人字齿轮啮合刚度计算与齿面载荷分布研究

为了精确地进行人字齿轮的强度计算和动态特性分析,首先建立了渐开线真实齿廓的人字齿轮三维模型,提出了一种基于有限元方法和齿轮啮合原理的准确计算人字齿轮啮合刚度和齿面载荷分布的有效方法.方法利用有限元方法计算齿面柔度系数,考虑了齿轮的动态啮合过程.运用该方法计算了一对人字齿轮模型,最后分析了斜齿轮和人字齿轮啮合刚度的关系,得出了斜齿轮和人字齿轮啮合刚度近似相等的结论,为后续的动力学分析提供了准确的刚度激励.     

基于传动误差数据的齿轮误差检测方法与系统

齿轮传动误差影响齿轮传动精度和平稳性,传动误差与齿距和齿廓偏差等齿轮误差数据有直接关系.利用单面啮合测试和虚拟仪器原理,构建了传动误差检测系统,研究了传动误差与齿距与齿廓偏差数据的关系,找到一种将齿距与齿廓偏差计算出来的方法.经过试验分析,验证了本方法和系统的准确性.     

谐波齿轮精确间隙分析可视化仿真

研究谐波齿轮传动优化问题,渐开线齿廓代替齿轮共轭齿廓时,存在齿轮重叠干涉影响精度问题。为保证齿轮既不发生干涉又能实现精确传动,且提高计算精度与收敛速度,提出根据齿顶干涉检验法的自动优化算法。通过图形界面参数化设计进行迭代计算,快速精确计算出最小啮合间隙,并对齿廓啮合过程进行了可视化仿真。结果表明,优化结果啮合状况良好,明显提高了计算精度与收敛速度。最后,通过大量实例分析,得到齿轮啮合过程中最容易发生干涉的转角,并采用变位修正法进行修正。为谐波齿轮加工与检验提供参考依据。     

双不确定参数作用下双稳态能量采集系统的随机响应分析

为改善纯电动汽车齿轮传动在整个工况范围内的工作性能,提出一种计及负载扭矩和转速工况影响的齿面修形方法.考虑时变啮合刚度、啮合冲击、齿面摩擦激励,建立了系统动力学分析模型.结合轮齿几何接触分析和承载接触分析,采用遗传算法优化获得全工况最优的齿廓、齿向抛物线修形系数,并对比分析了不同修形方案的抑振效果.结果表明：计及工况影响的齿面修形在全工况下的振动加速度均方根都保持在较低水平,说明这一齿面修形策略具有更好的全局抑振效果.     

纯电动汽车高速齿轮传动全工况抑振修形方法

为改善纯电动汽车齿轮传动在整个工况范围内的工作性能,提出一种计及负载扭矩和转速工况影响的齿面修形方法.考虑时变啮合刚度、啮合冲击、齿面摩擦激励,建立了系统动力学分析模型.结合轮齿几何接触分析和承载接触分析,采用遗传算法优化获得全工况最优的齿廓、齿向抛物线修形系数,并对比分析了不同修形方案的抑振效果.结果表明：计及工况影响的齿面修形在全工况下的振动加速度均方根都保持在较低水平,说明这一齿面修形策略具有更好的全局抑振效果.     

连续共轭啮合的双圆弧谐波齿轮齿廓设计及运动仿真验证

基于分段函数表达的参数化公切线双圆弧齿廓,利用柔轮装配变形的包络精确算法研究双圆弧齿廓原始齿廓参数对包络存在区间大小的影响及其共轭齿廓的可用性,提出使二次共轭现象成为可用齿廓的设计方法.首先按照柔轮中性层周向位移引起的转角及其轮齿对称线相对于径矢转角的精确计算方法,确定变形后柔轮轮齿的位置和方位,获得一系列柔轮齿廓相对于刚轮齿槽的啮合运动轨迹;然后从计算机图形学角度获得用柔轮齿廓外包络表达的刚轮齿廓,验证二次共轭现象及其可用共轭齿廓的存在性.实例结果表明,双圆弧齿廓谐波齿轮可以通过合理的参数设计实现在整个啮合区间上的连续共轭传动,使更多齿对同时参与共轭啮合,从而提高谐波齿轮的承载能力和传动精度.     

基于模态柔度的直齿圆柱齿轮微动磨损有限元分析

由于直齿圆柱齿轮微动磨损分析存在误差大的问题,为此,提出一种基于模态柔度的直齿圆柱齿轮微动磨损有限元分析方法.通过自动扫描装置对直齿圆柱齿轮齿面进行扫描处理,借助采集数据建立相关拟合有限元模型.分析模态柔度改变量对直齿圆柱齿轮微动磨损的敏感性,通过模态柔度对齿轮微动磨损情况与程度进行识别,构建磨损后齿廓线方程,在此基础上通过Archrd磨损公式进行磨损计算.实验结果表明,主动齿轮与从动齿轮磨损程度最高的都是齿根与齿顶部分;和其它方法相比,采用所提方法获取的齿轮磨损量误差改变更加平稳,大部分数值都在0值上下波动,误差很小.     

基于B 样条曲面插值误差控制的内超环面齿轮齿面建模

针对内超环面齿轮齿面数控加工精度难以保证的问题,提出一种基于B 样条曲面 插值误差控制的内超环面齿轮齿面建模的方法。该方法以内超环面齿轮理论齿面原型为依据, 运用B 样条曲面构造插值曲面,计算插值曲面片与理论齿面之间的误差。通过插值误差分析, 根据误差分布特点,将型值点网格不断细化,获得一组型值点阵,经插值重构后可得到满足精 度要求的内超环面齿轮齿廓模型。最后,通过数控加工验证了建模的有效性。基于B 样条曲面 插值误差控制的内超环面齿轮齿面建模方法为获得高精度的内超环面齿轮实体模型奠定了理 论基础。     

求解面齿轮啮合轨迹的新方法

根据面齿轮传动的点接触原理,提出一种求解面齿轮啮合轨迹的新方法,假设小齿轮、刀具、面齿轮三齿面同时啮合,通过求解小齿轮一刀具接触线和面齿轮一刀具接触线的交点,以确定它们在固定坐标系下的啮合线,从而反求面齿轮和小齿轮齿面上的啮合轨迹;通过MATLAB的数值计算功能,利用新方法求解了面齿轮传动的啮合轨迹,并与轮齿接触方法(TCA)求得的面齿轮啮合轨迹进行对比,发现结果一致,证明了方法的可行性;对安装误差下的面齿轮传动进行了分析,研究了不同安装误差对面齿轮啮合轨迹的影响.     

一种圆柱齿轮测量控制系统研究与设计

该文设计了一种圆柱形型齿轮测量测控系统。该系统由底层接口软件和上层应用软件两大模块组成,可控制齿轮测量仪完成齿轮齿廓、齿距、螺旋线等的测量,并可以对测量后产生的数据进行分析、评定,生成测量报告。     

An experimental study of sidewall adhesion in microelectromechanical systems

A surface micromachine was designed specifically for studying sidewall adhesion in microelectromechanical systems (MEMS). The dependence of surface adhesion on contact load and ambient conditions was investigated under quasistatic normal loading conditions. Insight was obtained into the relative contributions of van der Waals and capillary forces to the measured adhesion force. Several shortcomings in previous adhesion studies of MEMS were overcome, and measurement of the true adhesion force was achieved under different testing conditions. The present experimental procedure enables the isolation of the van der Waals component of the adhesion force and the determination of the contributions of both contacting and noncontacting asperities to the total adhesion force at the inception of surface separation. The major benefits of the developed experimental methodology and surface micromachine are discussed in the context of adhesion results obtained for different values of apparent contact pressure, ambient pressure, and relative humidity.     

Theoretical study of van der Waals dispersion force between macroscopic bodies with a periodic material distribution

A method has been developed for calculating the van der Waals dispersion force between a macroscopic body consisting of a uniform material and a macroscopic body with a spatially periodic material distribution. The periodic material distribution is one dimensional in the x-direction. The periodically distributed material property function is expanded as a Fourier series. The van der Waals forces for a distribution of two materials were then calculated as a typical example of a periodic material distribution. The effects of parameters such as the duty ratio of the material distribution, the refractive index ratio of the two materials, and the length of the uniform body on the van der Waals force were shown.     

Modeling the instability of CNT tweezers using a continuum model

Carbon nanotube (CNT) tweezers are composed of two parallel cantilever CNTs with a distance in between. In this paper, the static response and instability of CNT-made nano-tweezers is theoretically investigated considering the effects of Coulomb electrostatic force and van der Waals molecular attraction. For this purpose, a nano-scale continuum model is employed to obtain the nonlinear constitutive equation of the nano-tweezers. The Euler–Bernoulli beam theory is applied to model the elastic response of the CNT. The van der Waals attraction is computed from the simplified Lennard-Jones potential. In order to solve the nonlinear constitutive equation of the system, three approaches, e.g. the hemotopy perturbation method (HPM), the Adomian decomposition (AD) and the finite difference method (FDM) are employed. The obtained results are in good agreement with the experimental measurements. As a case study, freestanding CNT tweezers has been investigated and the detachment length and minimum initial gap of the tweezers are determined. Moreover, the effective operation range of the van der Waals attraction that affects the instability behavior of the CNT tweezers is discussed.     

范德华力作用下粗糙表面静态粘附的研究

通过在硅微接触表面上涂覆低表面能的憎水性OTS膜以除去接触面间的表面张力,把两表面均接地以除去接触面间的静电力,研究了仅有范德华力作用时硅微结构接触表面的粘附.根据实际粗糙表面凸峰自相似的高度分布,计算了发生粘附后,微观接触表面产生弹性和塑性变形的两种情况下的范德华粘附能,分析了表面形貌对其影响.     

Theoretical study of van der Waals dispersion pressures considering one-dimensional material distributions in the in-plane direction

The van der Waals dispersion pressures between a half-space consisting of a uniform material and a half-space with a one-dimensional material distribution in the in-plane direction have been theoretically derived. Two patterns of material distribution were considered: a periodic distribution of materials (Pattern 1) and a distribution of two materials with a single interface (Pattern 2). The van der Waals pressure for Pattern 1 was derived based on a Fourier series, while the van der Waals pressure for Pattern 2 was derived as elementary functions. Both of the van der Waals pressures derived consist of two terms: a conventional term between half-spaces made of uniform materials and a spatial fluctuation term due to the material distribution. The basic characteristics of these van der Waals pressures were quantitatively clarified. Furthermore, an approximate method for obtaining the van der Waals pressure of Pattern 1 from Pattern 2 was proposed.     

The Effect of Adhesion on the Static Friction Properties of Sidewall Contact Interfaces of Microelectromechanical Devices

Static friction between sidewall contact surfaces of polycrystalline silicon micromachines was investigated under different contact pressures, vacuum conditions, relative humidity levels, and temperatures. The static coefficient of friction exhibited a nonlinear dependence on the external contact pressure. A difference between in-contact and pull-out adhesion forces was observed due to the elastic recovery of the deformed asperities at the contact interface. The true static coefficient of friction was determined by considering the effects of the dominant adhesion forces (i.e., van der Waals and capillary forces) on the normal force applied at the sidewall contact interface. The roles of van der Waals and capillary forces in the sidewall friction behavior were analyzed in light of results for the interfacial shear strength and the adhesion force. The major benefits of the present friction micromachine and the developed experimental scheme are discussed in the context of static coefficient of friction and adhesion force results obtained under different environmental and loading conditions     

Smoothing haptic interaction using molecular force calculations

This paper presents a new method for smoothing haptic interaction with molecular force calculations that uses Lennard-Jones forcefield. The gradient of the forcefield is used unaltered when the distance between two atoms is greater than the sum of their van der Waals radii. However, when they are smaller, a hard-surface wall implemented using a spring model is used to repel two atoms. This eliminates the instability when two atoms are in contact in the presence of forcefields that have strong gradients. This method is tested on rigid hydrocarbon molecules with no bond creation or breaking.     

Influence of van der Waals force on the pull-in parameters of cantilever type nanoscale electrostatic actuators

In this paper, the influence of the van der Waals force on two main parameters describing an instability point of cantilever type nanomechanical switches, which are the pull-in voltage and deflection are investigated by using a distributed parameter model. The fringing field effect is also taken into account. The nonlinear differential equation of the model is transformed into the integral form by using the Green’s function of the cantilever beam. The integral equation is solved analytically by assuming an appropriate shape function for the beam deflection. The detachment length and the minimum initial gap of the cantilever type switches are given, which are the basic design parameters for NEMS switches. The pull-in parameters of micromechanical electrostatic actuators are also investigated as a special case of our study by neglecting the van der Waals force.     

Investigation of nonlinear dynamic behavior of a capacitive carbon nano-tube based electromechanical switch considering van der Waals force

Microsystem Technologies - In this study, nonlinear dynamic behavior of a capacitive carbon nano-tube switch is investigated considering van der Waals (vdW) force. The carbon nano-tube is...     

The oblique collision efficiency of nanoparticles at different angles in Brownian coagulation

The oblique collision efficiency of nanoparticles at different colliding angles in Brownian coagulation is investigated. A model of central oblique collision between two nanoparticles is presented to derive equations which are solved to get the collision efficiency by considering van der Waals force and elastic deformation force. Based on the calculated data of collision efficiency under different colliding angles and particle diameters, a new expression relating central oblique collision efficiency at different colliding angles to particle diameter is brought forward.