Journal of Vibroengineering
Not a member yet
3189 research outputs found
Sort by
Research on the influence of the normal vibration on the friction-induced vibration of the water-lubricated stern bearing
Full text linkDuring the slow voyage of ships, the friction-induced vibration noise often occurs in the contact region of the water-lubricated stern bearing and the tail shaft. The lateral vibration can impact the normal motion of the contact surface, then change the dynamic friction force, finally affect the behaviour of the friction-induced vibration. By adding the movement of the stern shaft journal into the normal load description of the dynamic friction, the equation of friction-induced vibration considering the effect of normal vibration was established. Then the effect law of normal vibration on friction-induced vibration was discussed by numerical simulation and test. The results show that the normal vibration would make the friction-induced vibration appear quasi-periodic, chaotic trend, and narrow the speed range in which the noise of friction-induced vibration appears
Bearing fault diagnosis based on improved VMD and DCNN
Full text linkVibration signal produced by rolling element bearings has obvious non-stationary and nonlinear characteristics, and it’s necessary to preprocess the original signals to obtain better diagnostic results. This paper proposes an improved variational mode decomposition (IVMD) and deep convolutional neural network (DCNN) method to realize the intelligent fault diagnosis of rolling element bearings. Firstly, to solve the problem that the number of decomposed modes of variational mode decomposition (VMD) needs to be preset, an IVMD method is proposed, where the mode number can be determined adaptively according to the curve of the instantaneous frequency mean of mode functions. With this method, the vibration signal can be decomposed into a series of modal components containing bearing fault characteristic information. Then, DCNN is employed to fuse these multi-scale modal components, which can automatically learn fault features and establish bearing fault diagnosis model to realize intelligent fault diagnosis eventually. Experimental analysis and comparison results verify that the proposed method can effectively enhance the bearing fault features and improve the diagnosis accuracy
Structural characteristics of twin-screw compressor rotor based on thermal-solid coupling method
Full text linkHigh-temperature gas will cause stress and deformation of the rotor during the operation of the twin-screw compressor, which will affect the structural performance of the screw rotor. Based on the CFD/CSD coupling solution technology, the method of thermal solid numerical analysis is developed. The fluid control equations are time-averaged differential equations, and the turbulence model is a two-equation Realizable K-ε model. The thermal deformation and thermal stress of the rotor are obtained by solving the structural static equilibrium equation. The reliability of the proposed method is verified by solving the thermal deformation of the L-shaped large-diameter buried pipeline. Finally, the thermal deformation and thermal stress of the rotor under different exhaust pressures and different speeds are mainly studied. Through simulation analysis, the variation law of rotor deformation, stress and modal under different temperature fields of the compressor is obtained, which can provide a certain theoretical reference for the compressor structural design and optimization
The inner product vector as an output-only cross-correlation-based feature to structural damage assessment
Full text linkThis paper presents a structural damage assessment method that relies on a cross-correlation-based damage sensitive feature known as Inner Product Vector (IPV). Such a feature is extracted from the dynamic response measured at different locations within a structure. Previous investigations on the use of the IPV in a damage detection framework were conducted through laboratory tests by manipulating the excitation source in an input-output approach. In this paper, a new output-only approach has been developed to extract the Inner Product Vector only from the structural response time histories without knowledge of the input excitation. This is a more realistic scenario in structural health monitoring applications where it is difficult (in some cases, impossible) to monitor the external forces. The new estimation of the IPV is accomplished by taking the cross-correlations between filtered contributions to the overall structural response. It is shown how the elements of the IPV are affected by changes of the structural properties induced by damage and how effective the proposed approach is in the presence of external disturbances. The proposed approach has been proven to be very effective in dealing with dense sensor networks requiring large computational efforts. Numerical and experimental tests have been performed to address the reliability of the proposed damage index as a damage sensitive feature in an output-only framework
3D numerical modelling and analysis of a magnetorheological elastomer (MRE)
Full text linkMagneto rheological elastomer (MRE) is a smart material consists of a polymer matrix embedded micro/nano-sized magnetic particles. Its mechanical properties are altered by external magnetic fields. In this article, a magnetic-mechanical coupled physics is done for MRE using COMSOL multi-physics finite element analysis (FEA) software for a particle level (micro-scale). Both linear and torsional transmissibility analysis are done on MRE under influence of magnetic fields. Simulation results indicate both linear and torsional stiffness increased with magnetic field. Under the initial influence of magnetic field, it is shown that an increase of 28.75 % and 20.12 % of the stiffness in linear and torsional modes, respectively. Transmissibility curve showed shift in the natural frequency due to increase in stiffness when exposed to a magnetic field. Vibration isolation was reached by achieving a minimum transmissibility factor
Sliding-mode control for coal shearer drum height adjustment based on variable speed reaching law
Full text linkAiming at the shortcomings of the automatic height control of the existing coal shearer drum, the control strategy of the coal shearer drums height adjustment sliding mode based on the variable speed reach law is proposed. Firstly, the mathematical model of the coal shearer height-adjusting cylinder is established, and the sliding mode switching function and its derivative including the deviation variable are derived. The exponential approaching law sliding mode controller is designed. Secondly, the hydraulic simulation of the drum height is established. The model compares and analyzes the control effects of traditional PID control and exponential approach law sliding mode control. The results show that the exponential approach law sliding mode control is superior to PID control in signal tracking dynamic response and steady state error; when the coal shearer is under load, the height of the drum under control of the exponential approaching law is basically unaffected; finally, the method of shifting the approaching law of dynamically adjusting the arrival speed by the fuzzy parameter optimization strategy is used to adjust the drum height. The simulation results show that compared with the traditional control method, the coal shearer control mode of the coal shearer drum based on the variable speed reach law not only ensures faster response speed and higher control precision, but also effectively reduces system chattering. Improve the reliability of the coal shearer cutting drive system
Prototype test study on dynamic stress of utility tunnel under traffic load
Full text linkIn order to ensure the safety of utility tunnel, the response of each measuring point of the utility tunnel at different speeds is analyzed under the condition that half of the vehicle body is within the boundary of the utility tunnel. The influence of different speeds on the structure of the utility tunnel under the same working condition is discussed, and the dynamic stress variation law of the utility tunnel under actual traffic load is analyzed. The results show that the influence of vehicle speed on the left wall and axillary of the longitudinal utility tunnel is greater than that of the cross-section. The peak values of transverse tensile stress and compressive stress of the right side wall are the largest. The peak transverse stress of the left wall is only 1/3 of that of the right wall. The peak value of the longitudinal compressive stress of the left wall is the largest. The peak value of longitudinal tensile stress of roof is the largest. In the design and construction, the weak position should be reinforced
Fault diagnosis of rotating machinery under time-varying speed based on order tracking and deep learning
Full text linkDue to the disadvantages that rely on prior knowledge and expert experience in traditional order analysis methods and deep learning cannot accurately extract the features in time-varying conditions. A fault diagnosis method for rotating machinery under time-varying conditions based on tacholess order tracking (TOT) and deep learning is proposed in this paper. Firstly, frequency domain periodic signals and estimated speed information are obtained by order tracking. Secondly, the frequency domain periodic signal is speed normalized using the estimated speed information. Finally, normalized features are extracted by deep learning network to form feature vector. The feature vector is fed into a softmax layer to complete fault diagnosis of the gearbox. The fault diagnosis of the gearbox results are compared with other traditional methods and show that the proposed fault diagnosis method can effectively identify the faults and obtain higher fault diagnosis accuracy under time-varying speed
Estimation and measurement of effective line mobility on a non-deterministic thin plate excited by a piezoelectric patch
Full text linkThis paper derived the expression to estimate the effective line moment mobility of a non-deterministic thin plate under moment excitation by a piezoelectric patch actuator. The piezoelectric patch actuator is assumed to generate purely line moments at each of its edges and regarded as a finite number of point moments acting on an infinite plate, which is achieved by integration method. The theoretical model is validated using MATLAB simulation and compared with experimental measurements on a randomized thin plate. The derived effective line moment mobility managed to closely estimate high-frequency response while cutting significant computational time and resource. Results from this study can be used in many applications ranging from vibration isolation where power transmission between the isolator with an area distribution and its host structure can be determined more accurately, and to design the optimal shunt circuit of a piezoelectric shunt damper for maximum power dissipation in order to reduce vibration of a non-deterministic thin plate
Crack growth simulation in 13th row of compressor blades under foreign object damage and resonant vibration condition
Full text linkIn this study, the cracks growth rate in the 13th row of the T56 compressor blades was studied to investigate their fatigue life. For this purpose, the centrifugal and aerodynamic forces on the blade were calculated and then the resulting stress field was obtained by using finite element method. Then, the critical points of stress were determined and the initial semi-elliptical cracks were modeled at these points. After modeling of the initial crack, the stress intensity factor on the crack front was calculated by ANSYS software. Furthermore, the number of required cycles for the crack growth and blade fracture were calculated by applying Paris law to a certain value. After crack growth at this stage, a crack with new length was also modeled at the same point and all the mentioned stages for its growth, were repeated. In this paper, the modal analysis of the blade was conducted and normal frequencies with possible stimulation on compressor velocity were determined by Campbell Diagram. After determining the stress field at resonant frequency, all stages of crack growth were repeated under these conditions to calculate the fatigue life