Time-Varying Mesh Stiffness Calculation and Dynamic Modeling of Spiral Bevel Gear with Spalling Defects

Time-varying mesh stiffness(TVMS)is a vital internal excitation source for the spiral bevel gear(SBG)transmission system.Spalling defect often causes decrease in gear mesh stiffness and changes the dynamic characteristics of the gear system,which further increases noise and vibration.This paper aims to calculate the TVMS and establish dynamic model of SBG with spalling defect.In this study,a novel analytical model based on slice method is proposed to calculate the TVMS of SBG considering spalling defect.Subsequently,the influence of spalling defect on the TVMS is studied through a numerical simulation,and the proposed analytical model is verified by a finite element model.Besides,an 8-degrees-of-freedom dynamic model is established for SBG transmission system.Incorporating the spalling defect into TVMS,the dynamic responses of spalled SBG are analyzed.The numerical results indicate that spalling defect would cause periodic impact in time domain.Finally,an experiment is designed to verify the proposed dynamic model.The experimental results show that the spalling defect makes the response characterized by periodic impact with the rotating frequency of spalled pinion.

Research on Propeller Dynamic Load Simulation System of Electric Propulsion Ship

A dynamic marine propeller simulation system was developed, which is utilized for meeting the experimental requirement of theory research and engineering design of marine electric propulsion system. By applying an actual ship parameter and its accurate propeller J＇ -KT＇ and J＇ - Kp＇ curve data, functional experiments based on the simulation system were carried out. The experiment results showed that the system can correctly emulate the propeller characteristics, produce the dynamic and steady performances of the propeller under different navigation modes, and present actual load torque for electric propulsion motor.

Particulate flow modelling in a spiral separator by using the Eulerian multi-fluid VOF approach

The Euler-Euler model is less effective in capturing the free surface of flow film in the spiral separator,and thus a Eulerian multi-fluid volume of fluid(VOF)model was first proposed to describe the particulate flow in spiral separators.In order to improve the applicability of the model in the high solid concentration system,the Bagnold effect was incorporated into the modelling framework.The capability of the proposed model in terms of predicting the flow film shape in a LD9 spiral separator was evaluated via comparison with measured flow film thicknesses reported in literature.Results showed that sharp air–water and air-pulp interfaces can be obtained using the proposed model,and the shapes of the predicted flow films before and after particle addition were reasonably consistent with the observations reported in literature.Furthermore,the experimental and numerical simulation of the separation of quartz and hematite were performed in a laboratory-scale spiral separator.When the Bagnold lift force model was considered,predictions of the grade of iron and solid concentration by mass for different trough lengths were more consistent with experimental data.In the initial development stage,the quartz particles at the bottom of the flow layer were more possible to be lifted due to the Bagnold force.Thus,a better predicted vertical stratification between quartz and hematite particles was obtained,which provided favorable conditions for subsequent radial segregation.

Modeling and Parameter Sensitivity Analysis of Valve‑Controlled Helical Hydraulic Rotary Actuator System

As a type of hydraulic rotary actuator,a helical hydraulic rotary actuator exhibits a large angle,high torque,and compact structure;hence,it has been widely used in various fields.However,its core technology is proprietary to several companies and thus has not been disclosed.Furthermore,the relevant reports are primarily limited to the component level.The dynamic characteristics of the output when a helical rotary actuator is applied to a closed-loop system are investigated from the perspective of driving system design.Two main aspects are considered:one is to establish a reliable mathematical model and the other is to consider the effect of system parameter perturbation on the output.In this study,a detailed mechanical analysis of a helical rotary hydraulic cylinder is first performed,factors such as friction and load are considered,and an accurate dynamic model of the actuator is established.Subsequently,considering the nonlinear characteristics of pressure flow and the dynamic characteristics of the valve,a dynamic model of a valve-controlled helical rotary actuator angle closed-loop system is described based on sixth-order nonlinear state equations,which has never been reported previously.After deriving the system model,a sensitivity analysis of 23 main parameters in the model with a perturbation of 10%is performed under nine operating conditions.Finally,the system dynamics model and sensitivity analysis results are verified via a prototype experiment and co-simulation,which demonstrate the reliability of the theoretical results obtained in this study.The results provide an accurate mathematical model and analysis basis for the structural optimization or control compensation of similar systems.

Topological Constraints on Scroll and Spiral Waves in Excitable Media

A conservation equation for topological charges of phase singularities （scroll and spiral waves） in excitable media is given. It provides some topological properties of scroll （spiral） waves： for example, the topological charge of the generated or annihilated spiral pair must be opposite. Additionally, we obtain another equation on scroll waves, which shows that singular filaments of scroll waves occur on a set of one-dimensional curves which may be either closed loops or infinite lines.

螺旋片导流式分离器压力简化计算

应用计算流体力学CFD(ComputationalFluidDynamics)方法,对湍流状态下不同结构参数的螺旋片导流式气液分离器螺旋结构中的流体流动场进行了数值模拟。通过分析比较螺旋个数和螺距分别对压力降的影响,从而修正达西公式,拟合出螺旋结构压力降的简化计算公式,并通过了试验验证。结果表明,用此简化计算公式计算的结果与试验数据基本一致,可以用于螺旋片导流式气液分离器螺旋结构设计计算。

薄壁零件高速铣削动态切削力

通过微元铣削力与瞬时未变形切屑厚度之间的线性关系,提出了螺旋圆柱铣刀的瞬时切削力模型。在此基础上,采用两自由度弹性-阻尼系统,建立了适合薄壁零件的综合考虑刀具子系统和工件子系统动态特性的动态铣削力模型。最后通过实际测量数据与模型计算数据的对比,验证了提出的动态铣削力模型的有效性。

螺旋钻采煤机输送机构振动频率的计算与分析

为了研究螺旋钻采煤机输送机构工作过程的振动,根据Lyapunov理论建立了用欧拉角描述的振动动力学方程,应用ANSYS软件建立了基于APDL语言的参数化有限元仿真模型,利用两种方法对某型螺旋钻采煤机输送机构的振动频率进行了计算和仿真,得到了输送机构前五阶的振动频率和最大振幅等效云图。其中通过ANSYS振动分析显示:横向共振发生在X和Z方向,最大共振振幅分别发生在500、100 Hz处,纵向共振发生在Y向,最大共振振幅发生在500 Hz处,其中X方向振幅最大,Z向振幅最小;应力云图显示,输送机构的底部应力较小,顶部应力较大,主轴与螺旋叶片交接处的应力最大,磨损及变形严重。研究表明:Lyapunov理论模型思路清晰,计算简便,而ANSYS模型使用灵活方便、求得结果直观明显,但计算精度与单元类型的选取、网格划分精度和振动提取方法有关。两种方法求得结果的最大误差为9.9%,能够反映其振动情况。

油气混输管道水合物防治动态控制技术研究

水合物防治动态控制技术在保证管道安全运行的同时可利用水合物储气密度高的特点来增大管道输送量。但是,管道内水合物生成位置难以预测性,及水合物颗粒运动规律的复杂性制约了该技术的发展。为解决该问题,利用气液两相螺旋管流强化天然气水合物生成技术,促使水合物在管道泵站出站处生成;并建立了描述水合物颗粒运动规律的流动体系水合物颗粒宏观运动模型。研究表明,气液两相螺旋管流特有流型螺旋弥散流会促使水合物在管线特定位置生成;而水合物颗粒运动距离小于管道相邻泵站间距。最后,给出管道内水合物生成量须控制在一定范围,并在水合物颗粒运动终点采取干预措施的建议。

基于多项式的等高齿锥齿轮时变啮合刚度建模

针对某型雷达装置的等高齿锥齿轮在啮合时的时变啮合刚度,提出一种多项式函数展开的时变啮合刚度新模型。通过转速、负载扭矩、阻尼因子系数分析,构建了多项式函数展开的时变啮合刚度模型,建立了等高齿锥齿轮的非线性动力学方程。将本文建立的时变啮合刚度模型与传统的多阶简谐波叠加形式的时变啮合刚度模型以及综合刚度参考数据模型进行分析对比,发现在小阻尼、重载工况下这种多项式形式的时变啮合刚度模型能更贴近于时变啮合刚度的实际特性,该模型为齿轮传动的减振、降噪、平稳传动等方面的动力学研究打下基础。

水下滑翔机李雅普诺夫稳定性分析

水下滑翔机作为一种新型的水下机器人利用了水平固定翼将净重力转换为前进驱动力,从而降低了水下机器人的功耗,在海洋科学研究、环境监测、资源探测和军事侦察等方面都具有广阔的应用前景。为了得到实际水下滑翔机稳定性与设计参数和控制参数之间的关系,将已建立的水下滑翔机一般数学模型应用于具体的实际水下滑翔机上。在此基础上将模型线性化,结合李雅普诺夫稳定性第一定理和第二定理,分析出水下滑翔机定常运动的动态稳定性随设计参数(初稳性高)和控制参数(姿态调节控制量)变化的规律。为水下滑翔机器人的设计和控制提供理论依据。

螺旋槽气体轴承动态特性及失稳分析

针对高速动静压气体轴承气膜的复杂非线性动力学行为,以球面螺旋槽动静压气体轴承为研究对象,建立润滑分析数学模型;采用有限差分法与导数积分法进行求解,得到动态扰动压力分布及动态特性系数,并研究切向供气条件下螺旋槽参数、径向偏心率、供气压力、转速对气膜刚度阻尼系数的影响规律;建立线性稳定性计算模型,预测气膜涡动失稳转速,分析运行参数对失稳转速的影响。结果表明:气膜阻尼是一种抑制涡动的因素,气膜的稳定性取决于气膜刚度与阻尼的协同作用;气膜刚度阻尼随着槽宽比、槽深比、螺旋角的增大,整体上呈先增大后减小的趋势;刚度随转速的升高而增大,阻尼则随转速的升高而减小;径向偏心率和供气压力越大,气膜刚度和阻尼越大;在一定范围内,提高供气压力、增大径向偏心率能够提高系统失稳转速;合理地选取轴承结构参数和运行参数,能够优化轴承动态特性,保证气体轴承较高的运行稳定性。

基于实际切齿方法的弧齿锥齿轮建模与仿真

提出了一种基于实际切齿方法的弧齿锥齿轮建模方法。利用展成法的原理,模拟弧齿锥齿轮的实际加工过程,把前后两次切齿刀刃所在直线的交点作为齿面点,推导出弧齿锥齿轮的数学模型。利用VB编程实现切齿参数的计算和调整,得到弧齿锥齿轮的齿面点。基于Pro/E用曲面重建的方法得到三维螺旋齿面,建立了弧齿锥齿轮的三维实体模型。利用Pro/E对齿轮副进行装配和动态干涉检测,以便进行切齿参数的调整,得到满足使用要求的齿轮副。通过一个实例说明了建模、装配、动态检测的过程。

新型双螺旋槽端面密封性能对密封腔压力扰动的动态响应分析

一种用于高速高压等极端工况下的新型双螺旋槽端面密封在实际运行过程中密封腔压力会出现波动,从而影响密封稳定性。提出了一种“开启力解析模型”的方法来求解稳态下密封性能对压力扰动的动态响应。计算结果表明,该密封装置在角频率大于7 000 rad/s的高频扰动下会失去稳定性。加入轴向阻尼元件可以改善稳定性,当加入阻尼为2 000 N.s/m时密封可以在任何频率扰动下稳定运行。

对数螺旋锥齿轮有限元接触分析前处理

对数螺旋锥齿轮动态接触分析的必要前提就是建立精确的有限元分析模型。在Hyper Mesh有限元前处理环境下,对对数螺旋锥齿轮的网格选择和划分方法进行研究,并在普遍采用的单齿网格划分方法的基础上提出一种新的单齿网格划分方法,提高了六面体网格的质量。对对数螺旋锥齿轮动态接触分析中的关键问题进行分析和研究,从而建立该齿轮精确的动态啮合有限元分析模型,为客观、真实地模拟对数螺旋锥齿轮动态啮合性能提供了必要的前提条件。

弧齿锥齿轮啮合稳定性的虚拟支承法动力学模型

提出一种在转子上设置虚拟支承的方法 ,以保证弧齿锥齿轮的啮合稳定性 ,并采用传递矩阵法 ,建立了弧齿锥齿轮 -转子系统的振动模型。给定的一对弧齿锥齿轮在工作过程中的啮合状态包括实际参与啮合的轮齿对数 ,每对轮齿分担的载荷和啮合点的位置 ,其中啮合点的位置应限制在一定的范围内而不应出现边缘接触 ,此即轮齿啮合的稳定性。由于实际工况的复杂性 ,通过改变虚拟支承的数量和位置 。

变螺旋铣刀结构设计与优化对铣削稳定性的影响

颤振是限制铣削生产率和影响工件加工质量的重要因素之一,稳定性图表和变螺旋铣刀结构设计是目前常用的抑制铣削颤振的方法。结合铣削过程中的稳定性极限三维叶瓣图对变螺旋铣刀结构进行设计优化,进而得到变螺旋铣刀最优螺旋角变量和齿距角变量。首先建立变螺旋铣刀铣削过程的动力学模型,结合仿真分析获得颤振稳定性三维叶瓣图,得到最大稳定性切削深度对应的最优螺旋角变量和齿距角变量值分别为1°和8.1°。实验结果可知,相较于常规结构铣刀,优化得到的变螺旋铣刀能够显著提高铣削稳定性极限、提高表面质量,为抑制铣削过程中颤振的变螺旋铣刀结构设计提供了理论基础。

惯性载荷对螺旋锥齿轮动态啮合特性的影响研究

根据动力学原理和Lagrange乘子约束,考虑惯性载荷对螺旋锥齿轮动态啮合分析的影响,提出一种新的有限元分析模型,分析惯性载荷对螺旋锥齿轮动态啮合特性的影响规律。计算结果表明,随着惯性载荷增大,齿面接触力也随之增大;惯性载荷对于啮合区宽度、齿面接触应力及最大应力位置均有影响。因此,惯性载荷对于螺旋锥齿轮动态啮合分析是必须考虑的因素。

螺旋立铣刀的动态切削力模型

以螺旋立铣刀为例,考虑切削厚度及切削宽度的变化以及切削过程中因激励而引起的动态切削位移,建立了动态切削力模型。为切削力的预报、仿真以及动态稳定性分析提供理论依据,具有理论研究及实用价值。

基于异地网络协同的螺旋锥齿轮模型集成设计

基于Web技术建立统一接口的服务发布向导和各平台的UDDI注册中心,成立了一个可实现螺旋锥齿轮异地网络协同设计的资源共享平台。通过对近些年来的螺旋锥齿轮研究的归纳与总结,定义了3种模型设计模块:由点到面的模型设计模块、由线构面模型设计模块、仿真加工模型设计模块,以实现模块化设计。同时,对模型设计任务逐层分解,数据互操作与信息资源的动态调配,多设计者决策的协调与优化,完成了螺旋锥齿轮的协同设计全过程,为螺旋锥齿轮的数字化设计和制造提供了方向和途径。