浅谈偏置面齿轮齿面方程及三维建模

为满足面齿轮设计效率和制造精度要求,以偏置式面齿轮传动系统为研究对象,根据微分几何和齿轮啮合原理,建立了理想状况下的面齿轮齿面数学模型。采用MATLAB语言编程,计算出齿面特征点坐标,并导入proe生成三维实体模型。该方法可使繁琐复杂的面齿轮建模变得准确易行。     

硬齿面渐开线齿轮强度的优化设计

本文对目前日益广泛应用的硬齿面齿的弯曲强度与接触强度进行了分析，提出了加权因子的方法来统一齿轮的弯曲强度与接触强度，使之符合等强度设计原则，进而构造优化设计的目标函数，进行硬齿面齿轮的参数设计，对硬齿面齿轮的强度设计具有一定的实际意义。     

渗碳齿轮齿面磨削裂纹的研究

渗碳齿轮磨削裂纹是齿轮制造过程中普遍存在一种现象,直接影响着齿轮表面质量和工作性能。本文以18CrNiMo7—6渗碳齿轮为研究对象,分析了磨削裂纹产生原因,并从材料、热处理和机械加工几个方面,提出预防磨削裂纹的工艺措施。     

不同形式齿廓偏差对直齿轮副振动的影响规律

通过建立齿轮承载接触分析模型,计算了考虑齿面误差分布时齿轮的啮合刚度和综合啮合误差。综合考虑时变啮合刚度激励、误差激励和啮合冲击激励的影响,建立了直齿轮副弯扭耦合动力学模型,分析了不同形式齿廓(中凸、中凹、正压力角、负压力角)偏差对系统振动的影响规律。结果表明,中凹齿廓齿轮的振动最大;负压力角偏差齿轮作从动轮时振动仅次于中凹齿廓;在多数载荷条件下,正压力角偏差齿轮的振动要小于负压力角偏差齿轮,中凸齿廓齿轮具有比理想齿廓齿轮更小的振动。研究结果为进一步提出齿轮误差控制原则提供了有效参考。     

面齿轮副齿面磨损动态响应及其典型特征分析EI北大核心CSCD

为了揭示齿面磨损对面齿轮传动的影响,提出了一种结合黏着磨损公式的面齿轮副齿面接触分析方法。通过齿面接触分析得到面齿轮副接触椭圆离散点上的相对位移及接触应力,再根据黏着磨损公式可以定量得到齿轮的磨损深度;编写了含磨损的面齿轮副齿面坐标,并在ABAQUS软件中计算了不同磨损下系统的啮合刚度;将齿面磨损等效为齿面偏差,讨论了不同磨损对静态传递误差的影响;对比了面齿轮副在正常和磨损时的动态响应,分析了转矩对磨损的影响。结果表明:齿面磨损主要影响啮合刚度和静态传递误差的幅值,并且会导致加速度与啮合力幅值的快速增长;转矩的增大会引起磨损加重;相比于无量纲统计指标,加速度均方根对于磨损故障更敏感。     

误差齿面下直齿轮副内部激励及动态特性分析

基于齿轮加工、安装误差的分布规律,建立了渐开线直齿轮的误差齿面模型,提出了适用于该误差齿面模型的齿轮承载接触分析算法,研究了不同误差对直齿轮副内部激励的影响规律;建立了直齿轮副弯扭耦合动力学模型,分析了不同误差下齿轮系统的动态特性。研究表明：加工误差中,齿距偏差是齿轮副内部激励的主要影响因素;齿距偏差作用下,综合啮合误差呈阶跃变化,当阶跃值超过一定范围后时变啮合刚度发生突变;安装误差影响下,综合啮合误差为一定值,时变啮合刚度随中心距和轴线倾斜误差的增加而减小;为减小齿轮系统动态传递误差的峰峰值,齿距偏差应根据载荷大小合理分配,同时应避免由轴线倾斜误差导致的偏载现象发生。     

考虑齿面变摩擦系数的斜齿轮传动变速过程动力学分析

建立了含齿面摩擦的平行轴斜齿圆柱齿轮传动变速过程动力学模型,在建立模型时,接触线的位置和滑动速度是由主动轮转角确定,使用齿轮线位移和角位移作为广义坐标,因此这样的模型可适用于斜齿轮传动系统的变速过程分析,而且在该模型中,齿面摩擦力是用变摩擦系数获得的。选择一对斜齿轮对其加速过程进行数值计算,并与采用定摩擦系数和不考虑摩擦的计算结果在时域和魏格纳分布上进行对比分析,结果发现:摩擦会降低斜齿轮传动系统出现脱啮现象的临界转速,且具有阻尼和激励的双重作用,能改变斜齿轮传动的动力学响应,而且采用变摩擦系数或定摩擦系数所获得的动力学响应也有所不同。     

辐板刚度、阻尼及齿面摩擦对齿轮振动特性的影响

在考虑齿轮副时变啮合刚度、齿面摩擦、齿侧间隙及辐板刚度和阻尼的情况下,建立了齿轮传动系统的三维非线性动力学模型。根据啮合点位置推导出啮合刚度、齿面摩擦系数与时间的关系,并考虑了齿轮动载荷在各齿轮副之间的实际分配情况。针对强非线性变微分方程组求解困难的问题,提出了利用添加方程组维数的方法将变系数微分方程组转化成常微分方程组,并采用4~5阶自适应变步长的龙格库塔法求解微分方程组的数值解。系统地分析了辐板刚度、阻尼以及齿面摩擦对齿轮副和辐板振动性能的影响,为更深入研究齿轮的阻尼减振提供了理论基础和研究方向。     

齿面摩擦对面齿轮传动系统振动特性的影响分析

为研究齿面摩擦力对正交面齿轮传动系统动态特性的影响,基于集中参数理论,建立了考虑齿面摩擦、齿侧间隙、传动误差、时变啮合刚度、啮合阻尼、支撑刚度和阻尼等参数的正交面齿轮多自由度耦合振动模型,采用龙格库塔数值积分法对系统的动力学方程求解,得到随摩擦系统变换的系统动态响应分岔特性。结果表明,随齿面摩擦系数的变化,面齿轮传动系统的动力学特性有周期响应和混沌响应,动态特性比较复杂。     

基于PSO算法的斜齿轮NURBS齿面重构研究

斜齿轮被广泛应用于高速重载的传动系统中,需要通过齿轮接触分析(TCA)以及齿轮承载接触分析(LTCA)进行强度校核。针对传统的齿轮接触分析所采用的有限元几何模型精度差的问题,提出了一种四阶斜齿轮齿面非均匀有理B样条(NURBS)拟合方法,并对齿轮渐开线曲面控制点权重进行粒子群优化(PSO)。通过参数化方程生成斜齿轮齿面型值点以进行节点矢量以及齿面控制点的计算,并利用粒子群优化算法,将拟合点到理论曲面的法向投影距离的最大差值作为拟合误差,对构成齿轮的渐开线曲面控制点权重进行调整,实现更为精确的斜齿轮齿面重构拟合。在10×6的网格控制点下,所生成的斜齿轮NURBS渐开线齿面拟合误差为2.059μm,优化后可以达到1.657μm,满足齿廓总偏差2级精度要求,可以为齿轮接触分析以及齿轮承载接触分析提供精确的几何模型。     

新型少齿差减速器动态特性分析及实验研究

摘 要 针对某新型少齿差行星减速器,进行了不同啮合位置时的多体接触有限元分析,求得轮齿时变啮合刚度,采用动力接触有限元法计算齿轮啮合冲击激励,得出包括时变刚度激励、误差激励、啮合冲击激励的齿轮啮合内部动态激励。建立减速器的有限元动力分析模型,在综合考虑内部激励和外部激励的情况下计算了减速器的时域和频域响应及加速度级1/3倍频程结构噪声。利用振动测试分析仪对新型少齿差内啮合减速器进行测试分析,并与有限元计算结果进行对比,二者较为吻合。     

随机起伏界面声散射的实验与理论研究

进行了二维粗糙海面声波散射特性的水池实验,测量了不同入射角、散射角以及方位角条件下所对应的散射强度。实验通过不同位置风扇对水面的吹拂获得粗糙水面,分别对水平面上互相垂直的两个方向上的水面波高变化进行了测量,利用周期图法估计出这两个方向上的空间功率谱,验证了实验中的粗糙水面是各向同性的。利用改进的空间域处理技术去除了总声波信号中的直达波和其他固定位置散射体的散射信号,获得了粗糙水面的声波散射信号。利用小斜率近似方法计算了二维粗糙海面的声散射特性。实验与模拟计算结果比较,证实了计算二维粗糙海面声波散射特性的小斜率近似方法的有效性与准确性,相互印证了实验与理论。     

小斜率近似方法分析粗糙界面声散射问题

利用小斜率近似方法计算了起伏海面的声散射特性,得到了具有高斯分布粗糙海面的平均反射系数（即镜反射系数）计算公式,并与微扰法和Kirchhoff近似做了比较,结果表明小斜率近似是一种非常有效的分析起伏表面散射特性的近似方法。最后讨论了海面镜反射系数随海面的不平整度（波浪的均方根高度）、声波频率和声波入射方向的变化关系,得出了只有在声波波长和起伏波浪高度可比拟时,才有明显的镜反射的结论。这为分析浅海目标声散射特性时,选择是否需要考虑海面（海底）所引起的多途效应提供了理论依据。     

A consistent approach for fluid-structure-contact interaction based on a porous flow model for rough surface contact

Simulation approaches for fluid-structure-contact interaction, especially if requested to be consistent even down to the real contact scenarios, belong to the most challenging and still unsolved problems in computational mechanics. The main challenges are 2-fold—one is to have a correct physical model for this scenario, and the other is to have a numerical method that is capable of working and being consistent down to a zero gap. Moreover, when analyzing such challenging setups of fluid-structure interaction, which include contact of submersed solid components, it gets obvious that the influence of surface roughness effects is essential for a physical consistent modeling of such configurations. To capture this system behavior, we present a continuum mechanical model that is able to include the effects of the surface microstructure in a fluid-structure-contact interaction framework. An averaged representation for the mixture of fluid and solid on the rough surfaces, which is of major interest for the macroscopic response of such a system, is introduced therein. The inherent coupling of the macroscopic fluid flow and the flow inside the rough surfaces, the stress exchange of all contacting solid bodies involved, and the interaction between fluid and solid are included in the construction of the model. Although the physical model is not restricted to finite element–based methods, a numerical approach with its core based on the cut finite element method, enabling topological changes of the fluid domain to solve the presented model numerically, is introduced. Such a cut finite element method–based approach is able to deal with the numerical challenges mentioned above. Different test cases give a perspective toward the potential capabilities of the presented physical model and numerical approach.     

Influence of shadowing on ellipsometric quantities of randomly rough surfaces and thin films

In this paper the formulae enabling us to calculate the values of the ellipsometric parameters of randomly rough surfaces and very thin films with randomly rough boundaries with respect to the influence of the shadowing between the irregularities of roughness are presented. These formulae are derived within the scalar diffraction theory of light. The first formula allows the calculation of the ellipsometric parameters using a numerical method, while the second formula is the approximative one but it expresses the ellipsometric parameters in a closed form. The numerical analysis of both formulae is performed for several examples of randomly rough surfaces and thin films. Moreover, the comparison of the results achieved using both formulae respecting the shadowing and an earlier formula not including this effect is performed. The experimental data of two samples of the randomly rough silicon surfaces covered with very thin surface layers are interpreted using all the formulae mentioned. Using this experimental study, the correctness of both formulae taking into account the shadowing, is confirmed.     

直线运动滚动导轨副混合润滑研究

综合考虑了直线运动导轨副接触几何、预紧力、真实表面粗糙度、曲率系数等因素,建立了直线运动导轨副混合润滑数值模型,研究了滑块移动速度、曲率半径系数、工作载荷、表面粗糙度对导轨接触副润滑特性的影响,得到结论:导轨副法向工作载荷、最大赫兹接触压力和赫兹接触半径随着外加总载荷的增大而增大,平均膜厚随着载荷的增大而减小;混合润滑模型可预测导轨副在大范围工况条件下完整的润滑状态;直线运动导轨大多工作在混合润滑状态下,随着滑块移动速度的增加,接触界面由边界润滑状态向混合润滑状态转变,润滑性能逐渐提高;适当增加曲率半径系数,有利于润滑油膜的形成与稳定。     

Simultaneous recovery of an infinite rough surface and the impedance from near-field data

In this paper, we consider an inverse rough surface scattering problem in near-field optical imaging. This problem is actually to reconstruct the scattering surface as well as its impedance coefficient from multifrequency near-field data, and can be reduced into an integral scheme by employing an integral representation. We solve this integral scheme by a non-linear integral equation method, and further develop a fast inversion algorithm for reconstructing both the rough surface and the impedance coefficient. Numerical experiments are presented to illustrate the effectiveness of the algorithm.     

Experimental and numerical determination of the lubrication force between a spherical particle and a micro-structured surface

In many particulate processes suspensions need to be handled. Hydrodynamic forces in presence of a liquid as a surrounding continuum medium can significantly affect the particle collision behaviour. When particles approach a wall, lubrication force can become dominant with decreasing distance. This force was described analytically by different authors for a smooth flat wall. Roughness was found to be an important factor in this context, but the mechanisms are still not fully understood. In this work, the effects of topology on the lubrication force were studied using a regular prismatic micro-structured titanium surface produced by micro-milling. A nanoindentation setup was modified for the direct measurement of this force during the particle approach to polished and micro-structured surfaces in liquid. For a more detailed insight on the behaviour of the fluid in the decreasing gap between particle and surface microstructure, resolved computational fluid dynamics (CFD) simulations were performed using an overset mesh method. The comparison of simulation results with nanoindentation tests and analytical solution showed a good agreement. The effects of structure size and particle contact location at various approaching velocities on the lubrication force were investigated.     

基于精确齿面建模的ZA蜗杆蜗轮有限元接触分析

为了研究不同情况下蜗杆蜗轮间的接触应力和蜗杆扭转角与驱动力矩之间的关系,根据齿面方程建立具有精确齿面的ZA蜗杆蜗轮实体模型,利用ANSYS对此模型在同一载荷不同啮合位置和同一啮合位置不同载荷条件下进行有限元接触分析,研究在一个轮齿啮合周期内,各啮合齿对的接触应力分布和载荷在不同齿对上的分配情况.分析结果表明:理论接触应...