Scale-Dependent Crystal Plasticity and Nanoindentation-Induced Dislocation Microstructure

尺寸相关的晶体塑性和纳米压痕引起的位错微观结构

• 批准号: 0800168
• 负责人: Yanfei Gao
• 金额: $ 31.66万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-05-01 至 2012-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0800168&HistoricalAwards=false
• 关键词: Scale; Dependent; Crystal; Plasticity; Nanoindentation

CMMI 0800168: Scale-Dependent Crystal Plasticity and Nanoindentation-Induced Dislocation MicrostructureYanfei Gao (PI), George M. Pharr (Co-PI)University of Tennessee, KnoxvilleThe objective of this research is directed to a mechanistic understanding of the scale-dependent plastic behavior of single crystals by a quantitative comparison of measured and simulated near-surface dislocation microstructure induced by nanoindentation. Existing theoretical/experimental comparison has generally been limited to macroscopic information such as hardness. Experimentally, nanoindentation tests will be employed to achieve controlled defect distributions by varying the material type, indenter shape, and crystallographic orientations. Artifacts in continuous stiffness measurement and reliable hardness extraction will be examined. The spatially resolved lattice-misorientation measurements with sub-micron resolution will be performed using microfocus x-ray technique. From modeling standpoint, the measured dislocation microstructure will be used as input to examine the crystallographic nature of the relationship between lattice rotation, incompatible lattice deformation, and geometrically-necessary-dislocation distributions. Thus various gradient plasticity theories can be validated and calibrated. The source limited behavior will be investigated by applying various degrees of pre-strain prior to indentation and qualitatively by utilizing a discrete dislocation model. The research will lead to benefits and impacts for mechanics theorists in the critical evaluation of scale-dependent constitutive models and for materials scientists in advancing design capabilities of small scale material structures. The multidisciplinary nature will be a disseminative example for undergraduate and graduate education. New instructional materials and hands-on laboratory demonstrations will be developed for incorporation into outreach and diversity programs, which are designed to inspire interests of high school students and to help recruit students from underrepresented groups in engineering sciences.

CMMI 0800168：尺度相关的晶体塑性和纳米压痕诱导的位错微结构。法尔（合作PI）田纳西大学，诺克斯维尔本研究的目的是针对一个机械的理解的尺度依赖性的塑性行为的单晶纳米压痕引起的测量和模拟近表面位错微观结构的定量比较。现有的理论/实验比较一般限于宏观信息，如硬度。在实验上，纳米压痕测试将通过改变材料类型、压头形状和晶体取向来实现受控的缺陷分布。将检查连续刚度测量和可靠硬度提取中的伪影。空间分辨的晶格取向差测量与亚微米分辨率将使用微焦点X射线技术进行。从建模的角度来看，测得的位错微观结构将被用作输入，以检查晶格旋转，不相容的晶格变形，和几何必要的位错分布之间的关系的晶体学性质。因此，各种梯度塑性理论可以验证和校准。通过在压痕之前施加不同程度的预应变，并利用离散位错模型定性地研究源限制行为。该研究将为力学理论家在尺度相关本构模型的关键评估和材料科学家在推进小尺度材料结构的设计能力方面带来好处和影响。多学科性质将成为本科生和研究生教育的传播范例。将开发新的教学材料和实践实验室演示，以纳入外展和多样性计划，这些计划旨在激发高中生的兴趣，并帮助从工程科学领域代表性不足的群体中招收学生。