齿面摩擦和啮合刚度对双渐开线齿轮传动动态特性的影响研究

针对双渐开线齿轮传动动态特性问题,通过建立双渐开线齿轮的有限元模型,综合考虑齿面摩擦与齿轮啮合刚度二因素,对双渐开线齿轮传动系统进行了有限元模态分析,运用响应曲面法研究了齿面摩擦与齿轮啮合刚度对双渐开线齿轮振动变形和模态频率的影响;选取不同模态阶数对双渐开线齿轮传动系统进行了动态特性研究,分析了不同模态阶数下双渐开线齿轮的振动变形与模态频率变化状况。研究结果表明,随着齿面摩擦因数与齿轮啮合刚度的增加,不同模态阶数下双渐开线齿轮传动系统各阶振动变形与模态频率均显著增加,齿面摩擦与齿轮啮合刚度对双渐开线齿轮传动动态特性有一定影响,在对齿轮传动系统进行动态特性研究时,必须对齿面摩擦与齿轮啮合刚度进行充分考虑。     

直齿圆柱齿轮动力学特性分析与ADAMS仿真研究

在考虑时变啮合刚度、啮合阻尼、齿面摩擦等因素的基础上,采用集中参数法建立了圆柱齿轮传动系统平移-扭转耦合动力学模型。根据齿轮箱设计参数,使用龙格-库塔法求得各齿轮的振动位移,计算了齿轮副的动态啮合力。并在Adams中建立齿轮传动系统的多体接触动力学模型并进行仿真,获得齿轮啮合传动过程中的动态啮合力和振动位移、振动速度。通过台架试验,测量齿轮传动系统的振动加速度,采用数值积分计算振动速度和位移,并分析其振动特性。结果表明,在齿轮的振动速度与位移方面,集中参数求解结果与实验数据具有良好的一致性;啮合力方面两种方法均得到与理论计算值一致的结果,验证了采用两种方法对比分析研究方法的可行性。     

人字齿轮分扭传动系统动力学建模与动态分析

以某航空发动机人字齿分扭传动减速器为研究对象,基于有限单元节点法建立考虑轴、齿轮转子陀螺效应、轴承支撑、系统阻尼及齿轮啮合作用的人字齿分扭传动系统动力学模型,计算人字齿时变啮合刚度,根据实测齿面计算出静态传递误差。根据建立的系统动力学方程,按振动理论方法计算得到轮系典型模态,经试验测试验证了计算模态的正确性;利用NewMark法对系统的时域及频域响应进行仿真计算,计算得到的系统时域响应收敛且存在调制现象,频域分析中存在啮合频率的次频、倍频与轴频。计算结果均与试验结果基本相符。研究工作为航空齿轮传动动态性能分析提供了有参考价值的方法。     

双啮合针齿凸轮分度机构模态分析与试验研究

为探究一种新型间歇机构——双啮合针齿凸轮分度机构的振动特性,考虑各零部件之间的复杂连接关系,建立机构有限元模型进行模态分析。提取有限元模型分别在分度期和间歇期的前六阶模态振型,最后对样机进行试验模态分析。对比发现试验模态分析固有频率与有限元计算结果相近,验证了有限元模态分析方法的可靠性。依间歇期的低阶频率,实际运转情况机构不会发生因输入引起的结构共振。通过模态分析为双啮合针齿凸轮机构振动特性分析,结构优化设计提供了试验支撑与理论依据。     

某乘用车手动变速器齿轮啸叫噪声研究

为解决某乘用车手动变速器存在的齿轮啸叫噪声问题,首先通过整车道路试验和变速器台架试验,识别出产生齿轮啸叫噪声的特征阶次及转速,然后建立该手动变速器齿轮传动系的多体动力学模型,考虑各对齿轮的时变啮合刚度、齿侧间隙、啮合阻尼,仿真获得了轴承动态载荷。利用在二挡工况下获得的变速器各轴承动载荷,采用有限元及边界元法计算了变速器壳体的振动响应及辐射噪声,并利用试验测得的结构表面振动加速度进行了试验验证。仿真获得了变速器壳体主要噪声源位置,为降低齿轮啸叫噪声提供了依据。     

电动汽车传动系统多工况动态传递误差分析

为探究电动汽车高速传动系统多工况下扭转振动规律和动态传递误差,建立某型电动汽车整车动力传动系统18自由度动力学模型。采用势能法计算出各级传动齿轮副的时变啮合刚度,运用切片法计算了考虑时变啮合刚度作用的各级传动齿轮副静态传递误差,并通过台架试验完成了静态传递误差检验与修正。对18自由度模型求解,得到系统的固有特性和不同工况下的动态传递误差,分析讨论了动态传递误差频谱特征。分析结果表明：各级齿轮副的异向扭转模态频率和车轮的扭转模态频率是各工况下动态传递误差频谱的主要成分,对应不同工况,各阶模态对动态传递误差的贡献量有很大不同。     

车辆动力传动系统弯扭耦合振动模型的建立及复模态分析

以某履带车辆的多轴齿轮动力传动系统为研究对象,按照一定的简化原则建立多自由度的弯扭耦合振动力学模型,并针对弯扭耦合振动力学模型的特点,利用有限元理论与数学模型的相结合,在ANSYS中建立考虑齿轮的啮合刚度和啮合阻尼,以及轴承的支承刚度和油膜阻尼的有限元模型,对有限元模型进行有阻尼的复模态计算,并对弯扭耦合振动特性进行分析.探讨耦合模态中的振动形式以及模态参与因子和有效质量,研究齿轮时变啮合刚度和啮合阻尼对多轴齿轮动力传动系统弯扭耦合振动模态的影响情况.对齿轮传动系统进行弯扭耦合振动台架试验,将试验数据与仿真计算结果进行对比,验证了有限元模型的正确性,为进一步的动力学分析奠定了基础.     

多间隙耦合齿轮转子系统动力学与试验研究

为了研究多间隙对齿轮转子系统动力学特性的影响,提出一种考虑多间隙耦合的齿轮转子系统动力学建模方法,并利用相应的动力学试验验证了建模方法的准确性。在动力学模型中,考虑了轴承径向间隙、动态齿侧间隙以及时变啮合刚度。分析转速和间隙大小对系统振动特性的影响规律。结果表明:从动轮加速度振动频谱主要包含径向振动频率和啮合振动频率。随着转速的提高,径向振动幅值增大,啮合振动也更为剧烈。径向间隙增大导致径向振动与啮合振动幅值升高,而齿侧间隙增大会导致机构回差增大。通过动力学验证试验,从频率和幅值上验证了理论计算和分析结果的正确性,但试验数据与理论计算之间仍存在一定误差,尤其是幅值误差较大,这些误差的主要来源是模型参数误差和测量误差。     

环板式针摆行星传动非线性动态啮合特性分析

根椐环板式针摆行星传动的动态啮合特性,采用有限元分析软件ANSYS/LS-DYNA模块,建立了针摆传动刚柔组合模型,动态模拟了针轮与摆线轮的啮合过程,求解了啮合过程中瞬时应力、变形和动态啮合刚度.分析了啮合应力沿齿宽和齿高方向的变化规律及啮合刚度的非线性特性.分析结果说明,非线性啮合刚度是样机振动的一个主要动态激励.因此,新样机制做要提高啮合刚度,以减少振动.     

高速直齿锥齿轮传动误差测试及动态性能分析

以某直齿轮-锥齿轮二级传动系统为对象,研究系统中的直齿锥齿轮动态传动误差测量、动态传动误差与齿轮传动振动之间的关系。构建直齿锥齿轮传动高速动态传动误差测试系统,研究得到高速情况下的相关测量技术,测得高速直齿锥齿轮传动动态传动误差曲线。采用滤波、频谱分析等信号处理方法分析测量的动态传动误差数据,得到高速直齿锥齿轮传动动态性能参数,与箱体对应部位测得的振动信号数据进行对比。研究结果表明,直齿锥齿轮的动态传动误差以轴频分量为主;直齿锥齿轮传动误差低频分量随转速变化大;动态传动误差与齿轮支撑轴承处的振动加速度在反映齿轮的动态特征时具有一致性。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.