Journal of Vibroengineering
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Numerical investigation on nonlinear dynamic responses to fluid-structure interaction in BTA deep-hole drilling shaft system
Get PDFNumerical investigation is conducted into the nonlinear dynamic responses to fluid-structure interaction in deep-hole drilling shaft system. Based on the theories of pipes and tubes conveying fluid, the governing equation of the drilling shaft system is obtained taking into account of the fluid-structure interaction and the effect of the motion constraints. The nonlinear partial differential governing equation of motion is discretized in modal space using the Galerkin method and then transformed into a set of ordinary different equations. Numerical solutions of these equations are then obtained using the fourth order Runge-Kutta method. The influence of the forcing frequency and the support constraints on the dynamic behaviors of the drilling shaft is examined. The nonlinear dynamic behaviors of the drilling shaft system are presented by the bifurcation diagram and phase diagram. It has been found that the magnitude of support stiffness and the number and position of support constraints have a significant influence on dynamic behaviors of the drilling shaft system. The study in the paper provides an effective guidance to maintain the stability of the BTA deep-hole drilling shaft system through selecting the favorable operation parameters in deep hole drilling process
Vibration dissipation of an axially traveling string with boundary damping
Get PDFAt present, the control of vibration problem of many engineering equipment can be simplified as a study on transverse vibration of axially traveling string system. In this paper, transverse vibration control and energy dissipation of axially traveling string system is investigated by using a boundary viscous damper. By analyzing the nature frequencies of the fixed length and the variable length of the string system, the resonance frequency of the external concentrated force is obtained. The amplitude and the energy reflection ratio of reflected wave to incident wave is investigated respectively by the force equilibrium principle and the energy equation at the boundary. According to amplitude and the energy reflection ratio, the range and the optimal value of damping coefficient are obtained. The effect of vibration dissipation with a viscous damper and an external concentrated force at the left boundary is investigated respectively by the numerical simulation
A parameter optimization method for stress simulation of double horse head pumping unit dynamics model with cable
Get PDFSome components in Double horse head (DHH) pumping unit may occur cracking failure due to high cycle alternating stress, and this makes the research on dynamic stress simulation for them more interesting topic in its maintenance operation. This paper aims to improve the accuracy of dynamic stress simulation model through a parameter optimization method for the cable joints in DHH pumping unit. A series of cylinders was employed to model the steel cable, and the back horse head was also transformed to flexible body, then a rigid-flexible multibody dynamics model with cable was constructed to simulate the dynamic stress of components in DHH pumping unit. Stiffness and damping coefficient in cable joints have a significant effect on the model performance, and an unreasonable value may cause a strong vibrational and undesirable model response, therefore, a Memetic Algorithms based method was proposed to optimize them for improving the simulation accuracy using tested stress as objective function. Results show that the dynamic stress simulated from improved model is much closer to the experimental test compared with the original model, and these optimized parameters are also valid for the model in other working condition
EEMD-Based cICA method for single-channel signal separation and fault feature extraction of gearbox
Get PDFThis paper proposes a novel fault feature extraction method with the aim of extracting the fault feature submerged in the single-channel observation signal. The proposed method integrates the strengths of the constrained independent component analysis (cICA) extracting only the signals of interest (SOIs) with the advantage of ensemble empirical mode decomposition (EEMD) alleviating the mode mixing. The method, which is named EEMD-based cICA, not only enables gear fault feature extraction but also offers a new independent component analysis (ICA) mixing model with source noise and measured noise for the single-channel observation signal. The efficiency of the proposed method is tested on simulated as well as real-world vibration signals acquired from a multi-stage gearbox with a missing tooth and a chipped tooth, respectively
Dynamic analysis and control of strip mill vibration under the coupling effect of roll and rolled piece
Get PDFAccording to the “Hill rolling force formula”, taking particular account of the influence from horizontal vibration of rolled piece in roll gap, a dynamic rolling force model is analyzed. Considering the interaction between vibration of strip and roll, the dynamic vibration model of rolling mill is established. On this basis, the time delayed feedback is introduced to control the vibration of the roll system. The amplitude frequency response of the coupled vibration control equation is obtained by using the multiple scales method. Different time delay parameters are selected to test the control effect. Research results show that the unstable vibration of the roll system can be suppressed with appropriate time delay feedback parameters. Because it is simpler and has good control effect in solving nonlinear mechanical vibration, so these results will make a difference for the research of strip mill vibration, and provide theoretical basis for strip steel production
The effect of lubricant inertia on fluid cavitation for high-speed squeeze film dampers
Get PDFThis work studies the effect of lubricant inertia on the fluid cavitation for partially sealed high-speed squeeze film dampers (SFDs) executing small amplitude circular-centered orbits (CCOs). The lubricant cavitation is modeled by both the Elrod algorithm and the Gumbel’s cavitation boundary condition to provide the comparison between the most common lubricant cavitation models. Additionally, the fluid inertia is integrated by adapting a finite-length SFD model for partially sealed dampers. The integrated SFD model is incorporated into a numerical simulation model and the results are validated by comparison with experimental data. The results of the analysis demonstrate that the fluid inertia effects significantly extend the cavitation region and influence the cavitation onset and the film reformation
Simplified calculation method for transverse seismic response of aqueducts considering fluid-structure interaction
Get PDFAqueduct is the key structure in water conveyance engineering, which may be damaged during earthquake. Although numerous water conveyance designs have been built, the current state of researches on aqueduct aseismic design is inadequate. In this paper, based on the fluid-structure interaction dynamics and response spectra analysis, a simplified analysis method was proposed to evaluate the transverse seismic response of aqueducts, and the simplified calculating results were compared with the results of the nonlinear finite element calculation of fluid-structure interaction and experimental results. The results showed that the simplified analysis method put forward in this paper could be used to evaluate the transverse seismic response of aqueducts. In the condition that the pier height is less than 40 m, the first-order lateral vibration mode of the aqueduct has a higher model contribution rate; the simplified calculation method can achieve extremely high accuracy. The simplified calculation precision decreases as the height increases when the pier height exceeds 40 m
Design and implementation of DC source fed improved dual-output buck-boost converter for agricultural and industrial applications
Get PDFThe proposed research involves, a design and implementation of DC source fed improved Dual output Buck-Boost converter for agricultural and industrial applications. It consists of step up and step-down converter, DC-link module. Compared with conventional two converters, the designed system results in reduction of voltage tension across the switches, compact power switches, DC source reckoning and reduced inrush current. DC-link switching is achieved by reduced ripple voltage which results in improved quality of obtained output power. Reduction in switch count makes the system more cost effective. In addition, the motor speed is regulated by PI controller. Brushless DC Motor produce torque ripple and cause mechanical vibration, acoustic noise due to structural imperfectness and control system, to overcome this suppression control method of vibration for brushless DC motor utilizing feedforward compensation with Fourier transform utilizing a vibration signal acquired by an acceleration sensor attached to the motor frame is proposed. A simulation and prototype model of Dual output Buck-Boost converter is developed, and its performance is analysed for various operating conditions
Numerical computation for the impact of flow rate and rotational speed on the flow-induced noise of the centrifugal pump
Get PDFThis paper adopted an indirect mixed method (computational fluid dynamics + boundary element method) based on computational fluid dynamics + Lighthill acoustic analogy theories to compute the flow field and flow-induced noise of the centrifugal pump, and experimentally verified the correctness of computational results. The pressure distribution of the centrifugal pump through an unsteady computation showed that there were obvious separation vortexes at the outlet of the centrifugal pump and pressure at the edge of impellers was obviously more than that of other parts. There were many peak noises on the sound pressure level curve at the outlet of the centrifugal pump. The sound pressure level gradually decreased with the increased frequency. However, sound pressure levels will be a stable value when the analyzed frequency was more than 3000 Hz. Sound pressures at the inlet and outlet of the centrifugal pump were relatively large. Sound pressures at the inlet pipeline gradually decreased from outside to inside and sound pressures of outlet pipeline gradually decreased from inside to outside. The structure of the centrifugal pump was not completely symmetrical, and the sound field was not symmetrical. In addition, the radiation noises in the external field at the inlet and outlet of the centrifugal pump were similar to the radiation of many point sound sources. Peak values of flow-induced noises at the outlet of the centrifugal pump were more than those at the inlet of the centrifugal pump under the working condition of different rotational speeds and flow rates. In the meanwhile, sound pressure levels at the inlet and outlet of the centrifugal pump did not show many differences in amplitudes when the rotational speed was small. When the rotational speed reached up to 3000 r/min, the sound pressure at inlet was more than that at outlet within 1500 Hz-4500 Hz. At many peak frequency points, peak noises at outlet were obviously more than those at inlet, which thus proved that fluid caused large pressure fluctuations due to the interaction between impellers and volutes after flowing through the centrifugal pump and flow-induced noises caused by pressure fluctuations were mainly reflected in blade frequency. The change of the rotational speed and flow rate would not only increase the flow-induced noise in the centrifugal pump, but also seriously affect the external radiation sound field of the centrifugal pump
Multi-axis fatigue loading system of wind turbine blade and vibration coupling characteristics
Get PDFThis paper presents a new method which focuses on the multi-axis fatigue loading mode for wind turbine blade and aims to shorten the fatigue loading cycle. The whole test scheme is design for the measurement of fatigue loading system. The two leading sources of fatigue loading system are asymmetric arrangement in the space. In addition, its vibration mathematical model is derived according to the Lagrange equation. The numerical simulation model is developed by means of Matlab Simulink. The vibration coupling characteristics including motor revolution speed, phase and amplitude of wind turbine blade is obtained. Moreover, the trajectory of wind turbine blade is obtained. Finally, a multi-axis fatigue loading platform for small wind turbine blade is built for the proposed study. The on-site test showed that if the revolution speeds of the two loading sources is the same as the natural frequency of wind turbine blade, the revolution speed, the phase angle of motor and the blade trajectory were relative changed smoothly. Thus, the amplitude of blade is state and the largest. Otherwise when the revolution speed of motor is different with the natural frequency of blade, the revolution speeds and phase angle of the two loading sources fluctuated largely. The above conclusion provided the theoretical basis for the subsequent decoupling control algorithm of multi-axis fatigue loading test