CAREER: Modeling Materials Across the Length Scales to Achieve Enhanced Thermomechanical Properties

这项学院早期职业发展(Career)计划拨款将专注于制定有效的模型和数值方案，以了解具有丰富微结构的材料的依赖于长度的热机械响应。虽然已经对特征微观结构长度尺度对材料的热性能和力学性能的影响进行了广泛的研究，但对于长度尺度对组合热机械响应的影响却知之甚少。这项研究工作将为分析具有改进的热机械性能的下一代材料提供建模和计算能力，以满足最苛刻的工程应用，包括但不限于用于发电和推进的热障涂层、耐磨保护系统和微电子设备的封装。该项目的教育部分将侧重于通过发展和实施向参加者介绍工程和机械知识的夏令营，促进拉美裔K-12学生对STEM职业的兴趣。训练营将采用互动学习方法，通过使用PI为移动平台开发的基于模拟的教育游戏，并允许通过3D打印实现结构。将对这一教育方法的有效性进行评估，并将广泛传播为夏令营制定的课程。本研究的目的是阐明微结构长度尺度和材料固有长度尺度与工程材料的热机械响应之间的关系。该模型包括(I)基于松弛时间近似下的Boltzmann输运方程的亚微米尺度的导热系数模型，(Ii)细观尺度的傅立叶热输运模型，(Iii)显式解析材料微观几何特征的机械变形的连续介质模型，以及(Iv)考虑材料中准静态和动态裂纹的形核和扩展的内聚模型。然后，该模型将被用来研究以下基本问题：对于稳态和动态热力学问题，晶粒度和晶粒度分布如何影响热裂纹的形核？在后一种情况下，温度速率和长度尺度对热裂纹的形核有何影响？长度尺度和热裂纹对宏观材料强度、导热系数和热膨胀的影响是什么？材料特征长度尺度的分级如何影响导热系数和裂纹形核？该项目将使PI能够在这一新领域进行持续的研究，为长期的职业成功奠定基础。

This Faculty Early Career Development (CAREER) Program grant will focus on the formulation of efficient models and numerical schemes for understanding the length-dependent thermomechanical response of materials with rich microstructures. While extensive research has been conducted on the impact of characteristic microstructural length scales on thermal and mechanical properties of materials, little is known about the effect that length scale could have on the combined thermomechanical response. This research effort will provide modeling and computational capabilities for the analysis of next-generation materials with improved thermomechanical performance as needed for the most demanding engineering applications, including but not limited to, thermal barrier coatings for energy generation and propulsion, wear protection systems, and packaging of microelectronic devices. The educational component of this project will focus on promoting interest in STEM careers among Latino K-12 students through the development and implementation of a summer camp introducing participants to engineering and mechanics. The camp will adopt an interactive learning approach through the use of a simulation-based educational game for mobile platforms developed by the PI, and allow the realization of structures by 3D printing. The effectiveness of this educational approach will be evaluated, and the curriculum developed for the camp will be widely disseminated. The objective of the research is to elucidate the connections between microstructural length scales and material inherent length scales in relation to the thermomechanical response of engineering materials. The model consists of (i) a sub-micron scale model for the thermal conductivity based on the Boltzmann transport equation under the relaxation time approximation, (ii) a Fourier heat transport model at the mesoscale, (iii) a continuum model of mechanical deformation that explicitly resolves the microscopic geometric features of the material, and (iv) a cohesive model that accounts for the nucleation and propagation of quasistatic and dynamic cracks in the material. The model will then be utilized to study the following fundamental questions: How does grain size and grain size distribution affect the nucleation of thermal cracks for the steady state and dynamic thermomechanical problem? In the latter case, how is the nucleation of thermal cracks affected by applied temperature rates and length scale? What is the effect of length-scale and thermal cracks on macroscopic material strength, thermal conductivity, and thermal expansion? How does grading of the characteristic length scale of the material affect thermal conductivity and crack nucleation? This project will enable the PI to perform sustained research in this new area, creating the basis for a long-term career success.