• 대한기계학회논문집A
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• 제25권6호
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• pp.930-937
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• 2001

The friction and wear behavior of short carbon fiber reinforced polyetheretherketone was studied experimentally under dry sliding conditions against SCM440(AISI 4140) disks with different surface roughness and hardness at the low sliding speeds and the high pressures on a pin-on-disk apparatus. Under the low disk surface roughness value the earsplitting noise and stick-slip were occurred. The increased adhesion friction and wear factor with stick-slip made the friction and wear behavior worse. Under the high disk surface hardness the break and falling-off of carbon fibers were accelerated. The carbon fibers fallen off from the matrix were ground into powder between two wear surfaces and this phenomenon caused abrasive friction and wear factor to increase. So the friction and wear behavior became worse. With the transfer film made of wear particles formed on a disk, the carbon powder film formed on a pin lowered a friction coefficient.

• 한국전기전자재료학회논문지
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• 제34권1호
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• pp.39-43
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• 2021

In the case of ZnO:Al thin films, it is the best material that can replace ITO that is mainly used as a transparent electrode in electronic devices such as solar cells and flat-panel displays. In this study, ZnO:Al films were fabricated by using the RF dual magnetron sputtering method at various substrate temperatures. As the substrate temperature increased, the crystallinity of the ZnO:Al thin films was improved, and the electrical conductivity and electrical properties of the thin film improved owing to the increase in grain size. In addition, the surface roughness of the ZnO:Al thin films increased due to changes in the surface and density of the thin films. Moreover, the substrate temperature increased the density of thin films and improved their transmittance. To be applied to solar cells and other several electronic devices in the future, the hardness and adhesion properties of the thin film improve as the substrate temperature increases.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1995년도 춘계공동학술대회논문집; 전남대학교; 28-29 Apr. 1995
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• pp.515-528
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• 1995

Slips and falls are the major causes of the pedestrian injuries in the industry and the general community throughout the world. With the awareness of these problems, the friction coefficients of the interface between floorings and footwear have been measured for the evaluation of slip resistant properties. During this measurement process, the surface texture has been shown to be substantially effective to the friction mechanism between shoe heels and floor surfaces under various types of walking environment. Roughness, either of the floor surface or shoe heels, provides the necessary drainage spaces. This roughness can be designed into the shoe heel but this is inadequate in some cases, especially a wear. Therefore, it is essential that the proper roughness for the floor surface coverings should be provided. The phenomena that observed at the interface between a sliding elastomer and a rigid contaminated floor surface are very diverse and combined mechanisms. Besides, the real surface geometry is quite complicate and the characteristics of both mating surfaces are continuously changing in the process of running-in so that a finite number of surface parameters can not provide a proper description of the complex and peculiar shoe - floor contact sliding mechanism. It is hypothesised that the interface topography changes are mainly occurred in the shoe heel surfaces, because the general property of the shoe is soft in the face of hardness compared with the floor materials This point can be idealized as sliding of a soft shoe heel over an array of wedge-shaped hard asperities of floor surface. Therefore, it is considered that a modelling for shoe - floor contact sliding mechanism is mainly depended upon the surface topography of the floor counterforce. With the model development, several surface parameters were measured and tested to choose the best describing surface parameters. As the result, the asperity peak density (APD) of the floor surface was developed as one of the best describing parameters to explain the ambiguous shoe - floor interface friction mechanism. It is concluded that the floor surface should be continuously monitored with the suitable surface parameters and kept the proper level of roughness to maintain the footwear slip resistance. This result can be applied to the initial stage of design for the floor coverings.

• 한국산업융합학회 논문집
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• 제4권3호
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• pp.237-242
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• 2001

Ti-6Al-4V alloy can be obtained the stability of organization and product treasure, the evaluation of the cutting ability and the mechanical characteristics after the heat treatment of annealing, solution and aging. The difficulty in machining titanium alloy is how treat the heat generated during the process. Because the heat conductivity of titanium alloy is regardfully low, the heat generated during grinding is accumulated in workpiece. and it causes the increasing of grinding wheel grits' wear and makes the ground surface rough. So, these characteristics in grinding of titanium alloy will change the mechanical properties of the titanium alloy. From this study. the mechanical characteristics of annealed one and solution and aging one treated Ti-6Al-4V alloy after grinding was concerned with checking out the bending strength and hardness. For the result, both of bending strength and hardness were increased at the burned area on the surface. Roughness value was remarkably high at the table speed of 10m/min.

• 한국기계가공학회지
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• 제2권1호
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• pp.32-38
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• 2003

Engineering ceramics have many unique characteristics both in mechanical and physical properties such as high temperature hardness, high thermal, chemical and electrical resistance. However, its machinability is very poor in conventional machining due to its high hardness and severe tool wear. In the current experimental study alumina($Al_2O_3$) was ultrasonically machined using SiC abrasives under various machining conditions to investigate the material removal rate and surface quality of the machined samples. Under the applied amplitude of 0.02mm, 27kHz frequency, three slurry ratios (abrasives water by weight) of 11, 13 and 15 with different tool shapes and applied pressure levels, the machining was conducted. Using the mesh number of 240 abrasive, slurry ratio of 11 and static pressure of $25kg/cm^2$, maximum material removal rate of $18.97mm^3/mm$ was achieved with mesh number of 600 SiC abrasives and static pressure of $30kg/cm^2$, best surface roughness of $0.76{\mu}m$ Ra was obtained.

• 한국생산제조학회지
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• 제24권3호
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• pp.334-341
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• 2015

This paper summarizes the results of an investigation into the environmental factors that have an indirect impact on parts quality, as well as those process variables and modeling information that have a direct impact. The effects of strength, surface hardness, roughness, and accuracy of shape, that is, qualities that users generally need to know, were evaluated with laminating direction experimentally. The 3D printing methods used in this experiment were fused deposition modeling (FDM), stereolithography apparatus (SLA), selective laser sintering (SLS), 3D printing (3DP) and laminated object manufacturing (LOM). The goal was to achieve a high standard of quality control and product quality by optimizing the fabrication process.

• 열처리공학회지
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• 제4권2호
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• pp.27-37
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• 1991

The adhesion strength of TiN films to substrate(STC 3) steel has been studied using the scratch adhesion test. Before deposition, the substrates were mechanically polished and TiN films were deposited at different substrate temperature($480^{\circ}C-540^{\circ}C$). The chemical properties of TiN films were investigated by RBS, and EDS, and the physical properties were investigated by micro-hardness tester, SEM, and X-ray diffractometer. According to results of this study, the adhesion strength of TiN films increase with increasing the deposition temperature. The roughness of the polished substrates surface were measured with a profilometer. It was observed that, as a general rule, the adhesion strength of deposited TiN films increase with decreasing the substrates surface roughness.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.194-194
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• 2009

3C-SiC thin films are widely used in extreme environments, radio frequency (RF) environments, and bio-materials for micro/nano electronic mechanical systems (M/NEMS). The mechanical properties of 3C-SiC thin films need to be considered when designing M/NEMS, so Young's Modulus and the hardness need to be accurately measured. Young's Modulus and the hardness are influenced by N-doping. In this paper, we show that the mechanical properties of poly (polycrystalline) 3C-SiC thin films are influenced by the N-doping concentration. Furthermore, we measure the mechanical properties of 3C-SiC thin films for N-doping concentrations of 1%, 3%, and 5%, by using nanoindentation. For films deposited using a 1% N-doping concentration, Young's Modulus and the hardness were measured as 270 GPa and 30 GPa, respectively. When the surface roughness of the thin films was investigated by using atomic force microscopy (AFM), the roughness of the 5% N-doped 3C-SiC thin film was the lowest of all the films, at 15 nm.

• 한국생산제조학회지
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• 제21권6호
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• pp.871-877
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• 2012

New materials widely used for automobile related industry, aircraft, space development area are mostly high hardness materials. The hardness value of some hardened materials is over HRC45 and machining of this hardened materials is called as hard turning. Hard turning has its advantage on processing flexibility, cycle time and tool cost reduction. Also this process obtains high efficiency in processing and precise surface roughness through application of the CBN tools. In hard turning process with CBN tool, surface integrity is the important factor for considering the design of machine part and component under high stress and load conditions. A purpose of this study is to analyze optimal condition in hard turning process of AISI 52100 steel (HRC62) with high CBN and low CBN on turning characteristics, tool wear mechanism comparison and surface integrity.

• 열처리공학회지
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• 제37권2호
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• pp.49-57
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• 2024

We investigated the changes in microstructure and surface roughness of the compound layer of GC250D gray cast iron, commonly used in brake discs, during gas nitriding. The gas atmosphere of the nitriding process was controlled with a hydrogen partial pressure of 49.5%, and the process was conducted at a nitriding temperature of 520℃ with various process times. As the nitriding process time of the GC250D material increased, both the depth of hardening and the thickness of the compound layer increased, with a maximum surface hardness of approximately 1265 HV_0.1 was measured. Additionally, the surface roughness increased with the process time. Phase analysis of the compound layer revealed an increase in the proportion of the γ' phase as the nitriding process time increased. Changes in the formation of the compound layer were observed depending on the orientation of graphite within the material, leading to the formation of wedges. Therefore, the increase in surface roughness appears to be attributed to the uneven compounds, the expansion of the compound layer and wedges formed on the surface during the nitriding process.