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The lateral vibration of cracked isotropic thick beams is investigated. Generally, the analysis of thick beam based on line elements can be undertaken using either Timoshenko beam theory or a third order beam theory (TSDT) such as Reddy beam theory. TSDT is superior to Timoshenko beam theory, as it eliminates the need for a shear correction coefficient. However, there is no available solution for a cracked beam based on Reddy beam theory which is the main focus of this paper. The investigated beam is divided into several elements where their stiffness and mass matrices are derived using Reddy beam theory. Each element has two nodes with 3 degrees of freedom (1 lateral and 2 rotational) at each node. The crack was modeled using two rotating springs with stiffnesses that varied with crack depth. These elements are used to connect the adjacent beam elements. The impact of boundary conditions, slenderness ratio, crack location, and crack depth are investigated. In addition, experimental and finite element analyses of cracked steel beams is undertaken to validate the results of the present model. The results show that the maximum deviation between the analytical and the experimental results is less than 3% up to the third mode shape. [ABSTRACT FROM AUTHOR]

At present, inverted pendulum model (IPM) has been recognized by increasing researchers due to its capability to capture the characteristics of pedestrian lateral excitation. However, the IPM still has a downside that has been continuously questioned: the velocity proportional pedestrian load coefficient c p is inconsistent with the on-site observations in the case of pedestrian walking with normal frequency. This problem is most likely resulted from that the IPM ignores the synchronization effect. The IPM is derived from indoor single-person experiment and cannot consider the synchronization in the crowd. Synchronization effects are classified into two types： pedestrian–bridge and pedestrian–pedestrian synchronizations. Pedestrian–bridge synchronization is stimulated by bridge vibration, whereas pedestrian–pedestrian synchronization is stimulated by surrounding crowd. In this study, a novel model for pedestrian-induced lateral vibration of footbridge is proposed. It uses the IPM as the basis and adopts a binary coupled Kuramoto model that originally derived from the collective synchronization phenomena to overcome the limitation in IPM. This model can consider the pedestrian–bridge and pedestrian–pedestrian synchronizations, which provides a new way to reveal the mechanism of pedestrian-induced lateral vibration of footbridge. The proposed method is verified through a case study of the London Millennium Bridge, and some useful conclusions are obtained. [ABSTRACT FROM AUTHOR]

Rubber-tired light rail vehicles are generally operated on lines which include a number of small curves, steep slopes, or track switching sections to reduce construction costs or to place multiple stations in densely populated areas. Recently, the tendency is to increase acceleration, deceleration, and operation speed to shorten travel time and to increase transportation capacity. These track characteristics and operation patterns may result in deteriorating lateral dynamic characteristics in rubber-tired light rail vehicles. Therefore, running gear in rubber-tired light rail vehicles needs to play a role in effectively damping lateral vibrations and shock transmitted from the guidance rails through the guidance wheels. In this paper, new running gear was proposed to improve the lateral vibration and ride comfort in rubber-tired light rail vehicles. The new running gear has been newly installed with lateral rubber shock absorbers that can dampen lateral vibration on curved routes. In addition, it has been installed with a bi-directional return spring in place of the existing restoring coil spring and hydraulic damper to improve lateral vibration on straight routes. The effect of improving the lateral dynamic characteristics of the new running gear was verified through dynamic analysis and actual vehicle driving tests (field tests). [ABSTRACT FROM AUTHOR]

The lateral vibration of drill string causes well deviation and the collision between drill collar and sidewall, and severe lateral vibration even affects the drilling safety or reliability. In view of the problems above, the lateral vibration characteristics of drill string need to be analyzed. Therefore, a newly vibration-collision model of BHA (bottom hole assembly) with random collision characteristics is proposed in this paper. Firstly, the dynamic model of drill collar with double stabilizer is presented by utilizing the Lagrange equations. Secondly, the dynamic characteristics of drill collar in air and mud drilling is analyzed with different collision frequencies. Subsequently, the displacement and motion trajectory of drill collar under different structure parameters of BHA and mechanical parameters of system are investigated by numerical simulation. Finally, the influence of rotation speed of BHA and length of drill collar on lateral vibration of drill collar is discussed. The results indicate that the lateral vibration of drill collar in air drilling is more serious than that in mud drilling; and the higher the collision frequency, the more severe the lateral vibration. Improving rotation speed of BHA, length of drill collar and WOB (weight on bit) have promoting influence on lateral vibration of drill collar; however, increasing stabilizer diameter has suppressing influence on lateral vibration of drill collar. The research findings give reasonable guidance for structure design of BHA and selection of mechanical parameters of system. [ABSTRACT FROM AUTHOR]

In this study, the Rayleigh–Ritz method is used to analyse the vibration of a point-supported rectangular plate with a concentrated mass. The deformation and the first-order natural frequency under various working conditions are calculated. The results are compared with those obtained by the finite element method. [ABSTRACT FROM AUTHOR]

Curved pedestrian bridges are important urban infrastructure with the desired adaptability to the landscape constraints and with aesthetic benefits. Pedestrian bridges feature thin cross-sections, which provide sufficient load capacities but lead to low natural frequencies that make the bridges susceptible to vibration under pedestrian excitation. This study investigates the lateral vibration of a curved bridge with a small radius down to 20 m, proposes an approach to mitigate the lateral vibration of bridges with large curvatures using distributed multiple tuned mass dampers (MTMD), and conducts in-situ bridge tests to evaluate the vibration mitigation performance. The lateral vibration was investigated through in-situ tests and finite element analysis as well as the code requirements. The key parameters of the distributed MTMD system were improved by strategically selecting the mass ratio, bandwidth, center frequency ratio, and damper number. The results showed that the curved bridge was subjected to significant lateral vibration due to the coupling of torque and moment, and the recommended design parameters for the studied bridge were derived, i.e., the total mass ratio is 0.02, bandwidth is 0.15, center frequency ratio is 1.0, and damper number is 3. The proposed approach effectively improves the deployment of MTMD for lateral vibration control of the curved bridge. The field tests showed that the vibration was reduced by up to 82% by using the proposed approach. [ABSTRACT FROM AUTHOR]

The stability of structures is an important aspect that the designer must pay particular attention to in order to ensure safety against collapse. This investigation is concerned with analytical and numerical analyses of the dynamic buckling of plane structures. A rigorous mechanical model is proposed, consisting of a beam-column element with nodal ends possessing two rotational springs of rigidities acting in parallel with the bending stiffness of the beam-column. The model is first analyzed with respect to the dynamic behavior by investigating the influence of the variation in the stiffness of the nodal springs on the fundamental frequency of the proposed mechanical model. Compression axial loading is applied to the beam-column in order to study the nonlinear dynamic behavior by introducing buckling. This novel approach is used to highlight the interaction between the fundamental frequency and the critical buckling load. Simple examples are treated using the approach and the results are compared with those obtained from a global analysis. The results revealed that it is possible to reproduce the stability analysis of a global structure by simply analyzing a target element, taking into account all elements adjacent to it with less than 1% error on the results. [ABSTRACT FROM AUTHOR]

Electromechanical coupling coefficient (k t) of piezoelectric composite is the core indicator for medical ultrasonic, nondestructive testing and underwater acoustic transducers applications. Generally, the k t of piezoelectric composite is susceptible to be interfered by its structure parameter and spurious modes. In this work, we figured out the effect of the polymer on the vibration mode by fixing the size of the piezoelectric rod and changing the content of different softness polymer. The spurious modes were related with resonant standing wave caused by classical Bragg scattering in periodic structures. The propagation of spurious mode vibration can be cut off by soft polymer. The maximum k t of 69% was obtained at a Pb(Zr,Ti)O 3 (PZT4) ceramic volume fraction of 24.5%. The k t was 5% ∼ 10% higher than that of other reported PZT4 ceramic composites and comparable to PZT5 ceramic composites. This work presented a paradigm for vibration modes modulation by changing the polymers ratio, which providing ideas for excellent performance acoustic transducer designing. [Display omitted] • By fixing the volume fraction and thickness of the piezoelectric phase, the thickness vibration resonance peak was basically unchanged. Along with increase of soft polymer, the frequency of the lateral vibration shifted and was close to the thickness vibration. And with the further increase of soft polymer, the propagate of transverse vibration could be cut off. • A high k t of 69% was achieved at a low ceramic volume fraction of 24.5%, which was 5 ∼ 10% higher than other reported PZT4 composites and comparable to other reported PZT5 composites, even larger PZT5 volume fraction composites. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamic response of soil around a laterally vibrating extended pile shaft and its application to the lateral parallel seismic (PS) integrity testing method. Considering the high pile to soil relative stiffness ratio, a new analytical model is proposed incorporating an extended half-space soil model excited by the laterally vibrating pile. The developed equations of the analytical model are solved by employing the Fourier-Hankel integral transform. This scheme avoids the complicated pile–soil coupling analysis while maintaining high accuracy. The developed model and its analytical solution are then utilized to verify the applicability of the lateral PS method to predict the unknown pile length. The effects of pile and soil properties on the soil dynamic response and technical aspects of the PS test are investigated through a comprehensive parametric study. The obtained results demonstrate that the lateral PS test could be successfully used in practice to overcome the limitations of the low-strain pile integrity test (PIT). [ABSTRACT FROM AUTHOR]

The pedestrian-induced lateral vibration of footbridges is essentially classified as a nonlinear stochastic vibration. Accordingly, bridge vibration stability falls within the field of nonlinear stochastic vibration stability. At present, the Lyapunov method is mainly used to analyze such stability. However, this method is qualitative, and it cannot quantitatively analyze the vibration stability probability. In this study, a new analytical method based on a comparison of the input energy and the variation of intrinsic energy (IEVIE) is used to analyze the nonlinear stochastic vibration stability of the lateral vibration of the footbridge. The improved Nakamura model is used to describe the lateral nonlinear stochastic vibration of the footbridge. A combination of the IEVIE method and the probability density evolution (PDE) method is then proposed, in which the IEVIE method is utilized to determine vibration stability. The PDE method is used to obtain the reliability of vibration stability. The proposed method is successfully applied to the Millennium Bridge, and its effectiveness is verified by comparing the Monte Carlo and Lyapunov methods. The proposed method can obtain the dynamic probability of the vibration as stable or instable and provide a reference for quantitative analysis of lateral nonlinear stochastic vibration stability of footbridges. [ABSTRACT FROM AUTHOR]

This article considers lateral vibration of an automobile in a so-called quasi-planar model where both the loss of contact and road deformation are taken into account. The automobile with dependent suspension is modeled as a vibration system which has two masses and four degrees of freedom. The deformed road is modeled as an elastic beam which has uniform rectangular cross-section, is simply supported at the two ends and lies on the Kelvin's visco-elastic ground. The loss of contact and the change in dimensions of contact areas are considered. The differential equations of motion of the vehicle-road coupled system which contains a partial differential equation are transformed into a set of all ordinary differential equations by applying the Bubnov-Galerkin's method. A procedure for numerically solving the transformed differential equations of motion is proposed. Some illustrating results coming from numerical consideration are also presented in the paper. [ABSTRACT FROM AUTHOR]

• An innovative model for pedestrian-footbridge synchronization is developed. • Contributions of pedestrians vary according to their moving positions on bridge. • Gait frequency of a pedestrian follows Gaussian distribution and pedestrians adjust their phase in response to bridge vibration. • Excessive lateral vibration of London Millennium Footbridge is reproduced. • Parametric investigations are made to detect main effects of pedestrians on bridge vibration. The mechanism which results in the synchronization of people walking across footbridges with the bridges fundamental horizontal frequency is studied. The lateral vibration of a bridge subjected to walking pedestrians is modelled by considering the bridge to be a slender beam. The effect of bridge motion on the footfall forces of walking pedestrians is not considered. The contribution of pedestrians varies with their position on the bridge. It is assumed that the walking gait frequency of a pedestrian follows a Gaussian distribution and pedestrians can unconsciously adjust the phase of their walking cycle closer to that of the bridge, based on the theory of coupled oscillators. A time-dependent nonlinear dynamic equation is derived using the modal expansion approach. The model is then applied to the north span of the Millennium Bridge in London, to produce its excessive lateral vibrations. Agreement between the results and the existing observations supports the rationality and reliability of the method. Several parameters, in particular the walking gait frequency of pedestrians, crowd sensitivity to bridge motion, bridge frequency, bridge damping and different load conditions are investigated. The numerical simulation shows that these parameters have different degrees of impact on the critical number of pedestrians triggering excessive vibrations. [ABSTRACT FROM AUTHOR]

Deep learning-based fault diagnosis models have been demonstrated to recognise machine health conditions from vibration data. However, most related studies have focused on lateral vibration data, and mostly neglected torsional vibration data. Yet, torsional vibration data can provide an advantage in diagnosing gear faults. Torsional vibration is typically less noisy than lateral vibration data as it can be measured directly from the rotating components. To this end, this study presents a large gear fault dataset with artificial faults of varying severity acquired from a downscaled thruster test rig operated at a vast range of rotating speeds. The test rig was equipped with multiple torque transducers, rotary encoders and piezoelectric accelerometers. The lateral and torsional vibration data acquired with these sensors were evaluated with three popular convolutional neural networks in extensive ablation studies. An interpretability analysis was conducted based on amplitude spectra and Grad-CAM visualisations. The results demonstrate that torsional vibration can be an effective source of data for gear fault diagnosis. For example, the models diagnose the most difficult gear conditions using only one torque transducer more accurately than using three accelerometers mounted on the gear box. Furthermore, the highest accuracy in each ablation study related to experiments with combined lateral and torsional vibration data. In addition, the interpretability analysis showed that the lower frequencies had relatively higher amplitudes in torsional vibration than in lateral vibration. The interpretability analysis also indicates that the models reached higher classification accuracies with torsional vibration data due to the lower dominating frequencies. Overall, this study highlights the potential benefits of using torsional vibration data for deep learning-based fault diagnosis of gears. • Experimental thruster drive train rig with faults is demonstrated. • Comparison of torque, angular and lateral acceleration for diagnosis purposes. • CNNs diagnose gear faults very accurately from torsional vibration data. • Interpretability analysis is conducted with Grad-CAM and amplitude spectra. [ABSTRACT FROM AUTHOR]

The reversal and lateral vibration of the drill string are very complex motion and can affect the normal operation of the drill string. The movement of the drill string in the stepped well is different from the movement of the drill string in the regular well. The vibration of the drill string in the stepped well varies with the size of the wellbore and can be visually reflected by the phase speed. To find out the relationship between reversal and lateral vibration, the natural frequency of lateral vibration of the drill string was solved by using the method of energy conservation. The analysis shows that the phase speed of flexural wave in the stepped well is faster in small size wellbore than in large size wellbore. The reversal and lateral resonance is easy to happen in small size wellbore, and the reversal will excite lateral vibration. When the sum of reversal and rotational angular frequencies approaches the natural angular frequency of lateral vibration, the lateral resonance will occur. [ABSTRACT FROM AUTHOR]

This paper presents the development of theoretical and experimental models for the study of rotodynamic behavior of a multistage rotor. The transfer matrix method, which includes the characteristics of stiffness and damping for the supports and the stages respectively as well as the characteristics of unbalance in the stages, is used for the theoretical model. The data from a physical model was employed as a way of validating the theoretical results. The first two critical speeds were determined with the theoretical model and they differ in a low percentage with respect to the values measured experimentally. Moreover, the vibration level recorded in the physical model rises 2.5 times when the multistage rotor approaches the first two critical speeds. In addition to this, significant displacements of the lateral critical speeds are noticeable when an increase in mass imbalance is induced in several of the rotor impellers. [ABSTRACT FROM AUTHOR]

This paper presents a study on the interaction of lateral vibration and friction vibration of a marine water-lubricated bearing when the bearing and stern shaft journal contact. The coupled vibration modes were modeled innovatively to analyze their interactions, where the lateral vibration response of the shaft journal into the normal load was applied to the dynamic friction force. The regular patterns were analyzed utilizing the theoretical derivation, numerical simulation and tests whose results show that the contacted motion statuses are relatively complicated and the feedback mechanism due to interference expressed as the term of KbC0r′ accelerates the instability of the coupled system in the negative area of the friction–speed curve. [ABSTRACT FROM AUTHOR]

Annular drilling fluid between the drillstring and borehole wall has a great influence on lateral vibration of drillstring and the influence involves the added mass. Assuming the drilling fluid is incompressible, we derive the added mass coefficient that annular drilling fluid influences on lateral vibration of drillstring in the case of axial flow of drilling fluid. When the axial flow of drilling fluid is considered, the added mass coefficient is difficult to solve. We apply CFD method and dynamic mesh technique to establish the calculation model for the flow in the annulus caused by the vibration of drillstring in the annulus. The pressure distribution and velocity distribution of annular drilling fluid are obtained. The added mass force of the drilling fluid acting on the drillstring along the direction of the drillstring is obtained from the pressure distribution, and the added mass coefficient of the lateral vibration of the drillstring is obtained. This paper provides the basis to solve the added mass coefficient of the lateral vibration of drillstring considering axial flow of drilling fluid. [ABSTRACT FROM AUTHOR]

Hydraulic jetting perforation and fracturing with coiled tubing (CT) has been widely applied in low-permeability reservoirs. In perforating operations, obvious oscillation of the CT between the spool and gooseneck often appears. This is mainly caused by the unstable fluid flow in the CT. This paper presents the analytical models for the stability of CT under unstable fluid injection. Lateral fluctuating force model of CT is proposed. The dynamic equations for lateral vibration of CT are established based on the structural dynamics theory. Moreover, the effects of rotation speed of fracturing pump, flow rate of fracturing pump, and length of CT on response displacement and natural frequency are discussed. The results indicate that under unstable fluid injection, the first-order and second-order response displacements for lateral vibration of CT present the fluctuation with increasing flow time. With increasing rotation speed and flow rate, the lateral vibration of CT becomes faster, and the resonance of CT is prone to occur. With increasing length of CT, the stability of CT becomes worse. In general, the unstable fluid flow in the CT caused by the unstable flow rate of fracturing pump has an influence on the stability of CT in perforating operations. Therefore, it is recommended to reasonably control the flow rate and rotation speed for fracturing pump in engineering applications. [ABSTRACT FROM AUTHOR]

In the present paper, the numerical solutions have been carried out for thermoelastic homogeneous isotropic nanobeam in the context of fractional order strain with one relaxation time model. Under simply supported and thermal loading conditions with fixed aspect ratios, the Laplace transform has been applied for the governing equations. The inverse of the Laplace transform has been calculated by using the Tzou method. The numerical results have been validated for a thermoelastic rectangular nanobeam of gold (Au) as a case when it is subjected to ramp-type heating. The numerical results have been shown in figures to stand on the effects of the ramping heat and fractional order parameter on all the studied functions. The ramp-type heat the fractional-order parameters have significant effects on the temperature increment, the lateral vibration, the deformation, the stress, the stress-strain energy distributions. The ramp-type heat parameter could be used as a controller to the vibration of the nanobeam and the damping of the energy. [ABSTRACT FROM AUTHOR]

The lateral vibration of monatomic chains considering atomic longitudinal displacements is studied by using the string vibration theory. The modes of lateral vibration of monatomic chains are assumed as the modes of string vibration. Based on the string assumption, the equation of string vibration for monatomic chains is established. Coordinates of the vibration atoms can be calculated by utilizing boundary conditions and symmetry conditions of monatomic chains. The natural angular frequencies of transverse vibration of monatomic chains are calculated by the string vibration method. The tension of the quantum limitation is given and the value of limitation can be used to distinguish nanoelectromechanical systems from quantum-electromechanical Systems. Natural angular frequencies and resonant frequencies of the monatomic chain string are associated with the axial tension acting on the string and the length of monatomic chains, and they can be altered by changing the length of the string and the axial tension acting on the string. The nonlinear vibration of single atomic chain can be analyzed using the improved Lindstedt–Poincaré multiscale method. The study found that the stiffness of the carbon monatomic chain can be altered by changing the length of the string and the tension acting on the string. [ABSTRACT FROM AUTHOR]

Abstract In this study, a rigorous poroelastodynamic solution is proposed for monopiles which accounts for 3D (three dimensional) dynamic interaction of the soil and pile. The dynamic Biot's theory is used to model the soil, while Timoshenko beam is used to model the monopile. The perfect contact conditions between the soil and monopile are realized by decomposing the pile's horizontal translation to radial, hoop and vertical displacements. Correspondingly, 3D radial, hoop and vertical stresses on the pile surface are used to formulate the governing equations of the interaction problem. Using the integral equation methods, the governing differential equations are reduced to coupled integral equations, which are solved numerically. Selected numerical results for coupled lateral and rocking dynamic impedances together with the 3D dynamic contact stresses at the soil-pile interface are studied for different pile and poroelastic material parameters and frequencies of excitation. The distributed soil reaction force and moment along the pile are also obtained by integrating the 3D radial, hoop and vertical stresses along the circumference of the pile at the soil-pile interface. Finally, bending moment, shear force, horizontal translation and rocking rotation of the monopile are obtained based on the classical dynamic Timoshenko beam theory. Highlights • A rigorous solution for offshore monopiles is obtained. • Three dimensional saturated soil and thin-walled pipe pile are considered. • 3D radial, hoop and vertical stresses along the circumference of the pile are obtained. • The non-dimensional impedance is influenced mostly by five parameters. • Simple formulas for the impedance functions are obtained. [ABSTRACT FROM AUTHOR]

In order to suppress lateral vibration transmission and reduce acoustic radiation of a shafting-hull coupled system, a new approach using electromagnetic bearings in the shafting system is proposed. The dynamic characteristics of the electromagnetic bearings, especially the equivalent stiffness and damping as well as the applicable scope of linearization of the electromagnetic bearings, are analysed at first. With the equivalent parameters, a dynamic model of the shaftinghull coupled system is established subsequently by using the frequency response synthesis method to derive frequency response functions associated with the lateral vibrations. Finally, the influence of the control parameters of the electromagnetic bearings on vibration transmission in the shafting-hull system is studied. Analysis results indicate that lateral vibration responses are suppressed significantly when electromagnetic bearings are introduced into the shafting-hull system, and as a result, sound radiation of the system is reduced, which demonstrates that the proposed approach is effective in controlling vibration transmission in the shafting system. [ABSTRACT FROM AUTHOR]

Abstract This paper presents an active control method for reducing the lateral vibration transmission in a shaft-hull coupled system of submerged vehicles under the excitation of propeller forces. In this method, a 6-DOF (degree of freedom) active stern support and the local velocity feedback control strategy are employed to suppress vibration transmission from the shaft to the hull. The dynamic model of the shaft-hull system embedded with the active stern support is established with the FRF (frequency response function)-based synthesis method and the FEM/BEM (finite element method/boundary element method). The six-channel local velocity feedback control strategy is employed to suppress vibrations of the strut-hull interface. Numerical results indicate that a noticeable attenuation of vibration and sound radiation can be achieved by the active stern support. In addition, the combination control at the stern support and the thrust bearing is able to obtain better attenuation at some critical frequencies. Suppression of the mean square velocity and radiated sound power of the hull surface are observed. Highlights • A novel active control method is proposed to suppress the lateral vibration transmission of the shaft-hull system. • A FRFSM/FEM/BEM method is adopted to analyze vibration characteristics under control. • A numerical implementation of the dynamic model validates the control performance. • A significant attenuation is obtained through the active stern support. • A combination control is able to achieve better attenuations of vibration and sound radiation. [ABSTRACT FROM AUTHOR]

Abstract In the present work, the dynamic responses of cast in-situ reinforced concrete vertical and batter pile groups constructed in the silty sand have been investigated. An experimental study was carried out on four pile groups: a group of three vertical piles and a group of three batter piles arranged in triangular pattern, and a group of four vertical piles and a group of four batter piles arranged in square pattern. All batter piles were inclined at 20° to the vertical. Each pile group had a rigid pile cap supporting the oscillator-motor assembly for generating the dynamic loads. The pile groups were tested by varying the exciting force level in different loading direction, and their responses were compared in terms of resonant frequency and peak displacement. The peak displacement of the batter pile group shows a significant reduction (about 25% and 50% in vertical and lateral directions, respectively) compared to their respective vertical pile groups. Graphical abstract fx1 Highlights • Field experiment on cast in-situ RC vertical and batter pile groups. • Effect of load intensity and excitation direction on dynamic behaviour. • Comparison of dynamic responses (resonant frequency and peak displacement). [ABSTRACT FROM AUTHOR]

In the air drilling process, the pre-bent pendulum bottom hole assembly (PBP-BHA) has excellent performance in controlling the well deviation and improving the wellbore quality, but the mechanism that is closely related to the dynamics of the PBP-BHA has not been ascertained. In this paper, an effective technique combining the weighted residuals method with the finite element method is presented to study the PBP-BHA lateral vibration. First, a three-dimensional nonlinear static model of pre-bent BHA is established under small deformation condition and solved by the weighted residuals method and optimization method, so as to define the tangent point according to the deformation characteristics of the PBP-BHA. This tangent point determines the end of the effective PBP-BHA length that starts from the drill bit. Subsequently, the finite element model of PBP-BHA is established to solve the lateral natural frequencies and mode shapes of the PBP-BHA. After considering the borehole wall constraint, the modal superposition technique is used to obtain the steady dynamic responses of the PBP-BHA. Meanwhile, the dynamic performance of the PBP-BHA used in the actual air drilling process is calculated to obtain its critical speeds and working status chart. The critical speeds of the PBP-BHA are 80 r/min and 190 r/min, which are far away from the surface rotary speed in the actual drilling site. Through comparing with the dynamic characteristics of regular BHA with the same structural parameters, it is discovered that the bend angle in the PBP-BHA plays a crucial role in improving the dynamic performance of the PBP-BHA. Moreover, the technique presented in this study can be used to make a reasonable design of BHA configuration and optimize drilling parameters. [ABSTRACT FROM AUTHOR]

Tubing string is one of the most important tools in flowing production. In the state of lateral vibration instability of the tubing string, severe collisions between the string and casing may lead to tubing string failure and borehole wall sloughing. Stability of the tubing string is a potential safety hazard in the process of oil and gas production and discussed in this paper. Considering interaction among the gravity, internal fluid hydrodynamic force, reservoir pressure and liquid cushion in the annular, a mechanical model of lateral vibration of the tubing string, which is simplified as a uniform pipe conveying fluid upwards in vertical well, is developed, and the stability of the system is analyzed by the finite element method. The influences of the flow velocity, the bottom hole pressure and the height and density of liquid cushion on the stabilities of tubing string are discussed. It is found that the increase of either the flow velocity or the bottom hole pressure can cause the buckling of tubing string, however, increasing the height or density of liquid cushion is helpful to improve the stability of tubing string. [ABSTRACT FROM AUTHOR]

Abstract In this paper, forced vibration was used to regulate the droplet migration, fully recording the transient migration of droplets on a micro-textured substrate under the resonance frequency by a high-speed camera. The influence of resonance frequency and dynamic migration characteristics of droplets on the solid micro-texture surface under lateral vibration were researched. The experiment demonstrates that the driving force is caused by the difference between the left and right contact angles made the droplet oscillate and migrate, and as time t increases, the left and right contact points are periodically shifted and the amplitude of migration increases. Therefore, based on the droplet migration behavior and its force balance mechanism, a spring vibration model of migration behavior of the vibrating droplet micro unit was set up to predict the complete trajectory of its migration on a solid surface. The calculation results show that the theoretical displacement is less than the experimental displacement, and the longer the time, the larger the difference. Affected by the vibration, part of the droplet permeates through the micro-texture, resulting in the droplet losing height and the contact angle becoming smaller as well. While the other part of droplet overcomes the internal surface tension to migrate. Highlights • A spring vibration model of migration behavior of the vibrating droplet. • The left and right contact points of droplet are periodically shifted. • As time increases, the theoretical displacement is less than the experimental. • As time increases, droplet overcomes the internal surface tension to migrate. • As the micro-texture substrate vibrates, the droplet infiltration state changes. [ABSTRACT FROM AUTHOR]

As mining vehicle operators are exposed to high level of Whole body vibration (WBV) for prolonged periods of time, approaches to reduce this exposure are needed for the specific types of exposures in mining. Although various engineering controls (i.e. seat suspension systems) have been developed to address WBV, there has been lack of research to systematically evaluate these systems in reducing WBV exposures in mining heavy equipment vehicle settings. Therefore, this laboratory-based study evaluated the efficacy of different combinations of fore-aft (x-axis), lateral (y-axis), and vertical (z-axis) suspensions in reducing WBV exposures. The results showed that the active vertical suspension more effectively reduced the vertical vibration (∼50%; p's < 0.0001) as compared to the passive vertical suspension (10%; p's < 0.11). The passive fore-aft (x-axis) and lateral (y-axis) suspension systems did not attenuate the corresponding axis vibration (p's > 0.06) and sometimes amplified the floor vibration, especially when the non-vertical vibration was predominant (p's < 0.02). These results indicate that there is a critical need to develop more effective engineering controls including better seat suspensions to address non-vertical WBV exposures, especially because these non-vertical WBV exposures can increase risks for adverse health effects including musculoskeletal loading, discomfort, and impaired visual acuity. [ABSTRACT FROM AUTHOR]

Industrial robot is widely used to accomplish the drilling work in aviation industry due to its flexibility and relatively low cost. However, the low stiffness property of robot makes it easy to induce lateral vibration in the drilling process and restricts further improvement of drilling quality and efficiency. It is urgent to propose a new method for robotic drilling which is able to reduce the cutting force and suppress the lateral chatter effectively. In this study, robotic rotary ultrasonic drilling (RRUD) technology is proposed firstly. And the dynamic model to compute the stability lobe for RRUD is developed. The stability problem is simplified as a two degrees of freedom model. After that, the axial chip thickness is achieved on base of kinematic characteristics analysis. Furthermore, exponential method is applied to develop the dynamic cutting force model. Then, the stability lobe diagrams are obtained by frequency domain analysis. It is found that the stability region of RRUD gets a larger extension compared with robotic conventional drilling (RCD). Finally, pilot experiments are conducted and the results indicate that these stability lobe diagrams agree well with the experimental results. [ABSTRACT FROM AUTHOR]

This paper focuses on the size dependency of lateral vibration of a micro overhung rotor-disk system subjected to an axial load based on the modified strain gradient theory. The governing equations of motions as well as the boundary conditions are derived from Hamilton’s principle. The assumed modes approach is employed to transform the governing partial differential equations into a set of infinite ordinary differential equations. The first two natural frequencies and associated instability rotational speeds of the system are analytically determined. The effects of variation in the parameters, such as the rotational speed, material length scale parameters, axial load and rotor length, on the natural frequencies and instability speeds are discussed and presented. The results obtained reveal that each of the material length scale parameters has a significant impact on the vibration response characteristics of the system. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Modelling the interaction between crowds and temporary demountable grandstands with identifying the human dynamic properties are challenges for structure optimal design. In this paper, for investigating and understanding the human and structural lateral dynamic features, a demountable grandstand was tested to obtain its model parameters firstly. Then it is tested at amplitudes between 0.16 m/s² to 1.54 m/s² with 75 random waves through a shaking table when occupied by twenty persons. Afterword a simplified two-degree of freedom lumped dynamic model of the joint humanstructure system is reinterpreted. Utilizing the state-space model, the passive crowd dynamic parameters are obtained, based on root mean square accumulation error analysis. Statistical analysis of the predictive results concludes that seated crowd model damping ratio is 0.5, and the probable natural frequency is 2.0 Hz with the model mass ratio 0.7. For standing crowd model, the probable natural frequency is 1.5 Hz with the model mass damping ratio 0.4, and the model mass ratio is 0.7. It may have ability to serve as a reference value that can be utilized in vibration safety and serviceability assessment of TDGs, to estimate realistically the vibration response on the occasions when crowd are seated or standing. [ABSTRACT FROM AUTHOR]

Rotor vibrations and its control is an important subject in many industries such as power plants and gas stations. When lateral vibrations of rotors during operation exceed allowable level, a huge damage will be occurred. Surge and stall may be some common reasons of these vibrations. This paper aims to present a simple model for surge and stall and assumes that its effect as a distributed force acting on a rotor-disk system. This is a basic and conceptual model for future investigations in this area. Therefore, the effect of a distributed axial force exerted on an assembled disk on a rotating shaft is investigated theoretically. The set of equations for free and forced whirling analyses of a rotor- disc is derived. Also, transverse load composed of unbalanced mass and total weight of the system is considered. For forced whirling analysis, static deflection of the rotor is considered as the initial conditions and rotational speed of the rotor is considered as a time variable parameter which increases from zero to its nominal value in a limited period of time. For a simply supported rotor, the free whirling analysis is investigated using Galerkin method and using Galerkin and Newmark-beta methods, the forced whirling analysis is studied numerically. Forward and backward frequencies and Campbell diagrams are presented in free whirling analysis and variation of deflection, and shear force in any point of the rotor are depicted versus time in forced whirling analysis. The most advantages of the presented paper are consideration of time-dependency of rotating speed in forced whirling analysis. Results indicate that the axial load has a considerable effect on the forward and backward frequencies and lateral vibration amplitude of the rotor. [ABSTRACT FROM AUTHOR]

The dynamics of axial vibration and lateral vibration coexisting in a poppet valve were studied. It is found that the axial movement affects the lateral movement of the poppet via three ways, including the axial displacement, the valve chamber pressure as well as collisions between the poppet and the valve seat. However, the impact of the lateral vibration on the axial one is only by means of collisions between the poppet and the valve seat. The influenced lateral or axial vibration undergoes a transition and sometimes changes from a damped vibration to a chaotic vibration [ABSTRACT FROM AUTHOR]

In this work we investigate forward and backward whirls of a drill-string using a novel experimental drilling rig (Wiercigroch, 2010) capable of reproducing major types of drill-string vibration, including stick-slip, bit-bounce and whirling. We focus our attention on whirling motion of the Bottom Hole Assembly (BHA) with a particular attention to the co-existence of forward and backward whirls. We present experimental results, showing for the first time co-existing whirling solutions and characterizing the parameter space in which different whirls can be observed. Those results are then used to calibrate a simple mathematical model, which can be used for further studies of whirling phenomena. [ABSTRACT FROM AUTHOR]

Assessment of the vibration of high-speed trains negotiating complex sections of terrain under strong wind conditions is very important for research into the operation safety and comfort of passengers on high-speed trains. To assess the vibration of high-speed trains negotiating complex sections of terrain under strong wind conditions, we performed a field measurement when the train passes through typical sections of complex terrain along the Lanzhou–Xinjiang high-speed railway in China. We selected the lateral vibration conditions, including the roll angle and lateral displacement of car-body gravity centre through two typical representative sections (embankment–tunnel–embankment and embankment–rectangular transition–cutting) for analysis. The results show that the severe car-swaying phenomenon occurs when the high-speed train moves through the test section, and the car-body lateral vibration characteristic is related significantly to the state of the terrain and topography along the railway. The main causes for this car-swaying phenomenon may be the transitions between different windproof structures, and the greater the scale of the transition region between different windproof structures or landform changes, the more obvious the car-swaying phenomenon becomes. The lateral vibration of the car-body is relatively steady when the train is running through terrain with minor changes in topography, such as the windbreak installed on the bridge and embankment, but the tail car sways more violently than the head car. When the vehicle runs from the windbreak installed on the embankment into the tunnel (or in the opposite direction), the tail car sways more intensely than the head car, and the head car runs relatively stable in the tunnel. [ABSTRACT FROM PUBLISHER]

The effective control of the transverse vibration is critical for the propeller-shaft coupling system, where excessive vibrations may cause reliability problems for working equipment and radiated noise of marine vessels. This paper is concerned with the active control method of reducing the lateral vibration transmission for the propeller-shafting system using a 1:10 scaled ratio experimental model. The lateral vibration characteristics of the propeller-shaft coupling system are investigated first by the experimental method, identifying the propeller mode and shafting modes that dominate the peak frequencies of system responses. The active vibration control system taking the electromagnetic actuator as the control power source and the raft vibration acceleration as the active control target is proposed for base-point control and cross-point control strategies. An adaptive feedforward controller based on the equivalent interference principle is developed by the improved LMS algorithm with parameter scale transformation. The designed adaptive algorithm accelerates the convergence rate of the controller parameters and tracks the unknown frequency fluctuations of the time-varying disturbance. Experimental implementation of the proposed active controller is carried out, demonstrating the applicability of the improved algorithm on the lateral vibration control of the propeller-shafting system. • An experimental model of the propeller-shafting coupling system is proposed. • The lateral vibration characteristics and vibration transmission paths of the coupling model are studied. • The active vibration control system is built considering the base-point and cross-point actuation. • A PST-based adaptive feedforward control algorithm is developed and effective for vibration attenuation. [ABSTRACT FROM AUTHOR]

Chaos control of a spinning disk having transverse vibration is considered in this article by stabilizing the system on its corresponding unstable periodic orbit (UPO). At the first step, the system continuous-time dynamic equations are quantized by utilizing a proper Poincare map. Then, using the regression method a linear description from the obtained cross points is achieved around the corresponding fixed point of the target UPO. Finally, through solving the Riccati equation, an optimal controller is introduced which stabilizes the system on its unstable fixed point. At the end, the effectiveness of the proposed control method is examined through numerical simulations. [ABSTRACT FROM AUTHOR]

Uneven rotation of the bottom hole drill stem assembly (BHA) and the drill string is a source of torsion shocks that create high-frequency and high-amplitude vibration. A correlation between torsional and lateral vibrations is discovered. An analysis demonstrates that an increased vibration load on the drill string and the bottom hole drill stem assembly leads to a decrease in the mechanical on-bottom drilling rate and premature wear of equipment. A suitable selection of all the elements of BHA that takes into account the possibility that different types of vibrations may arise and an adjustment of the drilling parameters (bit load, rotational speed) together lead to an increase in the drilling rate, the reliability of the drilling equipment, and a decrease in the time needed to construct the well. Real-time monitoring for shocks, vibrations, and stick-slip will help to increase the precision of estimates of the state of downhole equipment. [ABSTRACT FROM AUTHOR]

A method of suppressing vibration in lateral directions is investigated based on varying stiffness strategy. A vertically controlled magnetic suspension system is often subjected to vibration in lightly damped lateral directions. In this paper, a novel approach is proposed to detect the lateral displacement of such magnetic suspension system, and how this displacement can be used to reduce vibration by varying stiffness control is presented. The principle of edge effect is applied to detect the lateral displacement in a magnetic suspension system operated in differential mode. A switching stiffness control and a modified control strategies are used to vary the stiffness of the system in order to reduce lateral vibration. Several experiments are carried out to validate the efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

As an important aspect for dynamic design, the lateral vibration characteristics of friction hoist directly affect the friction hoist security work. To further study the relationship between frietional lateral vibration and related factors, the theory of elasticity mechanics was used to build the distributing theoretic model of coupled rope-cage vibration for friction hoisting system. Finite element method was used to verify the feasibility and effectiveness of the proposed model. The causes and effects of abnormal vibration and dynamic instability during the upgrade hoisting were analyzed. The results show that linear density of wire rope, operating load, hoisting speed have significant impact on lateral vibration, while the contact stiffness of container and can road has slight effect. [ABSTRACT FROM AUTHOR]

Drill string vibration is an important factor to influence the normal operation of drilling string system, and lateral vibration is the most complex and most severe vibration form. In order to further understand the lateral vibration characteristics of modes and dynamic for drill string, effectively prevent drill string failure, and improve the service life of drill string, a lateral vibration model of a drill string with transverse inertia effect is established. Then the variation trend of lateral vibration natural frequency of drill string under different conditions is analyzed. The analysis results show that under the influence of transverse inertial effect, the lateral vibration natural frequency of drill string is higher than that without considering the transverse inertia effect. At the same time, the natural frequency gradually decreases with the increase of drill string length; the natural frequency starts to increase and then decrease with the increase of borehole diameter, and the natural frequency gradually increases with the increase of the ratio of external and internal diameter of drill string. [ABSTRACT FROM AUTHOR]

This paper addresses the influence of lateral external force effects on the non-guidance force control of a hybrid-type electropermanent magnet suspension (EPMS) magnetic levitation (maglev) conveyor. The benefits of this maglev system are good ride comfort and frictionless and abrasion-free operation. However, it is possible for an unintended lateral force to generate lateral oscillation, and lateral displacement affects the levitation and guidance forces. These forces were calculated using a 3-D finite-element model, using the current, levitation air gap, and lateral displacement as inputs of the EPMS. To determine the influence of the lateral force effect, an experiment was conducted using an impact hammer to apply an impulse force at two points on the maglev. In one case, a lateral force was applied to the center of one side of a maglev conveyor. In this case, the external force affected the front and rear EPMSs equally. In the second case, a lateral force was applied to a corner of the maglev. In this case, the unbalanced external force affected the EPMSs unequally. The experimental results illustrate the effects of balanced and unbalanced external lateral forces on the lateral vibration, air gap, and input current. [ABSTRACT FROM PUBLISHER]

The lateral dynamic interaction of the soil and pile has been extensively studied, however, most of the existing studies simplified the soil medium as a one-phase (solid) or two phase (pore fluid, soil skeleton) medium, which is far from the true condition of the soil in nature. Based on the poroelastic continuum mechanics, a coupled dynamic unsaturated soil-pile interaction model is established in this paper. The potential function, operator decomposition method and variable separation method are introduced herein to obtain the lateral force of the unsaturated soil acting on the pile shaft. Afterwards, the analytical solution of the pile dynamic impedance in the frequency domain is derived by employing the soil-pile continuous deformation conditions and the boundary conditions of the pile. The reliability of the obtained solution is verified through the comparisons against classic simplified answers. The main conclusions found in this paper can be drawn as: (a) The increase in the saturation of the soil would decrease the soil strength, resulting in an increase in the displacements and internal force of the pile; (b) Both the increase in soil permeability and the decrease in soil saturation will lead to the decrease in the pore pressure at the side of the pile. And, the smaller the saturation is, the greater the matrix suction would be; (c) The natural frequency of the pile decreases with the increase of the soil saturation. • An analytical solution for the lateral dynamic response of pile foundation embedded in unsaturated soil is developed. • The lateral dynamic impedance of the pile decreases with the increasing soil saturation. • The fully saturated soil has much larger energy dissipation effect than the unsaturated soil condition. • Both the increase of soil permeability and decrease of the saturation can lead to the decrease of pore pressure. [ABSTRACT FROM AUTHOR]

The present study aims at developing a mathematical model to investigate the lateral dynamic response of offshore pipe piles. The lateral vibration characteristics of the pipe pile and the corresponding soil resistance are calculated by the Timoshenko beam theory and Biot's poroelastic theory, respectively. Considering the field condition of offshore piles, the influence of hydrodynamic pressure, which is derived based on the radiation wave theory, is also considered in the proposed model. The analytical solution for the lateral dynamic impedance of pile head has been determined and then validated by comparing with the experiment results. Numerical discussions are finally conducted to illustrate the influence of inner and outer hydrodynamic pressure, water depth, embedment depth, pile diameter-length ratio on the lateral dynamic impedance and natural frequency of offshore piles. The main findings can be summarized as: (1) the hydrodynamic pressure can significantly affect the first-order natural frequency. If the hydrodynamic pressure is not accounted for, the natural frequency will be obviously overestimated; (2) the inner water of offshore pipe piles will overall weaken the dynamic stability of the offshore pipe piles resisting to lateral dynamic loading. [ABSTRACT FROM AUTHOR]

ABSTRACT Fatigue is one of the principle damage mechanisms in materials especially at elevated temperatures. It possesses a great influence on the material properties and the possible working life. In this work, a novel technique for the analysis of fatigue at elevated temperature is suggested. Material fundamental frequency and its drop are used as the key parameters to predict the remaining useful life of a selected shape specimen, which is operated under low-cyclic fatigue loading at elevated temperature. Experiments are performed on aluminium 1050 with two different lengths of a non-prismatic cantilever beam at room temperature, 100, 200 and 300 °C, respectively. The experimental data is further transformed in to an empirical correlation that can predict specimen useful life. The error in this life prediction is less than 5%, and it reduces more once the frequency drop is increased. [ABSTRACT FROM AUTHOR]

Energy harvesters are devices that convert mechanical energy, usually vibration, into electrical energy that can be used to supply low power circuits (e.g. sensors). In this work, an energy harvester is designed for converting the mechanical energy of the lateral vibrations of shafts into electrical energy. For that, permanent magnets are mounted in the shaft and coils are mounted in a fixed structure. A configuration analysis is performed to find the appropriated polarization of the magnets and orientation of the coils in order to have electromagnetic induction without resisting torque on the shaft. Experimental tests are done for different electrical configurations of the coils: independent, in series and, in parallel. The results show that more electric power is induced when the coils are connected in series, and vibration reduction is more evident when the coils are connected independently. [ABSTRACT FROM AUTHOR]

Manipulators used for the transportation of large panel-shape payloads often adopt long and slender links (or forks) with translational joins to carry the payloads. As the size of the payload increases, the length of the links also increases to hold the payload securely. The increased length of the link inevitably amplifies the effect of the flexure in the link. Intuitively, the translational motion of the link in its longitudinal direction should have no effect on the lateral vibration of the link because of the orthogonality between the direction of the translational motion and the lateral vibration. If, however, the link was flexible and translated horizontally (perpendicular to the gravitational field) the asymmetric deflection of the link caused by gravity would break the orthogonality between the two directions, and the longitudinal motion of the link would excite lateral motion in the link. In this paper, the lateral oscillatory motion of the flexible link in a large-scale solar cell panel handling robot is investigated where the links carry the panel in its longitudinal direction. The Newtonian approach in conjunction with the assumed modes method is used for derivation of the equation of motion for the flexible forks where non-zero control force is applied at the base of the link. The analysis illustrates the effect of longitudinal motion on the lateral vibration and dynamic stiffening effect (variation of the natural frequency) of the link due to the translational velocity. Lateral vibration behavior is simulated using the derived equations of the motion. A robust vibration control scheme, the input shaping filter technique, is implemented on the model and the effectiveness of the scheme is verified numerically. [ABSTRACT FROM AUTHOR]

A new analytical solution for free lateral vibration of a rotating Timoshenko shaft with various boundary conditions is presented in this paper. Gyroscopic and rotary inertia effects, as well as the couplings associated with the shear deformation in Timoshenko shaft, are considered in the equation of motion. Both forward and backward undamped natural frequencies can be obtained for simply supported (S-S), clamped-clamped (C-C), clamped-simply (C-S), clamped-free (C-F) and clamped-guided (C-G) boundary conditions using state-space approach. A centrifugally induced axial force, which is produced as a result of Poisson's ratio, is also included in the equation of motion. The effect of this axial force on the lateral natural frequencies is investigated as the rotational speed increases. Numerical results and illustrative examples are given and comparisons are made between the results of the present method and those of the previous works. [ABSTRACT FROM AUTHOR]