滚轮传动系统振动噪声控制方法探讨

本文在阐述滚动传动系统的基本结构后,对滚轮系统辐射噪声的影响因素进行研究,并针对滚轮传动系统振动噪声采取了一定的降低噪声措施。     

拖拉机变速器对传动系噪声贡献量的特性分析

为了研究拖拉机变速器噪声对传动系统噪声的影响程度,文中以某款拖拉机变速器为研究对象,详细分析了对传动系统噪声贡献量的特性。通过噪声试验确定该拖拉机传动系统噪声数值;建立变速器箱体的有限元模型,通过箱体振动响应试验对所建仿真模型的准确性进行了验证,在此基础上得到了变速器箱体声学分析的边界条件,运用声学分析软件得到变速箱的振动辐射噪声;将试验所得传动系噪声和仿真所得变速器噪声代入声学贡献量公式计算,得出变速器噪声对传动系统噪声的贡献量。该方法为变速器噪声的降低提供了理论依据。     

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。     

准双曲面齿轮振动噪声试验与预估分析研究

为研究准双曲面齿轮传动机构的啮合振动、辐射噪声与传动误差的关系,建立三者之间的数据同步检测模型;并利用Y9550型锥齿轮滚动检验机搭建了综合试验平台。通过对一副准双曲面齿轮的振动与噪声信号的采集数据对比,分析振动与噪声的时域特征,并进一步分析振动与噪声谱中的频域相关特性。在Kato公式的基础上引伸出准双曲面齿轮的定量分析式,并借助传动误差的检测结果,对多次采集的数据进行以振动代替噪声的预估计算,试验结果表明:准双曲面齿轮的啮合振动能够较准确地反映出传动噪声的状态,并能够反馈到齿轮设计层面上,从而达到降低齿轮振动与噪声的目的,提高传动系统的稳定性。     

轴承刚度与齿轮螺旋角对减速器振动噪声影响的研究

以单级圆柱齿轮减速器为研究对象,综合考虑齿轮时变啮合刚度及误差激励的影响建立了传动系统动力学模型。以轴承动载荷为激励,采用FEM/BEM方法对减速器振动与声辐射特性进行了分析,得到了齿轮箱节点动响应时域历程及声场场点噪声谱,论述了激励中各谐波成分对齿轮箱振动噪声辐射的影响。计算了不同轴承刚度的动载荷与齿轮箱声辐射特性,得到了轴承动载荷各频率成分及声辐射随轴承刚度的变化规律。对比分析了直齿轮与斜齿轮及不同螺旋角下,齿轮时变啮合刚度波动与减速器各场点位置的噪声分布情况,为减速器的减振降噪提供了理论基础。     

基于LMS Motion的多级行星齿轮传动系统动力学仿真

以LMS Virtual.Lab Motion平台为基础,建立了二级行星轮传动系统模型;综合考虑了齿轮系统非线性振动问题,利用二级行星轮系统耦合模型在LMS中建立动力学仿真模型。通过仿真得到了各级齿轮啮合的时域以及频域载荷图谱,为后期计算齿轮系统的振动及噪声研究提供了数据源。通过仿真数据与理论计算相对比,验证了借助虚拟样机进行齿轮系统动力学分析的可行性,为该方面研究提供了新路径。     

电动汽车变速器壳体振动与辐射噪声的研究

以某款变速器为研究对象,首先建立轴齿系统动力学模型,求得变速器在某一工况下壳体所承受的动态时域历程和载荷谱。以动态载荷为激励,建立有限元和边界元的仿真模型,计算壳体表面振动加速度以及壳体近声场辐射噪声。其次搭建变速器壳体振动与辐射噪声测试平台,测试相同工况下的壳体表面振动加速度值和近声场1 m位置的噪声频谱图,并与仿真结果对比,验证了有限元模型及边界元模型的正确性。最后对变速器壳体不同局域进行优化,通过仿真计算,结果显示优化后变速器壳体振动幅值及辐射噪声均得到较好抑制。     

气动锚杆钻机齿轮传动系统运动特性分析研究

针对煤层硬度变化对气动锚杆钻机掘进效率影响较大的问题,采用ADMAS仿真软件,建立齿轮传动系统三维模型,对气动锚杆钻机齿轮传动系统进行动力学仿真分析.试验结果表明,齿轮传动系统运行过程中所受的岩层硬度载荷越大,各个齿轮产生的振动趋势越明显,同时,齿轮的传动级数越高,振动幅值变化越大,振动情况越激烈.通过试验验证,实际角速度、角加速度与仿真计算得到的角速度、角加速度变化趋势基本一致,相同载荷条件下,角速度和角加速度的实测最大值与仿真计算最大值相差较小,仿真计算结果准确.     

基于EMD和KNN的发动机辐射噪声预测研究

针对基于发动机表面结构单通道振动的辐射噪声预测问题,提出了一种结合经验模态分解(Empirical Mode Decomposition, EMD)和KNN(K-Nearest neighbor)的预测算法,通过EMD将单一振动时域信号分解为多个本征模态函数(Intrinic Mode Function, IMF)信号,并将每个IMF信号作为振动数据集的特征,最后以新的振动数据集为输入建立辐射噪声预测模型。试验结果表明,基于该算法建立的预测模型可解释方差分数为0.97,有着较小的预测误差。     

某柴油机喷油泵齿轮扭矩相位优化

齿轮敲击是发动机振动噪声的重要激励来源,减小齿轮敲击对于降低发动机辐射声压级、改善声音品质具有重要意义。为降低齿轮敲击噪声,建立了齿轮驱动系统及配气机构的动力学仿真模型,本模型考虑了各转速下的曲轴转速波动以及齿轮系各驱动附件的力矩,计算得到了各齿轮啮合副的随时间域的齿轮啮合力。通过改变喷油泵齿轮扭矩相位,得到一系列的时间域的齿轮啮合力和齿轮轴承载荷,通过将时域的齿轮轴承载荷转化为频域的齿轮轴承载荷,总结了齿轮轴承总力的计算方法,以此齿轮轴承总力来评价齿轮系激励力的大小。通过对比确定了轴承载荷较小的喷油泵齿轮扭矩相位,得出了最优的相位和最差的相位。在发动机台架试验中亦采用相应的扭矩相位进行发动机九点噪声试验,通过试验得到了喷油泵扭矩相位与噪声大小的关系。试验与仿真两者的扭矩相位对噪声的影响关系一致,验证了喷油泵齿轮扭矩相位优化方法的有效性,可通过此方法来对柴油机喷油泵的最佳相位进行优化。     

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.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.