• Proceedings of the KSR Conference
• /
• 2010.06a
• /
• pp.1918-1923
• /
• 2010

In electic railway, 25kV is applied to AC sections of overhead contact lines and pantographs of Korea Train eXpress(KTX) make contact at speeds of 300km/h. Thus, there is a need to utilize wireless, optic, contact-less sensors to implement condition monitoring systems. This paper is based on describing and analyzing the condition monitoring system implementation technologies for efficient catenary current ratio characteristic assessment. The conclusion of this paper should be widely applied to design, diagnosis, completion of construction, current collection status, fault diagnosis, and selection of contact wires and suspension wires.

• Proceedings of the KIEE Conference
• /
• 1990.07a
• /
• pp.261-264
• /
• 1990

The specific contact resistance(SCR) of metal-semiconductor interface is an important design parameter for VLSI interconnecting technology. As the critical feature size of the integrated structures decrease, the physical size of ohmic contacts will also decrease and the series contact resistance will increase. Al-Si contacts on the annealing condition are studied. The propreties of the contacts depend considerably on the annealing procedures. Barrier height is measured from Capacitance-Voltage characteristics. The specific contact resistance are analyzed using a modified four point method.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.11a
• /
• pp.13-18
• /
• 2001

In this paper, FFT(Fast Fourier Transform) analysis of friction was suggested as a method to interpret the contact conditions. Micro-grooves with various dimensions were fabricated on the silicon surface to investigate the frictional behavior with respect to the change in geometrical contact condition. Frictional forces between micro-grooved surfaces and spheres modeled as surface asperities were measured using a micro-tribotester which was built inside a SEM(Scanning Electron Microscope). The experimental results show that the relative dimensions and distributions of contact asperities between two surfaces can be predicted by the power spectrum and the main frequency in FFT-based analysis of friction coefficient. Also, it was shown that the friction coefficient for multi-asperities was the result of the superposition of that for each asperity.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.450-455
• /
• 2004

There is few research about contact problem for a rigid surface with an arbitrary shape in SPH. The variational equation based on the virtual work principle is derived and its solution is obtained by the penalty method. It is proposed a new method that can determine the parameters for a penetration and a penetration rate used in the penalty method. The reproducing condition is adopted to correct the deficiency of kernel on the boundary. In order to calculate a penetration of particles, after checking boundary particles for deformable body boundary normal vectors were determined on the rigid surface. Numerical simulations for models which have rigid surface with an arbitrary shape were conducted to validate the proposed method in 2D. The results of those analysis represent that the contact algorithm proposed in this study works properly.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.1 s.232
• /
• pp.30-37
• /
• 2005

There is few research about contact problem for a rigid surface with an arbitrary shape in SPH. The variational equation based on the virtual work principle is derived and its solution is obtained by the penalty method. It is proposed a new method that can determine the parameters for a penetration and a penetration rate used in the penalty method. The reproducing condition is adopted to correct the deficiency of kernel on the boundary. In order to calculate a penetration of particles, after checking boundary particles for deformable body, boundary normal vectors were determined on the rigid surface. Numerical simulations for models which have rigid surface with an arbitrary shape were conducted to validate the proposed method in 2D Cartesian and cylindrical coordinate. The results of those analysis represent that the contact algorithm proposed in this study works properly.

• Tribology and Lubricants
• /
• v.25 no.4
• /
• pp.231-235
• /
• 2009

In this study, the influence of contact pressure on the variation in coefficients of friction between porcine knee joint cartilage and Co-Cr alloy in a repeat pass sliding motion was investigated. Flat-ended cartilage pin specimens(9 mm diameter, 8 mm long) were prepared from porcine(6 months old) knee joints by a drill-type punch. Friction tests were conducted by using a pin-on-disk type friction tester for an hour in PBS lubricated condition under the contact pressures of 0.5, 1 and 2 MPa with 50 mm distance per a cycle at ambient condition. As a result, coefficients of friction increased as the test duration increased for all contact pressures. The maximum coefficients of friction were 0.082, 0.06 and 0.098 for 0.5, 1, and 2 MPa, respectively. It showed that coefficients of friction of porcine knee joint cartilage against Co-Cr alloy depended on the level of contact pressure and related to squeeze film lubrication mechanism.

• Journal of Korean Ophthalmic Optics Society
• /
• v.10 no.4
• /
• pp.313-321
• /
• 2005

To know the pollution level concerning the microbes contamination condition in soft contact lenses, 2 experiments were operated with different methods. Firs experiment, we observed lenses surfaces through a scanning electronic microscope after pollution sort contact lenses with the suspensions of Staphylococcus aureus, Pseudomonas aeruginosa and Entrobacter aerogenes which can be major bacteria causing keratitis as wearing on soft contact lenses. As 1 hour after pollution with the soft contact lenses, we observed that many bacteria adhered to the lenses, and the pollution condition got worse with passing time increase(2, 4, 6, 12, and 24 hours, respectively). At 12 hours lapse of polluting soft contact lenses with P. aeruginosa, some bacteria adhered to the lenses. And as 24 hours lapsed after pollution soft lenses with E. aerogenes, bacteria adhered to them, and atypical substance was observed some of the surface of lenses. Second experiment, we observed the microbe pollution condition in soft contact lenses by let 21 people in twenties(men & women), who doesn't eye disorders, wear soft contact lenses during 4 hours. As the result, many kinds of bacterium and fungus were observed, and especially, the bacteria could be identified with their colors and the shapes of colony, so we found that single type, two types, and three types of bacteria adhered to their lenses.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.7 s.94
• /
• pp.1658-1667
• /
• 1993

In this research, a numerical algorithm has been developed, which can be applied to the large deformation and large displacement contact problems between two deformable bodies. The contact conditions expressed in terms of the rate of angle change have been proposed considering the change in geometric shape and rate of contact force. A set of linear simultaneous equations is constructed by adding the geometric shape change and contact conditions to the original stiffness matrix. A new method to determine time increment has been proposed based on Euler method, in which the condition to prevent the contact bodies from penetrating and overrunning each other has been taken into consideration. Practical application to contact problem is extrusion in which bodies are sliding along the contact boundary.

• The Journal of Engineering Geology
• /
• v.8 no.3
• /
• pp.215-224
• /
• 1998

In this study, total strain was measured by LVDTs and local strains on the surface of specimens were measured by strain gauges. And axi-symmetrically elastoplastic FEM analyses was carried out for cylindrical specimens. Considering the influence of the restraint induced by the loading platen, in the case of H/D=1, the strain distribution on the side of a specimen is obviously affected by the condition of platen contact. Furthermore, it is clear that the larger H/D ratio becomes, the smaller the influence to the strain distribution is. For the smooth contact condition, the strain on the side is not influenced by the stiffness of the specimen, the shape and the scale effect, the strain distribution coincides with the nominal total strain. Whereas, in the case of rough contact condition, the strain distribution is remarkably affected. It is made clear that strain responses of hard rock specimens may more sensitive than these of soft rock specimens as a results of interaction between loading platens and specimen and the uniaxial strength of specimens may strongly depends on this interaction and stress-strain relation is affected by the contact condition.

• Journal of the Korean Society of Safety
• /
• v.32 no.1
• /
• pp.15-20
• /
• 2017

A large amount of research has been performed on the rolling contact fatigue(RCF) life of bearings, since it directly affects the safety and reliability of mechanical systems. It is well known that rolling contact fatigue life is influenced by several parameters including contact pressure, oil contamination by water or metal particles, and the surface conditions of bearings. However, the detailed damage mechanisms involved in rolling contact fatigue have not been clearly identified yet. In this paper the effects of water contamination of the lubricant and surface roughness of bearing steel on the rolling contact fatigue life were investigated. Two types of specimens with different surface roughness values were prepared through turning and lapping operations. They were tested under two different lubrication conditions, i.e. oil lubricant with 100% of oil and the water contaminated condition with 80% of oil and 20% of water using the rolling contact fatigue testing machine. The surface damage induced by the rolling contact fatigue was observed by using atomic force microscope(AFM). Experimental results show that the rolling contact fatigue life, $L_{10}$ was reduced by 24 to 33% depending on the lubrication condition. The reduction of fatigue life in the range of 53 to 57% was also observed at different surface roughness conditions.