• Restorative Dentistry and Endodontics
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• 제44권1호
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• pp.1.1-1.12
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• 2019

Objectives: The aim of this in vitro study was to test the effect of 2 finishing-polishing sequences (QB, combining a 12/15-fluted finishing bur and an EVO-Light polisher; QWB, adding a 30-fluted polishing bur after the 12/15-fluted finishing bur used in the QB sequence) on 5 nanotech-based resin composites (Filtek Z500, Ceram X Mono, Ceram X Duo, Tetric Evoceram, and Tetric Evoceram Bulk Fill) by comparing their final surface roughness and hardness values to those of a Mylar strip control group (MS). Materials and Methods: Twelve specimens of each nanocomposite were prepared in Teflon moulds. The surface of each resin composite was finished with QB (5 samples), QWB (5 samples), or MS (2 samples), and then evaluated (60 samples). Roughness was analysed with an optical profilometer, microhardness was tested with a Vickers indenter, and the surfaces were examined by optical and scanning electron microscopy. Data were analysed using the Kruskal-Wallis test (p < 0.05) followed by the Dunn test. Results: For the hardness and roughness of nanocomposite resin, the QWB sequence was significantly more effective than QB (p < 0.05). The Filtek Z500 showed significantly harder surfaces regardless of the finishing-polishing sequence (p < 0.05). Conclusions: QWB yielded the best values of surface roughness and hardness. The hardness and roughness of the 5 nanocomposites presented less significant differences when QWB was used.

• 대한기계학회논문집
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• 제12권5호
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• pp.1071-1082
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• 1988

본 연구에서는 시편의 재료를 회주철(Grey Cast Iron:GC 30)을 선정하였으며 보올의 지름이 각각 다른 5종류의 강철 보올(steel ball)을 사용하였다.

• Tribology and Lubricants
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• 제16권4호
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• pp.253-258
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• 2000

Frictional behavior of wire electric discharge machined surfaces of spheroidized annealed STDll steel was investigated. The surfaces were produced with a various series of finish cuts where pulse energy was reduced with increase in the number of finish cuts. Roughness and micro-hardness of the surfaces were also measured. It is observed that the increase in the number of finish cuts produces the surface exhibiting lower frictional resistance followed by higher resistance after considerable wear. Effects of finish cuts on the friction characteristics are discussed with the aid of roughness and micro-hardness of the surfaces.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.340-345
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• 2001

Surface hardness is one of the major sources on wear in the oil hydraulic axial piston pump. To increase the performance of the oil hydraulic axial piston pump, it is need to know the surface layer characteristics in the sliding contact parts of them. This paper reports an experimental study on surface treatment characteristics in the piston of the oil hydraulic axial piston pump. We investigated surface wear with not only surface hardness and surface roughness but also material of the piston. We obviously observed that the surface hardness of piston in the oil hydraulic axial piston pump plays an important role to high power density and remain long life.

• Design & Manufacturing
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• 제16권3호
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• pp.39-43
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• 2022

In this study, we designed an vibration cutting tool that can achieve improvements such as low cutting force, interrupted chip evacuation and better surface quality of cutting performance to obtain high-quality surface roughness and improvement of tool wear, which is an issue in the machining of high-hardness mold steel. Among the resonance frequency modes of the vibration cutting tool, the bending mode was used to maximize the driving amplitude of the vibration tool tip, and the resonance frequency was confirmed through the finite element method. After measuring the actual resonant frequency of the designed tool using an optical fiber sensor, the cutting force and machining surface of vibration cutting and conventional cutting were compared and analyzed in the turning process of high hardness mold steel (STAVAX). As a result of the experiment, the cutting force was reduced by about 20 % compared to the conventional cutting process, and the surface roughness was also improved by about 60 %. This study suggested that the tool wear and surface quality of high-hardness steel can be improved through the vibration cutting method in the machining of high hardness mold steel.

• 한국정밀공학회지
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• 제5권3호
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• pp.91-100
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• 1988

Surface rolling which is one of the plastic deformation have advantages to imporve surface roughness, hardness and fatigue strength with relatively simple processes. In this study, the effect of previous cutting process before rolling on the surface roughness in surface rolling for mild steel was investigated. The results obtained are as follows. (1) Waveness of the previous process has the effect on the precision of the works and coarse waveness resulted in less improvement of the surface roughness. (2) The reduction of diameter and increase of hardness can be obtained at the first rolling process.

• Restorative Dentistry and Endodontics
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• 제45권1호
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• pp.12.1-12.8
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• 2020

Objectives: The aim of this in vitro study was to evaluate the microhardness and surface roughness of composite resins before and after tooth bleaching procedures. Materials and Methods: Sixty specimens were prepared of each composite resin (Filtek Supreme XT and Opallis), and BisCover LV surface sealant was applied to half of the specimens. Thirty enamel samples were obtained from the buccal and lingual surfaces of human molars for use as the control group. The surface roughness and microhardness were measured before and after bleaching procedures with 35% hydrogen peroxide or 16% carbamide (n = 10). Data were analyzed using 1-way analysis of variance and the Fisher test (α = 0.05). Results: Neither hydrogen peroxide nor carbamide peroxide treatment significantly altered the hardness of the composite resins, regardless of surface sealant application; however, both treatments significantly decreased the hardness of the tooth samples (p < 0.05). The bleaching did not cause any change in surface roughness, with the exception of the unsealed Opallis composite resin and dental enamel, both of which displayed an increase in surface roughness after bleaching with carbamide peroxide (p < 0.05). Conclusions: The microhardness and surface roughness of enamel and Opallis composite resin were influenced by bleaching procedures.

• 한국표면공학회지
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• 제53권6호
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• pp.280-284
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• 2020

Electron beam irradiation is widely used as a type of surface modification technology to advance surface properties. In this study, the effect of electron beam irradiation on properties, such as surface hardness, wear resistance, roughness, and critical load of Titanium Aluminium nitride (TiAlN) films was investigated. TiAlN films were deposited on the SKD-61 substrate by using cathode arc ion plating. After deposition, the films were bombarded with intense electron beam for 10 minutes. The surface hardness was increased up to 4520 HV at electron irradiation energy of 1500 eV. In addition, surface root mean square (RMS) roughness of the films irradiated at 1500 eV shows the lowest roughness of 484 nm in this study.

• 한국재료학회지
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• 제16권8호
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• pp.461-465
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• 2006

Chromium (Cr) films were deposited on plain carbon steel sheets by DC and RF magnetron sputtering as well as by electroplating. Effects of DC or RF sputtering power on the deposition rate and properties such as, hardness, surface roughness and corrosion-resistance of the Cr films were investigated. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microcopy (SEM) analyses were performed to investigate the crystal structure, surface roughness, thickness of the Cr films. Salt fog tests were used to evaluate the corrosion resistance of the samples. The deposition rate, hardness, and surface roughness of the Cr film deposited by either DC or RF sputtering increase with the increase of sputtering power but the adhesion strength is nearly independent of the sputtering power. The deposition rate, hardness, and adhesion strength of the Cr film deposited by DC sputtering are higher than those of the Cr film deposited by RF sputtering, but RF sputtering offers smoother surface and higher corrosion-resistance. The sputter-deposited Cr film is harder and has a smoother surface than the electroplated one. The sputter-deposited Cr film also has higher corrosion-resistance than the electroplated one, which may be attributed to the smoother surface of the sputter-deposited film.

• 대한기계학회논문집
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• 제12권4호
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• pp.705-711
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• 1988

본 연구에서는 대구중공업(주)의 대형선반 베드면 재질과 동일한 회수철(KS D4301 GC30)시편을 선삭가공하고 볼베어링의 레이스를 이용한 구조로 설계된 볼형 표 면로울링기구를 사용하여 로울러 다듬질을 행함으로서 전가공에 따른 가압력이 표면조 도에 미치는 영향을 구명하는데 목적을 두었으며 아울러 로울링 회수에 따른 표면조도, 경도 및 직경의 변화량을 실험적으로 구명하였다.