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

这项学院早期职业发展(CALEAR)计划资助通过高级实验力学和分析对金属微尺度变形的力学进行研究。这项研究为国家材料基因组和先进制造计划做出了贡献。微结构-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结构构件--它们的颗粒--如何响应热机械载荷的变化。通过新颖的原位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射线会穿透材料。测量样品的X射线衍射变化将提供有关颗粒结构变化的可量化信息。考虑了一类新的现场试验，其中二维热机械载荷是现场施加的。独一无二的实验数据的共享将使其他研究人员能够测试它们的多轴、热机械、工艺-组织-性能关系。目前的研究方法将被纳入到新的非线性固体力学研究生课程中。一年一度的使用先进固体材料的国际设计大赛将通过专业工程学会发起。研究生将在地区高中、社区大学和图书馆接受培训，通过展示先进的材料和现场实验能力，以激发想象力和展示可访问性的形式进行推广。将开展一项无损、平面-双轴和感应加热相结合的原位X射线衍射实验。它将与新的数据分析方法一起用于研究热机械加载多晶样品中单个颗粒的并发相变、弹性和塑性。这项新的实验将被用来探索形状记忆合金和不锈钢微观力学相变的未知领域。由于晶体内单个变形机制和多晶体内单个晶体的作用将被量化，不同力学尺度之间的桥梁将被阐明。考虑了下列研究问题：(1)晶间边界条件如何引起微观组织间的应力分布？(2)在晶体尺度上激活不同相变、孪生和滑移系统所需的相互作用能是什么，以及微结构约束是如何影响它们的？(3)用于马氏体微观力学模拟的合适的微结构块是什么？(4)如何测量低对称马氏体结构的弹性各向异性？(5)形状记忆合金的热诱发相变和应力诱发相变的滞后为什么不同，为什么它随着加载方式的不同而变化。加工各向异性是否改变了相对于不同材料轴的相变滞后性质？

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?