• Tribology and Lubricants
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• v.24 no.6
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• pp.285-290
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• 2008

The purpose of this paper is to present the case study of tribological failure analysis on the gear damages, oil leakage, and sealant sealing in a manual transmission of front engine and front wheel drive vehicle. The manual transmission is to change the speed range and direction of the engines depending on the driving conditions by friction driving forces with input and output gear system. The material property and surface roughness of the gears are strongly related to the gear noise and micro-vibration, oil leakage and wear, which may decrease the real contact area of the gear and the strength of the oil film thickness between the driving gear and driven one. The O-ring damage of speedometer driven gear and bad sealant sealing of oil pan may produce oil leakage through the contact surfaces, which cause the oil shortage and seizure on the sliding surfaces of the transaxle gears. In the failure case study, the proper repair working and good lubrication are very important for the long life of the transaxle without any tribological failures and oil leakage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.11
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• pp.1099-1108
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• 2017

Data points obtained by conducting repetitive experiments under identical environmental conditions are, theoretically, required to correspond. However, experimental data often display variations due to generated errors or noise resulting from various factors and inherent uncertainties. In this study, an algorithm aiming to determine valid bounds of input variables, representing uncertainties, was developed using probabilistic and statistical methods. Furthermore, a reliability assessment was performed to verify and validate applications of this algorithm using bolt-fastening friction coefficient data in a sample application.

• International Journal of Automotive Technology
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• v.3 no.2
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• pp.63-70
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• 2002

Future on-board vehicle control systems can be further improved through new types of mechatronic systems. In particular, these systems' capacities for interaction enhance safety, comfort and economic viability. The Automotive Engineering Department (fzd) of darmstadt University of Technology is engaged in research of the mechatronic vehicle corner, which consists of three subsystems: sensor tire, electrically actuated wheel brake and smart suspension. By intercommunication of these three systems, the brake controller receives direct, fast and permanent information about dynamic events in the tire contact area provided by the tire sensor as valuable control input. This allows to control operation conditions of each wheel brake. The information provided by the tire sensor for example help to distinguish between staightline driving and cornering as well as to determine $\mu$-split conditions. In conjunction with current information of dynamic wheel loads, tire pressures and friction tyre/road, the ideal brake force distribution can be achieved. Alike through integration of adaptive suspension bushings, elastokinematic behaviour and wheel positions can be adapted to manoeuver-oriented requirements.

• 전기의세계
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• v.23 no.5
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• pp.54-60
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• 1974

Proposals were mode on how to differentiate radiation effects in morphological phases of polyethylene and discussions were developed with the results obtained on a low density polyethylene, SOCAREX, specified by number average molecular weight; overbar Mn=5,400, density; 0.92, and degree of branch; 3.4/100 carbon atom, which was irradiated to Co$^{60}$ .gamma. ray at the dose rate of 0.5 Mrad/hr in ambient temperature under the pressure of 10$^{-5}$ Torr. or 1 atm. respectively. The effect to crystalline phase in possibly deduced from dose dependent variation of relative area between (110) and (200) peaks on X ray diffraction spectrum and that, the effects to amorphous phase can be understood through dose dependent relaxation behaviours of .betha. peak on internal friction characteristics of the specimen. The results obtained thus far indicate that, in crystalline phase, relative crystallinity shows a rather rapid decrease up to 20 Mrad with increasing dose, however, little change of crystallinity can be observed in the region between 20-200 Mrad, and degradation appears to be more predominant than crosslinking up to 60 Mrad. While in amorphous phase the indication also shows that degradation is only predominant up to 20 Mrad. Furthermore several correlations can be seen with amenable explanation between dose dependent behaviours observed in both phases.

• Geomechanics and Engineering
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• v.1 no.3
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• pp.205-218
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• 2009

The bearing capacity factor $N_{\gamma}$ is computed for a rough conical footing placed over horizontal ground surface. The axisymmetric lower bound limit analysis formulation, in combination with finite elements and linear programming, proposed recently by the authors is used in this study. The variation of $N_{\gamma}$ with cone apex angle (${\beta}$), in a range of $30^{\circ}-180^{\circ}$, is obtained for different values of ${\phi}$; where ${\phi}$ is soil friction angle. For ${\phi}<30^{\circ}$, the magnitude of $N_{\gamma}$ is found to decrease continuously with an increase in ${\beta}$ from $30^{\circ}$ to $180^{\circ}$. On the other hand, for ${\phi}>30^{\circ}$, the minimum magnitude of $N_{\gamma}$ is found to occur generally between ${\beta}=120^{\circ}$ and ${\beta}=150^{\circ}$. In all the cases, it is noticed that the magnitude of $N_{\gamma}$ becomes maximum for ${\beta}=30^{\circ}$. For a given diameter of the cone, the area of the plastic zone reduces generally with an increase in ${\beta}$. The obtained values of $N_{\gamma}$ are found to compare quite well with those available in literature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.2
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• pp.113-120
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• 2008

Potential application of the scroll type machine to air compressor for fuel cell has been studied. Among the seven configuration factors which determine scroll wrap profile, the wrap thickness and the orbiting radius were chosen as two independent variables to generate various scroll wrap profiles. A conceptual design practice was conducted for scroll air compressor for SOFC with power output of 2 kW. With larger wrap thickness and orbiting radius, base plate area of the orbiting scroll becomes smaller, so is the axial gas force acting on the base plate, resulting in reduced thrust loss in spite of larger friction velocity. Performance analysis on the designed model showed that its total efficiency was 64.4% with the mass flow rate per unit compressor input of 0.00905 kg/(s kW) for the wrap thickness of 3.5 mm and the orbiting radius of 3.0 mm.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.1
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• pp.54-64
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• 1996

It seems that blowing air bubble out of the bulb surface of a ship of flat bottom will reduce the frictional resistance, since wetted area of the hull surface is reduced owing to air bubble staying close to the surface. To as certain this concept, at first, the limiting streamlines around the bow was observed, and local distribution of pressure and shear stress, due to the change of air-blowing position, air supply pressure, and the model speed, was investigated. It was found that the local friction was reduced near the bulb and air-bubble formations also play an important role as a drag component. This paper can be considered as a preliminary study on the drag reduction of conventional ships by the micro-bubble injection.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.427-434
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• 2002

In Korea, there are recently many attempts to expand a temporary soil nailing system into a permanent soil nailing system since the first construction in 1993. In the downtown area, it is important that the relaxation of the ground is minimized in the ground excavation works. Due to these problems, soil nailing systems are often used the flexible facing such as shotcrete rather than the rigid facing such as SCW, CIP, and jet grout types in Korea. The soil nailing systems with rigid facings are used greatly however it is insufficient researches for design and analysis of soil nailing systems with rigid facings. In this study, various laboratory model tests are carried out to examining the influence the rigidity of facings on the global safety of soil nailing system, failure loads, displacement behaviour, axial force acting on the nails, and distribution of earth pressure. Also, the parametric studies are carried out for the typical section of soil nailed walls according to thickness of concrete facings and internal friction angle of soil using the numerical technique as shear strength reduction technique.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1294-1300
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• 2009

Recently, excavations in highly congest urban area have been increased. For the excavations conducted in extremely narrow spaces, we have been developing a novel soil reinforcement system of temporary retaining walls by using deep cement mixing method. The developing method installs largerdiameter ($\Phi$=300~500mm) and shorter reinforcement blocks than previous reinforcement system for mobilizing friction with soils, therefore it has advantages of not only shortening the length of reinforcement system but also reducing the amount of reinforcement. In this study, we performed a numerical analysis of the new reinforcement system by using a commercial finite element program, and evaluated the behavior of the reinforced retaining wall system under various conditions of the length, the diameter, the spacing, and the angle of the reinforcement system.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.192-197
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• 2002

In this study, examined the cutting characteristics of alumuminum alloy AC8A-T6 that is used to present car piston materials. And in been holding materials machining empirically escape as result that experiment comparison changing the cutting speed and feed on various condition to choose efficient machining condition. The following results can be summarized from this research. 1. As the cutting speed decreased, principal cutting force and thrust cutting force is increased, and reason that cutting force interacts greatly in the low cutting speed is thought by result by BUE's stabilization. 2. The feed speed and cutting speed increase, friction factor is decrescent and the cause appeared the thrust cutting force is fallen than cutting force relatively because chip flow according to increase of the feed rate is constraint. 3. Though specific cutting resistance grows cutting area and the feed rate are few, the cause was expose that shear angle decreases by rake face of tool gets into negative angle remarkably as wear of a cutting tool or defect part of workpiece is cut. 4. Cutting speed do greatly depth of cut is slow, surface roughness examined closely through an experiment that becomes bad, and know that it can get good surface that process cutting speed because do feed rate by 0.1mm/rev low more than 250m/min to get good surface roughness can.