微尺度下金属介质激光冲击瞬态热力耦合行为研究

With the development of ultra-short laser pulse technology and its wide application in ultra-precision micromachining and surface microtreatment of metallic devices, it is becoming increasingly important to accurately describe the transient thermomechanical coupling behavior of metallic medium under laser shock in micro scale. In view of inherent drawback of the research method based on traditional continuum mechanics and failure of the present studies of molecular dynamics simulation in revealing the real condition of the transient thermomechanical coupling problem in metallic medium, the two-dimensional theoretical model of two-step heat transfer combined with molecular dynamics method in the context of the combination of macro and micro analysis will be established and the efficient and precise method for solving the two-dimensional theoretical model will be developed in the present project. The aim of this project is to reveal the nature of the transient thermomechanical coupling probelm in metallic medium from atomic scale more fully and deepen understanding and awareness of inherent mechanism of transient thermomechanical coupling in metallic medium. And by using a more rational interatomic potentials (such as embedded atom model, EAM), the transient thermomechanical coupling problems in metallic medium with microdefects (such as microcracks, dislocations, grain boundaries, atomic vacancy defects, etc.) are studied to obtain the microscopic interpretation of effects of microdefects in metallic medium. This research is to achieve the clearer and more comprehensive understanding of microscopic mechanism of transient thermomechanical coupling problem in metallic medium and provide theoretical and technical support for the application of ultra-short laser pulses in metallic ultra-precision machining and surface treatment.

随着超短激光脉冲技术的发展及其在金属器件超精微加工和表面微处理上的广泛应用，准确描述微尺度下金属介质激光冲击瞬态热力耦合问题显得日益重要。针对基于传统连续介质力学的宏观研究方法存在无法克服的缺陷以及目前的分子动力学模拟研究无法完全满足金属介质瞬态热力耦合问题要求的现状，本项目将基于宏、微观分析相结合的方法，建立金属介质的两步热传输-分子动力学相结合模拟二维理论模型并发展相应高效精确的求解方法，旨在从原子尺度全面地揭示金属介质瞬态热力耦合问题的本质，深化对金属介质瞬态热力耦合内在机制的理解和认识；采用更合理的原子间作用势（如EAM镶嵌原子势），研究含微缺陷（微孔、位错、晶界等）金属介质中的瞬态热力耦合问题，获得金属介质微缺陷效应的微观解释。通过本研究，获得对金属介质瞬态热力耦合现象的微观机理更清晰、更全面的认识，为超短激光脉冲在金属超精微加工和表面微处理中的推广应用提供理论和技术支持。

随着超短脉冲激光与微纳米技术的迅速发展，激光精密微加工已成为处理微纳尺度结构的有效手段并被广泛应用于加工各种微电子器件等微纳米结构。为了保证激光精密微加工的高精度，准确描述微尺度下金属介质激光冲击瞬态热力耦合问题是非常重要的。本项目基于宏、微观分析相结合的方法，建立了针对金属介质的电子-声子两步受热纳尺度热力耦合理论模型（即两步热传输-分子动力学相结合模拟理论模型），并发展了相应高效精确的求解方法。获得了全面准确的瞬态热力耦合响应，准确地描绘了金属介质中的瞬态热力耦合现象，从原子尺度层面认识了瞬态热力耦合问题的微观机理，使得对瞬态热力耦合问题的本质有了更清晰、更全面的认识。本项目还从宏观层面上（宏观尺度），采用有限元法对激光冲击金属薄膜的超快热力耦合问题开展了相关研究。此外，本课题还建立了针对非金属介质的声子主导受热纳尺度热力耦合理论模型，发现该模型对超快激光烧蚀石墨烯的预测结果与已有实验数据吻合较好。