• Journal of Magnetics
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• v.19 no.1
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• pp.37-42
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• 2014

The equivalent model of a permanent magnet (PM) plays an important role in electromagnetic system calculation. A type of subsection model for a PM bar is established, to improve the accuracy of the traditional equivalent circuit method. The mathematical expression, and its end verification condition, are presented. Based on the analytical method and finite element method, the leakage permeance calculation of a PM bar in an open magnetic circuit is investigated. As an example, for a given certain type of PM bar, the magnetic flux of each section is validated by experiment, and by simulation. This model offers a foundation for building a high accuracy equivalent magnetic PM model in an electromagnetic system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.2
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• pp.327-336
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• 1997

This paper addresses an analytical approach to the mechanical error analysis and tolerance design of a four-bar path generator with lubricated joints. The mobility method is applied to consider lubrication effects and the four-bar path generator is stochastically modeled by using the clearance vector model for methanical error analysis. To show the validity of the proposed method, the mechanical errors obtained by applying the method to a four-bar path generator are compared with those by Monte Carlo simulation. Based on this analytical method, an optimal tolerance design problem is formulated and solved for the four-bar path generator.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.10
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• pp.1087-1093
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• 2013

In this study, a measurement method of double ball-bar is proposed to measure the geometric errors of an ultra-precision roll mold machine tool. A volumetric error model of the machine tool is established to investigate the effects of the geometric errors to a radius error and a cylindricity of the roll mold. A measurement path is suggested for the geometric errors, and a ball-bar equation is derived to represent the relation between the geometric errors and a measured data of the double ball-bar. Set-up errors, which are inevitable at the double ball-bar installation, also are analyzed and are removed mathematically for the measurement accuracy. In addition, standard uncertainty of the measured geometric errors is analyzed to determine the experimental condition. Finally, the proposed method is tested and verified through simulation.

• Journal of the Korean Operations Research and Management Science Society
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• v.39 no.1
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• pp.1-12
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• 2014

This article proposes a variable sampling interval (VSI) $\bar{X}$ control chart using weighted standard deviation (WSD) method for skewed populations. The WSD method decomposes the standard deviation of a quality characteristic into upper and lower deviations and adjusts control limits and warning limits of a control chart in accordance with the direction and degree of skewness. A control chart constant is derived for estimating the standard deviation of skewed distributions with the mean of sample standard deviations. The proposed chart is compared with the conventional VSI $\bar{X}$ control chart under some skewed distributions. Simulation study shows that the proposed WSD VSI chart can control the in-control average time to signal (ATS) as an adequate level better than the conventional VSI chart, and the proposed chart can detect a decrease in the process mean of a quality characteristic following a positively skewed distribution more quickly than the standard VSI chart.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.827-828
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• 2006

This paper proposes a new method for detecting broken rotor bars in a squirrel-cage induction motor. The air-gap flux variation analysis was done using search coils inserted in stator slots when broken rotor bar occurs. An accurate modeling and analysis of air-gap flux variation in the induction motor are developed using finite-element(FE) software packages, and measurement of the flux are made using search coils. The simulation was done for the induction motor with 380 [V]. 7.5 [kW], 4 Poles, 1,760 [rpm] ratings using the commercial FE analysis tool. The simulation and experiment results can be useful for detecting the broken rotor bar of an induction motor.

• KCI Concrete Journal
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• v.13 no.2
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• pp.67-74
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• 2001

In this study, a numerical model for the simulation of reinforced concrete columns subject to cyclic loading is presented. The model consists of three separate models representing concrete, reinforcing steel bars and bond-slip between a reinforcing bar and ambient concrete. The concrete model is represented by the plane stress plastic-damage model and quadrilateral finite elements. The nonlinear steel bar model embedded in truss elements is used for longitudinal and transverse reinforcing bars. Bond-slip mechanism between a reinforcing bar and ambient concrete is discretized using connection elements in which the hysteretic bond-slip link model defines the bond stress and slip displacement relation. The three models are connected in finite element mesh to represent a reinforced concrete structure. From the numerical simulation, it is shown that the proposed model effectively and realistically represents the overall cyclic behavior of a reinforced concrete column. The present plastic-damage concrete model is observed to work appropriately with the steel bar and bond-slip link models in representing the complicated localization behavior.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.475-480
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• 2006

In this paper, a new approach for detecting broken rotor bars in a squirrel-cage induction motor is proposed. The air-gap flux variation analysis was done using search coils inserted in stator slots when broken rotor bar occurs. An accurate modeling and analysis of air-gap flux variation in the induction motor are developed using finite-element (FE) software packages, and measurement of the flux are made using search coils. The simulation was done for the induction motor with 380 [V], 5 [HP], 4 Poles, 1,742 [rpm] ratings using the commercial FE analysis tool. The simulation and experiment results can be useful for detecting the broken rotor bar of an induction motor.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.473-476
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• 2016

In this study, important design factors in Jansen leg mechanism by which two legs can be driven by only one input like a motor are considered through method of transmitting motion in three-bar linkage and Grashof law in four-bar linkage. In preliminary design, by using EDISON m-sketch and its simulation which can observe trace of feet, two identical four-bar linkages are initially designed and two three-bar linkages are added to four-bar linkages sequentially. By analyzing GL(Ground Length) and GAC(Ground Angle Coefficient), the adequacy of the preliminary design was estimated. Final design of walking apparatus is implemented using CAD software, Assembly2 of EDISON Designer. Finally, proposals to improve software used in this study are suggested.

• Journal of Power Electronics
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• v.12 no.6
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• pp.982-991
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• 2012

In this study, a new method has been presented for the detection of broken rotor bar (BRB) faults in inverter driven induction motors controlled via Field Oriented Control (FOC). To this end, a FOC controlled induction motor with a BRB fault was modeled using the Matlab/Simulink program. Experiments were carried out using the prepared simulation model at various loads and operating speeds. The motor current and speeds were monitored for healthy, 1, 2 and 3 BRB faults. The Resampling Based Order Tracking Analysis (RB-OTA) method was applied to the monitored signals. The obtained results were compared by using the classic Fast Fourier Transform (FFT) method. When the obtained results were analyzed via the FFT method no information regarding any faults was determined in the run up or run down regions of the motor and the presented method gave very good results. The reliability of the proposed method was validated with experimental results. The main innovative part of this study is that the RB-OTA method was implemented on the induction motor current signal for detecting BRB faults.

• International Journal of Automotive Technology
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• v.1 no.1
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• pp.35-41
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• 2000

The crashworthiness of vehicles with finite element methods depends on the geometry modeling and the material properties. The vehicle body structures are generally composed of various members such as frames, stamped panels and deep-drawn parts from sheet metals. In order to ensure the impact characteristics of auto-body structures, the dynamic behavior of sheet metals must be examined to provide the appropriate constitutive relation. In this paper, high strain-rate tensile tests have been carried out with a tension type split Hopkinson bar apparatus specially designed for sheet metals. Experimental results from both static and dynamic tests with the tension split Hopkinson bar apparatus are interpolated to construct the Johnson-Cook and a modified Johnson-Cook equation as the constitutive relation, that should be applied to simulation of the dynamic behavior of auto-body structures. Simulation of auto-body structures has been carried out with an elasto-plastic finite element method with explicit time integration. The stress integration scheme with the plastic predictor-elastic corrector method is adopted in order to accurately keep track of the stress-strain relation for the rate-dependent model accurately. The crashworthiness of the structure with quasi-static constitutive relation is compared to the one with the rate-dependent constitutive model. Numerical simulation has been carried out for frontal frames and a hood of an automobile. Deformed shapes and the Impact energy absorption of the structure are investigated with the variation of the strain rate.