Experimental modal test of the spiral bevel gear wheel using the PolyMAX method

To verify the effectiveness and correctness of free modal analysis results from a Spiral bevel gear (SBG) wheel by using Finite element method (FEM), an experimental platform was constructed through the free-hanging support of the SBG wheel. The experiment used the hammer knock percussion for excitation and a three-directional acceleration sensor as signal acquisition equipment and utilized the LMS modal analysis module. The geometric model of the SBG wheel was constructed using an eight-node octagon instead of the SBG wheel outer contour. The experiment then extracted the modal parameters of the wheel using the PolyMAX method and obtained the first- and second-order natural frequencies, damping ratios, and mode shapes of the SBG wheel at 0-7 kHz during the experimental modal test. The results of the experimental test were compared with those of the FEM free modal analysis. The first- and second-order natural frequency error rates by FEM were 0.25 % and 0.45 %, respectively. The experimental modal test result verified the rationality of the model by FEM, thus showing that the result of modal analysis by FEM is reliable and providing a basis for the dynamic characteristic analysis of SBG.     

齿轮传动加速度噪声辐射机理研究

从齿轮动力学的观点出发,分析了齿轮传动的加工误差和弹性变形所产生的冲吉力及冲击加速度的大小,利用声学理论论计算了齿轮啮合冲击时产生的声压和声功率等声学特性参数,从而可定量的计算化加速度噪声。这对齿轮系统的减振降噪和噪声控制具有重要意义。     

DETERMINATION OF UNKNOWN IMPACT FORCE ACTING ON A SIMPLY SUPPORTED BEAM

This work presents a predictive model for determining the location and amplitude of an unknown impact force acting on a simply supported beam. Both time and frequency domain prediction methods are developed, respectively. The structural modal parameters can be first obtained by theoretical modal analysis (TMA) or by experimental modal analysis (EMA). The structural response at time and frequency domains due to an unknown impact force can then be measured and recorded. The predicted response can also be formulated and expressed as functions of amplitude and location of the impact force. The sum of square errors between the predicted and measured response is then defined as the objective function, while the amplitude and the location of the unknown impact force are defined as design variables. The optimisation problem is thereby constructed and can be solved for the amplitude of the impact force. The mode shape information associated to the location of the impact force can also be resolved and compared to the structural mode shapes to determine the location of the unknown impact force. Both numerical and experimental prediction results are presented. Results show that the predictive model is feasible and leads to the prediction of magnitude and location of the unknown impact force for arbitrary structures as well.     

双层隔振系统模态匹配分析及其振动特性

针对出口内燃动车动力包的双层隔振问题,根据双层隔振系统的结构参数,建立双层隔振系统的有限元模型。对双层隔振系统进行了模态计算,掌握了系统的频率特性。根据柴油机组激振力的频率特性,定量对双层隔振系统进行模态匹配分析。对双层隔振系统进行谐响应计算,准确判断构架和机组是否发生共振,验证模特匹配的合理性。施加怠速工况下的各个激振力,对双层隔振系统进行了强迫振动计算,计算双层隔振系统的振动烈度和传递率。结果表明：双层隔振系统的隔振性能良好,能满足实际工程需求,研究结果可为实际工程提供参考。     

时间序列模型中的随机共振现象

在滑动自回归(auto regressive and moving average,简称ARMA)时间序列模型的基础上,利用模态稳定性图来确定系统真实模态,描述了在求解过程中产生的随机共振现象。借助悬臂梁的有限元模型,利用精细时程积分方法计算得到了其加速度脉冲响应函数,建立了用于振动模态识别的ARMA模型。在利用模态稳定性图来确定系统真实模态的过程中发现,加入合适的噪声信号可以有效地改善识别结果,剔除虚假模态,即产生了随机共振现象。对悬臂梁进行时变化处理后,随机共振现象较之前不变系统更加显著,对最终识别结果产生了明显的优化作用。     

基于结构与声场耦合模态分析的车内噪声控制方法

在汽车车内结构噪声的控制中，传统的结构振动模态分析不能准确地反映车身结构与车内声场的耦合特性，将车身结构与车内声场综合起来考虑，采用结构与声场耦合模态分析方法研究了汽车车内结构噪声的控制问题。在介绍结构与声场耦合模态分析方法理论的基础上，讨论了该方法在车内结构噪声控制中的工程实现。该方法在某车车内噪声控制的应用中取得了明显的降噪效果，证明了该方法的可行性和有效性。     

Exact static analysis of partially composite beams and beam-columns

The ordinary differential equations and general solutions for the deflection and internal actions and, especially, the pertaining consistent boundary conditions for partially composite Euler–Bernoulli beams and beam-columns are presented. Static loading conditions, including transverse and axial loading and first- and second-order analyses are considered. The theoretical procedure is applicable to general loading and boundary conditions for uniform composite beams and beam-columns with interlayer slip. Further, the exact closed form characteristic equations and their associated exact buckling length coefficients for composite columns with interlayer slip are derived for the four Euler boundary conditions. It is shown that these coefficients are the same as those for ordinary fully composite (solid) columns, except for the Euler clamped-pinned case. For the clamped-pinned case, the difference between the exact buckling length coefficient and the corresponding value for solid columns is less than 1.8% depending on the so-called composite action parameter and relative bending stiffness parameter. Correspondingly, the maximum deviation between the exact and approximate buckling load is at most 2.5%. These small differences can in most practical cases be neglected. Also, the maximum theoretical range for the relative bending stiffness for partially composite beams and beam-columns is derived. An effective bending stiffness, valuable in the determination of the critical buckling load for partially composite members, is derived. This effective bending stiffness is also suitable for analysing approximate deflections and internal actions or stresses in composite beams with flexible shear connection. The beam-column analysis is applied to a specific case. The difference in the approaches to the first- and second-order analysis is illustrated and the results clearly show the magnification in the actions and displacements due to the second-order effect. The magnification of the internal axial forces is different from magnifications obtained for the other internal actions, since only that portion of an internal axial force that is induced by bending is magnified by the second-order effect.     

基于光-压电的非接触式弹性圆环独立模态控制

在接近紫外波长的高能光束均匀照射下,极化的镧改性锆钛酸铅(PbLaZrTi,PLZT)铁电陶瓷具有反常的光生伏特效应,即在两极间会产生很高的电压。利用此电压信号来驱动层合于柔性板壳结构的压电作动器,可以实现对柔性板壳结构的非接触式控制。为实现弹性圆环的非接触式独立模态控制,利用模态展开技术及振型函数的正交性设计余弦状正交模态作动器,并利用PLZT产生的电压来驱动层合于圆环上的聚偏二氟乙烯(Polymeric polyvinylidene fluoride,PVDF)压电模态作动器。在控制策略上采用速度反馈的定光强控制,通过模态速度符号来调节压电作动器与PLZT的连接方向,以实现作动器产生控制力的正/负切换。采用Newmark-β法对弹性圆环在不同光强下的动态响应进行数值仿真分析。仿真结果表明,在PLZT产生的电压信号的驱动下,压电作动器对系统产生的驱动力随光照时间成指数倍增加,且光照强度越大控制效果越好。     

汽车动力总成悬置系统多工况运行模态试验研究

由试验测得发动机启动、怠速和急加速三种典型工况下的振动响应,进行了动力总成悬置系统的运行模态参数识别。采用多参考点最小二乘复频域法,通过试验测得的振动响应获得系统工作振型。由于发动机激励不具备零均值白噪声的特点,运用了多种模态置信度指标进行模态验证,获得了较可信的模态参数。试验结果表明,动力总成悬置系统的运行模态参数与发动机工况有关,对于大阻尼和密集模态的动力总成悬置系统,多工况的运行模态试验可以更准确地识别悬置系统的模态参数。研究结果对悬置元件参数设计具有重要的参考价值。     

Karhunen–Loève modes obtained from displacement and velocity fields: Assessments and comparisons

The Karhunen–Loève (KL) decomposition method can be used to expand a random process into series of deterministic functions (or KL modes) with uncorrelated random variables as the decomposition coefficients. In vibration analysis, the KL theory is classically developed from the displacement field. In this study, the displacement field, velocity field and displacement–velocity field are used with the KL theory based on an averaging operator involving time and ensemble averages. The three families of KL modes are compared and interpreted in terms of normal modes in the case of linear vibrating systems subjected to white-noise excitation.     

Dynamic characteristics analysis and experimental research on a new type planetary gear apparatus with small tooth number difference

Aimed at an internal mesh planetary gear with small tooth number difference (PGSTD) reducer, this paper proposes dynamic characteristics analysis. First, static finite element (FE) analysis is performed to check the structural strength with the stress distribution in the gear teeth. Second, by means of the dynamic contact FE method, the internal dynamic excitations of teeth mesh are obtained, including mesh stiffness excitation, transmission error excitation and mesh impact excitation. According to the established model for dynamic FE modal analysis, the natural frequencies and mode shapes of the planetary gear apparatus (PGA) are calculated, and its structural dynamic response and acceleration noise are researched with the comprehensive consideration of internal and external excitations. Finally, the noise and vibration testing on the PGA is carried out by utilizing the vibration test equipment. The results confirm that the predicted values are consistent with the experimental results.     

数字化进退针装置的设计与试验

针对细胞注射中微注射针刺膜速度慢和定位精度差等不足,研制一种基于惯性力与摩擦力交替作用的数字化进退针装置。阐述该装置工作机理,利用压电陶瓷低频振动产生的冲击式惯性力,克服摩擦力产生微进给。建立数字化进退针装置的动力学模型,利用数值方法求解其输入输出响应关系。该模型求解结果在性能试验得到了验证。在小鼠卵母细胞显微注射试验中,对数字化进退针装置进行了应用研究。研究结果表明：数字化进退针装置能够满足显微注射要求,其动力学模型是合理的。     

基于传递率函数的运行模态分析方法

传统的运行模态分析方法在推导过程中多假设激励为白噪声,造成在应用上有一定的局限性。提出了一种基于传递率函数的运行模态分析方法,无需采用白噪声假设,利用两种不同载荷情况下的传递率函数构造有理函数,通过有理分式Forsythe正交多项式法对其进行拟合,得到模态频率、阻尼和振型参数。最后,采用机翼模型仿真算例和悬臂梁实验,验证了在非白噪声激励情况下该方法的有效性与可靠性。     

基于随机集理论的并发故障诊断信息融合方法

为了诊断并发故障,提出一种基于随机集理论的信息融合方法.首先构造包含并发故障的论域,并在此论域的超幂集上定义扩展型随机集.基于该随机集和广义集值映射给出证据组合规则的随机集模型,用其构造可以同时适用于单发和并发故障诊断的新型组合规则.此外,根据传感器提供的故障信息构造故障样板模式与待检模式的模糊隶属度函数,利用模糊集的随机集表示以及随机集似然测度,获得两种模式匹配的程度作为待融合的诊断证据.最后通过在电机柔性转子平台上的试验,证明了所提方法可有效地减少单一传感器信息诊断的不确定性,显著提高转子系统故障诊断的精度.     

紊流润滑滑动轴承壁面压力脉动效应研究

壁面压力脉动是紊流润滑滑动轴承随机振动的主要激励源之一,建立紊流激励特性和轴承结构动力学响应之间的关联,对高转速、低黏度润滑滑动轴承的状态监测和故障诊断具有重要意义。为研究紊流润滑滑动轴承的壁面压力脉动效应,考虑流体油膜中存在逆压力梯度的影响,选用Rozenberg模型和广义Corcos模型表征壁面压力脉动的自功率谱和互功率谱,采用波数域模态叠加法求解滑动轴承紊流壁面压力脉动模型,分析滑动轴承在不同工况参数下壁面压力脉动的激励特性以及结构的响应特性。结果表明：低波数区域紊流脉动压力是轴承结构高频随机振动的主要因素;随着润滑油黏度的降低,高频范围内的轴承模态响应幅值增大,共振峰值附近产生较宽的频带和较高的振幅;随着轴颈转速和径向载荷的升高,紊流压力梯度增大,高频范围内的轴承模态响应幅值也随之增大。     

一种新的脉冲转换装置的结构设计与模态分析

基于稳态射线束流的快脉冲辐射场建立技术一直是核探测与计量领域的一大难题。内置式高速电机在旋转机械中应用后,可简化系统的结构、提高运行转速,满足转换脉冲的高频率要求。提出了一种新的脉冲转换装置的实现方案,建立了它的三维原理性模型。针对该模型,计算了脉冲转换的主要参数,并对其进行了基于ANSYS的模态分析,得到了转子的前几阶临界转速。该项研究工作为脉冲转换装置的实际设计制造和使用提供了一些参考。     

电力变压器缩尺模型振动试验及其声学模型

首先,根据某电力变压器的缩尺比例模型在不同激振频率下箱壁振动相位和振幅的测试结果,得出当激振频率超过7阶模态频率时,其相位和振幅呈随机分布的结论,确定了电力变压器简化为点声源的划分形式;其次,建立了户外半开空间内电力变压器相干虚源模型,该模型考虑了声线多次反射形成的无限个虚源之间的干涉效应;最后,应用该相干虚源模型对存在相位关系的电力变压器组辐射声场进行计算,通过与边界元模型、ISO9613模型计算结果与实测值进行对比。结果表明,该相干虚源预测模型因考虑了相位信息,能反映出声波在不同位置处的传播趋势,比原有的ISO9613模型更为准确,验证了所提理论模型的可行性。     

Dynamic response analysis of block foundations with nonlinear dry friction mounting system to impact loads

It is essential to establish a dynamic model to predict and evaluate the dynamic performance of a nonlinear dry friction mounting system during design procedure, when it is impossible to carry out the test of prototype. Unlike the conventional ideal dry friction model where the direction of dry friction force is always considered to be opposite to that of relative velocity, a new equivalent resistance model of dry friction force is proposed based on the bilinear hysteretic model by introducing a parameterg γ in this work. The equivalent resistance contains spring force and damping force, whose direction is not opposite to that of relative velocity. Then, a dynamic model of the block foundation with nonlinear dry friction mounting system is established. When the equivalent resistance is applied to the dynamic model, its dynamic responses are obtained under common practical forms of press loads: rectangular pulse, half-sine pulse, and triangular pulse. Compared to experimental results, the dynamic responses based on the equivalent resistance model are more consistent with the simulation results based on the ideal dry friction model and the validity of the equivalent resistance model for the bilinear hysteretic model in this work is verified. Furthermore, the effect of the pulse shape and pulse duration on the dynamic responses of the block foundation with nonlinear dry friction mounting system is investigated.     

轴向柱塞泵噪声源的识别策略:仿真和试验

在流体传动系统中,轴向柱塞泵的高噪声成为一个显著弊端,高噪声的噪声源主要来自于柱塞腔压力产生的各种作用力和力矩。首先通过集中参数仿真模型在时域和频域对轴向力和力矩进行分析,然后通过试验测量单点沿x、y和z轴,不同压力和排量等级下以及不同位置的振动特性来分析主要噪声源。对比仿真和试验结果发现:沿x轴力矩产生的振动成为主要噪声源;随着泵压力和排量升高,振动速度频域特性中一次谐波所占比重逐渐增大;对于悬臂安装的泵,距离安装面越远振动情况越剧烈。     

基于MCKD和改进HHT多尺度模糊熵的齿轮故障诊断方法

针对齿轮故障信号常伴有大量噪声,故障特征难以提取的问题,提出一种基于最大相关峭度解卷积(MCKD)和改进希尔伯特-黄变换(HHT)多尺度模糊熵的故障诊断方法。首先采用MCKD算法对采集到的齿轮振动信号进行降噪处理,以提高信号的信噪比;然后利用自适应白噪声完备经验模态分解(CEEMDAN)对降噪后信号进行分解,获得一系列不同尺度的固有模态函数(IMF),并通过相关系数-能量的虚假IMF评价方法选取对故障敏感的模态分量;最后计算敏感IMF分量的模糊熵,将获得的原信号多尺度的模糊熵作为状态特征参数输入最小二乘支持向量机(LS-SVM)中,对齿轮的故障类型进行诊断。实测信号的诊断结果表明,该方法可实现齿轮故障的有效诊断。