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Review of advances on longitudinal vibration of submarine propulsion shafting and its vibration reduction technology
Get PDFAnalyzed the formation mechanism of longitudinal vibration of the submarine propulsion shafting system, and introduced its existing vibration control technology. The content included the improvement design of propulsion shafting system, new types of thrust bearing, composite material shaft, dynamic vibration absorber, phonon crystal band gap damping and relative active control technology. A new method for the application of metal rubber technology in thrust bearing was put forward, which provided a new idea for the research work in the future
Modeling and analysis of performance degradation of bolted composite lap geometries subjected to shock load
Get PDFAn analytical model and 3D finite element analysis (FEA) is completed to determine the effect of shock loading on vibration characteristics and stiffness of composite laminates. The bolted carbon composite lap geometry is prepared by varying number of bolts from 1 to 3 in a 500 mm width of plate. Analytically, it is a mass-spring based model where bolt(s), laminates and the clamped region are represented by a series of springs and masses. The obtained equations of motion contain information about geometrical parameters such as length, width, thickness and mass properties of composite plates. The frequency response acquired from mathematical model is compared and validated with FEA results acquired through ANSYS. Conclusions reveal that the main contributing factors to cause changes in stiffness and reduction in frequency are presence of bolts, increase in number of bolts and regions of stress concentration. Moreover, the acquired frequency response may act as a means of detecting changes in structural stiffness and the applied methodologies might be used to model larger mechanical and aerospace structures
Acoustic emission localization on ship hull structures using a deep learning approach
Get PDFIn this paper, deep belief networks were used for localization of acoustic emission events on ship hull structures. In order to avoid complex and time consuming implementations, the proposed approach uses a simple feature extraction module, which significantly reduces the extremely high dimensionality of the raw signals/data. In simulation experiments, where a stiffened plate model was partially sunk into the water, the localization rate of acoustic emission events in a noise-free environment is greater than 94 %, using only a single sensor
Nonlinear vibration of rested Euler-Bernoulli beams on linear elastic foundation using Hamiltonian approach
Get PDFIn this paper, nonlinear vibration of Euler-Bernoulli beams resting on linear elastic foundation and subjected to the axial loads are studied analytically. Hamiltonian approach is new kind of analytical approaches are used to achieve the nonlinear frequency of the problem. The nonlinear vibration equation is also solved numerically using Runge-Kutta 4th technique. Comparison of Hamiltonian approach (HA) with Runge-Kutta 4th leads to highly accurate solutions using Hamiltonian approach
Determining coupling dynamic stiffness of structural connection by tested FRFs
Get PDFIdentifying coupling dynamic stiffness of structural connection is often needed in substructural dynamic analysis. To overcome the faultiness of conventional approaches existed, five indirect schemes of inverse substructuring analysis by using tested frequency response functions (FRFs) are provided. And the first indirect scheme is verified by three mass-rubber models constructed as two-level substructures with mono-coupling, bi-coupling and tri-coupling connection. Compared to existing direct scheme of inverse substructuring analysis, it shows better performance with acceptable precision of determining the stiffness
Kineto-dynamic optimization of seat-suspension
Get PDFA kineto-dynamic model of a cross-linkage air seat-suspension system is formulated to obtain relations for effective vertical suspension stiffness and damping characteristics. A two-stage optimization methodology is proposed to derive vehicle-specific optimal designs considering different classes of earthmoving vehicles. The results show that optimal air spring coordinates can yield nearly constant natural frequency during the deflection cycle, irrespective of the seated body mass and driver-selected seated height. Vehicle-specific optimal damping characteristics, identified in the second stage, provided substantial reductions in seat effective amplitude transmissibility (SEAT) and vibration dose values (VDV) for all classes of earthmoving vehicles considered in the study. The proposed kineto-dynamic model and optimization method could thus serve as an important tool for designing vehicle-specific suspension seats
Research on fault diagnosis method of rolling bearing based on AMD and LabVIEW
Get PDFAiming at the problem of rolling bearing fault diagnosis, a fault diagnosis method of rolling bearing is proposed based on analytical mode decomposition (AMD) and LabVIEW. For the fault feature frequency of rolling bearing is predictable, the AMD method can be used to extract the signal in the frequency band of fault characteristic frequency in rolling bearing signal, and seek frequency spectrum of vibration signal. If the spectrum contains fault characteristic frequency, then the rolling bearing fault can be diagnosed by vibration signal. A rolling bearing fault diagnosis system is developed based on LabVIEW and AMD, and the application of AMD algorithm is realized. The validity of the method is proved by the analysis of actual fault signal of rolling bearing
Sliding mode control of a 2-DOF manipulator with random base vibration based on modified exponential reaching law
Get PDFTo solve the precise position control problem of a two degree of freedom (2-DOF) manipulator with random base vibration, a sliding mode control method based on modified exponential reaching law is studied. The dynamic model of manipulator is established by using the second kind Lagrange equation. The nonlinear term generated by base random vibration is presented as external disturbance term. Based on dynamic models, the sliding mode control using improved exponential reaching law is applied in the manipulator system. It is verified by the simulation result that the control method can effectively suppress the influence of base random vibration, and bring the manipulator from a given initial state to a prescribed terminal state rapidly and precisely
Fault severity assessment of rolling element bearings based on bicoherence spectrum
Get PDFThe condition monitoring and fault diagnosis of rolling element bearings not only depend on fault type but also fault severity which is also essential for making proper maintenance decision. Aiming at fault severity assessment of rolling element bearings, a new indicator based on the bicoherence spectrum is proposed. The quadratic phase coupling (QPC) which is one of the most important nonlinear characteristics of fault-related signals can be detected by the bicoherence spectrum. The deepening fault severity usually results in more frequency components involving in coupling. In order to quantify the coupling degree which is closely related to fault severity, we choose the mean value of the bicoherence spectrum as an indicator. Experiments results showed that the quantitative trend prediction of different fault severities of bearing is realized
Planetary gearbox fault diagnosis based on pseudo-fault signal assisted EMD
Get PDFPseudo-fault signal assisted empirical mode decomposition (PFS-EMD) is put forward for fault detection and isolation, which is built upon EMD, envelope analysis and pseudo-fault signal. And this method has been proved that it is usable in fault diagnosis of simple gear pair. However, this method is still need further study that whether it can be used for fault diagnosis of complex gearbox. Moreover, planetary gearbox fault diagnosis is much more complicated than fixed-axis gearbox. This paper makes a further study of PFS-EMD and focuses on its application. Combining with the seeded failure experimental data of planetary gearbox, this paper show that PFS-EMD can enhance fault information and weaken other useless information in complex gearbox fault diagnosis