JVE International
Not a member yet
1200 research outputs found
Sort by
Randomness complexity as a family feature of rolling bearings’ degradation
Get PDFRandomness complexity is a kind of features which is widely used to describe bearings’ degradation. However, different randomness complexities present different properties. It is necessary to figure out different randomness complexities’ properties. In this paper, we are going to make comparisons of seven commonly used randomness complexities namely approximate entropy, sample entropy, fuzzy entropy, Shannon entropy, permutation entropy, Lempel-Ziv complexity and C0 complexity by simulation signals with three different aspects and two run-to-failure bearing’s data. By comparisons, we have found that there are a kind of similarity between them and we have proposed a trend similarity index to expound this similarity. Based on the comparisons, we can infer that randomness complexities are a family feature of rolling bearings’ degradation. Among the seven discussed complexities, sample entropy has the best performance, and it can be a good representative of the complexity features. In this paper, the difference between complexity features and other features when monitoring bearings’ degradation have been discussed. The research will provide a reference for rolling bearings’ multi-features dimensionality reduction by attribute selection method
Impact on auxetic and metal foams
Get PDFUsing the finite element method, we investigate the elasto-plastic impact of a rigid sphere on a half-space of auxetic and metal foams. The validity of the Hertz theory for elastic impacts is investigated for both positive and negative Poisson’s ratio. For elastic impacts, the results from Hertz theory are accurate within 20 % with the finite element simulations. The plasticity is modeled using the Deshpande-Fleck metal foam yield criterion. This yield criterion allows for plastic compressibility and can also accommodate materials having a negative Poisson’s ratio. The elasto-plastic simulations reveal that the coefficient of restitution decreases as the impact velocity is increased. The coefficient of restitution is also least for materials having a zero plastic Poisson’s ratio. Our study suggests for maximum energy dissipation the plastic Poisson’s ratio should be close to zero
Numerical modelling of shear thickening fluid in nanosilica dispersion
Get PDFIn this paper, a numerical model of the shear thickening fluid (STF) is generated and the rheological properties are compared with the experimental data. Power Law model has been used to fit the rheological data for STF. Experimental data is taken from a performed study and a user defined function (UDF) has been written to develop the shear thickening behavior. The purpose of this study is to exactly model the behavior of shear thickening fluids by using UDF, to explain the shear-thickening mechanisms under different shear rates. Different parameters like viscosity, shear stress and velocity of the STF have also been reported
Identification and location of ship pipeline leakage based on VMD
Get PDFPipeline plays an important role in various systems of the ship. However, due to the harsh environment, leakage often occurs in ship pipeline. This paper proposes a method to identity and locate the pipeline leakage. Using the variational mode decomposition (VMD) algorithm, the vibration signal is decomposed into band-limited intrinsic mode functions (BIMFs). The effective BIMFs are then selected by the correlation coefficient. Center frequency and energy value of the effective BIMFs are extracted as feature vector. Radial Basis Function (RBF) neural network is then used as a tool to identify and locate the leakage. The proposed method is finally verified by experiments
Multi-body dynamic simulation and vibration transmission characteristics of dual-rotor system for aeroengine with rubbing coupling faults
Get PDFIn this paper, a dual-rotor system multi-body dynamic model with rubbing coupling faults is established for practical aero-engine. In the model, the rubbing fault simulation method is introduced, the coupling effect between the internal and external rotor is considered. The numerical simulations of rotor vibration are accomplished by the utilization of multi-body dynamic platform, where the simulation model consists of discs unbalances and local rub-impact between discs and casing shells. The time-domain responses, the frequency spectra and the shaft-center trajectories of dual-rotor with different unbalance and different rubbing positions are obtained. The vibration and its transmission characteristics of the inner and outer rotors are calculated. Finally, the simulation results are compared with the measured vibration of a dual rotor tester with rubbing fault. The simulation results are consistent with the measured results, which confirms the feasibility of the established model and the multi-body dynamics simulation method in this paper. The application of multi-body dynamics simulation method in aero-engine can deepen the understanding of the internal operation nature and laws of aero-engine, reduce the repetition of physical tests, greatly improve the efficiency and quality of development, accelerate the research and manufacture process
Near-field acoustic holography for high-frequency weak sound sources under low signal-to-noise ratio
Get PDFThe mechanical noise in the cabin of the ship is so large that the leakage of high-pressure fluid is not easily noticed. In view of this situation, a near-field acoustic holography for high-frequency weak sound source under low signal-to-noise ratio is proposed. The method uses the empirical mode decomposition method to add weights to the time-domain sampling signals of each array element, and then uses the plane equivalent source near-field acoustic holography combined with compressive sensing to find the holographic surface acoustic pressure distribution. The simulation and experiment show that this method has certain feasibility under low signal-to-noise ratio, and the results are better than the method based on Fourier transform and the traditional boundary element method. It is of positive significance to apply it to engineering practice
Effect of change in position of particle dampers on wind turbine blade for vibration suppression
Get PDFWind turbine energy minimizes due to vibration of blade. In this research we focus on vibration suppression by using particle damping technique. Containers are used for fill the particles and mounted on the blade. As vibration of blade increases, it increases the movement of containers along with particles this brings particle to particle and particle to container wall collision takes place which results to energy loss. In this study we use four different positions for mounting containers, firstly on all four different positions we mount containers simultaneously and take three readings for three different ball sizes respectively, keeping 50 % fill constant in all readings. Then we reduce one container among four and take the readings. Repeat this procedure up to single container. Compare with damping results with without damping results and finding out optimum locations for mounting of dampers
Intelligent glove for suppression of resting tremor in Parkinson’s disease
Get PDFOne of the significant symptoms in Parkinson’s disease is resting tremor. Resting tremor occurs when the muscle is relaxed, causing the limb to shake. Rhythmic muscle movement of the patients commonly happens within the range of 4 Hz to 6 Hz. Thus, reducing this type of tremor will help improve patients’ quality of life. In this paper, to suppress resting tremors, an intelligent glove was designed utilizing the concepts of vibrations and gyro effect. A rotating brass disc attached to the glove creates a gyroscopic effect of the smart glove. Therefore, the disc will do their utmost to stay upright and counter any input forces instantaneously by providing the counterforce. A reduction of more than 50 % with the intelligent glove is also shown
Computational investigation of cavitating flow around two dimensional NACA 4424 and MHKF-240 hydrofoil
Get PDFThis study focuses on the comparison of the performance of two unsymmetrical hydrofoils, NACA 4424 and MHKF-240 at 60 angle of attack under cavitation. The Schnerr and Sauer cavitation model along with Realizable k-ε turbulence model is used for numerical computation in commercial software ANSYS Fluent. The lift, drag and pressure coefficients for different cavitation numbers were studied. Among both the hydrofoils MHKF-240 gives a higher lift coefficient which is the parameter of better performance
Gear shift simulation by using virtual prototype
Get PDFThe presented paper is focused on the simulation of gear shift and prediction of whole gearbox dynamic behavior during gear shift. For this complex task the methodology for simplified gearbox was developed first. The whole methodology is divided into three different level of numerical model, where each of them was developed and validated by technical experiment. Afterwards the methodology was applied on more complex gearboxes, in presented case the heavy-duty gearbox concept. The virtual prototype was extended by gear shift option. The numerical sensitivity study of different gear shift time, which are simulated by different clutch activation and deactivation, was performed and the surface normal velocity and torque were evaluated and compared. The simulation was performed to find the optimal gear shift progress with minimal affects vehicle comfort. For this purpose, the surface normal velocity is evaluated, which is directly connected to emitted noise of whole gearbox