• Advances in nano research
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• v.8 no.4
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• pp.277-282
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• 2020

Axially damped forced vibration responses of viscoelastic nanorods are investigated within the frame of the modal analysis. The nonlocal elasticity theory is used in the constitutive relation of the nanorod with the Kelvin-Voigt viscoelastic model. In the forced vibration problem, a cantilever nanorod subjected to a harmonic load at the free end of the nanorod is considered in the numerical examples. By using the modal technique, the modal expressions of the viscoelastic nanorods are presented and solved exactly in the nonlocal elasticity theory. In the numerical results, the effects of the nonlocal parameter, damping coefficient, geometry and dynamic load parameters on the dynamic responses of the viscoelastic nanobem are presented and discussed. In addition, the difference between the nonlocal theory and classical theory is investigated for the damped forced vibration problem.

• Structural Engineering and Mechanics
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• v.43 no.1
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• pp.15-30
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• 2012

A damped Timoshenko beam element is introduced for the DOF-efficient forced vibration analysis of beam-like structures coated with viscoelastic damping layers. The rotary inertia as well as the shear deformation is considered, and the damping effect of viscoelastic layers is modeled as an imaginary loss factor in the complex shear modulus. A complex composite cross-section of structures is replaced with a homogeneous one by means of the transformed section approach in order to construct an equivalent single-layer finite element model capable of employing the standard $C^{0}$-continuity basis functions. The numerical reliability and the DOF-efficiency are explored through the comparative numerical experiments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.844-847
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• 2006

In this paper, the forced vibration of damped composite beam with I-type section was analyzed. The damping material was assumed to have complex Young's modulus. Damped composite beam structure could be modeled using equivalent beam elements with less D.O.F. rather than solid elements. Finite element method for 6 D.O.F. equivalent beam element was formulated and programmed using complex values. The results of frequency responses revealed good agreement with those of NASTRAN in both Euler beam model and Timoshenko beam model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.411-414
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• 2006

In this paper, the forced vibration of damped composite beam with arbitrary section was analyzed. The damping material was assumed to have either complex shear modulus or complex Young???smodulus. Damped composite beam could be modeled using beam elements with less D.O.F. rather than solid elements. Finite element method for these methods was formulated and programmed using complex values. The results of frequency responses revealed good agreement with those of NASTRAN in several beam structures.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.1
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• pp.9-17
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• 2011

In this paper, the general equation of motion of damped sandwich beam with multi-viscoelastic material layer was derived based on the equation presented by Mead and Markus. The viscoelastic layer, which has characteristics of complex shear modulus, was assumed to be dominantly under shear deformation. The equation of motion of n-layered damped sandwich beam in bending could be represented by (n+3)th order ordinary differential equation. Finite element model for the n-layered damped sandwich beam was formulated and programmed using higher order shape functions. Several numerical examples were implemented to show the effects of damped material.

• Journal of Advanced Marine Engineering and Technology
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• v.11 no.2
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• pp.51-60
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• 1987

Recently, the problem of the axial vibration for the marine diesel engine shafting has become important due to the increased exciting forces resulting from high supercharging and large output, and the reduced natural frequencies resulting from long stroke and show speed. The effects of the axial vibration on the propulsion shafting induce cracks of the connecting point of crankpin and crankarm, the severe wear of thrust bearing, the fatigue failure of each fixing bolt and jointed parts, the hull and local hull vibrations, and also the wear and the noise due to intense hammering phenomena of thrust collar. Therefore, each classification society requires the calculation of natural frequencies and their amplitudes and also measurements of the forced damped axial vibration. At present, the technical and theoretical level is at the stage of estimating the resonant points and their maximum displacements, but the estimated displacements of the resonant points are not so reliable as the torsional one. In this study, induced stresses and amplitudes of the forced damped axial vibration are calculated. For this purpose, the equation of forced axial vibration with damping for the propulsion shafting is derived and its steady-state response is calculated by the mechanical impedance method. A computer program for above calculations is developed. The measured values are analyzed and the calculated results are compared with the measured ones. They show fairly good agreements and the reliability of developed program is confirmed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.608-611
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• 2005

In this paper the general equation of motion of damped sandwich beam including arbitrary viscoelastic material layer was derived based on the equation presented by Mead and Markus. The equation of motion of n-layered sandwich beam was represented by (n+3)th order ordinary differential equation. It was verified that the general equation of motion derived in this paper could represent the equations of motions for single-layered, three-layered, five-layered and multi-layered damped beam. Finite element method for the arbitrary-layered damped beam was formulated and programmed using higher order shape functions. Several numerical examples were implemented to show the effects of damped material.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.978-981
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• 2005

The vibration analysis of damped sandwich beam is conducted using finite element method. The equation of motion presented by Mead and Markus is used to formulate FEM. Also as the thickness of the core in the damped sandwich beam goes to zero, conventional beam theory based on the transformed-section method and the equation of Mead and Markus are compared. According to the change of thickness and loss factor of the core, the forced frequency response of beam is calculated and discussed. And then using the half-power band width method, the damping ratio of each mode is calculated and discussed about each case.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.6
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• pp.193-199
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• 2001

Active control of forced vibration of the cantilevered laminated composite plates using collocated piezoceramic sensor/actuator is analyzed numerically and verified experimentally for various fiber orientations. Impact on the stiffness and the damping properties is studied by varying stacking sequence of [$\theta$$_{4}$O$_{2}$90$_{2}$]s for the laminated composite plate. For the forced vibration control, the plate is excited by one pair of collocated PZT exciters in resonance and its vibrational response is suppressed by the other collocated PZT sensor/actuator using direct negative velocity feedback. It is shown that the active control of forced vibration is more effective for the smart laminated plate with higher modal damped stiffness(2ζ$\omega$/aup 2/) .

• Journal of Convergence for Information Technology
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• v.10 no.7
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• pp.131-137
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• 2020

The characteristics of forced vibration with excited sinusoidal force was introduced. Also, numerical analyses and FRF in frequency domain were performed in detail. In this regard, the responses of displacement, velocity and acceleration were investigated in a forced vibration model. The FRF characteristics in real and imaginary part around natural frequency are also discussed. This response approach of forced vibration in time domain is used for the identification and monitoring of sinusoidal forced vibration. For acquiring a displacement, velocity and acceleration, a numerical technique of Runge-Kutta-Gill method was performed. For the FRF(frequency response function), These responses are used. Also, the FRF can represent the intrinsic characteristics of the forced vibration. These performed results and analysis are successful in each damped condition for the forced vibration model. After numerical analysis of the different mass, damping and stiffness, the forced vibration response characteristics with sinusoidal force was discriminated considering its amplitude and frequency simultaneously.