• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.4
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• pp.28-33
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• 2009

Yoke is a part of rotor in unmanned helicopter. It was transferred power of engine to the rotor. It has been usually produced by machining and used wastefully material. And it has been considered to improve its proof stress against repeated loading of the products. Therefore we studied Forging process for satisfaction of these ability and process design for yoke forming has been studied by using FE analysis. Die design and forming analysis have been performed according to the conditions such as billet volume, flash control, cavity filling, and the distribution of damage in the products. In the comparison between die forging processes, side punch effects has been investigated by considering billet dimensions.

• Journal of Magnetics
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• v.13 no.4
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• pp.173-176
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• 2008

In this study, a new kind of instrument for measuring the magnetic shielding effectiveness (MSE) was developed using a double yoke; one a magnetizing yoke and the other a sensing yoke. Using the developed instrument, the MSE could be measured for a steel sheet specimen in the ELF range, where the magnetic permeability contributes to the MSE at low frequencies and eddy currents contributes to the MSE high frequencies with < 0.1 dB reproducibility. The developed measuring method can be applied to quality control in a steel sheet company producing EMI/EMC shielding materials.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.6
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• pp.37-46
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• 2003

This paper is to predict quality deterioration resulting from a caulking process of yoke which is a part of automotive steering system. The caluking is a plastic deformation process involving such as impact of high speed tool, contacts between part and fixtures and strain rate sensitivity of the part material. Elaborate application of finite element method is neccesary to calculate changes of part dimensions because they fall into a level of tolerances. Simple work hardening and strain rate sensitive model is proposed fur the material and applied for the simulation by using Abaqus which is able to cater for elastoplastic rate sensitive material and contacts. Numerical results of test models that represent tensile bar and tensile plate are compared with material data inputs. Dimensional changes for the yoke are calculated from simulations and compared to the mesurements and they show good agreement. The method presented here with the material model proved to be valuable to assess quality deterioration for similar metal forming processes.

• Journal of the Korean Magnetics Society
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• v.26 no.1
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• pp.19-23
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• 2016

In this study, we have constructed a measuring system to investigate tensile stress measurement of tendons, which is employed in bridges, by means of the non-destructive and non-contact method. The measuring system consists of tensile stress applying apparatus up to 2 GPa, and power supply for ac and dc current to tendon directly to magnetize tendon in circular direction and to coil wound on yoke to magnetize tendon in axial direction. We have used two kinds of tendon, which were produced by different companies, using the measuring system constructed in this work. Two kinds of experiments are carried out in this work; $1^{st}$ experiment : ac current was applied to the tendon and dc current was applied to coil wound on the yoke, and voltage induced from search coil wound on yoke (SCY) was measured and $2^{nd}$ experiment : dc current was applied to the tendon and ac current was applied to coil wound on the yoke, and voltage induced from search coil on tendon (SCT) was measured. In case of $1^{st}$ experiment, voltage induced from SCY was changed below 200MPa tensile stress but the voltage was not increased above 200 MPa. In case of $2^{nd}$ experiment, voltage induced from SCT was decreased up to 1.5 GPa linearly. We expect that $2^{nd}$ experiment could be applied to the non-destructive testing of tensile stress measurement of tendon.

• Journal of Aerospace System Engineering
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• v.18 no.1
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• pp.1-10
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• 2024

In a previous study, a structure of a superplastic yoke consisting of a thin FR4 layer laminated with viscoelastic tape on both sides of a shape memory alloy (SMA) was proposed to reduce residual vibration generated by a deployable solar panel during high motion of a satellite. Damping properties of viscoelastic tapes will change with temperature, which can directly affect vibration reduction performance of the yoke. To check damping performance of the yoke at different temperatures, free damping tests were performed under various temperature conditions to identify the temperature range where the damping performance was maximized. Based on above temperature test results, this paper predicts temperature of the yoke through orbital thermal analysis so that the yoke can have effective damping performance even if it is exposed to an orbital thermal environment. In addition, the thermal design method was described so that the yoke could have optimal vibration reduction performance.

• Journal of Electrical Engineering and Technology
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• v.4 no.2
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• pp.255-265
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• 2009

This paper presents the acoustic noise and mechanical vibration reduction of a coreless brushless DC motor with an air dynamic bearing used in a digital lightening processor. The coreless brushless DC motor does not have a stator yoke or stator slot to remove the unbalanced force caused by the interaction between the stator yoke and the rotor magnet. An unbalanced force makes slotless brushless DC motors vibrate and mechanically noisy, and the attractive force between the magnet and the stator yoke increases power consumption. Also, when a coreless brushless DC motor is driven by a $120^{\circ}$ conduction type inverter, high frequency acoustic noise occurs because of the peak components of the phase currents caused by small phase inductance and large phase resistance. In this paper, a core-less brushless DC motor with an air dynamic bearing to remove mechanical vibration and to reduce power consumption is applied to a digital lightening processor. A $180^{\circ}$ conduction type inverter drives it to reduce high frequency acoustic noise. The applied methods are simulated and tested using a manufactured prototype motor with an air dynamic bearing. The experimental results show that a coreless brushless DC motor has characteristics of low power consumption, low mechanical vibration, and low high frequency acoustic noise.

• Transactions of Materials Processing
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• v.21 no.8
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• pp.473-478
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• 2012

The yoke, a component of conventional motor-driven power steering system, often contains welding defects from its manufacturing process. To eliminate these defects, the precision cold forging process has been tried. In this study, the double-action complex forging has been used to manufacture a torsion joint yoke. The backward extrusion proved faster than the forward extrusion in forging of the product. The double-action complex forging process utilized an upper die composed of a punch, a punch guide, a disc spring and a coil spring. The forged material pushes up the punch guide, and then the disc spring and the coil spring balances the backward extrusion force. Consequently, the flow of material was essentially in the forward direction, resulting in a successful forging operation. The forging load of Al 6061-T6 was higher than that of the automotive structural hot rolled plate.

• Journal of the Korean Magnetics Society
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• v.26 no.6
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• pp.206-212
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• 2016

The shape of a iron bed supporting a permanent magnet in a large-sized motor is a important factor for determining the coupling strength with the yoke. In a large-sized motor, there is a difference in electromagnetic force with the yoke depending on the shape of the iron bed. In this paper, we show the differences and problems by calculating the electromagnetic force between the double bed and the single bed through the virtual air gap, and show that the single bed is superior in terms of the binding force. It is also shown that the binding force between the bed and the yoke is improved by carving the groove shape under the bed.

• Transactions of Materials Processing
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• v.28 no.3
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• pp.115-122
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• 2019

In this paper, finite element analysis of an automatic five-stage precision cold forging process of a yoke, a steering part of a passenger's car, is conducted with emphasis on spring back analysis at the yoke-forming stage and its experimental verification is subsequently made. An elastoplastic finite element method with MINI-element technique employed for the analysis of the entire process is explained. There is emphasis that the thin film of material formed between the punch and die in the stage may result to some errors especially in elastoplastic finite element analysis of spring back due to frequent remeshing. The numerical robustness of the spring back analysis in regards to remeshing is hence shown first through investigation into its effect on the predicted spring back. Experimental measurement of displacement due to spring back is carried out for comparison with the predicted results, and they are in a qualitative agreement with each other.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.3
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• pp.81-85
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• 2001

Processes for optimizing the coil shape of deflection yoke are proposed A very accurate and practical winding modeler is developed and volume integral equation method (VIEM) is used for field calculation. Two steps of optimizations are done by using (1+1) evolution strategy. Those are dimensional optimization and pin-position optimization Various techniques are applied for reducing computational time for the optimization.