Vibration Characteristics Of System Research Articles

Characterization of rotary valve control vibration system for vibration stress relief applications

To enhance the vibration system characteristic distortion and pressure loss, we propose a novel rotary valve control vibration system. The paper presents the designed structural composition and generation mechanism of the rotary valve control vibration system. It also derives the mathematical model for the rotary valve distribution process and the overall system. The flow field inside the rotary valve is dynamically simulated using the multiple reference frame model, allowing for the determination of the change rule of the rotary valve’s output characteristics. An AMESim model was developed to analyze the vibration characteristics of the rotary valve control system. The effects of parameters such as inlet pressure, motor speed, and oil supply pump displacement were investigated. A rotary valve control vibration system experimental bench was constructed to experimentally verify the output characteristics of the rotary valve and the vibration characteristics of the system. The results indicate that the characteristic curve of the designed vibration system closely resembles a sinusoidal wave. Additionally, the rotary valve exhibits low pressure loss, making it more suitable for vibration stress relief applications. By appropriately increasing the inlet pressure and decreasing the motor speed, the vibration characteristics of the system can be improved.

Study on Dynamic Characteristics of Vibration System with Two Degrees of Freedom and Multiple Rigid Constraints

A dynamic model of a vibration system with two degrees of freedom and multiple rigid constraints is constructed, the dynamics constraints of the segmented smooth vibration system under the multi-body impact coupling condition are given. Based on the cell mapping principle, a two-parameter co-simulation is carried out with two important parameters of excitation frequency and constraint gap as control variables. The model types and distribution rules of the periodic motion of the system response on the [Formula: see text]-whole two-parameter plane are obtained. The correlation between the dynamic response of the system and the model parameters is analyzed, and the evolution and bifurcation characteristics of fundamental periodic vibrations in the low-frequency small-gap parameter domain of the two-degree-of-freedom multi-rigid constrained vibration system are discussed. The diversity and regularity of subharmonic shock vibrations in the translational domain of the lingual domain are found.

Typical Fault Modeling and Vibration Characteristics of the Turbocharger Rotor System

To study the typical failure mechanism (rotor unbalance, rotor friction, and rotor crack) and vibration characteristics of the turbocharger rotor system, a rotor system dynamics simulation model was established by an improved four-node aggregate parameter method. The geometric and physical characteristics of the rotor system under three failure states and its dynamics under operation were analyzed. Thus, a typical failure dynamics simulation model of the rotor system was established. On this basis, the output failure simulation signal was extracted using the Hu invariant moment feature extraction method to analyze the system vibration characteristics under each typical failure state of the rotor system. The results show that the model in this paper can effectively reduce the computational volume and computational time, and the errors of numerical simulation were less than 3%. When an unbalance fault occurred in the rotor system, the shaft trajectory was “0” shaped and the response spectrum was dominated by 1X. When the rotor system was frictional, the shaft trajectory was a slightly concave “8” shape, and the response spectrum was dominated by 0.5X. When the rotor system was cracked, the axial trajectory was a “vortex”, and the response spectrum was dominated by 0.5X. Thus, the study of typical failure mechanism and vibration characteristics of a turbocharger rotor system by simulation calculation is effective and has good research prospects, providing an important technical reference for dynamic analysis and fault diagnosis of the rotor system.

Vibration analysis of rotating functionally graded graphene platelet reinforced composite shaft-disc system under various boundary conditions

A unified dynamic model of a rotating shaft-disc system with multilaminar functional graded graphene platelet reinforced composite (FG-GPLRC) disc is established in order to study the vibration characteristics of the system. Based on first-order shear deformation theory, Timoshenko Beam theory and differential quadrature finite element method, the discrete energy matrices of shaft and disc are obtained. Then the total differential equation of the system is procured by assembling the shaft and disc element matrices. The accuracy and reliability of the model are verified by comparing with the software simulation results. Besides, the influence of boundary conditions, GPL distribution types, GPL weight, disc layers and physical dimensions on the system vibration characteristics is analyzed. It reflects that the GPL distribution types and boundary conditions will make a certain difference to the frequency parameters of shaft-disc system. Furthermore, the vibration characteristics of different GPL distribution types are differently sensitive to the variation in material and geometric parameters.

Vibration characteristics of rotor-bearing system with angular misalignment and cage fracture: Simulation and experiment

The rolling bearing misalignment may lead to fracture failure of the cage. However, the research on the vibration response of the rotor system caused by bearing misalignment and cage fracture has not attracted enough attention. In this paper, the vibration characteristics of cage fracture fault are studied from two aspects of simulation and experiment. Firstly, a five-degree of freedom nonlinear bearing force model with the bearing misalignment and cage fracture fault is given. Secondly, the bearing restoring force model is introduced into the rotor finite element model. Then, the dynamic model of the deep groove ball bearing-rotor system is established. The effects of key parameters such as cage fracture degree, radial load, and bearing clearance on the vibration characteristics of the system are simulated and analyzed. Thirdly, the bearing test pieces with real cage fatigue fracture fault are obtained by carrying out the bearing life cycle test. On this basis, the vibration signals of bearing with cage fracture under different loads are collected.The simulation and test results show that the system amplitude increases when cage fracture occurs. The obvious impact vibration characteristics appear in the time domain waveform. The vibration energy gradually concentrates to low-frequency vibration. The frequency components related to cage frequency, such as nfc and nfr ± mfc can be more obviously observed in the envelope spectrum. The results can provide a useful reference for the identification and diagnosis of rolling bearing misalignment and cage fracture.

Vibration Characteristics of Rotor System with Loose Disc Caused by the Insufficient Interference Force

The rotating parts looseness is one of the common failures in rotating machinery. The current researches of looseness fault mainly focus on non-rotating components. However, the looseness fault of disc-shaft system, which is the main work part in the rotor system, is almost ignored. Here, a dynamic model of the rotor system with loose disc caused by the insufficient interference force is proposed based on the contact model of disc-shaft system with the microscopic surface topography, the vibration characteristics of the system are analyzed and discussed by the number simulation, and verified by the experiment. The results show that the speed of the shaft, the contact stiffness, the clearance between the disc and shaft, the damping of the disc and the rotational damping have an influence on the rotation state of the disc. When the rotation speed of the disc and the shaft are same, the collision frequency is mainly composed of one frequency multiplication component and very weak high frequency multiplication components. When the rotation speed of the disc and the shaft is close, the vibration of the disc occurs a beat vibration phenomenon in the horizontal direction. Simultaneously, a periodical similar beat vibration phenomenon also occurs in the waveform of the disc-shaft displacement difference. The collision frequency is mainly composed of a low frequency and a weak high frequency component. When the rotation speed of the disc and the shaft has great difference, the collision frequency is mainly composed of one frequency multiplication, a few weak high frequency multiplication components and a few low frequency multiplication component. With the reduction of the relative speed of the disc, the trajectory of the disc changes from circle-shape to inner eight-shape, and then to circle-shape. In the inner eight-shape, the inner ring first gradually becomes smaller and then gradually becomes larger, and the outer ring is still getting smaller. The obtained research results in this paper has important theoretical value for the diagnosis of the rotor system with the loose disc.

Vibration Characteristics of the Dual Electric Propulsion System of Vessels under Electromechanical Coupling Excitation

An electromechanical coupling driving system is a commonly used system for large overloading ships. In this paper, a dual input electromechanical coupling model, including an inverter power supply, three-phase induction motor, fixed-axis gear, and load, is established. The influences of the gear error, inverter, and coupling stiffness on the vibration characteristics of the system are studied, and the influences of each parameter on the vibration characteristics are analyzed. The inverter power supply part considers the constant voltage–frequency ratio control and sinusoidal pulse width modulation, as well as the inverter. The motor part uses the dynamic motor model based on the equivalent circuit. The fixed-axis gear section uses a translation–torsion model with time-varying mesh stiffness and damping. The mechanical part and the motor part are coupled with the load torque of the motor. The results show that the greater the error of the gear, the greater the vibration of the system, and the rotation frequency error is the main factor. Secondly, by comparing the influence of error value and accuracy difference on vibration, we found that when an accuracy difference exists, the dominant factor of system vibration is the accuracy difference. Thirdly, the use of an inverter also increases the vibration of the electromechanical coupling system. Finally, we found that the lower stiffness of the elastic coupling reduced the vibration of the system.

Nonlinear vibration characteristics of gear-rotor-bearing system

Based on the Timoshenko beam element model in the finite element theory and the lumped mass method, the meshing dynamics equation of helical gears was established considering the time-varying meshing stiffness of helical gears, tooth side clearance, bearing support stiffness and other factors, and the nonlinear dynamics model of the gear-rotor-bearing system was established. Through the analysis of the dynamics model, meshing stiffness, backlash and the influence of bearing stiffness for the system vibration characteristics, studies have shown that the bearing stiffness for the purpose of this article studies the effect to the stability of the main reducer system transmission, vibration noise of the gear-rotor-bearing system parameter selection, and provides theory basis for diagnosis.

Analysis of flow-induced vibration of cylinder with splitter plate based on overset grid method

In actual engineering, asymmetric flow often occurs, but rigid partitions are often installed in the direction of the flow field and are symmetric in the flow direction. This will result in a deflection angle between the dividing plate and the direction of the incoming flow. The research results show that when the declination angle is low, the partition plate has a limited impact on the system; when the deflection angle is about 10 degrees, the system vibration characteristics will have abrupt changes, the amplitude will decrease, and the vortex frequency will increase; at the deflection angle 10 degrees to 45 degrees As the declination angle increases, the amplitude increases, and the vortex frequency decreases; it can be seen from the motion trajectory that the declination angle changes suddenly after 10 degrees, and the system has a small amplitude between 10 degrees and 25 degrees. That is, in this declination interval, the partition plate has a better control effect on the vibration of the cylindrical system.

Vibration Analysis of Cylindrical with Splitter Plates under Different Deflection Angles at High Reynolds Number

In order to study the influence of the splitter plate in the elastic support system, the SST k-omega turbulence model is used to solve the problem, and the cylindrical system with splitter plate is numerically simulated by overset mesh. This paper studies the effect of the splitter plate on the vibration system at different deflection angles. The results show that the splitter plate has little effect on the system when the deflection angle is low. When the deflection angle is about 10 degrees, the system vibration characteristics will have a sudden change, the amplitude will decrease, and the vortex frequency will increase. Between the deflection angle of 10 degrees and 45 degrees, as the deflection angle increases, the amplitude increases and the vortex frequency decreases. It can be seen from the motion trajectory that the deflection angle changes suddenly after 10 degrees, and the system has a very small amplitude between 10 degrees and 25 degrees. In this declination interval, the splitter plate controls the vibration of the cylindrical system better.

Evaluating the influence of mechanical system vibration characteristics on servo motor efficiency

In this study, the influence of mechanical vibration characteristics on the efficiency of a servo motor was experimentally investigated. For this purpose, a dedicated apparatus comprising two servo motors connected to a coupling was used. The efficiency of the motor was investigated by first considering the signals of voltage and current; then, the mechanical power was calculated from the acquired torque and angular velocity supplied by the motor. Subsequently, working conditions involving different angular velocities and loading torques were investigated to generate a motor efficiency map. To clarify the influence of the vibration characteristics on the motor efficiency, two types of couplings differing in torsional stiffness and damping characteristics were considered—Type A and Type B. The efficiency was calculated for eight vibration conditions imposed via the selection of the velocity control gain settings for both types. Resultantly, the manner in which the efficiency is affected by the vibration conditions was clarified. Moreover, coupling in the case of better vibration damping characteristics was confirmed to yield a higher motor efficiency for all gain settings. Furthermore, motor working conditions corresponding to high and low motor efficiencies were evaluated, and the motor thermal behavior was investigated. Overall, a lower motor efficiency was confirmed to be associated with increasing temperatures. These results suggest the importance of the vibration characteristics of mechanical systems for achieving high efficiency.

Study on Influence of Multi-Parameter Variation of Bladed Disk System on Vibration Characteristics

As the main components of the rotor system of aero-engines and other rotating machinery equipment, the bladed disk system has high requirements on its structure design, safety and stability. Taking the rotor disk system of aero-engines as the research object, modal calculation of the rotor disk system was based on the group theory algorithm, and using the fine sand movement on the experimental disk to express the disk vibration shape. The experimental vibration mode is used to compare with the finite element calculation results to verify the reliability of the finite element analysis. Study on the effect of dissonance parameter changes on the bladed disk system vibration characteristics concluded that the vibration mode trends of the blisk system and the disc are, basically, consistent. As the mass of the blade increases, the modal frequencies of the entire blisk system gradually decrease, and the amplitude slightly increases. When the mass increases at different parts of the blade, the effect on the modal frequencies of the bladed disk system are not obvious. When the bladed disk system vibrates at low frequency, the disc will not vibrate and each blade will vibrate irregularly. The bladed disk should be avoided to work in this working area for a long time, so as not to cause fatigue damage or even fracture of some blades.

Blade fault diagnosis using Mahalanobis distance

The fault diagnosis of a rotating multi-blade system has been conducted using the vibration characteristics of the system. For the fault diagnosis, multi-dimensional features related to the system vibration characteristics were extracted and used for monitoring the system health condition in most of previous studies. Recently, blade tip timing (BTT) method becomes increasingly popular to measure the vibration signals of rotating multi-blade systems. Due to the under-sampling characteristics of the method, relatively low frequency components of the vibration signal can be only collected with the BTT method. In this study, a statistical index called the Mahalanobis distance is defined and employed for the fault diagnosis of a rotating multi-blade system having a crack. The effects of crack existence and signal to noise ratio on the reliability of the proposed method using BTT signals obtained with a simulation model are investigated in this study.

Evaluation of torque-dependent coupling characteristics and their influence on the system vibration characteristics

Coupling characteristics that depend on the applied torque and the influence of this torque dependency on the system response are investigated in this study. A dedicated apparatus, consisting of two servomotors connected by a coupling, was specifically designed for this purpose. To measure the frequency response of the apparatus, a sweep signal with a frequency between 100 Hz and 2000 Hz was imposed as a torque command of the motor through a servo analyzer. To evaluate the coupling characteristics, such as torsional stiffness and damping, from the frequency response, the apparatus was modeled as a two-degrees-of-freedom system. The characteristics were identified, based on the resonance frequency and the vibration amplitude at the frequency. The relationship between the coupling characteristics and the coupling working time was investigated by conducting dedicated experiments after every 30 min of working time for 3.5 h. The relation between the torque magnitude and the coupling frequency response was also investigated by imposing several torque settings on the sweep signal. It was found that both the working time and the sweep magnitude significantly affected the coupling characteristics. Finally, the velocity step-response test was simulated, based on the identified coupling stiffness and damping, and the results were compared with the experimental acquisitions with various feedback-gain settings. The response oscillated under a higher gain setting. The torque dependency of the coupling characteristics was implemented in the model, based on the evaluated results. It was confirmed that the velocity step response can be accurately simulated by the model, when the torque dependency of the coupling characteristics is considered. In other words, the torque dependency of the coupling characteristics plays an important role in the vibration characteristics of the system.

Vibration analysis of scale-dependent thin shallow microshells with arbitrary planform and boundary conditions

The current article presents a thorough investigation into the natural frequencies and mode shapes of thin doubly curved shallow microshells by taking into account the influence of material length scale parameter. The mathematical model of system is obtained by applying the Hamilton's principle along with the modified couple stress theory and the Kirchhoff-Love's shell theory. In order to extract the free vibration characteristics of system, the finite element method is employed. Several comparative studies are then conducted to verify the quadrilateral thin shallow shell element. The numerical results are presented for the thin cylindrical, spherical, and hyperbolic paraboloidal shallow microshells with different planforms including rectangle, triangle, circle, and ellipse. Thin microplate as a special case of thin shallow microshell is also analyzed. A profound examination on the numerical results is also performed to divulge the impacts of scale-dependency accompanied by the geometrical parameters and boundary conditions on the free vibration response of system.

A Two-Stage Diagnosis Framework for Wind Turbine Gearbox Condition Monitoring

Advances in high-performance sensing technologies enable the development of wind turbine condition monitoring systems to diagnose and predict the system-wide effects of failure events. This paper presents a vibration-based two-stage fault detection framework for failure diagnosis of rotating components in wind turbines. The proposed framework integrates an analytical defect detection method with a graphical verification method to ensure diagnosis efficiency and accuracy. The efficacy of the proposed methodology is demonstrated with a case study using the gearbox condition monitoring Round Robin study dataset provided by the National Renewable Energy Laboratory (NREL). The developed methodology successfully detected five faults out of a total of seven with accurate severity levels and without producing any false alarm in the blind analysis. The case study results indicate that the developed fault detection framework is effective for analyzing gear and bearing faults in wind turbine drivetrain systems based on system vibration characteristics.

Dynamic response analysis of unbalanced rotor-bearing system with internal radial clearance

This paper presents a dynamic model to predict the rotor-bearing system's vibration characteristics using Dimensional Analysis (DA). A small increment in rotor unbalance, and radial clearance can cause multiple faults, ultimately causing catastrophic failure. Hence, this model considers the influence of rotor unbalance and radial clearance on the dynamics of the rotor-bearing system. Experimental investigation reveals the effects of multiple defects at different rotor speeds. Employed Response Surface Method (RSM) correlates the clearance, unbalance, and rotor speed. Comparing experimental results with the RSM and DA indicates the effectiveness of the proposed methodology for condition monitoring of high-speed machinery in process industries.

Torque distribution method based on vibration instability of PS-HEV transmission system

The power-split hybrid electric vehicle has multiple working modes, which can be switched to different working mode according to different working conditions. The main switching process involved in the vehicle driving is the switch from the pure electric mode to the hybrid driving mode. This paper studies the mode switching process involved in the power-split hybrid electric vehicle driving process, and a nonlinear dynamic equation of the electromechanical coupling of the corresponding transmission system is established. Then the multi-scale method is employed to solve the dynamic equation, and the amplitude-frequency response curve is drawn. According to the curve, the effects of load, mechanical input excitation of the engine and motor electromagnetic excitation on the electromechanical coupling torsional vibration of the transmission system are studied. The engine and motor torque distribution schemes are obtained by analyzing the amplitude-frequency response curve of the torsional vibration characteristics of the system. The analysis results show that the vibration instability phenomenon of the transmission system can be avoided by establishing the nonlinear dynamic equation of the transmission system, analyzing the vibration characteristics of the vibration system, and optimizing the torque distribution of a PS-HEV at different working modes.

Non-Linear Coupled Dynamics of a Flexible Propeller-Shaft System Supported by Water Film Bearings

Abstract A slice method to determine the boundary conditions between the stern bearing and shaft by dividing the journal in the stern bearing into several slice elements along the axial direction is proposed for the first time. A comprehensive finite element model considering the nonlinear force of the water film and the flexibility of the propeller blade is established for a propeller-shaft system. The long bearing approximation is adopted to calculate the pressure distribution around each journal element in the stern bearing. The mode superposition method is employed. The nonlinear equation of motion is solved iteratively using the Newmark method. A parametric study is implemented to analyze the nonlinear vibration characteristics of the system. It is shown that the real motion state of the journal in the stern bearing can be simulated more precisely by the slice method proposed. The responses of the system alternate among period-one, quasi-periodic, multi-periodic, and chaotic motions as the rotating speed increases. The damping ratio has a significant effect on the dynamic characteristics of the propeller-shaft system. The motion of the system is unstable when the damping ratio is very small. At this time, the modes of the flexible propeller blades can be excited readily. The slice method, which can also be extensively used in similar rotor-bearing systems in the engineering field, is very simple and efficient to analyze the nonlinear vibration characteristics of a flexible propeller-shaft system supported by water film bearings.

Vibration characteristics of the stepped drill string subjected to gas-structure interaction and spinning motion

This paper studies the vibration characteristics of a drill string in gas drilling under gas-structure interactions, and affected by the combined effects of several parameters including the spinning motion, the weight on bit, the hydrodynamic force, the damping force of drilling fluid and the stabilizer. Based on the Hamilton's principle, the dynamic equations of the spinning drill string subjected to the weight on bit and gas-structure interaction are established and solved by using the Galerkin's method. The exact solutions of the i-th natural frequencies of the drill string with uniform section are derived considering the gas-structure interaction and the spinning motion, and the characteristic curves of the non-dimensional natural frequencies versus different parameters are obtained respectively. The results show that the spinning angular speed, the weight on bit, the flow velocity, the viscous damping force of drilling fluid, the ratio of the external diameter of drill pipe to that of the drill collar and different installation positions of the stabilizer have significant influences on the dynamic characteristics of the drill string. In addition, the effects of the gas drilling fluid and the mud drilling fluid on the system vibration characteristics are discussed and compared, which reveal that natural frequencies of the drill string in gas drilling are higher than that in mud drilling.