• Journal of Technologic Dentistry
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• v.43 no.3
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• pp.93-98
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• 2021

Purpose: The aim of this study was to observe the surface roughness and surface topography of cobalt-chrome (Co-Cr) alloys with grinding time in dental barrel finishing. Methods: This study involved two types of Co-Cr alloys. Specimens were manufactured with the dimensions 10×10×2 mm. Each specimen was cast according to the manufacturer's instructions. The cast alloys were polished for 35 minutes at intervals of five minutes in an automatic barrel finishing. Specimens were imaged with a three-dimensional optical microscope to measure surface roughness. Results: BC specimens and GM specimens had the highest roughness (Ra) values in the ungrained control group, and the lowest Ra values were measured 20 minutes after grinding. Conclusion: The best conditions for grinding Co-Cr alloy using a dental barrel finishing were a weight ratio of polishing media, water, and compound of 150 g:200 g:5 g, and a rotation speed of 450 rpm. Grinding time to obtain appropriate surface roughness should be limited to 15 to 30 minutes.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.3
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• pp.131-137
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• 2017

In this study, we evaluated the surface roughness of mold and injected parts manufactured by polycarbonate (PC) injection molding. The mold surface was polished to produce six differentiated roughnesses with 12 areas using stones (#800, #1200), sandpapers (#800, #1200), and diamond compounds (#8000, #14000). Injected parts were created using 20mm/s injection speed, 80 bar holding pressure for 5 seconds, and $70^{\circ}C$ cooling water. Injected parts surface roughness (Sa) was measured randomly in 10 of 30 using an interferometer (NewView8000, zygo, USA). In the same way, mold surface was measured randomly 10 times on 12 polished areas. Surface roughness of molds and injected parts were compared, and a regression equation to predict mold surface roughness was proposed for specific injection molding parameters.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1768-1771
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• 2003

Hard turning replaces grinding for finishing process with expectations of higher productivity and demanded surface quality. Especially for the surface roughness as surface quality demanded in finishing process of hard turning, know-how of machining characteristics of hardened materials by cutting force analysis should be accumulated in company with achievement of precision of elements and high stiffness design technology in hard turning. Considering chip formation mechanism of hardened materials, adequate cutting conditions are selected for machining experiments and cutting forces are measured according to cutting conditions. Increase of cutting forces especially thrust force and increase of dynamic instability could occur in hard turning. Analysis of dynamic characteristics of the cutting forces is executed to investigate relation between dynamic instability and surface roughness in hard turning. Investigation on effects of relative motion of machining system generated by vibration due to dynamic instability shows that ultimate surface roughness could be predicted considering relative motion of machining system with geometrical surface roughness.

• International Journal of Oral Biology
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• v.39 no.4
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• pp.187-192
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• 2014

Nonthermal atmospheric pressure plasma has attracted great interest for biomedical applications. The plasma consists of charged particles, radicals, and a strong electric field as the fourth state of matter. This study evaluated the change in the surface roughness after tooth bleaching by plasma in combination with a low concentration (15%) of carbamide peroxide, specifically whether the application of plasma produced detriments, such as demineralization and structural change, with the goal of efficient and safe tooth bleaching. After being combined with plasma and 15% carbamide peroxide, the hydroxyapatite surface was significantly smoother with a low roughness average value. Tooth bleaching with 15% carbamide peroxide alone produced an irregular surface and increased the surface roughness with high roughness average value. Tooth bleaching with plasma resulted in no significant variations in hydroxyapatite in terms of change in surface roughness and surface topography. The application of tooth bleaching with plasma is not deleterious to dental hard tissue, implicating it as a safe tooth bleaching technique.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.6
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• pp.375-382
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• 2005

This paper presents the results of experimental investigation for the effect of heat conduction on the evaporation cooling of water droplet in the process of heat treatment. The experiments are mainly focused on the surface temperature, the surface roughness and the droplet diameter at aluminum. The range of surface temperature is from $80^{\circ}C$ to $140^{\circ}C$, surface roughness is from $R_a=0.18{\mu}m$ to $R_a=1.36{\mu}m$ and droplet diameter is from 2.4 mm to 3.0 mm. The results show that the total evaporation time is shorter for the larger surface roughness, the time averaged heat flux has maximum value for the larger surface roughness and exist the critical heat flux. The total evaporation time has a big influence on the evaporation region for the smaller droplet size, but the total evaporation time has not influence on the nuclear boiling region.

• Journal of Powder Materials
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• v.18 no.5
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• pp.406-410
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• 2011

Green strength is an important property of powders since high green strength guarantees easy and safe handling before sintering. The green strength of a powder compact is related to mainly mechanical and surface characters, governed by interlocking of the particles. In this study, the effect of powder surface roughness on the green strength of iron powders was investigated using a transverse rupture test. Three-dimensional laser profiler was employed for quantitative analyses of the surface roughness. Two different surface conditions, i.e. surface roughness, of powders were compared. The powders having rough surfaces show higher green strength than the round surface powders since higher roughness leads increasing interlocked area between the contacting powders.

• Journal of the Korean Society of Safety
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• v.10 no.3
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• pp.30-41
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• 1995

This paper proposed a simple method for measuring surface roughness of ground surface. Utilizing non-contact in-process measuring system using the diode laser. The measurement system is consisted of a laser unit with a diode laser and a cylindrical lens, a detecting unit with polygon mirror and CCD array sensor, and a signal processing unit with a computer and device. During operation, this measuring system can provide information on surface roughness in the measuring distance with a single sampling and simultaniously monitor the state of the grind wheel. The experimental results, showed that the Increase of the feed rate and the dressing speed an caused increase in the surface roughness and when the surface roughness is 4Rmax-10Rmax, the cutting speed is 1653m/min-1665m/min, the table speed is 0.2n1/min -0.9m/min, the dressing speed is 0.2mm/rev～0.4mm/rev, the stylus method and the in-process method can be obtained the same results. Thus, under limited working conditions, using the proposed system, the surface roughness of the ground surface during cylindrical grinding can be obtained through the in-process measurement method using the diode laser.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.2
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• pp.9-17
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• 2020

In this study, the surface changes of titanium alloy using laser surface treatment and the surface analysis using laser-induced plasma spectroscopy were carried out. The laser surface treatment induced changes in surface roughness and the diffusion of atmospheric elements. Excessive melting or less melting caused roughness changes, but when moderate levels of energy were applied, a smoother surface could be obtained than the initial surface. In the process, the diffusion of atmospheric elements took place. To analyze the diffusion of atmospheric elements with respect to surface morphology, the surfaces were re-shaped with grinding. In this experimental conditions, the effect of plasma formation by surface roughness was identified. Compensated plasma signals for the material properties were obtained and analysed by removing the background plasma signal.

• Korean Journal of Metals and Materials
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• v.46 no.8
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• pp.495-505
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• 2008

With the high proportion of zinc coated steels in body-in-white assembly, newly developed surface roughness textured galvannealed steel sheets have been introduced. In this study, zinc coated and surface roughness textured steel sheets were welded by resistance spot welding to investigate its weldability including electrode wear test. Based on the results of tensile-shear test, nugget diameter changes, and electrode tip growth test, it was clear that both surface roughness textured steels (GA-T and GA-E) showed good weldability. Also, there was no large difference in weldability and electrode wear behavior between GA-T and GA-E steels which have different surface roughness morphology. An analysis of electrode degradation showed Fe and Zn penetration through the electrode tip surface at 2400 welds reached $55{\sim}60{\mu}m$ and $75{\sim}80{\mu}m$, respectively. Therefore, there is no significant effect of surface roughness morphology on spot weldability of surface roughness textured galvannealed steel sheets. However, slight difference in thickness of alloying layers existing on electrode tip was found between GA-T and GA-E steels.

• Korean Journal of Geomatics
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• v.3 no.1
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• pp.43-51
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• 2003

This paper presents the benefits of using close-range digital photogrammetric techniques for measuring the roughness of rock surfaces, using digital stereo images obtained from a Rolleiflex 6006 metric camera. To precisely measure surface roughness, we researched on how to use the flat and curved reference surface obtained from geometrically corrected digital images of the rock surface by using the least squares method. To test the precision of the proposed technique, the surface roughness has been measured between the reference surface and sample areas of very smooth-surfaced rock. Then the results were compared with the measurements obtained from a laser sensor profilometer.