• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.3
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• pp.39-46
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• 2011

The automotive air conditioning hose is used for connecting the components of air conditioner in a vehicle. The hose is usually manufactured by the swaging process to connect the rubber hose with the metal fitting at the end of the hose. In case that the clamping force is small, the refrigerant gas in the hose can leak locally under the severe operating circumstances. The practical test of clamping force is performed by means of the measurement of separation force. In this study, the swaging process of a hose is simulated with the finite element method, to investigate the effect of friction coefficient on the clamping force. The contact condition is used in consideration of real manufacturing process, and the material properties for the Mooney-Rivlin model is obtained by the experimental results. The result interpretations are focused on the contact forces, which is displayed graphically with respect to friction coefficient, on the surfaces between the hose and the metal fittings.

• Carbon letters
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• v.12 no.4
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• pp.249-251
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• 2011

Carbon/epoxy woven composites are prominent wear-resistant materials due to the strength, stiffness, and thermal conductivity of carbon fabric. In this study, the effect of oilabsorption on the wear behaviors of carbon/epoxy woven composites was investigated. Wear tests were performed on dry and fully oil-absorbed carbon/epoxy woven composites. The worn surfaces of the test specimens were examined via scanning electron microscopy to investigate the wear mechanisms of oil-absorbed carbon/epoxy woven composites. It was found that the oil absorption rate was 0.14% when the carbon/epoxy woven composites were fully saturated. In addition, the wear properties of the carbon/epoxy woven composites were found to be affected by oilabsorption. Specifically, the friction coefficients of dry and oil-absorbed carbon/epoxy woven composites were 0.25-0.30 and 0.55-0.6, respectively. The wear loss of the oilabsorbed carbon/epoxy woven composites was $3.52{\times}10^{-2}\;cm^3$, while that of the dry carbon/epoxy woven composites was $3.52{\times}10^{-2}\;cm^3$. SEM results revealed that the higher friction coefficient and wear loss of the oil-absorbed carbon/epoxy woven composites can be attributed to the existence of broken and randomly dispersed fibers due to the weak adhesion forces between the carbon fibers and the epoxy matrix.

• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.225-231
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• 2001

A mathematical model for the analysis of roll gap phenomena in the strip temper rolling process is described. A new approach to solve the roll indentation and diverging problem in modeling of severe temper rolling cases is obtained by adopting the preliminary displacement principle of two contacted rough bodies to describe the friction behavior in the roll gap. The mechanical peculiarities of the temper rolling process, such as a high friction value with high roughness rolls and a non-circular contact arc, low reduction and non-negligible entry and exit elastic zones as well as central preliminary displacement zone etc., are all taken into account. The deformation of work rolls is calculated with the influence function method and an arbitrary contact are shape is permitted. The strip deformation is modeled by the slab method and the entry and exit elastic deformation zones are included. The preliminary displacement principle is used to determine the boundaries and to calculate the friction of the central preliminary displacement zone. The model is calibrated against the production mill data and installed in the setup computer of a temper rolling mill in POSCO. The validity and precision of the model have been proven through a comparison of the measured roll forces and the predicted ones.

• Journal of The Korean Astronomical Society
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• v.40 no.4
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• pp.179-182
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• 2007

Dynamical friction plays an important role in reducing angular momenta of objects in orbital motions. While astronomical objects usually follow curvilinear orbits, most previous studies focused on the linear-trajectory cases. Here, we present the gravitational wake due to, and dynamical friction on, a perturber moving on a circular orbit in a uniform gaseous medium using a semi-analytic method. The circular orbit causes the density wakes to bend along the orbit into asymmetric configurations, resulting in the drag forces in both opposite (azimuthal) and lateral (radial) directions to the perturber motion, although the latter does not contribute to the orbital decay much. For a subsonic perturber, the bending of a wake is only modest and the resulting drag force in the opposite direction is remarkably similar to the linear-trajectory counterpart. On the other hand, a supersonic perturber is able to overtake its own wake, possibly multiple times, creating a high-density trailing tail. Despite the dramatic changes in the wake morphologies, the azimuthal drag force is in surprisingly good agreement with the formulae of Ostriker for the linear-trajectory cases, provided $V_pt=2R_p,\;where\;V_p\;and\;R_p$ are the velocity and orbital radius of the perturber, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.5
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• pp.578-585
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• 2007

A vacuum circuit breaker (VCB) with permanent magnet actuator (PMA) has been studied in this study. Electromagnetic field analysis and dynamic simulations have been carried out for optimal design of VCB by using commercial software Maxwell and ADAMS. This simulation model can be an effective method for the VCB, which has non-linear output force of PMA, friction, and impact for operations. An experiment has been conducted to evaluate correctness of the simulated model. By using this evaluated model, the displacement and velocity characteristics of the VCB have been simulated with following conditions : (1) The different output forces of PMA have been applied, (2) The friction conditions in follow lever shaft and moving part have been changed, (3) The mass conditions of moving part have been changed. The simulated results shows that the velocity characteristics are mainly determined by the output force of PMA. The effects due to the changes of friction conditions against the dynamic characteristics was small, and the mass conditions of the moving parts affect the velocity and a bouncing phenomenon of VCB. From these results, the optimal design conditions for the VCB have been derived.

• Structural Engineering and Mechanics
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• v.76 no.6
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• pp.823-837
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• 2020

In this research, the idea of improving the seismic response of an existing steel structure with use of friction dampers between external walls and the structure is discussed. The main difference of this method with other methods of seismic rehabilitation is that interior spaces of the existing structure remain untouched and new parts including external walls and dampers are added outside of the structure. Three frames having 3, 6 and 9 stories are modeled in SAP2000 software before and after seismic retrofit and responses of the system are investigated under the effect of seven earthquake records. Initially, different ratios of seismic weight of stories are presumed for slip forces of the dampers with a distribution based on given equations. The optimized capacity of dampers is obtained by investigating the average of maximum displacement, acceleration and base shear of the structure caused by earthquakes. For this optimized values, maximum inter-story drifts and acceleration are obtained through numerical models. Results show that in 3, 6 and 9-story frames peak roof displacement decreased up to 80%. Maximum roof acceleration and base shear of the frames also decreased 46, 40 and 32% and 84, 67 and 65%, respectively for three building structures.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.1
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• pp.42-49
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• 2010

In general, the direct experimental approach to study machining processes is expensive and time consuming, especially when a wide range of parameters are included: tool, geometry, materials, cutting conditions, etc. The aim of this study is to verify the effectiveness of finite element method for orthogonal cutting process by comparing the simulated cutting forces with measured results. Two commercialized finite element codes $AdvantEdge^{TM}$ and Deform-$2D^{TM}$ have been used to simulate the cutting forces in orthogonal cutting process. In this paper, estimated cutting and feed force components are compared with experimental results for different two materials. As a result, it has been found that FEM simulation is effective for understanding and predicting the orthogonal cutting process although some improvements on friction model and remeshing process are needed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.768-773
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• 2004

Developed in this paper a mass-spring engine to represent and manipulate deformable objects. The deformable object model is a basic technology in the ‘Tangible Space Initiative’. The mass-spring model consists of structural, shear and bending springs. Various forces like external, friction, gravity, spring, and damping forces are considered and collision with planes and spheres are treated. When a sphere collide mass-spring model, mass-spring engine calculates external force to interface mass-spring model. A prototype system is implemented in C on an MS windows machine.

• Tribology and Lubricants
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• v.21 no.6
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• pp.263-267
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• 2005

The tribological performance of multi-walled carbon nanotubes (MWNT) in mineral oils is investigated at ambient temperature. The frictional forces, wear amounts and cycles to scuffing of the oils with nanotubes and without those were measured using the ball-on-disk tester. It was found that there were little differences in the frictional forces and wear amounts of two oils. However, the scuffing times of oils with nanotubes were much longer than those of oils without nanotubes in sliding tests. The nanotubes were very effective on maintaining the oil gap and protecting the surfaces in boundary lubricated sliding.

• The Journal of Korea Robotics Society
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• v.2 no.4
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• pp.289-296
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• 2007

The docking and recharging system for a mobile robot must guarantee the ability of the mobile robot to perform its tasks continuously without human intervention. In this paper, two docking mechanisms are proposed with localization error-compensation capability for the auto recharging system. Friction forces or magnetic forces are used between the docking parts of the docking module and those of the docking station. In addition, an auto recharging system is developed to control the power. Since the system is modularized, it can easily be adapted to other robots.