【作者】 张鑫；

【导师】 孙军辉；

【作者基本信息】 西南交通大学 ， 机械工程， 2023， 硕士

【摘要】 摩擦的来源是摩擦学基础研究的核心科学问题。固体界面的微观摩擦溯源于跨界面的原子间相互作用,电子耦合行为是产生摩擦的基础。因此,认识跨界面电子耦合规律是理解摩擦来源的关键内容,但目前学术界在固体界面摩擦的电子耦合机理研究方面尚存在欠缺,尤其缺乏普适性基础理论。本文基于滑动势垒对摩擦产生决定性影响的一般原理,从滑动能垒起伏的电子作用原理的角度,对摩擦的来源进行了如下研究:1.在电子层面建立科学描述摩擦能垒起伏的研究方法。基于密度泛函理论的第一性原理方法,以二维过渡金属硫族化合物材料为例,系统研究了相对滑动所引起的势能起伏和电子密度演化间的关系,建立电子水平摩擦来源的研究方法。与现存定量研究方法的进行对比分析,对二维材料滑动过程中不同堆叠状态的平面差分电子密度演化进行全域积分,定义一种明确具体的电子密度随接触构型沿滑动路径的演化量化分析方法,发现电荷演化与能量耗散的一般线性关联,并从特定到一般地总结分析出电子密度演化的基本积分过程细节以及各方法的区别联系。2.固体界面微观摩擦产生的电子作用普适机理。在上述方法的建立基础上,对多种类型摩擦界面,包括从范德华、金属、离子键到共价键合等数十种典型固体界面的摩擦行为进行系统研究。结果表明,对上述不同类型的固体界面摩擦,滑动过程中的能垒起伏与沿滑动路径的电子密度均同步演化,体现了摩擦耗散对电子演化存在的普适性线性依赖关系,其关联系数反映了摩擦过程能量耗散对电子密度的响应幅度。当前工作在电子水平提出摩擦的普适性来源机理。指出摩擦能垒为相对滑动过程摩擦界面电子密度相对动态变化所致,实现了跨越材料类型的摩擦起源解释,完善了基础摩擦理论,为长期以来的关于电子行为与摩擦势垒关系的争议提供统一性解释。同时,推出的摩擦能垒与电子演化的关联系数能够深刻认识剪切强度这一摩擦学基本概念的物理本质,对摩擦力与真实接触面积成正比这一经典假设提供基于电子水平的物理依据。因此,当前提出的电荷演化模型可能帮助在电子层面认识摩擦产生的内在根源,并在应用层面为摩擦调控提供理论指导。更多还原

【Abstract】 The origin of friction is the core scientific problem of tribological basic research.The micro-friction of the solid interface is traced to the interaction between atoms across the interface and the electron coupling behavior is the basis of friction.Therefore,understanding the law of cross-interface electron coupling is the key to understanding the origin of friction,but there are still some deficiencies on the mechanism of electron coupling of solid interface friction in academic community at present,especially the lack of universal basic theory.In this thesis,based on the general principle that the sliding potential energy barrier has a decisive effect on friction,and from the point of view of the electron interaction principle of the fluctuation of the energy barrier,the origin of friction is studied as follows:1.Establish a research method for scientifically describing the fluctuation of the frictional energy barrier at the electronic level.Based on the first-principles method of density functional theory,taking two-dimensional transition metal chalcogenide materials as an example,the relationship between the potential energy fluctuation caused by relative sliding and the evolution of electron density is studied systematically,and the research method of the origin of electron level friction is established.Compared with the existing quantitative research methods,the evolution of plane electron density difference in different stacking states of two-dimensional materials is integrated in the whole region.A clear and specific quantitative analysis method of electron density evolution along the sliding path with contact configuration is defined,and the general linear correlation between charge evolution and energy dissipation is found.The details of the basic integration process of the evolution of electron density and the differences of each method are summarized and analyzed from specific to general.2.Universal electron interaction mechanism of microscopic friction generation at solid interface.On the basis of the above methods,the friction behaviors of dozens of typical solid interfaces,including van der Waals,metals,ionic and covalent bonding,were studied systematically.The results show that for all the above different types of solid interface friction,the energy barrier fluctuation in the sliding process evolves synchronously with the electron density along the sliding path,which reflects the universal linear dependence of friction dissipation on electron evolution.The correlation coefficient reflects the response of energy dissipation to electron density in the friction process.The current work puts forward the universal origin mechanism of friction at the electronic level.It is pointed out that the friction energy barrier is caused by the relative dynamic change of electron density at the friction interface in the process of relative sliding,which realizes the explanation of the origin of friction across material types and improves the basic friction theory.it provides a unified explanation for the long-standing dispute about the relationship between electronic behavior and friction potential barrier.At the same time,the correlation coefficient between friction energy barrier and electron evolution can deeply understand the physical nature of the basic tribological concept of shear strength,and provide a physical basis based on the electronic level for the classical assumption that the friction force is proportional to the real contact area.Therefore,the current charge evolution model may help to understand the internal causes of friction at the electronic level,and provide theoretical guidance for friction regulation at the application level.更多还原