Journal of Vibroengineering
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Dynamic simulation analysis of spur gear space driven system with large inertia load
Get PDFThe wide application of large inertia loads in space drive mechanisms is relatively rare in theoretical research. An 8-degree-of-freedom nonlinear dynamic model is established for the time-varying and nonlinear perturbation problems of a large inertia load space drive mechanism. The model is a two-stage spur gear model in which the effects of backlash and time-varying stiffness are considered. The 3D model was imported into ADAMS, and the nonlinear dynamic response of the system was studied by motion simulation. This paper sets up a large inertia experimental device to collect and process data. Comparing experimental results with Adams results, the correctness of the numerical model was verified, and the reasons for the differences between the two were explained. A comparative analysis of the load response under different inertia was performed to illustrate the importance of studying large inertia loads. The simulation results show that the output shaft has a great influence on the dynamic response. Changing the material of the gear can improve the transmission precision of the gear system. The analysis results in this paper enrich the research on the dynamic response of gear system, and provide a theoretical basis for the subsequent design of large inertia load gear system and improve vibration and noise during operation
A new fault diagnosis method using deep belief network and compressive sensing
Get PDFCompressive sensing provides a new idea for machinery monitoring, which greatly reduces the burden on data transmission. After that, the compressed signal will be used for fault diagnosis by feature extraction and fault classification. However, traditional fault diagnosis heavily depends on the prior knowledge and requires a signal reconstruction which will cost great time consumption. For this problem, a deep belief network (DBN) is used here for fault detection directly on compressed signal. This is the first time DBN is combined with the compressive sensing. The PCA analysis shows that DBN has successfully separated different features. The DBN method which is tested on compressed gearbox signal, achieves 92.5 % accuracy for 25 % compressed signal. We compare the DBN on both compressed and reconstructed signal, and find that the DBN using compressed signal not only achieves better accuracies, but also costs less time when compression ratio is less than 0.35. Moreover, the results have been compared with other classification methods
Effect of vehicle-track vertical coupling vibrations on frame-mounted traction motor dynamics
Get PDFIn order to reveal the effect of the vehicle-track vertical coupling vibrations on the frame-mounted traction motor dynamics, a vehicle-track vertical coupling dynamic model with considering the influence of the frame-mounted traction motor is established, and the correctness of the model is verified by real vehicle test. In case of the investigated vehicle model, the influences of the vehicle-track vertical coupling vibrations and the suspension parameters on the frame-mounted traction motor dynamics are discussed. The results show that the traction motor is significantly affected by the train system, when the motor is equivalent to the bogie frame mass, the phenomenon of underestimation exists to evaluate the vibration of the motor. In addition, suspension parameters have a great impact on the traction motor dynamics, rational selection suspension parameters can help to attenuate the vibration of the traction motor, and alleviate uneven the distribution of the air gap magnetic field of the traction motor
Study on two-stage mounting systems having distributed intermediate mass
Get PDFNowadays, two-stage mounting system having integral intermediate mass is widely applied and researched to attenuate vibration of marine machinery equipment, while two stage mounting system having distributed intermediate mass which has the feature of lightweight and installation dimension is rarely used and studied. The theoretical models of two types of mounting systems are set up and force transmissibility rate of the two mounting systems are deduced through four-pole parameters method. A scale experimental prototype is established to test the isolation efficiency of the two-stage mounting system having distributed intermediate mass. FEMs of the two systems are established to make a comparison ascertaining the difference between the two about vibration isolation efficiency at the different frequency. The result shows that two stage mounting system having distributed intermediate mass achieve better vibration isolation efficiency and take less space than two-stage mounting system having integral intermediate mass if with equivalent intermediate mass. Two-stage mounting system having distributed intermediate mass can meet the requirements of practical projects and provides a new way for engineer to refer to when meet with machinery equipment vibration problems
An improved higher-order analytical energy operator with adaptive local iterative filtering for early fault diagnosis of bearings
Get PDFEarly fault diagnosis in rolling bearings is crucial to maintenance and safety in industry. To highlight the weak fault features from complex signals combined with multiple interferences and heavy background noise, a novel approach for bearing fault diagnosis based on higher-order analytic energy operator (HO-AEO) and adaptive local iterative filtering (ALIF) is put forward. HO-AEO has better effect in dealing with heavy noise. However, it is subjected to the limitation of mono-components. To solve this limitation, ALIF is adopted firstly to decompose the nonlinear, non-stationary signals into multiple mono-components adaptively. In the next, the resonance frequency band as the optimal intrinsic mode function (IMF) is selected according to the maximum kurtosis. In the following, HO-AEO is utilized to highlight weak fault characteristics of the selected IMF. Finally, the early bearing fault is diagnosed by the energy operator spectrum based on fast Fourier transform (FFT). Comparisons in the simulation indicate that the fourth order HO-AEO shows the best performance in fault diagnosis compared with Teager energy operator (TEO), analytic energy operator (AEO), the second and the third order HO-AEO. The simulated test and experimental results demonstrate that the proposed approach could effectively extract weak fault characteristics from contaminated vibration signals
Vibration investigation of rotor system with unbalance and blade-casing rubbing coupling faults
Get PDFIn order to investigate the mechanism of a rotor system with unbalance and blade-casing rubbing coupling faults, the vibration and rub force in a rotor system resulting from unbalance and blade-casing rubbing coupling faults are simulated. At first, a dynamic model of 0-2-1 form rotor is established, and a blade-casing model, which considered blade number, clearance between the blade tip and stator, stiffness and size of the blade, is introduced to the rotor model. The characteristics of unbalance and blade-casing rubbing coupling faults are analyzed by waterfall plot, spectrum, time domain chart of vibration and rub force, and the effects of speed and clearance between the blade tip and stator. Secondly, a rotor system tester is established according to the model structure. The experimental test of rubbing is simulated by adjusting the Feeding Device to control the clearance between the blade and stator. After simulation and experimental results were compared, it was found that fraction frequencies and high integer frequencies were affected by a blade-casing rubbing fault, the clearance and speed had different influence on the dynamic characteristic of rotor system with blade-casing rubbing fault
Effects of combustion parameters on antiexplosion performance: model tests and numerical simulations
Get PDFThis study presented a reference for design, analysis, and assessment of typical reinforced concrete (RC) piles subjected to a near-field non-contact explosion. In particular, the effects of radius on the dynamic response of the RC piles under such explosion conditions were investigated using the model tests. Furthermore, the damage and safety as well as the failure modes of such piles were analyzed using the numerical simulations. It was demonstrated that such explosions can cause a partial damage for the piles during the stage of shock waves, whereas for the stage of bubble actions, it can lead to a serious damage of the piles. For a certain distance, the failure of the piles was earlier than the bubble pulsation pressure caused at the end of the first pulsation cycle. Compared with the steel bar, the damage of concretes was more serious because the bonds between the steel bar and the concretes became more severe. Based on the experimental and numerical simulation results, a method to assess the damage of such piles under the explosion conditions was proposed, which could be applicable for the anti-explosion design and the safety and fault diagnosis of various industrial facilities and equipment
Effects of variable parameters on the behaviour of the single flexibly-mounted rod in a closely-packed array
Get PDFExperiments of flow-induced vibrations using a closely-packed triangular rods array with a pitch-to-diameter ratio of 1.1 in water cross-flow were carried out to analyse the detected effects of system parameters in the frequency domain and vibration amplitudes. Single flexibly mounted rod with two degrees of freedom at each end of it was located in the second or the fourth row in the bundle with 21 row. Influence of increasing/decreasing flow, the test rod mass and support stiffness changes were analysed. Reynolds number based on the freestream velocity and a rod diameter was up to 1.64·104. Accelerometers and laser sensors were used to measure the time-varying response of the test rod. FFT approach was adopted to reconstruct the displacements from accelerometer measurements. Experimental results show that the behaviour of the flexibly-mounted rod is dependent on the flow time-history. Dominant flow-dependent and flow-independent frequencies were observed in the frequency domain. Changes in the frequency spectrum introduced by the test rod mass and support stiffness were identified. Oscillation regime of the test rod when the state equilibrium position becomes unstable with the limited oscillations was detected. Metamodeling approach was applied to develop mathematical approximation using three parameters: flow rate, stiffness coefficient and frequency ratio. Good accordance has been found between the inverse model and laboratory experiments
Determination of the deformation characteristics of the foam concrete as a sub-base
Get PDFFoam concrete (FC) is utilizable in various fields of application in civil engineering practice. It's most often used as a leveling sub-base in the floors of the buildings or foundation structures or as a fill material in open spaces such as unused underground structures. Foam concrete contains void pores so it has much lower bulk density than regular concrete. Together with the saving of material inputs, physical and mechanical parameters and low thermal conductivity, it predestinates its use as a structural element of the structures such as sub-base layers. Strain modulus from the second load cycle is the common control parameter in the sub-base design. Some elements of conventional PLT equipment are not usable for foam concrete testing because of larger deflection radius due to the larger stiffness of foam concrete. When reliable relation between dynamic modulus and conventional strain modulus is determined, LWD testing can substitute the PLT test as a quick and simple method. This paper is the first approach to estimate this relation
Damage detection of composite plate based on an improved DAS algorithm by time difference due to anisotropy
Get PDFThis paper proposes a damage detection method based on an improved DAS imaging algorithm by introducing time difference due to anisotropy of composite material. First, the finite element characteristic frequency method is used to obtain the dispersion curve of the composite plate, and the validity of the dispersion curve is verified. Next, the average phase velocity of the Lamb wave at mixed modes in the composite plate is obtained by two-dimensional Fourier transform (2-D FFT). The mixed modal group velocity is calculated according to the corresponding phase velocity, the mean change rate of the phase velocity and the dispersion curve obtained by simulation. The time difference due to anisotropy of composite material is investigated, and the damage location is estimated by the delay-and-sum (DAS) imaging algorithm. Experiments on carbon fiber multilayer composite plates verify the effectiveness of the proposed method