粗糙表面接触动力学特性的微观构造特征测试研究

【作者】 张毅；

【导师】 何博侠；

【作者基本信息】 南京理工大学 ， 精密仪器及机械， 2016， 硕士

【摘要】 机械系统是由零部件按照一定的技术要求装配而成的,零部件相互接触的表面称为机械结合面,简称“结合面”。从微观尺度看,零部件表面是由许多形状、高度及分布不同的微凸体构成的凹凸不平的表面,这样形成的结合面在动载荷作用下表现出既有刚度又有阻尼的复杂动力学特性。机械系统的动态精度与性能直接受结合面动力学特性的影响,掌握结合面动力学特性对整机动态特性分析及优化设计有着重要意义。但是,由于结合面之间的接触问题是复杂的跨尺度几何物理问题,结合面动力学特性的微观构造特征至今未尚未掌握,因而无法对结合面动力学特性参数进行解析求解。本文主要从微观角度研究粗糙表面接触动力学特性的构造特征测试技术,主要工作如下：(1)基于经典的赫兹接触理论,研究随机粗糙表面接触过程,分析粗糙表面接触过程中接触载荷与结合面接触趋近距离之间的关系,并分析表面粗糙度和接触载荷对真实接触面积和接触应力的影响。(2)基于菲涅尔衍射积分理论,利用数字全息技术记录和再现技术,搭建测量粗糙表面微观形貌的数字全息测量系统,对后续激光声表面波波速和结合面动力学特性测试所用试块的表面形貌进行测量。(3)讨论激光超声激发机制,将激光超声传输理论和固体声弹效应相结合,搭建用于测量激光声表面波波速的测试系统,通过测量声表面波传播速度来反映结合面接触应力的变化。得出结论：结合面接触应力随面压增大而增大且为非线性关系；结合面表面粗糙度越大,接触应力相对较大。(4)设计并制作了粗糙表面法向动力学特性参数测试传感器,对不同接触状态下的结合面法向动态刚度和阻尼进行测量,建立了以名义接触面积、接触面压和表面粗糙度为参变量的法向刚度和阻尼计算模型。得出结论：对于结合面单位面积法向动刚度和阻尼,面压和结合面积的影响幅度比较接近,而表面粗糙度的影响幅度弱于面压和结合面积；单位面积法向动刚度与面压成正相关,与结合面积和表面粗糙度成负相关；单位面积法向阻尼与面压和结合面积成正相关,与表面粗糙度成负相关。(5)将建立的结合面法向动力学特性参数模型应用于KVCN1050N立柱-床身结构有限元分析,有限元分析与模态试验计算结果最大误差为12.45%,最小误差为-3.92%,平均误差不超过7.4%。更多还原

【Abstract】 The mechanical system is made up of mechanical parts according to certain assembly technical requirements. The contact surface of the components is called mechanical joints. The surface of the parts is uneven and composited with many asperities which is different in shape, height and distribution from the microcosmic viewpoint. The complex dynamic characteristics of both stiffness and damping are exhibited under the dynamic load. The dynamic accuracy and performance of the mechanical system is directly affected by the dynamic characteristics of the mechanical joints. It is of great significance to grasp the dynamic characteristics of the mechanical joints to analyze and optimize the dynamic characteristics of the whole machine. However, due to the contact problem of the mechanical surfaces is a complex cross scale geometric physics problem, the formation mechanism of the dynamic characteristics of the mechanical joints has not yet mastered. Therefore, the dynamic characteristic parameters can not be solved analytically. The microscopic structure feature of the contact dynamic characteristics of rough surface is studied in this paper, and the main work is as follows:(1) Based on the classical Hertz contact theory, the contact process of random rough surface is studied. The relationship between the contact load and the relative contact distance and the influence of the roughness and the contact load on the real contact area and the contact stress is analyzed.(2) Based on Fresnel diffraction integral theory, the principle of the recording and reconstruction process of digital holography is analyzed. A digital holographic measurement system is built to measure micro topography and the roughness of rough surface. The measurement and evaluation method of rough surface roughness is studied. And the system is used to measure the surface roughness of the specimen of ASW velocity test and the dynamic characteristic test of the mechanical joints.(3) The mechanism of laser ultrasonic excitation is discussed. The experimental system for measuring the velocity of laser ultrasonic ASW is built by combining the theory of laser ultrasonic transmission and solid sound effect. It is concluded that the contact stress of the mechanical joints increases with the increase of the load and the relationship is nonlinear. Under the same conditions, the larger the surface roughness, the larger the contact stress.(4) A sensor is designed to test the dynamic characteristics of the rough surface contact. The dynamic stiffness and damping of the mechanical joints can be measured in different contact states. The calculating models of normal stiffness and damping which employ the surface area, pressure and roughness as variables are founded. It is concluded the normal dynamic stiffness of unit area method is positively correlated with the surface pressure, which is negatively correlated with the area and roughness. The normal dynamic damping of unit area method is positively correlated with the surface pressure and the area, which is negatively correlated with the roughness.(5) Applying the model, the finite element model of the structure of machine tool bed and column of KVCN1050N is constructed. The finite element analysis and modal test results show that the maximum error is 12.45%, the minimum error is -3.92%, the average error is not more than 7.4%.更多还原