microstructural features in macroscopic mathematical models. Specifically there is need for incorporating the effects due to crystallographic texture and deformation localization and failure. This project is to develop accurate anisotropic thermo- elastic-viscoplastic constitutive equations and computational procedures for modeling and simulation of inelastic deformations due to both crystallographic slip and twinning in face-centered cubic and hexagonal-closed packed alloys. The computational capability will be useful in simulating the development of anisotropy due to the evolution of crystallographic texture, and the development of material processing defects associated with localized shear bands at large deformations at both low and high homologous temperatures. The mathematical models should be useful in the design and analysis of a variety of cold and hot deformation processing operations. Such models will allow the faster and more accurate design of tools and procedures for forming metal parts.