• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.658-667
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• 2006

Fractional derivative models, which are used to describe the viscoelastic behavior of material, have received considerable attention. Thus it is necessary to put forward the analysis solutions of dynamic systems containing a fractional derivative. Although previously reported such kind of fractional calculus-based constitutive models, it only handles the particularity of rational number in part, has great limitation by reason of only handling with particular rational number field. Simultaneously, the former study has great unreliability by reason of using the complementary error function which can't ensure uniform real number. In this paper, a new approach is proposed for an analytical scheme for dynamic system of a spring-mass-damper system of single-degree of freedom under general forcing conditions, whose damping is described by a fractional derivative of the order $0<{\alpha}<1$ which can be both irrational number and rational number. The new approach combines the fractional Green's function and Laplace transform of fractional derivative. Analytical examples of dynamic system under general forcing conditions obtained by means of this approach verify the feasibility very well with much higher reliability and universality.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.825-828
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• 2005

Experimental and numerical study was done to confirm the effect of the flexible tube in pipeline on transient flow oscillation. Experiment was made for a pipeline with and without deformable flexible tube using a single pumping system of main stainless pipe. The wave speeds of main pipe and flexible tube were calculated from the pipe material properties, structures, and boundary conditions. Time dependent pressure fluctuations were calculated for the pipeline using the simple and the Kelvin-Voigt viscoelastic models for the deformation of main pipe and flexible tube. Pressure calculated by the Kelvin-Voigt viscoelastic model showed better agreement with measured one than pressure by the simple model. Experimental and numerical results show that the maximum pressure as well as amplitude of pressure oscillation was decreased by inserting short flexible tube in pipeline. Hence, inserted short flexible tube to pipeline was found to be effective for the suppression of strong pressure oscillation. Moreover, the wave speed in pipe was discussed based on numerical and experimental results.

• Journal of Biosystems Engineering
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• v.20 no.2
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• pp.133-140
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• 1995

The model of Poisson's ratio of the fruits was developed on the basis that the cylindrical fruits specimen became the barrel shape when it was being compressed. The model of the corrected creep compliance of the fruits was developed under considering the developed model of Poisson's ratio. Both of the Poisson's ratio and the corrected creep compliance of the samples showed the nonlinear viscoelastic behavior. Those models were a similar form, but their coefficients of the model were different, and these behaviors of the samples were well described by the nonlinear model as a function of the initial stress and time. Effects of storage condition and period on the Poisson's ratio of the samples were investigated, and comparisons between the corrected and the uncorrected creep compliance of the samples were made.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.4
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• pp.114-122
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• 2002

Up to now, many constitutive models for clay have been proposed and studied based on the elasto-plastic or elasto-viscoplastic theory and it has been recognized that the effect of time on the loading process is a salient feature. In the present study, cyclic behavior characteristics of clay was studied with a viscoelastic-viscoplastic constitutive model for clay based on the non-linear kinematic hardening rule. In order to examine the behavior of clay several cyclic untrained triaxial tests and also their numerical simulations were performed. As results of that, it was found that the proposed model can well describe cyclic behaviors of clay such as frequency dependent characteristics, and have the high feasibility of numerical simulation for dynamic analysis.

• Structural Engineering and Mechanics
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• v.38 no.3
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• pp.301-314
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• 2011

The paper constitutes the second part of the author's study. The first part (Podworna 2010) formulates four fundamental tasks in dynamics of the bridge-track-train systems. The following cyclic moving loads are considered: a concentrated forces stream (model P), an unsprung masses stream (model M), a single-mass viscoelastic oscillators stream (model $M_o$) and a double-mass viscoelastic oscillators stream (model $MM_o$). Three problems precluding to the numerical simulations have been developed, i.e., prediction of the forced resonances, the parameters of integration of equations of motion, the output results. A computer programme was written in Pascal and numerical research in the scope of the fundamental tasks was worked out. The investigations were focused on adequacy evaluation of the moving load models, P, M, $M_o$, $MM_o$, in predicting dynamic processes in railway bridges.

• Structural Engineering and Mechanics
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• v.52 no.6
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• pp.1069-1084
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• 2014

The long-term performance of plates resting on viscoelastic foundations is a major concern in the analysis of soil-structure interaction. As a powerful mathematical tool, fractional calculus may address these plate-on-foundation problems. In this paper, a fractionalized Zener model is proposed to study the time-dependent behavior of a uniformly loaded rectangular thin foundation plate. By use of the viscoelastic-elastic correspondence principle and the Laplace transforms, the analytical solutions were obtained in terms of the Mittag-Leffler function. Through the analysis of a numerical example, the calculated plate deflection, bending moment and foundation reaction were compared to those from ideal elastic and standard viscoelastic models. It is found that the upper and lower bound solutions of the plate response estimated by the proposed model can be determined using the elastic model. Based on a parametric study, the impacts of model parameters on the long-term performance of a foundation plate were systematically investigated. The results show that the two spring stiffnesses govern the upper and lower bound solutions of the plate response. By varying the values of the fractional differential order and the coefficient of viscosity, the time-dependent behavior of a foundation plate can be accurately captured. The fractional differential order seems to be dependent on the mechanical properties of the ground soil. A sandy foundation will have a small fractional differential order while in order to simulate the creeping of clay foundation, a larger fractional differential order value is needed. The fractionalized Zener model is capable of accounting for the primary and secondary consolidation processes of the foundation soil and can be used to predict the plate performance over many decades of time.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.271-278
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• 2000

In this study the effect and applicability of viscoelastic dampers on the seismic reinforcement of steel framed structures are investigated in the context of the performance based design approach. The effect of the damper on dissipating the input seismic energy was investigated with a single degree of freedom system. For analysis models a five-story steel frame subjected to gravity load, a ten-story and twenty-story structure subjected to gravity and wind load were designed. The code-specified design spectrums were constructed for each soil type and performance objective, and artificial ground excitation records to be used in the nonlinear time history analysis were generated based on the design spectrums. Inter-story drift was adopted as the primary performance criterion. According to the analysis results, all model structures turned out to satisfy the performance level for most of the soil conditions except for the soft soil(operational level). It was also found that the seismic performance could be greatly enhanced, and the structures were led to behave elastically by installing viscoelastic dampers on appropriate locations.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.429-437
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• 2006

Existing basic mechanical models which are methods characterizing viscoelastic materials were first reviewed to account for viscoelastic behavior of the asphalt pavement structure in this paper. A viscoelastic mechanical model considering a single load of vehicles subsequently was suggested and an equation that indicates the time-dependant behavior of asphalt pavements was derived from the proposed model. Non-destructive tests using falling weight deflectometer(FWD) were performed for a test section to estimate the application of the model. Both deflections and strains procured by the equation were compared to testing results according to loading history. By observing field measurements and theoretical evaluations, if two results are compared by the features of deflection according to time history, it could be concluded that the proposed model is expected to be suitable for prediction of the behavior of asphalt pavements because there is hardly difference between field data and calculated data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.581-586
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• 2004

This paper presents Newtonian formulation of the dynamics of plates treated fully with Active Constrained Layer Damping (ACLD). The developed equations of the plate/ACLD system provide analytical models far predicting the dynamic of laminated plates subjected to passive and active vibration damping controls. Numerical solutions of the analytical models are presented fir simply-supported plates in order to study the performance of the plate/ACLD system for different control strategies. The developed models present invaluable means for designing and predicting the performance of the smart laminated plates that can be used in many critical engineering applications.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.187-190
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• 2003

In order to apply a cyclic elasto-plastic and a viscoelastic-viscoplastic constitutive model to actual multi-layered ground conditions during large earthquake, numerica simulations were performed by a liquefaction analysis in the present study. From the liquefaction analysis, it was verified that the models can give a good description of the damping characteristics and liquefaction phenomena of ground accurately during large event which induces plastic deformation in large strain range.