CAREER: In-situ Advancements for Study of Multi-axial Micromechanics of Solid Materials

该学院早期职业发展（CAREER）计划资助通过先进的实验力学和分析支持对金属微尺度变形力学的研究。该研究有助于国家材料基因组和先进制造计划。微观结构-性能关系是理解材料力学响应的核心。对于固体材料，这样的模型需要了解微观结构的构建块-它们的颗粒-如何响应热机械载荷的变化。通过新的原位X射线衍射实验，将获得对这些过程的新见解。当热机械载荷改变时，X射线将穿透材料。测量从样品衍射的X射线的变化将提供关于晶粒结构变化的可量化信息。一类新的原位实验被认为是二维热机械载荷施加在原位。独特的实验数据的共享将使其他研究人员能够测试他们的多轴，热机械，工艺-微观结构-性能关系。目前的研究方法将被纳入一个新的非线性固体力学研究生课程。将通过一个专业工程学会发起一项使用先进固体材料的年度国际设计竞赛。研究生将接受培训，在地区高中，社区学院和图书馆通过呈现先进的材料和现场实验能力，激发想象力和展示可访问性的格式进行推广。一个非破坏性的，结合平面双轴和感应加热原位X射线衍射实验将开发。它将被采用沿着与新的数据分析方法，用于研究并发相变，弹性和塑性的热机械加载的多晶试样内的单个晶粒。新的实验将用于探索形状记忆合金和不锈钢中微观力学相变的未知领域。由于晶体内的单个变形机制和多晶体内的单个晶体的作用将被量化，不同尺度的力学之间的桥梁将得到阐明。研究了以下问题：（1）晶间边界条件如何引起微结构间的应力分布？(2)在晶体尺度上，激活不同的相变、孪生和滑移系统所需的相互作用能是什么？微观结构约束如何影响它们？(3)什么是合适的马氏体微观力学模型的微观结构的基石？(4)如何测量低对称马氏体组织的弹性各向异性？(5)为什么形状记忆合金的热致相变和应力致相变的滞后不同，为什么它随加载模式而变化，以及加工各向异性是否改变了相对于不同材料轴的相变滞后的性质？

This Faculty Early Career Development (CAREER) Program grant supports research on the mechanics of the microscale level deformation of metals through advanced experimental mechanics and analysis. The research contributes to national Materials Genome and Advanced Manufacturing Initiatives. Microstructure-property relationships are central to the understanding of the mechanical response of materials. For solid materials, such models require knowledge of how microstructural building blocks - their grains - respond to thermo-mechanical load changes. New insights into these processes will be gained through novel in-situ X-ray diffraction experiments. X-rays will penetrate materials while thermo-mechanical loads are changed. Measuring changes in X-rays diffracted from samples will provide quantifiable information about changes of the grain structures. A novel class of in-situ experiments is considered where two-dimensional thermo-mechanical loads are applied in-situ. The sharing of the unique experimental data will enable other researchers to test their multi-axial, thermo-mechanical, process-microstructure-property relationships. The present research methodologies will be incorporated into a new Nonlinear Solid Mechanics graduate course. An annual international design competition using advanced solid materials will be initiated through a professional engineering society. Graduate students will be trained to perform outreach at area high schools, community colleges, and libraries by presenting advanced material and in-situ experiment capabilities in a format that stimulates imagination and demonstrates accessibility. A non-destructive, combined planar-biaxial and induction heating in-situ X-ray diffraction experiment will be developed. It will be employed along with new data analysis methodology for studying concurrent phase transformation, elasticity, and plasticity of individual grains within a thermo-mechanically loaded polycrystalline specimen. The new experiment will be used to explore uncharted territory in the micromechanics phase transformation in shape memory alloys and stainless steels. Since the roles of individual deformation mechanisms within crystals and individual crystals within polycrystals will be quantified, bridges between different scales of mechanics will be elucidated. The following research questions are considered: (1)How do inter-granular boundary conditions give rise to stress distributions amongst microstructures? (2) What are the interaction energies required to activate different transformation, twinning, and slip systems at the crystal scale, and how do microstructural constraints affect them? (3) What is the proper microstructural building block for micromechanical modeling of martensite? (4) How do we measure elastic anisotropy of low symmetry martensite structures? (5) Why is hysteresis different in thermal vs. stress-induced transformation of shape memory alloys, why does it vary with loading mode, and does processing anisotropy change the nature of transformation hysteresis with respect to different material axes?