Maintenance, Reliability and Condition Monitoring
Not a member yet
1200 research outputs found
Sort by
Novel complete ensemble EMD with adaptive noise-based hybrid filtering for rolling bearing fault diagnosis
Get PDFA feature extraction of fault bearing has attracted considerable attention in recent years. However, weak fault feature is difficult to extract under heavy background noise. To solve this problem, a novel multi-layer filtering method is proposed to filter out noise and extract weak fault feature. The first layer introduces a metric based on de-trended fluctuation analysis (DFA) to identify intrinsic mode function (IMF) that reflect period impulsive information for vibration signal adaptively. The second layer uses non-local mean (NLM) method as a pre-filter of the third layer to realize extraction of singular value decomposition (SVD) which reflect the most information of IMFs. The last layer introduces a relative energy difference criterion of a singular value to extract important feature of Hankel matrix of IMFs. The filtered signal is obtained by re-constructed signal from identified singular value of SVD. Experiment results on simulation and real vibration signals indicate that the hybrid filtering method removes heavy noise successfully and extract weak fault feature of rolling bearing effectively
An explicit closed-form solution for transverse and longitudinal vibration of beam with multi-directional elastic constraints under an arbitrary moving load
Get PDFBeams with elastic constraints are widely used in dynamic systems in engineering. A general explicit solution is presented here for the vibration of simple span beam with transverse, rotational and axial elastic boundary constraints due to an arbitrary moving load. The Euler-Bernoulli beam theory is adopted, in which the boundary constraints are treated as multi-directional boundary springs. After the modal analyses, the explicit closed-form solutions of transverse and axial vibration of the beam under a constant, sinusoidal and cosinoidal moving loads are obtained, respectively. And the vibration of a beam subjected to an arbitrary moving load is derived by the superposition of Fourier series. The current analytical solution is exact and can be applied in multiple engineering fields to obtain accurate structural vibrations. In numerical examples, the effects of the boundary springs on the natural frequencies, modes, deflection, bending moment and boundary reaction of the beam are studied in details. The effects of the number of terms in Fourier series of arbitrary moving load are also discussed
Experimental study on ground vibration response in gun firing environment
Get PDFIn order to know the ground vibration response law of gun firing environment, a large caliber gun was taken as the research object, and the ground vibration response law of gun firing environment was tested. Several acceleration sensors are arranged on the ground around the gun, and the ground vibration acceleration response laws of the gun position in the firing environment are obtained. The firing of gun will cause the ground vibration of gun position. In the bore period, as long as the projectile is fired, there will be acceleration response on the ground of the gun position. The maximum acceleration response of ground vibration in the bore period of projectile is less than 0.03 g. The maximum acceleration response of ground vibration is less than 0.1 g after projectile exits the muzzle and before the muzzle shock wave reaches the ground. If the sensor bracket is placed on the ground around the gun, when the muzzle shock wave does not reach the sensor position, the influence of ground vibration on the sensor can be neglected. Once the muzzle shock wave reaches the sensor position, its influence should be paid attention to
Electromagnetic buffering considering PM eddy current loss under intensive impact load
Get PDFThe intensive impact load will generate a huge acceleration in the primary part of the Electromagnetic buffers (EMBs), resulting in an instantaneous increase in the eddy current loss of the permanent magnet (PM). In this paper, the PM eddy current loss is taken into account in the electromagnetic buffering under intensive impact load. The reason why the eddy current damping force differs between two different buffer stages is analyzed. The experimental results signify that the model considering the PM eddy current loss is more accurate
On-site vibration test and dynamic response analysis of wind turbine of intertidal zone
Get PDFIn our study, the vibration signal of impulse response and attenuation response are extracted using the correlation function and power spectrum, and the natural frequency of wind turbine is determined. Compared with the rotation frequency of the blades of wind turbine which are 1p (one blade) and 3p (three blades), and wind vibration performance of the wind turbine is determined. The natural frequency of wind turbine is between the frequencies of one blade and three blades of wind turbine, which can avoid resonance phenomenon and meet the precision requirement for engineering application. The laws of acceleration and strain response along the wind turbine under ordinary wind load are obtained by installing acceleration sensor and strain gauge along the wind turbine. We found that the acceleration at the wind turbine top increases 10 times than that at the bottom. The acceleration influenced by tide is 1.14 times than that with no tide. The strain produced maximum value at the opening place of wind turbine and near the top, it should be paid attention in the engineering design
Dynamic characterization and modeling of steel foam sandwich structure
Get PDFThe purpose of the recent project is giving empirical research of the dynamic properties along with measuring the damping ratio for different metal foam sandwich specimens, and mathematical modeling of these particular structures. Besides, the various specimens were modeled by employing ANSYS for the FEM analysis. Concerning to have a reliable result for two-phase sample the random noise outcomes have been applied and associated with the FE model. The final results depict an appropriate evaluation of the vibrational damping for two-phase specimens
Effects of mechanical non-linearity on the dynamic behaviour of ring-based inertial rate sensors
Get PDFThis paper presents a mathematical model to describe the 2θ in-plane response of supported ring-based MEMS Coriolis Vibrating Gyroscopes (CVGs), including mechanical non-linearity in ring and support structures. Whilst it is well-known that the drive mode resonance frequency of unsupported rings depends on drive amplitude, the proposed model investigates the effects of support geometrical non-linearity on the dynamic behaviour of the 2θ modes. Results indicate that the non-linear stiffness of the supports, combined with the ring non-linearity, breaks the rotational symmetry of the resonator when 8 supports are used, leading to a reduction in sensor gain. In contrast the symmetry of the resonator and performance are maintained when 16 supports are used. The proposed model also demonstrates how the mechanical support non-linearity can be used to guide the design of resonators having a linear drive mode frequency backbone curve
Pedestrian traffic induced lateral vibration including the effect of TMD
Get PDFThis study explores the dynamic behavior of beam induced by bipedal pedestrian traffic and corresponding vibration reducing method by tuned mass damper. Each pedestrian from motion crowd simplifies as a bipedal robot comprised of a lump mass and two massless spring-damping legs. In addition, the tuned mass dampers are installed on the bottom of structure to relieving the vibration of structure. The interactions among pedestrians, tuned mass dampers and structure are considered to establish a governing equation. Research indicates that both the tuned mass damper and pedestrian evidently alter the structural properties of the structure by affecting its frequency and damping capacity. The structure tends to be gently flexible at a lower frequency as pedestrian walk across its surface, but the corresponding damping capacity of the structure is improved. The tuned mass damper always improves both the vibration response and dynamic properties of structure. However, its self-dynamic characteristics of the tuned mass damper tend to deteriorate. The tuned mass damper relieves effectively the lateral vibration in a slender structure than the rigid structure. The change in the mass ratio of tuned mass damper to structure affects significantly the dynamic behaviors of structure. In addition, the layouts of the tuned mass dampers on structure also have remarkable influences on the behaviors. The results of this study provide potential pathways for understanding the vibratory mechanisms of slender structures such as footbridges, grandstands, or stations under crowd excitations
Defect elimination in torsional harmonic reducer based on harmonic resonance
Get PDFThis paper will introduce the torsional vibration test method and signal analysis for a harmonic reducer in industrial robot. The harmonic reducer is generally applied to the fifth and sixth axes of the industrial robots, and the torsional vibration will affect the mechanical performance. To understand the torsional vibration condition of the harmonic reducer, the test device is set up through loading the corresponding moment of inertia. In the study, the curve of torsional characteristic is obtained, and it can be used to assess the mechanical performance; Using zoom spectrum technology on harmonic resonance, the characteristic frequency is identified in detail. The manufacturing defect of the harmonic reducer is diagnosed based on characteristic frequencies of its transmission, and defect elimination is successfully realized by adjustment of components in the harmonic driver; Some nonlinear vibration characteristics caused by stiffness with time periodic dependent, including bi-spectrum and harmonic resonance, etc., are investigated. The experimental results show that the test and analysis of torsional vibration have positive significance for the online quality assembly assurance of harmonic reducer
Acoustic vibration response and power generation characteristics of airborne acoustic generator system
Get PDFAiming at the problem of insufficient power supply in modern intelligent fuze, it is of great theoretical significance and practical guidance to study the relationship between acoustic vibration response and power generation characteristics of airborne piezoelectric generators and maximum energy output. Theoretical analysis and experimental verification show that: 1. As long as the frequency of the acoustic wave induced by the flow coincides with the frequency of the acoustical modal in the cavity, a sinusoidal vibration excitation signal will be generated in the cavity; 2. With the increase of the flow rate, the frequency of the vibration signal coupled by the fluid sound source also increases. If the frequency of the acoustic wave is near the anti-resonance frequency of the piezoelectric vibrator, the displacement amplitude of the piezoelectric vibrator increases greatly. The maximum output open circuit voltage is the maximum power generated when the external circuit is connected; 3. The amplitude of the open circuit voltage of the electromechanical coupling output is linear with the amplitude of the displacement of the piezoelectric vibrator, the frequency is the same, the phase angle is the same, and the displacement and the exciting force of the piezoelectric vibrator have the characteristics of the same frequencies and backward phases, the maximum displacement of the piezoelectric vibrator is related to the amplitude of the exciting force and the angular frequency of the exciting force. This characteristic can be used to solve the piezoelectric stress factor under different initial conditions from the experimental point of view