• 전기학회논문지
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• 제59권12호
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• pp.2319-2323
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• 2010

The existing contact-type bearings using rolling or sliding require continuous maintenance due to abrasion caused by friction and are not suitable for high-speed rotation and slimming. A magnetic bearing without contact can overcome such problems but the performance depends on the allocation of magnets and the structure of bearings. This paper proposes a method designing parameters of a passive magnetic bearing to improve levitation force. The proposed method employs Halbach array as the allocation of magnets, uses particle swam optimization to determine the structure of bearings. The numerical experiment shows that the levitation force is improved by the proposed method compared with the existing one using finite element analysis.

• 대한기계학회논문집A
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• 제33권3호
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• pp.190-195
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• 2009

All the failure in fatigue of torsion, bending and rolling contact, and in sliding wear begins mostly from surface. So much efforts have been invested to the surface technology which deal these problems during past decades, but the industrial demand keeps growing and more significant requirements are added to researchers and engineers. Nano crystal surface modification technology which makes the surface layers into nano crystalline, induces big and deep compressive residual stress, increases surface hardness, improves surface hardness, and make micro dimples structure on surface is an emerging technology which can break limits of current surface technology and relieve the burden of researchers and engineers. In this study, a nano crystal surface modification technology which is calling UNSM(Ultrasonic nano crystal surface modification) technology, is introduced and how it has been applied to industry to solve these failure problems is explained.

• 한국자동차공학회논문집
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• 제18권1호
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• pp.1-7
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• 2010

The paper proposes a multi-body dynamic simulation to numerically evaluate the generated axial force(G.A.F) and plunging resistant force(P.R.F) practically related to the shudder and idling vibration of an automobile. A numerical analysis of two plunging types of CV joints, tripod joint(TJ) and very low axial tripod joint(VTJ), is conducted using the commercial program DAFUL. User-defined subroutines of a friction model illustrating the contacted parts of the outboard and inboard joint are subsequently developed to overcome the numerical instability and improve the solution performance. The Coulomb friction effect is applied to describe the contact models of the lubricated parts in the rolling and sliding mechanisms. The numerical results, in accordance with the joint articulation angle variation, are validated with experimentation. The offset between spider and tulip housing is demonstrated to be the critical role in producing the 3rd order component of the axial force that potentially causes the noise and vibration in vehicle. The VTJ shows an excellent behavior for the shudder when compared with TJ. In addition, a flexible nonlinear contact analysis coupled with rigid multi-body dynamics is also performed to show the dynamic strength characteristics of the rollers, housing, and spider.

• 농업과학연구
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• 제5권2호
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• pp.127-135
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• 1978

경운장치(耕耘裝置)의 재량(改良)과 새로운 경운장치(耕耘裝置)의 설계(設計)를 위(爲)한 실험(實驗)을 실내(室內)에서 실시(實施)하기 위하여 Soil bin과 자연토양(自然土壤)과 유사(類似)한 39.35%의 bentonite, 48.10의 모래 및 12.55%의 SAE 10W oil을 사용한 인공토양(人工土壤)을 제조(製造)하였으며 경운실험(耕耘實驗)을 위(爲)한 인공토양(人工土壤)의 물리적(物理的)인 특성(特性)을 구명(究明)하기 위해 전압회수(轉壓回數), 전압속도등(轉壓速度等)을 변화(變化)시켜 가면서 인공토양(人工土壤)의 절대경도(絶對硬度), 밀도(密度), 인공토양(人工土壤)과 철판(鐵板) 및 고무판(板) 및 고무판(板)의 동마찰계수(動摩擦係數)를 측정(測定)하였으며 인공토양(人工土壤)의 밀도변화(密度變化)에 따른 점착력(粘着力)과 내부마찰각(內部摩擦角)의 변화(變化)를 조사(調査)한 결과(結果)를 요약(要約)하면 다음과 같다. 1. 전압회수(轉壓回數)가 증가(增加)할수록 밀도(密度)는 증가(增加)하였으며 그 관계식(關係式)은 다음과 같다. $y=1.073200+0.070780x-0.002263x^2$ 여기서, y : 밀도(密度)($g/cm^3$) x : 전압회수(轉壓回數) 전압속도(轉壓速度) 4.5~10.4 cm/sec의 범위(範圍)에서 전압속도(轉壓速度)는 밀도(密度)에 큰 영향(影響)을 주지 않았다. 2. 토양절대경도(土壤絶對硬度)는 전압속도(轉壓速度) 4.5~10.4cm/sec의 변화(變化)에 거의 영향(影響)을 받지 않았으며 토양절대경도(土壤絶對硬度)(y)는 전압회수(轉壓回數)(x)의 증가(增加)에 대(對)하여 곡선적(曲線的)으로 증가(增加)하였는데 그들 관계식(關係式)은 다음과 같다. $y=37.74{\frac{(0.64 +0.17x-0.0054x^2}{(3.36-0.17x-0.0054x^2)^3}}$ 3. 밀도(密度)(Bulk density : y($g/cm^3$))와 토양절대경도(土壤絶對硬度)(absolute soil hardness : x($kg/cm^3$))의 관계식(關係式)은 다음과 같다. $y=37.74{\frac{2.46x-2.02}{(6.02-2.46x)^3}$ 4. 밀도(密度)의 변화(變化)는 점착력(粘着力)과 내부마찰각(內部摩擦角)에 영향(影響)을 주는데 밀도(密度)가 1.60~1.75에서 함수비(含水比) 29.5%인 자연토양(自然土壤)의 사질(砂質)loam과 유사(類似)한 값을 나타내었다. 5. 동마찰계수(動摩擦係數)는 철판(鐵板)의 경우 0.3~0.4, 고무판(板)의 경우 0.64~0.72로 나타났으며 자연토양(自然土壤)에서의 값과 유사(類似)하다.