Nano-and Microscale Experiments and Theoretical Modeling for Strain Gradient Plasticity

应变梯度塑性的纳米和微米级实验及理论建模

• 批准号: 9820770
• 负责人: William Slaughter
• 金额: $ 18万
• 依托单位: University of Pittsburgh
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-09-01 至 2003-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9820770&HistoricalAwards=false
• 关键词: Nano; Microscale; Experiments; Theoretical; Modeling

Nano- and Microscale Experiments and Theoretical Modelingfor Strain Gradient PlasticityWilliam S. Slaughter and Scott X. MaoAbstractMicro-electromechanical systems (MEMS), micro-electronic packaging, and micromechanical sensors and actuators commonly use thin films and multilayers whose behaviors are found to be significantly different from that of the bulk materials from which they are made. As such, there is a need to deal with design and manufacturing issues at micron levels, and even down to nanometer levels.Experimental evidence shows that the microscale behavior manifests itself as a strong size effect on the plastic flow stress of metals and ceramics when the characteristic length scale of deformation is on the order of several microns or less. Conventional theories of plasticity are unable to explain and predict these effects, which reflect some inherent nature of the material. The cause of these size effects is rooted in the dependence of plastic flow stress on not only the plastic strain, but also on the gradient of plastic strain. Plastic strain gradients are, in general, inversely proportional to the length scale over which plastic deformation occurs so that strain gradient effects tend to become important at these small scales.This proposal is aimed at understanding the deformation mechanisms behind large plastic strain gradients in thin films and multilayers and using continuum strain gradient plasticity theories to characterize the deformation. Large strain gradients will be generated through innovative nano- and microscale bending and indentation tests. The proposal will provide a thorough, experiment-based examination of the basic deformation behavior and mechanisms for various thin films and wires at nano- and microscales, and a development of the strain gradient plasticity theory with emphasis on determining the values of pertinent material properties.The proposal includes the study of (i) strain gradient plasticity in monolithic materials using bending tests for thin foils and wires, and indentation tests; and (ii) strain gradient plasticity and layer thickness effects in nano- and micro-layered materials. The former will include the development of new experimental methods for nanomechanics and will validate current theories of strain gradient plasticity for nanoscale deformation. The latter will examine material length scales associated with both strain gradient plasticity and with layer thickness.

纳米和显微镜实验和理论建模，用于应变梯度可塑性William S. Slaughter和Scott X. Maoabstractmicro-electromegricical Systems（MEMS），微电包装，微机械传感器以及微力传感器，以及经常使用的薄膜和多层膜和多层次是显着不同的。从制成的批量材料中。 因此，有必要在微米级别处理设计和制造问题，甚至达到纳米水平。实验证据表明，显微镜的行为表现为对金属和陶瓷的塑料流量应力的强大尺寸影响变形的特征长度尺度在几微米或更小的范围内。 传统的可塑性理论无法解释和预测这些影响，这反映了材料的某些固有性质。 这些尺寸效应的原因不仅源于塑性流应力不仅对塑性应变的依赖性，而且还源于塑性应变的梯度。 通常，塑性应变梯度与发生塑性变形的长度尺度成反比，以使应变梯度效应在这些小尺度上倾向于变得很重要。该提案旨在理解薄膜中大型塑料应变梯度背后的变形机制和多层并使用连续性应变梯度可塑性理论来表征变形。大型应变梯度将通过创新的纳米和微观弯曲和压痕测试产生。 该提案将对纳米和显微镜的各种薄膜和电线的基本变形行为和机制进行彻底的，基于实验的检查，并开发应变梯度可塑性理论，重点是确定相关材料特性的值。该提案包括（i）使用薄层和电线的弯曲测试以及凹痕测试的（i）整体材料中的应变梯度可塑性的研究； （ii）纳米和微层材料中应变梯度可塑性以及层厚度效应。 前者将包括开发用于纳米力学的新实验方法，并将验证纳米级变形的菌株梯度可塑性的当前理论。 后者将检查与应变梯度可塑性和层厚度相关的材料长度。