Meso-Scale Plasticity and Deformation Processing

细观塑性和变形过程美国加州大学圣巴巴拉分校的Henry T.Y.Yang，普渡大学西拉斐特分校的CASRinivesan Chandrasekar最近发现了一种现象，对细观(0.1-10 mm)的塑性变形产生了重要影响，这是应变梯度塑性，指的是应变梯度对材料流动行为的集体影响。应变梯度塑性的发现源于测量，测量表明，当与非均匀塑性变形相关的特征长度尺度较小时，材料在其力学响应中表现出强烈的尺寸效应。探索了两种新的方法来估算存在应变梯度的金属和合金的流动应力-应变曲线。第一种是细观压痕的模拟和测量，以研究硬度随压头顶角的变化。这种方法的一个独特之处是使用具有不同顶角的锥形压头在固体中施加广泛但可控的应变和应变梯度。第二种技术涉及准静态、介观加工中材料响应的研究，在这种加工中，应变梯度甚至比压痕更强烈。这里，细观加工是一种估算本构应力-应变曲线的工具。这项研究旨在提供对细观塑性现象的基本见解；开发和验证与变形加工相关的细观流动应力数据的估计技术；以及为材料加工操作的多尺度建模生成详细的应力-应变数据。这将促进可持续材料加工系统的发展，这些系统在创造更高质量的产品的同时，以高效率运行。

Meso-Scale Plasticity and Deformation ProcessingHenry T. Y. Yang, University of California, Santa Barbara, CASrinivasan Chandrasekar, Purdue University, West Lafayette, INA recently 'discovered' phenomenon with important consequences for plastic deformation at the meso-scale (0.1-10 mm) is strain gradient plasticity, which refers to the collective effects of strain gradient on flow behavior of materials. The discovery of strain gradient plasticity has its origins in measurements, which show that materials display strong size effects in their mechanical response when the characteristic length scale associated with non-uniform plastic deformation is small. Two novel techniques are explored for estimating the flow stress-strain curves of metals and alloys in the presence of strain gradients. The first of these involves simulation and measurement of meso-scale indentation to study the variation of hardness with indenter apical angle. A unique aspect of this approach is the use of cone indenters with different apical angles to impose a wide, but controlled, range of strains and strain gradients in a solid. The second technique involves a study of material response in quasi-static, meso-scale machining where strain gradients are even more intense than in indentation. Here, meso-scale machining is a vehicle for estimating the constitutive stress-strain curve. The research is intended to provide fundamental insights into meso-scale plasticity phenomena; develop and validate techniques for estimating meso-scale flow stress data of relevance to deformation processing; and generate detailed stress-strain data for multi-scale modeling of materials processing operations. These should facilitate the development of sustainable materials processing systems that operate at a high level of efficiency, while creating products of enhanced quality.