Search

Analytic study of rotor vibration plays an important role in design, and fault detection and diagnosis of rotating machines. In this paper, vibration characteristics of a flexible rotor due to a central mass unbalance were analysed numerically under two cases. In Case I, bearings have symmetric, isotropic stiffness and damping matrices, while in Case II they have asymmetric, non-isotropic stiffness and damping matrices. It was found in Case I that critical speed occurs at 1690 rpm and the orbital trajectories of rotor mass stations are circular and corotational. In Case II, response orbit of either the bearing or the disk is elliptic and the size, shape, and orientation of the elliptical orbit changes with shaft speed, and also from the bearing to the disk.

The application of equal displacement rule simplifies the evaluation of lateral displacement demand forSDOF system. For complex multi-degree-of-freedom (MDOF) structures such as continuous bridge systems, however, it requires more investigations. In this paper, a comprehensive parametric study of the ratio of maximum inelastic displacement to maximum elastic displacement for typical continuous bridges is performedto advance the application of equal displacement rule to MDOF systems. Particurlarly for the bridges with long periods, this adapted methodlogy is further simplified. It is concluded that equal displacement rule of MDOF is applicable to continuous bridges when the periods of the main modes are no less than the limiting period, which usually serves as an indication to the level of inelastic deformation for a bridge subjected to an earthquake.

The aft part of large scale vessel propulsion shaft is a cantilever with a propeller. As the shaft doing the lateral vibration, the trail of propeller shaft center-line, which appears together with the movement, is the cone surface with the shaft center as the symmetrical axis, at the same time the propeller will vibrate with the shaft. In order to investigate the influence of propeller effect to shaft lateral vibration, the main work in the paper includes modeling the finite element of a large scale vessel propulsion shaft, studying the factors of water mass adhered to propeller, pin softening and gyroscopic moment to the shaft lateral vibration. The calculation shows that: if the propeller's gyroscopic moment is positive, the free frequency of shaft will increase, while added water mass and spin softening will obviously decrease the free vibration frequency of shaft.

For an electromagnetic suspension (EMS)-type urban Maglev train using U-shaped electromagnets, both the vertical and the lateral air gaps for levitation are maintained only by the electromagnet. The train can run over curved rails without active lateral air gap control because the U-shaped electromagnet simultaneously produces both a levitation force and a guidance force, which is dependent on the levitation force. Owing to the passive control of the lateral air gap, the lateral vibration could exceed the limits of the lateral air gap and acceleration. In this study, dynamic analysis of a Maglev train is carried out, and the effectiveness of a lateral damper for vibration reduction is investigated. To more accurately predict the lateral vibration, a Maglev vehicle multibody model including air-sparing, guideway irregularities, electromagnets, and their controls is developed.

This paper presents a framework of nonlinear dynamic analysis of a low-speed moving maglev (magnetically levitated) vehicle subjected to cross winds and controlled using a clipped-LQR actuator with time delay compensation. A four degrees-of-freedom (4-DOFs) maglev-vehicle equipped with an onboard PID (Proportional-Integral-Derivative) controller traveling over guideway girders was developed to regulate the electric current and control voltage. With this maglev-vehicle/guideway model, dynamic interaction analysis of a low-speed maglev vehicle with guideway girders was conducted using an iterative approach. Considering the time-delay issue of unsynchronized tuning forces in control process, a clipped-LQR actuator with time-delay compensation is developed to improve control effectiveness of lateral vibration of the running maglev vehicle in cross winds. Numerical simulations demonstrate that although the lateral response of the maglev vehicle moving in cross winds would be amplified significantly, the present clipped-LQR controller exhibits its control performance in suppressing the lateral vibration of the vehicle.

The integrity of extended pile shaft is paramount for ensuring safe and acceptable performance of supported bridge structures. However, it is difficult to conduct the vertical excitation low-strain integrity test for an extended pile shaft that supports an existing bridge. This paper investigates the feasibility of employing lateral low-strain test to predict the pile length of an extended pile shaft. An analytical model is developed to simulate the behavior of a pile, partially embedded in soil, with a pile cap and superstructure under a lateral low-strain excitation. Considering the frequency spectrum of an impulse excitation, the developed model employs the modified Timoshenko beam theory to accurately simulate the lateral pile vibration accounting for both rotary inertia and shear. The analytical solution is then utilized to analyze the dispersion of the pile-soil system when subjected to the lateral excitation. The effects of pile and soil properties on the pile dynamic response and wave propagating velocity are investigated through a comprehensive parametric study. A simplified method is proposed to approximately evaluate the pile length of this case on site.

This paper attempts to explain the motion behaviour of the marine riser coupled to a drill string when the vortex induced vibration (VIV) is involved. Vibrations have been reported to have a major effect on the drilling performance, affecting the rate of penetration (ROP), causing severe damages to the drilling tools and also reduces the efficiency of the drilling process. There are two major components of drilling tools that are subjected to vibration, namely the marine riser and the drilling string. Analysis of vibration in the marine riser and drill string are two topical areas that have individually received considerable attention by researchers in the past. Though these two subjects are interrelated, borne by the fact that the marine riser encapsulates and protects the drill pipe, there have been few attempts to investigate them together as a unity. Due to the complexities of the models, simplified assumptions were made in order to undertake the investigation by using staggered approach. The results were compared with the experimental and simulation data from the open literature. It was found that the maximum displacement with negative damping occurs at low frequency and rotation speed.

Contents: machinery particulars ; lateral scheme ; conclusions ; notes ; zaključci ; napomene ; calculation data ; calculation results: summary, natural vibrations, forced vibrations ; load cases: normal operation, wind-milling condition ; options: with and without support. Total 22 pages.

Bogie is one of the major critical components of the dynamic track stabilizer, and its vibration characteristics will affect the dynamic characteristics of the dynamic track stabilizer directly. It is very important to improve the running safety by analyzing the lateral vibration characteristics of the bogie. The time domain loads of the track irregularities were gained based on the U.S. spectral density of the track irregularities using the method of numerical simulate. Then the lateral vibration characteristics of the dynamic track stabilizer bogie under the excitation of the track irregularities were analyzed on the bases of the ANSYS/LS-DYNA. The results of numerical simulation and the associated experiment are basically consistent, and the analysis results can provide foundation for research on the running stationarity and safety of the dynamic track stabilizer. This research method also can provide a new effective method for further researching on the dynamic characteristics of the bogie and the dynamic track stabilizer.

In this paper, the vehicle-bridge lateral vibration mechanism was analyzed; the vehicle-bridge vibration model was built and the lateral reinforcement schemes of open steel plate bridges were designed. Numbers of analysis were carried out for the lateral vibration of 40m deck steel plate bridges before and after reinforcement, under input of random artificial hunting waves and track irregularity. The results showed that, the frequency of hunting motion is approaching loaded frequency of the girder. The larger lateral amplitude appears on the bridge when the hunting wavelength is around 8~9m and the velocity of the train is around 55~70km/h. The wavelength is longer, the resonant velocity of the bridge is higher.

The mechanism of train derailment is demonstrated to be the loss of the lateral vibration stability of train-bridge (track) system. Based on the theory of energy increment analysis for system movement stability, the method of stability analysis of lateral vibration for train-bridge (track) system and the energy increment criterion for derailment evaluation are put forward. The method of analyzing critical speed of train derailment is proposed on the basis of the energy increment criterion for derailment evaluation. The critical speed of freight train derailment on Youshui bridge and Laoluanhe bridge are calculated as 66.5 km/h and 65.2 km/h respectively, which are close to actual derailment speed 70 km/h. It is manifested that the method of stability analysis of lateral vibration for train-bridge (track) system is reasonable. The critical speed of train derailment on the Yanconggou bridge of Jingtong line are calculated as 73.0 km/h, and the results has provided important reference for operation department to take appropriate measures.

When studying the vibration of a bridge-vehicle coupled system, most researchers focus on the vertical vibration of bridges under moving vehicular loads. In reality, the moving vehicular loads can also induce significant lateral vibrations of high-pier bridges. This study is focused on establishing a new methodology considering the bridge's lateral vibration induced by moving vehicles. Thevehicle tire is modeled as a three-dimensional elementary spring model, and the contact patch is assumed to be a rectangle. Three significant factors that affect the lateral forces, including the slip angle, camber angle, and vehicle tires moving with an "S" shape, are introduced in studying the effect of the lateral forces on the lateral vibration of bridges. The bridge-vehicle coupled equations are established by combining the equations of motion of both the bridge and vehicles using the displacement relationship and interaction force relationship at the contact patch. The accuracy and efficiency of the present method are verified by comparing the simulations and the field test results of a typical high-pier bridge, showing that the proposed method can rationally simulate the lateral vibration of the bridge under moving vehicular loads. DOI: 10.1061/(ASCE)BE .1943-5592.0000170. © 2011 American Society of Civil Engineers. CE Database subject headings: Bridges; Vehicles; Vibration; Piers; Load factors. Author keywords: Bridge-vehicle coupled system; Bridge; Vehicle; Lateral vibration; Patch contact; High-pier bridge.

Lateral vibration is recognized as the leading cause of drillstring and bottom hole assembly (BHA) failures, shocks and severe damages to borehole wall. This study presents a finite element model using ANSYS software to investigate the drillstring lateral vibrations in slightly deviated wells. The analysis proceeds in two stages. At first, a nonlinear static analysis is performed to determine the effective length of the string where it is free to vibrate in the lateral direction. The second stage consists in modal, harmonic and transient dynamic analyses to obtain the lateral vibration modes and natural frequencies, frequency response and time dependent response respectively. The modeling is developed in the presence of mud, friction and nonlinear contact between drillstring and wellbore wall. The effects of drilling mud, drillstring length, well inclination and WOB are considered. The model was compared with experimental and simulated results obtained from several BHA configurations, giving excellent results. Key words: Drillstring, finite element model, lateral vibration, nonlinear contact model.

A ride comfort of elevator system is one of the important factors to enhance the product value. Elevator lateral vibration is the main problem that affects ride comfort. In order to improve ride comfort, it is important to achieve an estimation and optimum design of the cage suspension system. In this paper, a time domain simulator for elevator lateral vibration is developed. We made detailed simulation models of roller guide system and slide guide system in order to evaluate ride comfort on the design stage. Comparing with the simulation results and experiment results, guide system behaviors under various conditions become clear. The simulation models are improved with these behaviors. Fine matching of simulation and experiment are confirmed with the improved models.

Summary An effective modulation of lateral vibration of a bottomhole assembly (BHA) is that some prebent deflection is made on the lower stabilized section of drill collars. This is because the restorable deflection of a drill collar confined in a borehole depends on the prebent deflection. If the prebend nears the limit that the borehole can contain, there will be no sufficient restorable deflection to produce restoring force for lateral vibration. To understand the nature of this phenomenon, a dynamic model for lateral vibration of a stabilized prebent drill-collar section in an inclined well is presented. The governing nonlinear equations are obtained by using a Lagrangian approach, which are characterized by a prebend-dependent nonlinear bending stiffness term. They also include the effects of clearance/friction of stabilizers with borehole wall, contact friction of drill collar with borehole wall, axial forces from weight-on-bit (WOB) and bit/formation interactions, and hydrodynamic damping of drilling mud. The gyroscopic moments are proved to be negligibly small terms within a range of operating conditions of drilling. Poincaré map bifurcation diagram, phase diagram, Liapunov exponent, and power spectrum analysis are used to evaluate the dynamic behaviors. Simulation results both in a vertical well and in an inclined well show that lateral vibration is sensitive to the prebent deflection in some degree, presenting periodic motion, chaotic motion, or alternating in turn as usual. However, when prebent deflection is more than 87% in a vertical well and more than 45% in a 20°-inclined well (of the average clearance between the drill collar and the borehole), lateral vibration will vanish. Such a characteristic is crucially important for practical applications. For example, we may effectively prevent a drill string in an inclined well from severe whirling motion with a properly designed prebent drill collar.

The severe lateral vibration and impact of drill string will not only cause the damage of drill string but also have bad effects on the quality of directional drilling operation. It is difficult to control lateral vibration amplitude and impact intensity even with advanced measurement apparatus while drilling. So it is feasible to use a theoretic method to analyze and predict lateral vibration of drill string in order to adjust and optimize drilling parameters in real-time. On the basis of beam-column series and spring-concentrated mass model, a new analytical model is established to realize the control of lateral vibration and impact by controlling some key factors, such as under-gauge stabilizer, initial phase angle and initial deformation, WOB (weight on bit) and ROB (rotation of bit).

Incidents of pedestrian-induced large lateral vibrations of footbridges reveal the occurrence of an instability-type phenomenon in pedestrian-induced vibration. However, the mechanism involved has yet to be clearly explained. In this work, a novel model for predicting the lateral vibration of footbridges is proposed. Under an algebraic framework of nonlinear stochastic vibration, the narrow-band vibration caused by the pedestrian intra-subject randomness and the phase lag between the footbridge motion and the pedestrian load are considered. The critical condition that triggers the large lateral vibration of the footbridge is identified using the stochastic averaging method and the concept of stability based on the Lyapunov exponent. The validity of the proposed method is confirmed through case studies of three bridges. Through a parametric analysis, the effects of several crucial parameters on the stability/instability of vibration are discussed. Finally, conclusions are drawn regarding insights that can be useful to the future designs of footbridges.

Influence of lateral spring constant on energy dissipation and load reduction factor with erespect to lateral vibration of steel sheet pile installed by vibratory pile driver. Energy dissipation and load reduction factor varying with free length of steel sheet pile are more affected by eccentricity than flexural rigidity of steel sheet pile regardless of the magnitudes of lateral spring constants. Load reduction factors were converged when lateral spring constant was equal or larger than 10000N/m. Key Words : Lateral Vibration Model, Lateral Spring Constant, Energy Dissipation, Load Reduction Factor 본 논문은 선문대학교의 연구년 연구과제로 수행되었음. * 교신저자 : 이승현(shlee02@sunmoon.ac.kr)접수일 10년 01월 06일 수정일 10년 02월 04일 게재확정일 10년 03월 18일 1. 서론 강널말뚝의 시공에 주로 사용되는 진동타입기의 기본적인 구조는 그림 1에서와 같다. 그림 1에 나타나 있는 바와 같이 진동타입기는 크게 사하중(bias mass)과 기진블럭(exciter block)으로 구성되어 있으며 기진블럭 내부에 있고 서로 반대방향으로 회전하는 한 쌍의 편심질량체의 회전운동에 의해 진동타입기의 연직운동이 가능하게 되고 말뚝이 지중에 관입되게 된다. 진동타입기에 의해 시공되는 강널말뚝과 관련해서 주된 관심사는 관입속도(rate of penetration)가 되는데 현재까지 몇몇 예측기법이 개발된 바 있다[1-3]. 이러한 기존의 예측기법에 pile clampexciter blockIsolation bias massspring

In a previous work, magneto-rheological (MR) dampers were originally designed and implemented for reducing the vertical low-frequency vibration occurring in precise semi-conductor manufacturing equipment. To reduce the vibrations, an isolator levitated the manufacturing machine from the floor using pneumatic pressure which cut off the external vibration, while the MR damper was used to decrease the transient response of the isolator. However, it has been found that the MR damper also provides a damping effect on the lateral vibration induced by the high-speed plane motions. Therefore, in this work both vertical and lateral vibrations are controlled using the yield and shear stresses of the lateral directions generated from the MR fluids by applying a magnetic field. After deriving a vibration control model, an overall control logic is formulated considering both vertical and lateral vibrations. In this control strategy, a feedback loop associated with the laser sensor is used for vertical vibration control, while a feed-forward loop with the motion information is used for lateral vibration control. The experimental results show that the proposed concept is highly effective for lateral vibration control using the damping effect on multiple directions.

Ultrasonic welding is one of the main applications of high-power ultrasound and is used in the automotive industry and aerospace. Transducers and tool are important parts of the ultrasonic welding system. Different tools are required for different welding objects. For larger plastic welded parts, it is necessary to weld them with large-sized welding tools. Due to the large size of the welding tool, under the excitation of the transducer, the tool will produce a coupling effect of longitudinal vibration and lateral vibration. Lateral vibration will cause the radiation surface of the tool to be non-uniformly displaced, and the working efficiency and welding results of the welding system will also be affected. So, in this paper, the phononic crystal bandgap theory and coupling vibration theory are used to study the coupled vibration of large-sized rectangular plastic ultrasonic welding tools. In order to improve the work efficiency and radiation surface's displacement uniformity of the tool, the phononic crystal structure is used to suppress the lateral vibration of the large-sized plastic ultrasonic welding tool, and the lateral vibration band gap of the phononic crystal structure is calculated. The longitudinal resonance frequency of the system is designed in the band gap range of the lateral vibration of the tool. So the lateral vibration of the tool can be effectively suppressed. The longitudinal vibration displacements on the radiation surface of the rectangular tool before and after vibration suppression are analyzed and compared with each other. The vibration mode of the ultrasonic welding system is simulated by the Comsol Multiphysics finite element software. The large-scaled tool with phononic crystal structure has a radiation surface displacement compared with the tool without phononic crystal structure, and the results show that the radiation surface displacement with phononic crystal structure will increase and tend to be uniform, greatly optimize the welding effect, improve the working efficiency of the welding system, and meet the needs of practical engineering. It is concluded that the longitudinal resonance frequency of the ultrasonic plastic welding system within the lateral vibration bandgap on the phononic crystal structure can not only suppress the lateral vibration, but also make the longitudinal displacement of the radiation surface more uniform and larger. Therefore, the work efficiency is greatly improved.

According to the structure and stress trait of bearing bolts, a lateral-vibration mechanics model was established for them, and the relation between lateral-vibration frequency and axial load was analyzed; then, lateral-vibration trait of bearing bolts was studied through laboratory simulation test. The results indicate that vibration frequency of bolt support system increases as well as axial force, the detection on axial load of bolts can be made by generating lateral vibration of bearing bolts. Theoretical and experimental research results show that frequency method is effective for detecting the axial force of bolt support system.

In magnetic tape drives, lateral in-plane vibration of the tape leads to misalignment between data tracks and read/write head's position resulting in reduced storage capacity. To attenuate this lateral tape motion (LTM), surface guides-which include grooved, porous or roughened rollers-are used. The axial motion of the tape over the roller surface switches between two states: a sticking state when the axial force is smaller than the static frictional force; and a slipping state when the axial force is larger than the frictional force. A good understanding of the physical phenomena involved in this frictional interaction between the magnetic tape and surface friction guides will allow the appropriate and optimal choice of roller characteristics. We conduct a parametric study of frictional interaction between roller surface and the traveling magnetic tape by systematically varying the axial tension and transport velocity of the tape. An experimental setup is used to independently control these parameters and obtain lateral vibration measurements at two equidistant points-upstream and downstream-from the tape-roller interface. Techniques from spectral analysis are applied to the two signals to analyze and isolate the effect of stick-slip friction on LTM. It is noticed that the coherence function between the LTM signals provides valuable insight into the nature of stick-slip friction at the interface. We subsequently use it as a metric to construct and understand the “dynamic phase diagram,” i.e., to demarcate regions in the tension-velocity phase-space where predominance of stick or slip occurs.

Se desarrolló un programa computacional mediante el método de elementos finitos, que permite predecir las frecuencias y modos transversales de vibración en el Ensamblaje de Fondo (BHA) de las sartas de perforación. Este modelo se puede aplicar tanto en la planificación como en tiempo real durante la operación de perforación, con la finalidad de evitar problemas de resonancia en el sistema. Este análisis se lleva a cabo en dos etapas. En la primera se resuelve el problema bidimensional y no lineal de la deformación estática de la sarta; esto proporciona su perfil deformado y las fuerzas en los puntos donde contacta las paredes del hoyo. De esta forma se determina la longitud efectiva del ensamblaje de fondo que está libre de vibrar lateralmente. La segunda, consiste en un análisis dinámico del sistema para obtener las frecuencias y modos de vibración transversales. El modelo fue validado con varias configuraciones de sartas de perforación utilizadas en otros estudios y en mediciones experimentales, obteniéndose excelentes resultados.A computer program based on the finite element method was developed to predict the lateral vibration modes and frequencies in the Bottom Hole Assembly (BHA) of a drillstring. This model is applicable in both a planning and a real time mode of operation to avoid resonance problems. The analysis used in this model proceeds in two stages. The first stage solves the two-dimensional nonlinear static deformation of the drillstring; this gives the deformed shape of the BHA and the side forces at points where the BHA touches the wellbore wall. In this way, the length of the BHA that is free to vibrate in the lateral direction is obtained. The second stage consists in a dynamic analysis of the system, to obtain the lateral vibration modes and frequencies. The model was compared with experimental and simulated results obtained from several BHA configurations, giving excellent results.

Starting from the analysis of tire ground contact characteristics, the formulas of ground contact patch of tires are obtained, which are verified by tests, and the calculation formula of lateral stiffness of tread element is determined using the energy method. On this basis, a dynamic model of tread's lateral vibration is established, and the effects of vehicle speed, vertical load and tire pressure are analyzed. The results show that: the lateral self-excited vibration will occur under certain conditions, and vehicle speed, vertical load and tire pressure have great influence on the vibration characteristics; the lateral self-excited vibration of tread is a kind of stable periodic vibration caused by Hopf bifurcation of system.

There are many benefits to reducing friction along the drill string while drilling directional wells. Higher rates of penetration (ROP), improved tool-face control, reduced drag, and reduced stick/slip are only some of the benefits documented in previous technical papers. There are generally two types of downhole tools used to generate benign vibrations within the drill string and/or bottom-hole assembly (BHA) to reduce friction: axial oscillation tools (AOTs) and lateral vibration tools (LVTs). This paper reviews the benefits and drawbacks of each of these types of tools and presents the results of mathematical modeling and field data to conclude which type of tool is more effective at reducing friction in horizontal wells. Axial oscillation tools typically employ a valve driven by the mud flow to generate pressure pulses. A shock tool is run above or incorporated into the AOT to convert these pressure pulses into an axial oscillating motion. This motion travels up and down the drill string to reduce friction between the pipe and the borehole wall. Lateral Vibration Tools (LVTs) typically employ one or more eccentric rotating masses driven by the mud flow. This creates a vibration in the lateral direction, perpendicular to the long axis of the tool, creating motion between the tool and the borehole wall and thereby reducing friction. To investigate the potential benefits of each type of tool, a mathematical model of a BHA and drill string was created and, using finite element methods, the friction reduction effect (in terms of drag reduction) was compared between the AOT and LVT. In each scenario evaluated in the study, a benchmark calculation was first made with no oscillation. Then, the oscillation for each tool was applied and the response of the system evaluated with respect to the improvement in weight transfer along the drill string. Afterwards, the results were compared to an actual case study for verification. The research concludes that axial oscillation tools provide significantly more effective friction reduction, which enhances drilling performance in horizontal wells. The paper also provides several additional examples of comparative field results.

The prestressed concrete (PC) stress ribbon footbridge is a type of suspension bridge without towers, which has been applied in Japan and all over the world for years in light of its low construction cost and aesthetic merit. It generally consists of the precast concrete slabs with embedded cables. However, the walking-induced lateral vibration trouble of the Millennium Bridge in London in 2000 gave a lesson to the engineers that the lateral vibration feature must be taken into consideration for the footbridge vibration evaluation. In this sense, the field investigations on the lateral vibration features of 14 pre-stressed concrete stress ribbon footbridge in Japan was carried out by artificial impact and damping free vibration tests. According to the investigations, the larger the bridge span, the lower the frequencies of lateral-related vibration modes. In addition, based on the damping-free vibration field tests, there was a tendency toward the damping constant degradation when bridge span became larger.