An Investigation of the Evolution of Mechanical Properties of Materials During Metalworking

小行星9617227 金属加工 例如轧制， 成形、锻造、挤压、冲压等在美国是数十亿美元的产业。 近年来，金属加工产品越来越多地用于制造从食品容器到汽车车身面板的各种产品。 金属加工工艺对这些产品的性能和可靠性有很大的影响，因为， 影响 （这样的 作为 进化 的晶体 纹理， 脱位 结构 和沉淀物）和在金属加工过程中引起的残余应力在确定它们的机械性能中起着至关重要的作用。 本提案的目的是研究金属力学性能的演变，特别强调在板材成形过程中各向异性的预测。 轧制和成型工艺。 这 将 通过首先发展本构理论来模拟轧制和板材成形对材料的突出机械性能（如屈服面）的影响。 该理论的主要思想是，材料的响应取决于多个 结构（如 晶格 结构、位错网络等）这些是通过假设材料具有一个以上的演变自然配置建模。 就弹性响应和屈服函数而言，演化的自然构形是材料的无应力构形。 这个概念允许详细讨论的弹性响应和屈服面的各向异性的演变。 屈服行为是最重要的方面， 材料的力学性能 -.3ince 它决定了可成形性、颈缩行为等， 的材料。 即使是模型中的一个微小错误， 屈服行为显著地降低了这些重要参数的预测。 在过去的三年里，美铝技术中心的科学家们一直在合作， 和 匹兹堡大学 开发全面的本构假设，以准确地模拟变化的各向异性。 目前的建议建立在这一努力，并把它带到下一个阶段，即详细的实验和本构理论的验证。 该理论的预测能力有望为研究人员提供一些必要的工具，以可靠地估计板材的机械性能 金属 产品信息 关于 它所经历的制造过程。 在这个过程中，它将帮助研究生获得工业和学术培训。

9617227 Rajagopol Metalworking processes such as rolling, forming, forging, extrusion, stamping etc. are a multibillion dollar industry in the USA. In the recent years, metalworked products are being increasingly used to make a variety of products ranging from food containers to automobile body panels. The metalworking processes have a big impact on the performance and reliability of these products because, microstructural effects (such as evolution of crystallographic texture, dislocation structures and precipitates) and residual stresses which are induced during the metalworking process play a vital role in determining their mechanical properties. The goal of this proposal is to examine the evolution of the mechanical properties of metals with a special emphasis on the prediction of evolving anisotropy during sheet rolling and forming processes. This will be accomplished by first developing a constitutive theory to model the effect of rolling and sheet forming on the salient mechanical properties (such as the yield surface) the material. The principal idea of the theory is that the response of the material depends upon the evolution of multiple structures (such as the lattice structure, dislocation networks etc.) These are modeled by assuming that the material possesses more than one evolving natural configuration. As far as the elastic response and the yield function are concerned, the evolving natural configurations are the stress-free configurations of the material. This notion allows for a detailed discussion of the evolution of the anisotropy of the elastic response and the yield surface. The yield behavior is the most significant aspect mf the mechanical behavior of the material -.3ince it determines the formability, necking behavior etc., of the material. Even a slight error in the modeling of the yield behavior significantly degrades the prediction of these vital parameters. For the past three years, there has been a collaboration between Scientists at the Alcoa Technical Center and the University of Pittsburgh to develop comprehensive constitutive assumptions to accurately model the changing anisotropy. The current proposal builds upon this effort and takes it to the next stage, namely detailed experimentation and validation of the constitutive theory. The predictive capabilities of the theory are expected to provide researchers with some of the tools necessary to make reliable estimates of mechanical properties of the sheet metal product from information regarding the manufacturing processes that it has undergone. In the process, it will help graduate students to gain both industrial and academic training.