• 대한기계학회논문집
• /
• 제13권5호
• /
• pp.820-830
• /
• 1989

본 논문에서는 타이어의 각 부분의 물성치 계산을 위한 식을 유한요소법에 적용할 수 있도록 제안하였다. 이 식은 강철 코드의 굽힙효과를 고려 하였으며, 특히 각 요소에서 전단변형이 일어나는 동안의 굽힘효과를 고려하였다. 유한요소 공식화는 가상일의 원리에 의하여 평형 방정식으로부터 유도하였고, Updated refer- ence coordinate에 대해 증분해석을 적용하여 Updated Lagrangian공식화를 하였다. 그리고 차량하중에 의하여 타이어가 노면에 접지될때의 응력상태를 게산할 수 있도록 접촉문제 공식화를 유한요소 공식화에 첨가 하였다.

• 대한금속재료학회지
• /
• 제48권6호
• /
• pp.533-542
• /
• 2010

The specific motivation for joining an Al alloy and Zn-coated steel arises from the need to save fuel consumption by weight reduction and to enhance the durability of vehicle structures in the automobile industry. In this study, the lap joining A6K31 Al alloy (top) and SGARC340 Zn-coated steel (bottom) sheets with a thickness of 1.0 mm and 0.8 mm, respectively, was carried out using the friction stir weld (FSW) technique. The probe of a tool did not contact the surface of the lower Zn-coated steel sheet. The friction stir welding was carried out at rotation speeds of 1500 rpm and travel speeds of 80~200 mm/min. The effects of tool geometry and welding speed on the mechanical properties and the structure of a joint were investigated. The tensile properties for the joints welded with a larger tool were better than those for the joints done with a smaller tool. A good correlation between the tensile load and area of the welded region were observed. The bond strength using a larger tool (M4 and M3) decreased with an increase in welding speed. Most fractures occurred along the interface between the Zn-coated steel and the Al alloy. However, in certain conditions with a lower welding speed, fractures occurred at the A6K31 Al alloy.

• Tribology and Lubricants
• /
• 제35권5호
• /
• pp.267-273
• /
• 2019

Wheel bearings are important automotive parts that bear the vehicle weight and translate rotation motion; in addition, their seals are components that prevent grease leakage and foreign material from entering from the outside of the bearings. Recently, as the need for electric vehicles and eco-friendly vehicles has been emerging, the reduction in fuel consumption and $CO_2$ emissions are becoming the most important issues for automobile manufacturers. In the case of wheel bearings, seals are a key part of drag torque. In this study, we investigate the prediction of the drag torque taking into consideration the hyperelastic and viscoelastic material properties of automotive wheel bearing seals. Numerical analysis based on the finite element method is conducted for the deformation analyses of the seals. To improve the reliability of the rubber seal analysis, three types of rubber material properties are considered, and analysis is conducted using the hyperelastic material properties. Viscoelastic material property tests are also conducted. Deformation analysis considering the hyperelastic and viscoelastic material properties is performed, and the effects of the viscoelastic material properties are compared with the results obtained by the consideration of the hyperelastic material properties. As a result of these analyses, the drag torque is 0.29 Nm when the hyperelastic characteristics are taken into account, and the drag torque is 0.27 Nm when both the hyperelastic and viscoelastic characteristics are taken into account. Therefore, it is determined that the analysis considering both hyperelastic and viscoelastic characteristics must be performed because of its reliability in predicting the drag torque of the rubber seals.

• 한국추진공학회지
• /
• 제17권4호
• /
• pp.56-62
• /
• 2013

액체로켓엔진의 초기 개념설계를 위한 시스템 통합 해석 및 설계 프로그램을 개발하였다. 개발된 프로그램은 주어진 요구조건과 입력 변수들에 대한 시스템 성능해석을 수행하고 유전 알고리즘 등의 최적화 기법을 통하여 높은 비추력과 추력중량비를 갖는 설계변수의 조합을 찾아낸다. 사용자의 편의를 위해 간단한 GUI를 구성하고 프로그램의 설계 결과는 형상 파라미터를 가시화하여 확인할 수 있도록 CATIA와 연동하여 3차원 도면으로 나타낼 수 있도록 하였다. 본 연구는 이후 우주발사체의 기본 설계에서 추진기관의 선정 및 해석 과정에 활용될 수 있을 것으로 기대된다.

• 고려인삼학회:학술대회논문집
• /
• 고려인삼학회 2002년도 학술대회지
• /
• pp.385-391
• /
• 2002

Panax ginseng (family- Araliaceae) is a native plant of Korea and has been used for past several years among oriental people. To evaluate the radioprotective potential of P. ginseng on the formation of giant cells in the testis of Swiss albino mice, the animals were divided into four groups: -(I)-Only vehicle was administered. (II)P. ginseng treated group: -The animals received 10 mg/kg body weight P. ginseng root extract (in DDW) i.p. continuously for 30 days. (III) Irradiated group: -The animals were exposed to 8 Gy gamma radiation at the dose rate of 1.69 Gy/min at the distance of 80 ems. (IV) Combined treatment group: -Animals were given P. ginseng extract for four days and on fourth day they were irradiated to 8 Gy gamma radiation after 30 minute of extract administration. The animals of these three groups were autopsied on day 1,3, 7, 14 and 30 days. In ginseng treated group, active spermatogenesis was observed without any toxic effect. Histopathological studies of irradiated group (II) revealed reduction in germ cell count, loss of sperms and formation of multinucleated giant cells on day 7th. These giant cells were formed by round nuclei of early or late spermatids. In combination group (III), although germinal epithelium was still disorganized with loss of cells in few tubules, but no giant cell formation was observed. In order to know the mechanism of radioprotection of ginseng, LPO and GSH were estimated. It was observed that pretreated irradiated animals showed inhibition of LPO and increase in GSH. Thus the present study suggests ginseng protects male gonads. This may be attributed to the inhibition of LPO and increase synthesis of GSH byginseng.

• 대한한방부인과학회지
• /
• 제28권3호
• /
• pp.54-73
• /
• 2015

Objectives The object of this study was to evaluate the effect of Yikgeebohyul-tang aqueous extracts (YKBHT) on the propylthiouracil (PTU)-induced rat hypothyroidism. Methods The rats were divided into 6 groups : intact vehicle control, PTU control, LT4, YKBHT 500, 250 and 125 mg/kg treated groups. Hypothyroidism was induced by daily subcutaneous treatment of PTU 10 mg/kg for 28 days. YKBHT aqueous extracts were administered once a day as an oral dose of 500, 250 and 125 mg/kg for 42 days. The changes were observed : weight of body, thyroid gland, liver, testis, epididymis and prostate, serum thyroid hormone levels, serum male sex hormone levels, serum lipid profiles, liver and testis antioxidant system. These results were compared with LT4 0.5 mg/kg intraperitoneally treated rats. Results These PTU induced hypothyroidism and related hepatic and male reproductive organ damages were favorably and dose-dependently inhibited by treatment of YKBHT 500, 250 and 125 mg/kg, and YKBHT also effectively regulated the PTU-induced abnormal antioxidant defense factor changes in the both liver and testis. Although, LT4 also inhibited PTU-induced hypothyroidism and relative liver damages. But it deteriorated the hypothyroidism related testis, epididymis and prostate damages through testicular oxidative damages. Conclusions : The result of this study suggests that YKBHT has favorable effects on the hypothyroidism and related liver and reproductive organ damages with augmentation of antioxidant defense factor in the testis and liver. YKBHT 500, 250 and 125 mg/kg dose-dependently inhibited PTU-induced hypothyroidism and related liver and male reproductive organ damages in rats.

• 한국지반공학회논문집
• /
• 제37권7호
• /
• pp.35-42
• /
• 2021

본 연구에서는 다양한 카올리나이트 혼합비에 따른 카올리나이트-모래 혼합토의 특성을 실험적으로 분석하였다. 이를 위하여 기본물성실험과 다짐시험을 실시하고 그 결과를 분석하였으며, 카올리나이트와 모래입자 간의 상호 구조를 더욱 자세히 분석하기 위하여 현미경 사진을 이용한 관측을 추가적으로 수행하였다. 실험결과, 카올리나이트 혼합비가 증가할수록 비표면적의 증가에 따른 함수비의 증가 및 모래입자와의 강한 결합구조를 형성하는 것으로 나타났으며, 최대 건조밀도는 감소하고 초기간극비는 증가하는 것으로 나타났다. 현미경 사진 분석 결과, 세립분 함량의 증가에 따라 모래의 특성이 지배적인 비율, 중간 비율, 세립분의 특성이 지배적인 비율을 확인할 수 있었으며, 세립분의 함량이 25-40% 정도인 경우에 입자간 상호작용이 잘 이루어지는 것을 관측할 수 있었다.

• 한국산학기술학회논문지
• /
• 제19권11호
• /
• pp.513-520
• /
• 2018

본 논문은 포신의 길이 및 발사되는 탄약의 압력에 따른 포신 내부 및 배연기의 유동 특성에 대한 연구 내용이다. 탄약 설계 전 포신길이 및 탄약 압력에 따른 배연기의 유동 특성을 분석함으로서 탄약 운용 간 발생할 수 있는 Flareback 현상을 사전에 예방 할 수 있으며, 기존 탄약의 설계 요소인 속도, 정확도, 관통성능, 사거리 외에 운용성 향상을 위한 포신과 탄약의 호환성이 탄약 설계의 주요 요소임을 추가로 도출하였다. 유동 해석 수행 결과 포신 길이가 길고, 사격되는 탄약의 압력이 낮을수록 포신의 배연기 작동시간이 느려져 전투차량 내부로 추진제 가스가 들어올 확률이 높아짐을 확인하였다. 따라서, 본 연구를 통해 확인 된 포신 길이 및 탄약 압력에 의한 배연기 유동 특성 상관관계 해석 기법은 신규 탄약 설계 시 운용성 향상을 위한 주요 요소로 고려되어 탄약의 무게 결정과 추진제 압력 선택에 활용이 가능 할 것으로 판단된다.

• 한국산학기술학회논문지
• /
• 제20권4호
• /
• pp.1-8
• /
• 2019

우리나라는 고령화 사회로 급속하게 진입함에 따라 휠체어 사용 교통약자는 지속적으로 증가하고 있다. 그러나, 휠체어를 사용하는 교통약자가 고속버스를 이용하는 것은 거의 불가능하다. 따라서, 휠체어 사용자의 이동권 확보를 위한 고속버스의 개발이 필요하다. 이러한 휠체어 사용자를 위한 버스는 측면부에 휠체어 승객이 자유롭게 이동할 수 있는 전용 출입구, 휠체어 승객을 차실로 안전하게 이동시킬 수 있는 리프트 및 공간 활용성을 고려하여 휠체어 사용자가 탑승하지 않는 경우 일반 좌석으로 사용할 수 있는 가변 좌석의 개발이 필수적이다. 고속버스용 휠체어 전용 출입구의 개발은 기존 고속버스 차량에 대한 설계 변경, 개조 및 프레임 보강을 필요로 한다. 본 연구에서는 휠체어 사용자를 위한 승강구 시스템 개조부 설계와 유한 요소 모델을 이용한 구조 건전성을 평가하였다. 구조 해석을 통해 비틀림 강성 및 고유 모드 해석이 수행되었으며, 개조부 프레임에 대한 민감도 평가를 수행하고 개조부에 대한 최적화를 통해 경량화를 수행하였다. 휠체어 출입구 개조부에 대한 본 연구결과는 차량 개조 및 복지산업에 활용될 수 있을 것으로 기대된다.

• Advances in aircraft and spacecraft science
• /
• 제6권2호
• /
• pp.117-144
• /
• 2019

High Altitude and Long Endurance (HALE) aircraft are capable of providing intelligence, surveillance and reconnaissance (ISR) capabilities over vast geographic areas when equipped with advanced sensor packages. As their use becomes more widespread, the demand for additional range, endurance and payload capability will increase and designers are exploring non-conventional configurations to meet the increasing demands. One such configuration is the joined-wing concept. A joined-wing aircraft is one that typically connects a front and aft wings in a diamond shaped planform. One such example is the Boeing SensorCraft configuration. While the joined-wing configuration offers potential benefits regarding aerodynamic efficiency, structural weight, and sensing capabilities, structural design requires careful consideration of elastic buckling resulting from the aft wing supporting, in compression, part of the forward wing structural loading. It has been shown already that this is a nonlinear phenomenon, involving geometric nonlinearities and follower forces that tend to flatten the entire configuration, leading to structural overload due to the loss of the aft wing's ability to support the forward wing load. Severe gusts are likely to be the critical design condition, with flight control system interaction in the form of Gust Load Alleviation (GLA) playing a key role in minimizing the structural loads. The University of Victoria Center for Aerospace Research (UVic-CfAR) has built a 3-meter span scaled and flexible wing UAV based on the Boeing SensorCraft design. The goal is to validate the nonlinear structural behavior in flight. The main objective of this research work is to perform Ground Vibration Tests (GVT) to characterize the dynamic properties of the scaled flight vehicle. Results from the experimental tests are used to characterize the modal dynamics of the aircraft, and to validate the numerical models. The GVT results are an important step towards a safe flight test program.