• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.239-240
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• 2007

변압기 코어소재로 사용하는 방향성 규소강판의 가공 방법에 따른 물성을 조사하기 위하여 테이프 와인딩 코어 형태, 곡률반경을 20, 30, 40mm로 하여 토로이달 형태 변압기 시료의 B-H 자성 특성을 조사하였다. 곡률반경이 40mm, 높이는 10mm의 비율에서 보자력은 0.02Oe, 포화자속밀도는 0.98, 1.85T으로 보자력(Hc)은 낮고 포화자속일도(Bs)는 제일 큰 값을 나타내었고, 국내에서 생산되고 있는 방향성 규소강판의 자속밀도값 보다 약간 크게 나타났으며, 본 연구로부터 방향성 규소강판을 이용하여 권자심 코어을 제작할 때 고려해야하는 탄성변형에 대한 중요성과 코어 소재의 가공방법이 자기적 특성에 미치는 영향을 고찰하였다. 또한 토로이달 코어형태의 변압기를 설계 제작시 높이와 곡율반경, 가공 방법에 따라 용량, 효율 등이 다르므로 사전에 소재의 물성을 면밀히 검토 후에 전기기기에 적용해야함을 재확인하였다.

• 동력기계공학회지
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• 제10권4호
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• pp.78-82
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• 2006

Recently, The demands for the reduction of noise generated by transformers have been increasing. Almost all of the noise generated by transformers is a result of magnetostricitive vibration in the core. The noise radiates into the atmosphere from the tank through the insulation oil. As the noise of transformer irritates residents, needs for decreasing the noise of transformer have been arised. One method of reduction such a noise is to build a free-standing enclosure of concrete and steel plates around the transformer. However, this method has some disadvantages. Another method of noise reduction is to mount a close-fitting sound insulation panel on the side of a transformer tank. Side plate vibrations of transformer are transmitted to such a sound insulation panel along two paths. In one case, they are transmitted through air by sound pressure and in the other through supporting structures. In the paper, the vibration and noise effect which is transferred from reinforce channel to insulation panel generated by transformer have been identified for the several kinds of insulation panel and damping sheet analytically and experimetally.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.86-91
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• 2005

The stack, the core unit of the MCFC system, is composed of the three main parts which are the electrodes, the matrix keeping the electrolyte and the separator. Among these, the separator made of low carbon steel is manufactured by some sheet metal forming processes. The flatness of flange of the mask plate of the separator is crucial not only to enhance the stack performance but also to reduce the production cost. This study has focused on the enhancement of flatness of the mask plate flange by controlling some process parameters like the punch and die comer radii, the blank holding force, the friction coefficient and so on. The springback phenomenon occurring in the flange drawing process has been studied first using the finite element method (FEM) in order to understand what causes the springback. The distribution pattern of local longitudinal stress in the flanged part has been revealed very important in predicting the final shape of the flange. This fact has been backed up by the experimental results carried out with the developed test dies.

• 대한조선학회논문집
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• 제54권4호
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• pp.286-293
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• 2017

This paper presents ballistic limit velocity results of a variety of materials generally used in warships. Ballistic limit velocity is the velocity required for a projectile to penetrate a target with 50 percents of time and is widely used as a measure of armour bulletproofing. For this study, live fire experiments were implemented using AK-47 $7.62{\times}9mm$ mild steel core as a projectile as well as various thickness warship materials as a target. Also, methods of MIL-STD-662F, NIJ-STD-0101.06 and support vector machine were applied to measure the ballistic limit velocity and then their results were graphically analyzed for comparison. The minimum of their results was considered as the ballistic limit velocity in a conservative way.

• 한국기계가공학회지
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• 제20권9호
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• pp.90-96
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• 2021

As real-time data of factories can be collected using various sensors, the adaptation of intelligent unmanned processing systems is spreading via the establishment of smart factories. In intelligent unmanned processing systems, data are collected in real time using sensors. The equipment is controlled by predicting future situations using the collected data. Particularly, a technology for the prediction of tool wear and for determining the exact timing of tool replacement is needed to prevent defected or unprocessed products due to tool breakage or tool wear. Directly measuring the tool wear in real time is difficult during the cutting process in milling. Therefore, tool wear should be predicted indirectly by analyzing the cutting load of the main spindle, current, vibration, noise, etc. In this study, data from the current and acceleration sensors; displacement data along the X, Y, and Z axes; tool wear value, and shape change data observed using Newroview were collected from the high-speed, two-edge, flat-end mill machining process of SKD11 steel. The support vector machine technique (machine learning technique) was applied to predict the amount of tool wear using the aforementioned data. Additionally, the prediction accuracies of all kernels were compared.

• Current Optics and Photonics
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• 제5권5호
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• pp.532-537
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• 2021

We present a compact endoscopic probe in a needle form which has a fast beam-scanning capability for optical coherence tomography (OCT). In our study, a beam-scanning OCT imaging needle was fabricated with a 26G syringe needle (0.46 mm in outer diameter) and a thin OCT imaging probe based on the stepwise transitional core (STC) fiber. The imaging probe could freely rotate inside the needle for beam scans. Hence, OCT imaging could be performed without rotation or translation of the needle body. In our design, the structural integrity of the needle's steel tubing was preserved for mechanical robustness. Probing the optical signal was performed through the needle's own window formed at the end. For hand-held operation of our imaging needle, a light and compact scanner module (130 g and 45 × 53 × 60 mm³) was devised. Connected to the imaging needle, it could provide rotational actuation driven by a galvanometer. Because of its finite actuation range, our scanner module did not need a fiber rotary joint which might add undesirable complexity. The beam scan speed was 20 Hz and supported 20 frames per second at the maximum for endoscopic OCT imaging.

• 열처리공학회지
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• 제32권5호
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• pp.224-229
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• 2019

PVD coating is a technology that can be applied to various industries, and is widely used for processing molds and machinery, improving performance of core parts, and extending the life. Therefore, there is a need for a research on a device and a process technology that can adjust the performance to suit each application. In this study, a PVD coating device with ion density control was used to deposit a coating layer on SKD 11, a cold die steel, with magnetron currents of 1 A, 2 A, 3 A at arc currents of 80 A, 100 A, 130 A. It examined the mechanical properties for each condition. Increasing the arc current and magnetron current could improve the thickness, adhesion, and hardness of the coating layer. Especially, When the magnetron current was high, it suppressed the droplets that could be generated by the high arc current, showing excellent surface uniformity and adhesion of the coating layer.

• Steel and Composite Structures
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• 제32권6호
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• pp.753-767
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• 2019

Vibration control in mechanical equipments is an important problem where unwanted vibrations are vanish or at least diminished. In this paper, free vibration active control of the porous sandwich piezoelectric polymeric nanocomposite microbeam with microsensor and microactuater layers are investigated. The aim of this research is to reduce amplitude of vibration in micro beam based on linear quadratic regulator (LQR). Modified couple stress theory (MCST) according to sinusoidal shear deformation theory is presented. The porous sandwich microbeam is rested on elastic foundation. The core and face sheet are made of porous and three-phase carbon nanotubes/resin/fiber nanocomposite materials. The equations of motion are extracted by Hamilton's principle and then Navier's type solution are employed for solving them. The governing equations of motion are written in space state form and linear quadratic regulator (LQR) is used for active control approach. The various parameters are conducted to investigate on the frequency response function (FRF) of the sandwich microbeam for vibration active control. The results indicate that the higher length scale to the thickness, the face sheet thickness to total thickness and the considering microsensor and microactutor significantly affect LQR and uncontrolled FRF. Also, the porosity coefficient increasing, Skempton coefficient and Winkler spring constant shift the frequency response to higher frequencies. The obtained results can be useful for micro-electro-mechanical (MEMS) and nano-electro-mechanical (NEMS) systems.

• Steel and Composite Structures
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• 제41권6호
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• pp.805-820
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• 2021

In this research, the buckling and free vibration of three-phase carbon nanotubes/ fiber/ polymer piezoelectric nanocomposite face sheet sandwich microbeam with microsensor and micro-actuator surrounded in elastic foundation based on modified couple stress theory (MCST) is investigated. Three types of porous materials are considered for sandwich core. Higher order (Reddy) and sinusoidal shear deformation beam theories are employed for the displacement fields. Sinusoidal surface stress effects are extracted for sinusoidal shear deformation beam theory. The equations of motion are derived by Hamilton's principle and then the natural frequency and critical buckling load are obtained by Navier's type solution. The determined results are in good agreement with other literatures. The detailed numerical investigation for various parameters is performed for this microsensor-microactuator. The results reveal that the microsensor-microactuator enhanced by increasing of Skempton coefficient, carbon nanotubes diameter length to thickness ratio, small scale factor, elastic foundation, surface stress constants and reduction in porous coefficient, micro-actuator voltage and CNT weight fraction. The valuable results can be expedient for micro-electro-mechanical (MEMS) and nano-electro-mechanical (NEMS) systems.

• 한국초전도ㆍ저온공학회논문지
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• 제11권4호
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• pp.8-11
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• 2009

This study introduced wastewater treatment method by High Gradient Magnetic Separation (HGMS). HGMS treatment was high efficient method for various industrial wastewaters. The system is currently research state, but we have surveyed commercialize the technology for industry. In rolling plate process, coolant wastewater was recycled by sedimentation and sand filter system. It needs several large reservoirs and long time to remove suspended solid (SS) like metal fines and iron oxide in hot rolling plate making process. If removing rate of suspended solid in rolling coolant wastewater is improved by using HGMS system, the productivity of working process can be increased and the area of reservoir can be reduced. We manufactured high temperature superconducting HGMS system that had a purpose to treatment of coolant wastewater in rolling plate process. We fabricated the prototypes of magnetic matrix filter consisting of stainless steel 430 mesh, which is a core component in the magnetic separation system, In our basic preliminary experiment using HGMS system, it has been clear that the fine paramagnetic particles in the coolant wastewater obtained from rolling plate process of POSCO can be separated with high efficiency.