• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.10
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• pp.1752-1758
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• 2008

This paper deals with the reduction of friction torque in permanent magnet motors by using the heat treatment of stator core. The stator core is made of electrical steel sheared by the punching die. From the punching process, large mechanical stress acting on the edge of stator tooth induces significant plastic and elastic deformation and then cause the change of magnetization properties. Then, the mechanical and magnetic unbalance in the sheared region of stator tooth produced by material cutting has influence on the friction torque. This paper investigated the effect of the punching process on the magnetization process and the mechanical deformation, and then proposed the stress relief annealing method for the reduction of friction torque among one of motor characteristics.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1491-1494
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• 2003

A specific experimental method, the Split Hopkinson Pressure Bar (SHPB) technique has been widely used to determine the dynamic material properties under the impact compressive loading conditions with strain-rate of the order of 103/s∼104/s. This type of test procedure has been used to examine the dynamic response of materials in various modes of testing. In this paper, dynamic deformation behaviors of rubber materials widely used for the isolation of vibration from varying structures under dynamic loading are determined using a Split Hopkinson Pressure Bar technique.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.585-590
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• 2003

It analyzed the reinforcement effect according to reinforced period for FREP. It found that reinforcement effect of P-Type that was reinforced during the usage decreased compared to I-Type that was reinforced before the usage. So when reinforcing a existing structure that is being used, it should consider the stress that is produced due to the fixed load. It evaluated bending and shear of RC reinforcing beam based on the test and analytical conditions of this study. It found that stress concentration was concentrated due to rapid change of bending rigidity in reinforced cutting part as a result of excessive reinforcement thickness of FREP. It resulted in rip-off failure. It means that it should evaluate the shear when designing reinforcement.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.12
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• pp.142-147
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• 2003

Mechanical properties of the materials used for transportations and industrial machinery under high strain rate loading conditions such as high impact loading are required to provide appropriate safety assessment to varying dynamically leaded mechanical structures. The Split Hopkinson Pressure Bar(SHPB) technique with a special experimental apparatus can be used to obtain the material behavior under high strain rate ]ending conditions. In this paper, the dynamic deformation behavior of a brass under both high strain rate compressive loading conditions has been determined using the SHPB technique.

• Bulletin of the Society of Naval Architects of Korea
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• v.12 no.1
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• pp.1-8
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• 1975

As a first step of a thermal stress analysis in a watertight bulkhead plate during welding of a spool type penetration piece, the bulkhead plate has been idealized as infinite plate with a circular hole. The exact solution for the transient temperature distribution and the associated quasi-static thermal stress which arise in a infinite plate subjected to an instantaneous point source of heat acting on the periphery of the circular hole. And the solutions have been extended to the case of a moving heat source with the aid of the Duhamel's superposition integral. The solutions can be applied to the problems such as a circular cutting or welding of a plate.

• Proceeding of KASS Symposium
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• 2006.05a
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• pp.214-223
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• 2006

Membrane structures, a kind of lightweight soft structural system, are used for spatial structures. The material property of the membrane has strong axial stiffness, but little bending stiffness. The design procedure of membrane structures are needed to do shape finding, stress-deformation analysis and cutting pattern generation. In shape finding, membrane structures are unstable structures initially. These soft structures need to be introduced initial stresses because of its initial unstable state, and happen large deformation phenomenon. Therefore, in this study, to find the structural shape after large deformation caused by initial stress, we need the shape analysis considering geometric nonlinear term. And we investigate the evaluation of shape analysis technique's convergence and efficiency according to the control method

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.1
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• pp.41-48
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• 1992

Various soil behaviors usually occurring in the geotechnical problems, such as, cutting and embankments, stability of slope, seepage, consolidations, shearing failures and liquefaction, should be predicted and analyzed in any way. An approach of these predictions may be followed by the development of the constitutive equations as first and subsequently solved by numerical methods. The purpose of this paper is develop the constitutive equation of sands uder monotonic or cyclic loadings. The constitutive equation which is based on elasto-plastic theory, modified anisotropic consolidated stress parameter by Sekiguchi et al and Pender's theory is derived. And the equation is included a new stress parameter, hardening function, Bauschinger's effects and Pender's theory. The model is later evaluated and confirmed the validity by the test data of Ottawa sand, Banwol sand Hongseong sand. The following conclustions may be drawn: 1. The consititutive equation which is based on elasto-plastic theory, modified anisotropic consolidated stress parpameter by Sekiguchi et al and Pender's theory is derived. The equation in included a new stress parameter, hardening function, Bauschinger's effect and Pender's theory. 2. For Ottawa sand, the result of the constitutive equation shows a better agreement than that of Oka et al. The result of axial strain agrees well with the tested data. However, the result of horizontal strain is little bit off for the cyclic loadings or large stress. It is thought that the deviation may be improved by considering Poisson's ratio and precise measurement of shear modulus. 3. Banwol sand is used for the strain and stress tests with different relative densitites and confining pressures. The predeicted result shows a good agreement with the tested data because the required material parameters were directly measurd and determined form this laboratory. 4. For Hongseong sand, the tests under same amplitude of cyclic deviatoric stress shows a similar result with the tested data in absolute strain. It shows the acute shape of turning point because the sine wave of input is used in the test but the serrated wave in prediction.

• Polymer(Korea)
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• v.25 no.1
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• pp.63-70
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• 2001

The objective of this study was to investigate the effect of cure type on the processing and physical properties under conditions of similar stress-strain properties. On the carbon black filled natural rubber(NR) based compound, the induction time decreased, but the cure rate became fast with increasing loading of sulfur donor agent. Tensile strength was little affected on the curing type. However, elongation generally decreased with increasing accelerator. Effect of cure type on the blow-out properties was followings: CV

• Journal of the Korean Society for Precision Engineering
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• v.33 no.12
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• pp.971-977
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• 2016

Recently, the problem of the accumulation of fine sludge from the cutting oil generated during machining processes has become a major threat to the environment. The fine sludge has adverse affects on the human body and the environment, and significantly contributes to marine pollution. However, a microfiltration technique that can process the sludge still needs to be studied and developed on a global scale. Therefore, it is necessary to develop eco-friendly equipment such as an ECO vacuum filter system and eco-friendly technologies for processing cutting oil. In this study, a structural analysis was carried out using a finite element method (FEM). Improved models of the suction chamber for the ECO vacuum filter system were proposed based on the analysis of the displacement and stress of the system. The model with the best result was then optimized using the commercial software, ANSYS. It was confirmed that, in the optimized model, displacement and stress were reduced in comparison with the initial model. Finally, the structural stability of the optimized model was verified through analysis.

• Structural Engineering and Mechanics
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• v.41 no.2
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• pp.231-242
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• 2012

This research work aims to develop an optimal design using Finite Element (FE) and Genetic Algorithm (GA) methods to replace the traditional concrete and timber material by a Synthetic Polyurethane fibre glass composite material in railway sleepers. The conventional timber railway sleeper technology is associated with several technical problems related to its durability and ability to resist cutting and abrading action of the bearing plate. The use of pre-stress concrete sleeper in railway industry has many disadvantages related to the concrete material behaviour to resist dynamic stress that may lead to a significant mechanical damage with feasible fissures and cracks. Scientific researchers have recently developed a new composite material such as Glass Fibre Reinforced Polyurethane (GFRP) foam to replace the conventional one. The mechanical properties of these materials are reliable enough to help solving structural problems such as durability, light weight, long life span (50-60 years), less water absorption, provide electric insulation, excellent resistance of fatigue and ability to recycle. This paper suggests appropriate sleeper design to reduce the volume of the material. The design optimization shows that the sleeper length is more sensitive to the loading type than the other parameters.