• Tribology and Lubricants
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• v.11 no.5
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• pp.40-46
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• 1995

This study concerns the design and development of the non-vibrating capacitance probe which could be used as a non-contact sensor for tribological wear. This device detects surface charge through temporal variation in the work function of a material. Experiments are performed to demonstrate the operation of the probe on a roating aluminum shaft. The reference electrode of the probe, made of lead, is placed adjacent (< 1.25-mm distance) to the shaft. Both surfaces which are electrically connected, form a capacitor. An artificial spatial variation in the work function is imposed on the shaft surface by coating a segment along the shaft circumference with a colloidal silver paint. As the shaft rotates, the reference electode senses changing contact potential difference with the shaft surface, owing to compositional variation. Temporal variation in the contact potential difference induces a current through the electrical connection. This current is amplified and converted to a voltage signal by an electoronic circuit with an operational amplifier. The magnitude of the signal decreases asymptotically with the electrode-shaft distance and increases linearly with the rotational frequency. These results are consistent with the theoretical model. Potential applications of the probe on wear monitoring are proposed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.2
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• pp.137-143
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• 1999

The study of the high speed machining of inclined plane using ball end mill is performed. The use of ball end mill is rapidly growing in die and mold manufacturing. The cutting characteristics, such as cuttin g force, surface roughness and surface profile, are varied according to the variation of cutting directions. Free surface is cut using ball end mill, the surface profile is greatly varied depending upon the cutting direction. So this study will deal with the characteristics of cutting such as cutting efficiency according to the inclined plane of the workpiece, the cutting force according to tool path, surface profile and the roughness of surface. The optimal cutting direction to be applied the cutting for 3-D sculptured surfaces can be show through the results of this study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.3
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• pp.250-257
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• 2008

We calculate the variation of the surface stresses according to uniaxial and biaxial strains in face-centered cubic (FCC) metals. In our study, three mainly observed free surfaces of seven representative FCC metals are considered. Employed method is molecular mechanics, in which the interaction of atoms is described by empirical interatomic potentials. As uniaxial strain increases to tensile direction, the surface stresses on {100} and {110} free surfaces decrease monotonously, while those on {111} surface increase. These tendencies are the same regardless of the species of metals and interatomic potentials employed. However, when the system is under biaxial strain, surface stresses change different according to the surface directions, the species of metals, and even interatomic potentials. On {100} and {111} surfaces, heavy metals (Pt, Au) show the opposite variation to light metals (Ni, Cu). In the cases of Pd and Ag, the surface stresses reveal the opposite tendency, depending on interatomic potentials used.

• Journal of the Korean GEO-environmental Society
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• v.20 no.4
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• pp.11-16
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• 2019

The low temperature and temperature difference (variation) may cause to deteriorate the integrity of tunnel constructed in cold region. An insulation material was developed and applied to the tunnel lining surface to keep the temperature of tunnel lining constant in spite of temperature variation at outdoor. The lining surface where the insulation material applied showed the less sensitive to temperature variation than non-applied lining surface.

• Journal of the Korean Society of Safety
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• v.28 no.2
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• pp.14-20
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• 2013

All most of floors can become less slip resistant with wear. The deterioration of slip resistance can often occur rapidly. So relatively new products can become hazardous within a short period of time. The main objective of this study was the comparison of slip resistance variations caused by traffic wear and accelerative wear. The second objective was to ascertain the effect of wear, and to find out the causes of slip resistance change. Although statistical differences were observed between results of traffic wear and accelerative wear, the trend of the variations of slip resistance caused by traffic wear and accelerative wear was very similar. The measured slip resistance of tested floor changed up to 29%(and 26.5%) after 100,000 steps(and 750 cycles). As the traffic wear and accelerative wear were progressed, the surface roughness of the tested floor became smoother, and so the floor became more slippery under the wet condition. The abraded(worn out) floor surface tended to become hydrophilic surface, while the new floor surface tended to show hydrophobic nature. This phenomenon would change the wettability of floor surface, and the wettability would affect the variation of slip resistance.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.11a
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• pp.36-39
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• 2000

A small electrical potential difference which appears on any solid body when subjected to illumination by a modulated light beam generated by laser is called photocharge voltage(PCV)[1,2]. This voltage is proportional to the induced change in the surface electrical charge and is capacitatively measured on various materials such as conductors, semiconductors, ceramics, dielectrics and biological objects. The amplitude of the detected signal depends on the type of material under investigation, and on the surface properties of the sample. In photocharge voltage spectroscopy measurements[3], the sample is illuminated by both a steady state monochromatic bias light and the pulsed laser. The monochromatic light is used to created a variation in the steady state population of trap levels in the surface and space charge region of semiconductor samples which does result in a change in the measured voltage. Using this technique the spatial variation of PCV can be utilized to evalulate the surface conditions of the sample and the variation of the PCV due to the monochromatic bias light are utilized to charactrize the surface states. A qualitative analysis of the proposed measuremen is present along with experimental results performed on amorphous silicon samples. The deposition temperature was varied in order to obtain samples with different structural, optical and electronic properties and measurements are related to the defect density in amorphous thin film.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.36-39
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• 2000

A small electrical potential difference which appears on any solid body when subjected to illumination by a modulated light beam generated by laser is called photocharge voltage(PCV)[1,2]. This voltage is proportional to the induced change in the surface electrical charge and is capacitatively measured on various materials such as conductors, semiconductors, ceramics, dielectrics and biological objects. The amplitude of the detected signal depends on the type of material under investigation, and on the surface properties of the sample. In photocharge voltage spectroscopy measurements[3], the sample is illuminated by both a steady state monochromatic bias light and the pulsed laser. The monochromatic light is used to created a variation in the steady state population of trap levels in the surface and space charge region of semiconductor samples which does result in a change in the measured voltage. Using this technique the spatial variation of PCV can be utilized to evaluate the surface conditions of the sample and the variation of the PCV due to the monochromatic bias light are utilized to characterize the surface states. A qualitative analysis of the proposed measurement is present along with experimental results performed on amorphous silicon samples. The deposition temperature was varied in order to obtain samples with different structural, optical and electronic properties and measurements are related to the defect density in amorphous thin film.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.3
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• pp.503-510
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• 2010

The quick variation of the canister wall temperature causes the modification of the shape of canister wall. This paper is the possibility of adoption and the error analysis about the transient heat flux method. The commercial code(Fluent Ver6.2.16) was employed for the calculation of surface temperature in the case of steady and unsteady heat flux condition. Based the surface temperature variation and surface material property, transient heat flux method can calculate the surface heat flux. In the case of steady heat flux condition, the error is about 2%, and in the case of unsteady heat flux condition, the error is about 3.6%. With the unsteady heat flux condition, the time which reach the maximum surface heat flux is almost same between the numerical analysis and transient heat flux method.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.36-41
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• 2001

In this work, the changes in the friction force(lateral force) with respect to nanoscale geometric variation were investigated using an Atomic Force Microscope and a Lateral Force Microscope. It could be concluded that the changes in the friction force correspond well to the slope change rather than the surface slope itself, and that the influence of slope change on the frictional behavior is dependent on the magnitude of the slope and the torsional stiffness of the cantilever. Also, the nominal friction force is found to be more significantly affected by the material and the physical-chemical state of the surface rather than by nanoscale geometric steps. However, the change in nanoscale geometric details of the surface cause instantaneous change and slight variation in the friction signal.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.935-944
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• 1987

The surface rolling, one of the plastic working processes, provides good surface roughness with the reduction of diameter and the increase of surface hardness. In this study three Nachi 6000ZZ bearing were used for surface rolling on ductile cast iron. The results obtained are as follows; (1) The good surface roughness can be obtained with roller surface radius of curvature of 24mm after the 2nd rolling. (2) The surface roughness of ductile cast iron was 0.48.mu.mRmax by the contact pressure of 140kgf/mm$^{2}$ and surface hardness was Hv 395 with roller surface radius of curvature of 24mm after the 2nd rolling. (3) The reduction of specimen diameter of ductile cast iron were -12.8.mu.m due to rolling. (4) Within the diameter variation of -11.mu.m, surface roughness and surface hardness were increased, but at the range of exceeding -14.mu.m of the diameter variation the surface roughness became worse and the surface roughness became worse and the surface hardness was increased. (5) Dynamic contact area was about 25% to 30% of static contact area. The calculated contact pressure showed a good agreement with the experimental contact pressure.