• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.1
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• pp.113-120
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• 1994

The dynamic characteristics of turning processes are complex, non-linear and time-varying. Consequently, the conventional techniques based on crisp mathematical model may not guarantee cutting force regulation. This paper presents a fuzzy controller which can regulate cutting force in turning process under varying cutting conditions. The fuzzy control rules are extablished from operator experience and expert knowledge about the process dynamics. Regulation which increases productivity and tool life is achieved by adjusting feedrate according to the variation of cutting conditions. The performance of the proposed controller is evaluated by cutting experiments in the converted conventional lathe. The results of experiments show that the proposed fuzzy controller has a good cutting force regulation capability in spite of the variation of cutting conditions.

• Earthquakes and Structures
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• v.4 no.1
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• pp.85-108
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• 2013

The research presented in this paper deals with the seismic protection of existing frame structures by means of passive energy dissipation. A displacement-based procedure to design dissipative bracings for the seismic protection of frame structures is proposed and some applications are discussed. The procedure is based on the displacement based design using the capacity spectrum method, no dynamic non linear analyses are needed. Two performance objective have been considered developing the procedure: protect the structure against structural damage or collapse and avoid non-structural damage as well as excessive base shear. The compliance is obtained dimensioning dissipative braces to limit global displacements and interstorey drifts. Reference is made to BRB braces, but the procedure can easily be extended to any typology of dissipative brace. The procedure has been validated through a comparison with nonlinear dynamic response of two 2D r.c. frames, one bare and one infilled. Finally a real application, on an existing 3D building where dissipative braces available on market are used, is discussed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.117-124
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• 2002

The major purpose of this study is to determine the dynamic behavior of soil-pile-structure interaction system considering the underground cavity. For the analysis, a numerical method fur ground response analysis using FE-BE coupling method is developed. The total system is divided into two parts so called far field and near field. The far field is modeled by boundary element formulation using the multi-layered dynamic fundamental solution that satisfied radiational condition of wave. And this is coupled with near field modeled by finite elements. For the verification of dynamic analysis in the frequency domain, both forced vibration analysis and free-field response analysis are performed. The behavior of soil non-linearity is considered using the equivalent linear approximation method. As a result, it is shown that the developed method can be an efficient numerical method to solve the seismic response analysis considering the underground cavity in 2D problem.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.270-275
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• 2008

In this study, computer applied engineering (CAE) techniques are full? used to conduct structural and dynamic analyses of a huge composite rotor blade. Computational fluid dynamics is used to predict aerodynamic load of the rotating wind-turbine blade model. Static and dynamic structural analyses are conducted based on the non-linear finite element method for composite laminates and multi-body dynamic simulation tools. Various numerical results for aerodynamic load, dynamic analyses are presented and characteristics of structural behaviors are investigated herein.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.320-330
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• 2008

This paper presents an improved dynamic programming (IDP) approach to solve the economic power dispatch problem including transmission losses in power systems. A detailed mathematical derivation of recursive dynamic programming approach for the economic power dispatch problem with transmission losses is presented. The transmission losses are augmented with the objective function using price factor. The generalized expression for optimal scheduling of thermal generating units derived in this article can be implemented for the solution of the economic power dispatch problem of a large-scale system. Six-unit, fifteen-unit, and forty-unit sample systems with non-linear characteristics of the generator, such as ramp-rate limits and prohibited operating zones are considered to illustrate the effectiveness of the proposed method. The proposed method results have been compared with the results of genetic algorithm and particle swarm optimization methods reported in the literature. Test results show that the proposed IDP approach can obtain a higher quality solution with better performance.

• Journal of the Korean Society of Industry Convergence
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• v.11 no.2
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• pp.71-82
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• 2008

In this study, 3 dimensional non-linear race car vehicle model including Chassis, steering and suspension systems were modeled by using Multi-Body Dynamics Simulation Program, DADS 9.5(Dynamic Analysis and Design System),which was used in kinematic and dynamic analysis. A full race car vehicle dynamics model using DADS program was presented and analysis was carried out to estimate the handling characteristics that may be very useful to design a race car in early design stage. The simulation of vehicle handling behavior for step steering input was simulated and compared with different design parameters: torsional stiffness of the front and rear anti roll bars, the motion ratio of the front and rear suspension system, the location of the tie rod joint, in multibody dynamic model. Therefore this simulation model before race car construction in early design step will be helpful for race car designer to save time and limited budget.

• Wind and Structures
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• v.13 no.4
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• pp.327-346
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• 2010

During the past decade, many electrical transmission tower structures have failed during downburst events. This study is a part of a research program aimed to understand the behaviour of transmission lines under such localized wind events. The present study focuses on the assessment of the dynamic behaviour of the line conductors under downburst loading. A non-linear numerical model, accounting for large deformations and the effect of pretension loading, is developed and used to predict the natural frequencies and mode shapes of conductors at various loading stages. A turbulence signal is extracted from a set of full-scale data. It is added to the mean component of the downburst wind field previously evaluated from a CFD analysis. Dynamic analysis is performed using various downburst configurations. The study reveals that the response is affected by the background component, while the resonant component turns to be negligible due large aerodynamic damping of the conductors.

• Computers and Concrete
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• v.14 no.2
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• pp.163-174
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• 2014

Damping as a material property plays an important role in decreasing dynamic response of structures. However, very little is known about the evaluation and application of the actual damping of Fiber Reinforced Polymer Confined Reinforced Concrete (FRP-C RC) material which is widely adopted in civil engineering at present. This paper first proposes a stress-dependent damping model for FRP-C RC material using a validated Finite Element Model (FEM), then based on this damping-stress relation, an iterative scheme is developed for the computations of the non-linear damping and dynamic response of FRP-C RC columns at any given harmonic exciting frequency. Numerical results show that at resonance, a considerable increase of the loss factor of the FRP-C RC columns effectively reduces the dynamic response of the columns, and the columns with lower concrete strength, FRP volume ratio and axial compression ratio or higher longitudinal reinforcement ratio have stronger damping values, and can relatively reduce the resonant response.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.544-549
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• 2003

In this study, non-linear dynamic FE analysis of a tracked vehicle under the traveling load is performed by FE code ABAQUS. The stability of vehicle is examined using the structure analysis for the road wheel. The dynamic analysis is performed by traveling load. The traveling load include the 6 step loading spectrum about road wheel. The stress level around road wheel are 30 MPa ${\sim}$ 40 MPa. These value are indicated under modified fatigue strength 50.3 MPa. It takes about 3 second to be stable the structure after traveling load.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.78-83
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• 2009

In this study, computer applied engineering (CAE) techniques are fully used to conduct structural and dynamic analyses of a whole huge wind turbine system including composite blades, tower and nacelle. For this study, computational fluid dynamics (CFD) is used to predict aerodynamic loads of the rotating wind-turbine blade model. Multi-body dynamic structural analyses are conducted based on the non-linear finite element method (FEM) by using super-element method for composite laminates blade. Three-dimensional finite element model of a wind turbine system is constructed including power train(main shaft, gear box, coupling, generator), bedplate and tower. The results for multi-body dynamic simulations on the wind turbine's critical operating conditions are presented in detail.