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pp. 187-207 | DOI: 10.5890/JVTSD.2018.09.001
S.D. Yu, M. Fadaee
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The Newmark integration scheme, originally developed for simulating responses of linear dynamical systems, is modified in this paper to effectively model nonlinearities through introduction of the incremental displacements and the effective mass, damping and stiffness matrices. Based on the results of comparisons with the analytical solutions and the Runge-Kutta (RK) method for well-known nonlinear oscillators, the proposed scheme is found to capture accurately dynamical behaviors of nonlinear systems such as amplitude-dependent stiffening or softening natural frequencies, jump phenomena, superharmonic resonances, sub-harmonic resonances, and even chaos and bifurcations. The proposed scheme is more efficient than the RK method for large scale nonlinear systems with some type of sparsity for which a targeted algebraic equations solver can be employed to speed up the solution for each time step.
pp. 209-219 | DOI: 10.5890/JVTSD.2018.09.002
Krzysztof Kecik, Angelika Zaszczynska, Andrzej Mitura
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The paper presents an experimental study of a special non−linear low frequency system dedicated to vibration mitigation and energy recovery. The dual−function design was based on an autoparametric vibration system, which consists of an oscillator with an added pendulum vibration absorber. Its structure includes an energy harvesting device: a levitating magnet in a coil. The pendulum motion shows simultaneously the effects of vibration reduction and energy recovery. The influences of the magnet−coil configurations, and load resistances on vibration reduction and energy harvesting were studied in detail.
pp. 221-237 | DOI: 10.5890/JVTSD.2018.09.003
Gang Jiang, Yiming Deng, Lili Liu, Canghai Liu, Zihong Liu, Yong Jiang
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In systematic identification for real bridge engineering structural damage evaluation, lack of “negative samples” is the main reason for misjudgment and false classification. Aimed at this problem, the paper proposed a new kinetic-parameters-analysis-based method of damage identification for bridge structures, using both numerical simulation and real experiments under controlled lab conditions. PROE and ADAMS were adopted to build structural models and integrate with simulation experiments under virtual force, frequency response data were gathered and used as “simulation datasets”. In real structural experiments, accelerators and advanced signal acquisition equipments were used to collect signals from real structures hit by real force. Signals gathered by equipments were used as “real datasets”, corresponded with “simulation datasets”. After that, features were extracted from these two kinds of datasets. Authors found that numerical simulation models were not always accurate, while real model had its own advantages and disadvantages. To fill this gap, relationships between simulation and actual measurements were investigated in this paper. Finally, Support Vector Machine (SVM) method was used to perform pattern recognition experiments and showed its good performance on structure damage identification. The proposed method is scalable and can be extended to a bigger structure, such as the entire bridge faults diagnosis.
pp. 239-247 | DOI: 10.5890/JVTSD.2018.09.004
M. Sundin, A. Babaei, S. Paudyal, C. Yang, N. Kaabouch
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Health monitoring and fault diagnosis are essential to ensuring reliable operation of machinery in industry. In this paper, we present the design of a low cost device for sensing mechanical vibrations and detecting excessive vibration. Advantages of the device include cost effectiveness and simplicity of the design. Piezoelectric-based sensor, light emitting diodes, resistors, and liquid crystal display, and an Arduino board are the main components of the device. The effectiveness of designed device was tested on simple electric motors, such as fan and drill motors. This vibration measurement device can be used to monitor machinery health by detecting unwanted oscillations and subsequent potential hazards.
pp. 249-256 | DOI: 10.5890/JVTSD.2018.09.005
Vinicius B. Silva, Joao P. Vieira and Edson D. Leonel
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In this paper we prove the following theorem: consider a N-dimensional dynamical system that is reduced to its center manifold. If it is proved the system satisfies the conditions of a Hopf bifurcation theorem then the original system of differential equations describing the dynamics can be rewritten in a simpler analytical expression that preserves the phase space topology. The theorem proposed and proven effectively reduces the work done to obtain the normal form for the class of dynamical systems with the occurrence of Hopf bifurcation.
pp. 257-269 | DOI: 10.5890/JVTSD.2018.09.006
K. Lu, Y. Lu, B. C. Zhou, W. Jian, Y. F. Yang, Y. L. Jin, Y. S. Chen
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The transient proper orthogonal decomposition (TPOD) method is applied for order reduction in the rotor system in this paper. A 26DOFs rotor model with crack is established by the Newton’s second law, and the dynamical behaviors (bifurcation diagram, amplitude frequency curve, etc.) of the crack fault are discussed. The optimal reduced model can be provided by the proper orthogonal mode (POM) energy method, the TPOD method is applied to reduce the original system to a three-DOFs one at a certain speed corresponds to the maximum energy. The efficiency of the TPOD method is verified via comparing with the bifurcation diagram of the original and reduced rotor system. The order reduction method provides qualitative analysis to study the reduced model of the high-dimensional rotor system.
pp. 271-280 | DOI: 10.5890/JVTSD.2018.09.007
Zhong Luo, Yan-hui Wei, Xiao-jie Hou, Fei Wang
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In allusion to the unbalanced vibration of rotor system, sensitivity analysis and balance method of rotor system were studied. Based on rotor dynamics, combined sensitivity analysis with the balancing methods of three trial weight and modal, a hybrid method was proposed which can be balanced without phase information. Firstly, the model of rotor was established by the finite element method and the correction plane is selected by the sensitivity analysis. Furthermore, the balance speed is determined according to the modal equilibrium theory and the weight calculation is conducted by the balancing method of three trial weight Finally, a dynamic balance experiment was carried out on the rotor model test station. The results of simulation and experiment show that the proposed balance method can not only effectively reduce the residual vibration of rotor, but avoid the blindness of selecting the correction plane and balance speed by the traditional balance method, which is expected to improve the balance efficiency.
pp. 281-290 | DOI: 10.5890/JVTSD.2018.09.008
Guangping Liu, Yongping Jin, Youduo Peng, Buyan Wan
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Taking the deep sea sediments air-tight sampler flap seal valve as the research object, using the response surface method (RSM) and finite element analysis method to carry out the flap sealing valve geometry design parameter optimization design research. First of all, a set of eccentrically set flap seal valve is designed for the requirement of the pressurized seal of the marine deep sediment air-tight sampler, three-dimensional geometric model of the flap seal valve is built using Solidworks.Then, The flap sealing valve eccentricity angle θ , the valve cap upper end diameter D3, and the valve cover length l as the design variables, the bottom end opening diameter D5 of the valve body and the material strength under a given safety factor are set as constraints, the maximum stress value and weight of the flap seal valve are set as optimization goals.The response surface model of the flap sealing valve eccentricity angle θ , the valve cap upper end diameter D3, the valve cover length l and the flap sealing valve maximum stress and weight is constructed. Finally, The geometrical structure parameters of the flap sealing valve are optimized.
pp. 291-296 | DOI: 10.5890/JVTSD.2018.09.009
Varadharaj Dinakar, Krishnan Balachandran
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We consider the degenerate Lotka-Volterra system with three equations in the linearized form. The internal observations with two measurements are allowed to obtain the stability result for the inverse problem consisting of simultaneously retrieving three coefficients in the given parabolic system with the help of Carleman estimates for the degenerate Lotka-Volterra system.
