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A novel time domain structural damage diagnosis method using Jensen-Shannon Divergence
Get PDFStructural vibration response under ambient excitation is a stochastic process. The change in the characteristics of stochastic process can be used to evaluate the state of structure. Jensen-Shannon Divergence (JSD) is a mathematical expression widely used in time series analysis to account for the similarity of measurements. The aim of this article is to extend the JSD index, in conjunction with the Natural Excitation Technique, phase space reconstruction and singular value decomposition, for detecting damage in structures at an early stage. A simulation on the ASCE Benchmark structure with various damage scenarios and a laboratory experiment for a truss-type structure are carried out to validate the proposed JSD damage index. Both numerical and experimental results show that the proposed approach has better performance in contrast to other existing similar damage index such as Cross-entropy, and no mathematical model of the analyzed structure is required a priori
Vibration analysis of the beam structure under the moving mass
Get PDFAnalytical solution of vibration of simply supported beam under the action of centralized moving mass and two numerical methods using life and death element method and displacement contact method are analyzed in this paper. The results show that vertical acceleration resulted from speed and centrifugal acceleration resulted from load moving must be taken into consideration for large quality and high speed. The characteristics and applicable situations of the two numerical methods are also studied to provide a basis for analyzing and considering structural dynamic problems of moving load mass
Finite element modeling and active vibration control of high-speed spinning flexible beam
Get PDFFinite element modeling and active vibration control of a high-speed spinning flexible coupled electromechanical beam is investigated using a first-order approximation coupling (FOAC) model. Due to centrifugal forces caused by eccentricity in a spinning flexible beam, there exists coupling between axial and transverse vibration modes. The partial differential equations of motion of the beam governing this coupling are derived using Hamilton’s principle based on an FOAC model, and a finite element method for discretization is given. It is observed that the zero-order approximate coupling (ZOAC) model is valid for dynamic description of the flexible beam spinning at low speeds, but no longer valid at high speeds. However, the validity of FOAC model is confirmed at different speeds. Piezoelectric elements for active vibration control of the spinning flexible beam are analyzed and a velocity feedback controller is proposed. Simulation results demonstrate good performance of the proposed velocity feedback controller
Vibration characteristics analysis of a centrifugal impeller
Get PDFCrack fault of a centrifugal impeller occurred while working. The finite element model of the impeller was established and vibrational characteristics were analyzed for to find the reason of the crack fault in this paper. The resonance frequencies of the impeller were identified with the help of Campbell diagrams. The modal experiments were carried out with hammering method, the modal parameters were obtained and the correct of the simulations was verified under the same constraints with the FEM model. Computation effort was saved while accuracy was retained making use of the cyclic symmetry technique in ANSYS. The results showed that simulating results agreed well with that of the experiments
A high-throughput WSN for structural health monitoring
Get PDFA challenge with existing WSNs used for structural health monitoring (SHM) is how to increase the data transmission rate (DTR) for large amounts of sampling data. To handle this issue, this paper proposes a new design method of a high-throughput WSN with multi-radio sink node (M-RSN) which can increase the data transfer ability of WSN. Additionally, a tight scheduled approach and multi-radio time synchronization method are designed for the stable implementation of the proposed network. A high data throughput of 1020 Kbps of the developed network has been proved. To evaluate the effectiveness and robustness of the proposed network designing method, experiments for aircraft composite wing boxes monitoring are carried out. The evaluation results have shown the advantages of the proposed methods
A vibration-based damage identification technique free of structural baseline information: experimental validation in multi-component plane structure
Get PDFA vibration-based method for damage identification was established based on the “weak” formulation of Pseudo-excitation (PE) technique. The method can be effectively conducted without any prior knowledge of structural baseline parameters, e.g., Young’s Modulus, and is capable of detecting multi-damage in both one- and two-dimensional structural components. Moreover, relying on point-wise examination of structural dynamic equilibrium conditions, the baseline parameters of inspected structure can be inversely estimated in a statistical way, showing promising potential in engineering practices. As a proof-of-concept investigation, multi-damage in a plane structure, containing both beam and plate components, were identified experimentally using the proposed method
Stability analysis of the rolling mill multiple-modal-coupling vibration under nonlinear friction
Get PDFConsidering the unstable oscillation in the rolling process caused by the lubrication conditions change, a dynamic rolling process model considering the nonlinear friction is built using the Bland-Ford-Hill rolling force model. In addition, based on the structure model which can characterize the coupling vibration of rolling mill, and taking the dynamic variations of rolling force and rolling torque as the feedback excitation, the rolling mill vertical-torsional-horizontal coupled dynamic model under nonlinear friction is established. On this basis, the system Hopf bifurcation points at different rolling speeds are calculated by Hurwitz algebraic criterion. And the system stability domain is determined by analyzing the eigenvalue of the system. Finally, using the parameters of a 2030 cold rolling mill, the correctness of the bifurcation point calculation and the stability domain analysis are verified by numerical simulation. The results show that the system stability domain is enclosed by the instability critical lines of vertical vibration modal, torsional vibration modal and horizontal vibration modal. And under different conditions, the system Hopf bifurcation induced by the variation of the friction coefficient can cause system instability with different vibration modals. The study can help to optimize the rolling process, and achieve a reasonable dynamic modification strategy of the rolling mill structure as well
Study on wheel-rail interaction based on rail roughness
Get PDFEnvironmental vibration and noise pollution caused by the operation of subway is a hot topic of concern at home and abroad. There is a need to research dynamic interaction between trains and track in order to solve environmental vibration and noise pollution caused by the operation of train. As an excitation source of the train vibration, rail surface roughness has significant impact on the wheel-rail interaction. In order to study the effect of rail roughness on the wheel-rail vibration load, the wheel-rail interaction model is established based on excitation of rail surface roughness in this paper. The effect of rail roughness on train vibration load is calculated by this model according to the measured rail roughness data in Beijing subway in the MATLAB program. Wheel-rail force in the most adverse situations is also calculated. The property of wheel-rail force under different conditions such as track forms, driving speed and curve radius is also analyzed in this paper
Impact analysis of lateral damper on the ride quality of metro vehicle
Get PDFIn view of the lateral and vertical vibration problem of car body in actual operation, dynamic simulation and relevant line tests are carried out to study the impact of lateral damper on the ride quality. To facilitate comparative analysis, dynamic models of metro vehicle are set up and simulation results indicate that ride quality when using a single lateral damper is better than when using double dampers. On this basis, line comparison tests are conducted, with ride index in time domain as an indicator. Acceleration sensors are utilized to conduct lateral and vertical acceleration tests when using a single lateral damper and double dampers, respectively. Ride index of every 5 seconds at normal operating velocity is obtained after post-processing of data collected from the tests. Comparison of ride index of two adjacent stations obtained by statistics has found that, in actual operation, metro vehicle with a single lateral damper mounted on the bogie has a better ride quality both laterally and vertically than that with double dampers. Single lateral damper model can also effectively solve abnormal vibration problem of the metro vehicle
The empirical analysis on the portfolio optimization’s effective border
Get PDFThis paper discusses the portfolio optimization problem in an effective boundaries were drawn based on the efficient frontier portfolios which is analyzed using mean-variance model empirical method and simulated annealing algorithm. The conclusions show that drawing the efficient frontier based on simulated annealing algorithm is relatively accurate