齿轮副非线性接触特性与动力学耦合分析方法

为了更深入地研究齿轮副非线性动力学现象的产生机理,提出了一种高效的齿轮副瞬态接触特性与动力学耦合分析方法。该方法考虑齿轮接触特性与系统振动之间的交互作用,将齿轮副动态承载接触分析(DLTCA)和系统动力学分析进行耦合,形成了系统“激励-响应-反馈”闭环动力学分析流程。研究发现,振动位移的反作用会改变齿面动态接触状态,影响动态啮合刚度和综合啮合误差等振动激励。在共振区附近,振动位移的增大可能会使齿面出现完全脱啮,产生响应幅值跳跃等非线性现象。增加啮合阻尼和螺旋角均会使系统非线性特性减弱直至消失。该方法可计入齿面误差、修形、齿侧间隙等多因素的影响,并通过试验进行了验证。结果表明,该方法能够更真实地模拟齿轮副动态啮合过程,可作为现有齿侧间隙非线性动力学的有效补充。     

少齿差金属橡胶复合摆线齿轮副动态特性分析

金属橡胶具有很强的变形补偿能力,可帮助实现高精密传动。介绍了复合摆线齿轮副的结构及原理,建立了齿轮副的三维模型,并在ADAMS中建立起此金属橡胶齿轮副的刚柔混合模型后进行动力学仿真,分析了弹性模量变化、双联齿轮间隙及两对齿轮副中心距对少齿差复合摆线齿轮副角速度、角加速度、啮合力和传动误差的影响,同时对比分析了刚性、刚柔复合2种齿轮副输出轮角速度以及传动误差的差异。结果表明增大少齿差齿轮副中心距、适当增大金属橡胶弹性模量和双联齿轮间隙可减小振动波动,刚柔复合摆线齿轮的角速度和传动误差整体波动均比刚性齿轮副小,说明金属橡胶在新型NN型两级少齿差齿轮副中起到了减振效果。     

高重合度斜齿轮多齿对啮合的补偿修形设计与分析

为准确计算齿面修形量以降低承载传动误差波动幅值,考虑齿轮传动过程中不同啮合区之间轮齿承载变形的变化规律,提出了高重合度斜齿轮多齿对啮合的补偿修形设计方法。基于标准齿面在设计载荷下的承载传动误差波动幅值大小和方向,预设修形齿面的几何传动误差;通过优化几何传动误差控制齿面修形量大小,实现轮齿不同啮合区的精确补偿修形;建立齿向改进修形齿面模型,以齿条刀具附加转角和齿向修形参数为优化变量,采用快速非支配排序遗传算法(NSGA-II)基于承载传动误差幅值最小确定齿面最佳修形量。研究结果表明:啮合齿对变化引起不同啮合区之间轮齿承载变形的变化是承载传动误差幅值波动的主要原因;齿面补偿修形后,承载传动误差幅值大幅下降,在设计负载下,承载传动误差幅值几乎降到零;改进修形也能够有效补偿不同啮合区之间轮齿承载变形的差异,同时避免了边缘接触,降低了齿轮副的振动与噪声。     

渐开线少齿差内啮合齿轮副齿间油膜力分析

一、引言由于渐开线少齿差内啮合齿轮副齿廓的几何形状和尺寸极其接近,齿廓的曲率中心又处于同一侧,因此,当内外齿轮作相对运动时,在齿侧之间能形成相当大的油膜力。迄今,国内外对渐开线少齿差内啮合齿轮副齿间油膜力直接进行分析较少。本文尝试采用简单的近似方法计算该种传动齿间油膜力的大小。本文考虑到渐开线少齿差内啮合齿轮副的齿廓比较接     

少齿差行星减速器非线性耦合振动研究

以少齿差行星减速器为研究对象,综合考虑时变啮合刚度、齿轮传递误差、齿侧间隙及轴承支撑刚度和阻尼等因素,采用集中质量法建立了弯-扭耦合8自由度非线性振动模型,运用四阶五级的RKF法对动力学方程进行求解;研究了减速器的非线性耦合振动,并进行实验分析对比.结果表明:双联齿轮振动位移和速度最小,固定齿轮扭转角位移和角速度最小,且扭转方向比y方向的振动平缓;固定齿轮、输出齿轮振动为近混沌状态,双联齿轮振动复杂为混沌运动状态;齿轮动态啮合力和轴承动载荷均呈现周期性.该耦合动力学模型仿真结果与实验测试结果基本符合.     

高重合度与低重合度齿轮系统动力学分岔特性对比分析

针对高重合度齿轮和低重合度齿轮,采用有限元方法计算其啮合刚度;建立含齿侧间隙和时变刚度的齿轮系统的扭转振动模型,对模型啮合线位移解的分岔特性和跳跃性进行研究。研究结果表明:当忽略误差,仅考虑齿侧间隙的影响时,高重合度齿轮系统啮合线位移的解,连续平稳,不存在跳跃现象,低重合度齿轮系统啮合线的位移解,多处发生了跳跃现象;齿频误差激励在高速区域(无量纲转速?为1.1~2.1区域)其对低重合度齿轮的动力学影响要大于对高重合度齿轮的影响;随着偏心误差的增加,啮合线位移增加,系统的周期稳定性逐渐降低,偏心误差对普通齿轮的影响比高重合度齿轮的影响要大;在误差作用下,高重合度齿轮的周期稳定性要高于普通齿轮的周期稳定性,运行更加平稳,采用高重合度齿轮可以降低齿轮的振动和噪声。     

刚柔复合齿轮结构参数对其动态特性的影响分析

刚柔复合齿轮是通过内部柔性部件自适应变形协调实现高可靠精密传动的新型齿轮.为了探究复合齿轮变形协调参数对其动态特性的影响,在建立刚柔复合齿轮综合啮合刚度模型的基础上,采用ADAMS建立了刚柔复合齿轮副虚拟样机.分析了齿圈与轮毂之间的间隙、齿轮副的中心距、金属橡胶的弹性模量对复合齿轮齿圈加速度、角加速度、啮合力和动态传动误差等动态特性的影响规律.仿真结果表明:减小齿轮副中心距使得齿圈与轮毂角加速度和齿轮副啮合力明显减小,传动精度也有所提高;增加金属橡胶弹性模量可以有效抑制齿圈振动加速度,但啮合力增加;齿圈与轮毂间隙增大,齿圈的加速度增加,传动误差增大,角加速度有所减小.综合以上因素,减小齿轮副中心距和齿圈与轮毂间隙,增加金属橡胶弹性模量可以减小复合齿轮振动,提高传动精度.     

基于参数非线性的二级行星减速器扭转振动分析

为掌握多元非线性参数对二级行星减速器动态特性的影响,在综合考虑齿轮副之间的时变啮合刚度、综合传递误差、啮合阻尼以及齿侧间隙的情况下,基于集中参数法建立了减速器纯扭转振动模型,采用变步长的Runge-Kutta法求解系统动态响应,获得了各级内、外齿轮副之间的振动特性时域数据,以及动态啮合力.理论求解与实验结果最大误差值0.98,平均误差0.05,一级振动及动态啮合力大于二级;同级中太阳轮振动大于行星轮,内、外啮合齿轮副动态啮合力基本相当.频域分析显示:主要振频为齿频和啮频相互耦合所致;一级行星轮齿频为12.93Hz,接近第一阶主振频12Hz;二级啮频62.37Hz,接近第二阶主振频62Hz,成为系统前两阶激振源.     

2K-H行星齿轮传动非线性动力学

为研究2K-H行星齿轮传动在外扭矩作用下受齿轮副啮合综合误差激励的非线性动力学特性,建立了间隙型非线性动力学模型,其中考虑了齿侧间隙和时变啮合刚度。用自适应变步长Gill数值积分方法对系统的动力学微分方程进行求解。以3行星轮的2K-H行星齿轮减速器为算例,得到系统在不同参数条件下的简谐、非简谐单周期、次谐波、准周期和混沌稳态强迫响应。利用时间历程、相平面、Poincaré映射以及Fourier频谱,表明行星齿轮传动由于齿侧间隙存在会呈现丰富的强非线性动力学行为。     

滑动轴承支撑下齿轮耦合转子系统弯扭耦合振动特性分析

在综合考虑齿轮副齿侧间隙以及滑动轴承的油膜力等非线性因素的基础上,建立滑动轴承-双转子-齿轮耦合系统的非线性动力学模型。通过数值仿真的方法研究耦合系统参数对齿轮副啮合冲击特性的影响规律,以及系统稳定性随转速的分岔规律。研究结果表明,滑动轴承的油膜对齿轮耦合转子系统的混沌运动具有显著的镇定作用;滑动轴承间隙以及转子质量偏心设计不当将会导致系统齿轮副产生单边冲击现象。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with