考虑热松弛效应的纳米结构材料热弹耦合行为研究

This project aims to investigate the heat transportion and the thermo-mechanical responses of nanodevices at small space and time scales, and explore the significance of the heat conduction relaxation and surface/interface effects. Surface effects become significant for nanostructures due to the large surface to volume ratio. The main contents include: First, under the frames of surface/interface thermodynamics and continuum mechanics,the generalized thermoelastic constitutive models for the surface /interface with heat conduction relaxation effects is developed to descirbe the deformation and movement of the surface under the actions of different heat and mechanical loadings. The parameters for the proposed surface model are achieved by Molecular Dynamics simulations. Secondly, the initial stresses in the bulk, induced by the surface residual stress, will be studied; then, the generalized thermoelasticity with initial stresses and heat conduction relaxation is proposed.Combining the surface and the bulk models,we develop the heat transport model and heat-mechanical couple model for nanostructures at micro time scale. Based on these models, the laser induced vibrations and thermoelastic damping characteristics of nanoresonators is investigated theoretically and experimentally to explain the influnce of heat conduction relaxation and surface effects. This research provides a theoretical basis for the design and development of highly stable and sensitive nanoresonators.

本项目拟对微时间尺度下和微空间尺度下纳米结构材料热输运规律和热-力耦合物理机制进行研究，探讨热传导松弛行为的影响。纳米结构材料其具有非常大的比表面积，表/界面效应显著；首先，基于表/界面热动力学和连续介质力学框架，建立考虑热传导松弛行为的广义热弹性表/界面理论，揭示微时间尺度下不同热载荷和机械载荷作用下表面的变形和运动规律；理论模型和多尺度计算相结合，通过分子动力学模拟，为上述理论模型提供相关的材料参数。然后，建立考虑热传导松弛行为且具有初应力的纳米结构材料体相的广义热弹性理论；表面与体相材料模型相结合，建立微时间尺度下纳米结构材料热输运模型和热-力耦合模型。理论分析、多尺度计算和实验相结合，探讨不同结构形式纳米谐振器的激光诱导热振动和热弹性衰减特性，阐明热传导松弛行为、表面效应和初应力的影响。本项研究对于高稳定性、高灵敏性纳米谐振器件的性能设计与开发具有重要的意义。

研究微时间尺度下和微空间尺度下纳米结构材料热输运规律和热-力耦合物理机制，探讨表/界面效应和热传导松弛行为的影响，对于高稳定性、高灵敏性纳米谐振器件的性能设计与开发具有重要的意义。纳米结构材料其具有非常大的比表面积，表/界面效应显著；基于表/界面热动力学和连续介质力学框架，选取温度和表面应变为内禀热力学量，考虑非经典传热条件，建立了表面的广义热弹性本构模型；表面与体相材料模型相结合，分析如下纳米结构材料热输运模型和热-力耦合特性：（1）半空间表面纳米尺度范围内局部受热问题研究；（2）端部受约束纳米线的热屈曲振动问题；（3）考虑实际材料结构的对称性，将各向同性本构模型推广到各向异性情况，深入研究横观各向同性模型的线弹性表示形式；（4）考虑不同温度条件，表面效应和热松弛行为对纵向振动纳米谐振器衰减特性的影响；（5）考虑不同端部条件，分析表面效应和热松弛行为对纳米谐振器横向振动衰减特性影响；（6）分子动力学仿真微时间尺度下和微空间尺度下热传播松弛行为、（含缺陷）端部约束纳米线的热屈曲、热弹性振动阻尼等。理论分析、多尺度计算和实验相结合，探讨纳米谐振器的热弹性衰减特性，阐明微空间尺度下和微时间尺度下热传导松弛行为和表面效应对纳米结构热弹性振动特性有显著影响。