拍频激励下的冲击钻进机械系统动力学特性研究

考虑系统的振动和钻进运动,建立了能够将高频低幅激励转化为低频高幅响应的冲击钻进机械系统的力学模型。分析了系统部件在碰撞以后出现“同步”和“非同步”运动的条件。
采用了具有低频调制激励与振动系统固有频率（所期望的低频）吻合以及只用调制波正值部分激励质量块M2这两种特征的拍频运动激励,结果表明,该激励能够产生有效的冲击力,即锤击效应。给出了两种能够获得稳定钻进运动的途径。
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High passive-stability diode-laser design for use in atomic-physics experiments

We present the design and performance characterization of an external-cavity diode-laser system optimized for high stability, low passive spectral linewidth, low cost, and ease of in-house assembly. The main cavity body is machined from a single aluminum block for robustness to temperature changes and mechanical vibrations, and features a stiff and light diffraction-grating arm to suppress low-frequency mechanical resonances. The cavity is vacuum sealed, and a custom-molded silicone external housing further isolates the system from acoustic noise and temperature fluctuations. Beam shaping, optical isolation, and fiber coupling are integrated, and the design is easily adapted to many commonly used wavelengths. Resonance data, passive-linewidth data, and passive stability characterization of the new design demonstrate that its performance exceeds published specifications for commercial precision diode-laser systems. The design is fully documented and freely available.     

Measurement of high-frequency milling forces using piezoelectric dynamometers with dynamic compensation

Piezoelectric dynamometers are widely used to measure machining forces during milling operations. While dynamometers are precise in measuring the low-frequency content of machining forces, their electromechanical dynamics distort the high-frequency content of the forces, resulting in critical measurement errors particularly in high-speed or highly intermittent milling processes. Existing methods (e.g. Augmented Kalman Filter) that are used to remediate the high-frequency content of the forces measured by dynamometers require tuning multiple parameters based on prior knowledge of the measurement noise and accurate models of the dynamometer dynamics, which continuously change during the process as material is machined away from the workpiece. Two new methods are presented in this paper to address this issue. The first method uses regularized deconvolution to estimate machining forces from the output signal of the dynamometer. In this method, regularization does not require prior knowledge of the measurement noise or variations of the system dynamics, but it cannot be implemented in online force monitoring and control systems. The second method designs a Sliding Mode Observer (SMO) to estimate milling forces recursively at each measurement timestep. The SMO can be implemented in online force estimation, is robust against the variations of system dynamics, and requires tuning only one gain that is independent from the system dynamics or measurement noise. The presented experimental results verify the effectiveness of these methods in accurately estimating high-frequency milling forces from dynamometer measurements.     

底部钻柱近钻头动态力测量及声传输方法

为研究随钻测井时底部钻柱近钻头动力学特性,设计直梁应变片式测力传感器,研制一种基于虚拟仪器平台的模拟钻柱动态力无线测量装置,用于模拟钻柱旋转过程中轴向力、侧向力和转矩的多线程检测。在此基础上,比较井下数据传输方法,以纵波为传输载体,设计模拟钻柱声传输装置,对动态力数据进行脉冲时延和OOK(On-off keying)调制,沿管轴方向对有限长模拟钻柱施加纵向激励,进行模拟钻柱信道动态力测试信号的声传输试验。结果表明,系统在实验室内实现动态力数据经时延脉冲OOK信号调制后沿模拟钻柱信道的低频声波传输,为近钻头传感器测量数据的低频声传输系统的应用提供理论与试验依据。     

Vibration from a shaft-bearing-plate system due to an axial excitation of helical gears

In this paper, a simplified model is studied to predict analytically the vibration from the helical gear system due to an axial excitation of helical gears. The simplified model describes gear, shaft, bearing, and housing. In order to obtain the axial force of helical gears, the mesh stiffness is calculated in the load deflection relation. The axial force is obtained from the solution of the equation of motion, using the mesh stiffness. It is used as a longitudinal excitation of the shaft, which in turn drives the gear housing through the bearing. In this study, the shaft is modeled as a rod, while the bearing is modeled as a parallel spring and damper only supporting longitudinal forces. The gear housing is modeled as a clamped circular plate with viscous damping. For the modeling of this system, transfer matrices for the rod and bearing are used, using a spectral method with four pole parameters. The model is validated by finite element analysis. Using the model, parameter studies are carried out. As a result, the linearized dynamic shaft force due to the gear excitation in the frequency domain was proposed. Out-of-plan displacement from the forced vibrating circular plate and the renewed mode normalization constant of the circular plate were also proposed. In order to control the axial vibration of the helical gear system, the plate was more important than the shaft and the bearing. Finally, the effect of the dominant design parameters for the gear system can be investigated by this model.     

NUMERICAL SIMULATION OF SOUND RADIATION ON GEARBOX'S HOUSING

The fluid-structure coupling finite element model and the boundary element model of a complex gearbox＇s housing are built based on the theory of fluid-structure coupling finite element method and boundary element method. At the same time, the exciting forces of the housing are analyzed and applied to the finite element models. Firstly, vibration of the housing is calculated by the fluid-structure coupling finite element model; secondly, the calculated result is verified by the experiment; finally, sound radiation of the housing is calculated by the boundary element. According to the calculated results, the housing adds some ribs not only to increase the strength, but also to reduce the sound radiation of the housing. At last, the sound radiation of the modified housing is calculated, which shows that the sound radiation of the modified housing with ribs is lower.     

Nonlinear interactions of elastic waves in a two-component solid shear mixture under conditions of phase-group synchronism

Nonlinear interaction of quasi-harmonic longitudinal waves propagating in a two-component solid shear mixture is theoretically studied. Interaction between low-frequency (a vibration field) and high-frequency (ultrasound) waves is shown to generate an ultrasonic wave with a summed frequency that may exist in phase-group synchronism with the vibration field. Calculated results qualitatively agree with data on generation of ultrasound by seismic forces.     

椭圆齿轮驱动的结晶器非正弦振动系统振动特性研究

为解决椭圆齿轮驱动的连铸结晶器非正弦振动系统的低频共振问题，建立了该系统的动力学模型，推导出动力学方程。结果表明，时变参数决定共振频率，激振力幅值决定共振峰值，合理设计弹簧刚度、预压力，减小铸坯摩擦力可大大减小共振峰值，提高结晶器运行平稳性。     

TC4钛合金低频振动钻削切屑形态和钻削力研究

为研究TC4钛合金低频振动钻削过程中切屑形态与钻削参数和振动参数对钻削力(轴向力和扭矩)的影响规律,基于一种自主研制的低频振动刀柄,分别采用单因素法和正交试验法对钛合金进行了低频振动钻削试验,分析了不同钻削条件下的切屑形态和钻削力,建立了轴向力和扭矩的经验公式,并对钻削力的影响因素进行直观分析与方差分析。结果表明:试验系统在低频振动钻削TC4钛合金时,振幅与进给量之比接近临界断屑值0.81时断屑可靠,排屑顺畅;低频振动瞬时钻削力呈现出规律的正弦波形,钻削力动态分量远大于普通钻削,轴向力和扭矩均值可比普通钻削分别降低10%～15%和15%～20%;进给量对钻削力影响最为显著,振幅次之,钻削速度影响最小;建立的振动钻削经验模型误差保持在10%以内,可以较为准确地对该试验系统所选参数范围内的钻削力进行预测。     

Fluid Flow Analysis for Friction Torque around Rolling Element in Ball Bearings

Ball bearings (e.g., deep-groove, angular-contact, and roller bearings) support loads in a rotor system and provide lubrication between the shaft and housing. The deep-groove ball bearings used in a turbopump do not differ significantly from angular-contact ball bearings or the bearings found in other applications. Deep-groove ball bearings consist of rolling elements, an inner raceway, an outer raceway, and a retainer to guide the rolling elements. In ball bearings, the resistive (churning or drag) forces and torques acting on the rolling elements and raceways are affected by the fluid flow rate and direction, as well as the rotational speed. These churning and drag forces and torques affect the internal dissipation or power losses into the bearing, which become very significant for high-speed applications. This study numerically investigated the characteristics of the flow conditions for deep-groove ball bearings, with a particular focus on the friction distribution on the rolling elements. A simple analytical model of the fluid flow inside a ball bearing was developed using a computational analysis, and the flow characteristics at high rotational speeds are presented.     

轴向低频振动辅助皮质骨钻削的钻削力和温升

为了研究轴向低频振动钻削方式在皮质骨钻削中对钻削力和温升的影响,基于一种自主研发的低频振动钻削设备,对常规和轴向低频振动辅助皮质骨钻削的钻削力和温升进行了实验,建立了钻削力和产热速率模型.实验结果表明:轴向低频振动钻削方式的进给力和转矩明显减小,温升降低了3～5℃;通过统计方法确定主轴转速是影响钻削力和温升的最显著因素...     

Development of radially movable multichannel Reynolds stress probe system for a cylindrical laboratory plasma

A new radially movable multichannel azimuthal probe system has been developed for measuring azimuthal and radial profiles of electrostatic Reynolds stress (RS) per mass density of microscale fluctuations for a cylindrical laboratory plasma. The system is composed of 16 probe units arranged azimuthally. Each probe unit has six electrodes to simultaneously measure azimuthal and radial electric fields for obtaining RS. The advantage of the system is that each probe unit is radially movable to measure azimuthal RS profiles at arbitrary radial locations as well as two-dimensional structures of fluctuations. The first result from temporal observation of fluctuation azimuthal profile presents that a low-frequency fluctuation (1-2 kHz) synchronizes oscillating Reynolds stress. In addition, radial scanning of the probe system simultaneously demonstrates two-dimensional patterns of mode structure and nonlinear forces with frequency f = 1.5 kHz and azimuthal mode number m = 1.     

基于模态分析的乘用车变速器壳体振动优化设计

乘用车变速器作为整车动力总成的一个重要部分,其振动模态的优劣是整车NVH性能的重要一环。由于壳体是变速器振动的主要零部件,所以对变速器壳体的模态分析就显得十分有意义。讨论了各种主要变速器壳体振动激励源及基于有限元技术的乘用车变速器壳体的约束模态分析及优化方法。     

Online monitoring of a pipe conveyor. Part I: Measurement and analysis of selected operational parameters

The need to maximize the performance and operational reliability of ecological continuous conveyor systems is increasing nowadays and their requirements are difficult to fulfil. One of the main reasons to this is the complexity of ecological continuous conveyor systems. Regular tracking and monitoring of systems selected parameters and indicators support their proper functioning and operational reliability. However, the process becomes useless if the parameters are not tracked and evaluated. The paper shall present the results of research aimed at determination of evaluation criteria for selected parameters. The research was carried out by a method of experimental measurement on an experimental rig the construction of which is similar to the construction of real pipe conveyors used in practice. Some of the convenient parameters to be tracked on a tube conveyor are a tension force and contact forces on hexagonal idler housing. The paper aims to track the course of contact forces and their mutual relations with intensity of tension forces. In order to create a comprehensive evaluation and analysis of the research, the experimental measurements were carried out for two cases, with and without material. The experimental tests are evaluated with the use of basic mathematical and statistics methods.     

QP钢低频振动辅助拉伸力学行为与微观组织演变研究

相比传统塑性加工,振动辅助成形有降低成形力和改善表面质量等有益效果,为解决QP钢成形力大和起皱等问题提供了新的可能性。通过自行设计的液压激振装置在QP1180的拉伸试验中引入低频振动,研究低频振动场对QP钢拉伸力学行为与微观组织演变的影响。结果表明,在施加振动阶段,低频振动的叠加引起QP钢拉伸应力剧烈波动,同时出现瞬时振动软化现象;振动去除后出现瞬时残余硬化现象,振动软化量和残余硬化量随着振幅的增大逐渐提高。EBSD结果表明：QP钢振动辅助拉伸过程中振动场的叠加促进了位错增殖,位错增殖量随着振幅的增加而增大。通过XRD探究了振动场对QP钢TRIP效应的影响,结果显示振动场的叠加可有效促进残余奥氏体向马氏体的转变,且随着振幅的增大TRIP效应愈加明显。     

Numerical model of spindle/disks assembly–shaft–housing system for vibro-acoustic analysis of HDD in idle mode

This paper presents the mathematical models of the spindle/disks–shaft–housing system for vibro-acoustic analysis of hard disk drives operating in idle mode. A complete model of a spindle/disks assembly–shaft–housing system is developed using a multi-body system Lagrangian formulation. The transfer functions between source excitations and induced vibration on the housing are derived. The effect of adding flexibility to the non-spinning components (i.e. housing and shaft) is examined and the model capabilities are demonstrated through parameter studies.     

Experimental and Numerical Study of Multibody Contact System with Roller Bearing–-Part II: Semi-Finite Element Analysis and Optimal Design of Housing

A typical roller bearing system consists of five contact parts: the housing, outer ring, inner ring, roller set, and the shaft. A finite element calculation procedure is described to analyze a five-body contact roller bearing system. If an analytical solution is used to calculate the deformations of the roller and the ring/shaft combination, a semi-finite element governing equation can be derived by simplifying the five-body contact bearing system into a three-body contact system. The semi-finite element calculation results correlate closely with the test results obtained in Part I of this paper (1). The analysis indicates that the initial gap between the housing and the outer ring and the loading positions have significant influence on the load distribution in the bearing. By optimal design of the housing, the load distribution becomes more uniform and the fatigue life of the bearing can be increased.     

Rotordynamic Analysis of an Oil-Free Turbocharger Supported on Lobed Gas Foil Bearings—Predictions versus Test Data

This article presents the predictions of the rotordynamic performance of oil-free turbochargers (TCs) for various lobed gas foil bearings (GFBs) with the first-generation bump-type configuration and compares these predictions to the measured test data reported earlier. The three-lobed GFBs used for the simulations have increased bearing clearances and mechanical preloads with a fixed minimum bearing clearance, thus yielding larger average bearing clearances and higher wedge effects at the same time. The engine-induced TC housing excitation is found to have no influence on the critical speeds and damping ratios of the rotor rigid modes. The synchronous and asynchronous GFB analyses imply decreases in destabilizing forces for the highly lobed GFBs. The predicted critical speed and damping ratio of the TC rotor supported on the lobed GFBs demonstrate increasing system natural frequency and enhanced rotordynamic stability with increasing mechanical preload. The rotordynamic and bearing analyses of the lobed GFBs validate the beneficial effects of the mechanical preload on the rotordynamic stability of GFBs even with an increased average bearing clearance, which leads to a decreased bearing friction torque as well.     

基于PLZT高速VOA的光源低频强度噪声抑制

提出一种基于掺镧锆钛酸铅(PLZT)高速可变光衰减器(VOA)实现光源低频强度噪声抑制新的技术方案.设计基于高速前馈-反馈控制技术的VOA驱动控制系统,通过高速调节,实现了光源低频波动的平滑与抑制,同时可克服PLZT的电回滞效应和环境温度变化所引起的器件参数漂移等问题,实现光信号的稳定输出.实验结果表明在控制回路信号延迟2.1 μs 下,系统可将频率范围在0～800 Hz的低频扰动幅度抑制到小于1％的水平.