• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.472-476
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• 2004

In this study, we investigate the change characteristic of friction coefficient of disk brake lining for rolling stock according to disk type, The actual brake tests were carried out under constant brake force and operating sequence by using dynamo-tester. Test results showed that instant friction coefficient was higher in the case of devided disk type rather than single body disk type, Also, averge friction coefficient was appeared similer to the above result. It is thought that ,in the case of devided disk type, friction resistance was increased due to the gap between both side of half disk.

• International Journal of Precision Engineering and Manufacturing
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• 제7권1호
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• pp.57-61
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• 2006

The research on surface modification technology has been advanced to improve the properties of engineering materials. Ion implantation is a novel surface modification technology that enhances the mechanical, chemical and electrical properties of substrate's surface using accelerated ions. In this research, nitrogen ions were implanted into AC7A aluminum substrates which would be used as molds for rubber molding. The composition of nitrogenion implanted aluminum and distribution of nitrogen ions were analyzed by Auger Electron Spectroscopy (AES). To analyze the modified surface, properties such as hardness, friction coefficient, wear resistance, contact angle, and surface roughness were measured. Hardness of ion implanted specimen was higher than that of untreated specimen. Friction coefficient was reduced, and wear resistance was improved. From the experimental results, it can be expected that implantation of nitrogen ions enhances the mechanical properties of aluminum mold.

• Elastomers and Composites
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• 제53권4호
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• pp.234-238
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• 2018

The influence of reinforcing UHMWPE powder on the tribological and mechanical properties of HDPE was investigated. The circularizing of UHMWPE powder was improved by high-speed rotation to enhance particle distribution and flowability. HDPE composites reinforced with UHMWPE powder in the range of 0-50 wt% were prepared by co-rotating twin screw extrusion. The abrasion resistance, plane friction coefficient, tensile strengths, and impact strengths of the composites were investigated as a function of the UHMWPE content. An increasing UHMWPE content decreased the plane friction coefficient and increased the abrasion resistance and impact strength. It is expected that HDPE composites reinforced with spherical UHMWPE powder particles can be used to improve the durability of products such as pipes in the future.

• Tribology and Lubricants
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• 제30권6호
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• pp.330-336
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• 2014

Sintered metallic brake pads and low alloy heat resistance steel disks are applied to mechanical brake systems in high energy moving machines that are associated with recently developed 200km/h trains. This has led to the speed-up of conventional urban rapid transit. In this study, we use a lab-scale dynamometer to investigate the effects of the composition of friction materials on the tribological characteristics of sintered metallic brake pads and low alloy heat resistance steel under dry sliding conditions. We conduct test under a continuous pressure of 5.5 MPa at various speeds. To determine the optimal composition of friction materials for 200 km/h train, we test and the evaluate frictional characteristics such as friction coefficients, friction stability, wear rate, and the temperature of friction material, which depend on the relative composition of the Cu-Sn and Fe components. The results clearly demonstrate that the average friction coefficient is lower for all speed conditions, when a large quantity of iron power is added. The specimen of 25 wt% iron powder that was added decreased the wear of the friction materials and the roughness of the disc surface. However when 35 wt% iron powder was added, the disc roughness and the wear rate of friction materials increased By increasing the amount of iron powder, the surface roughness, and temperature of the friction materials increased, so the average friction coefficients decreased. An oxidation layer of $Fe_2O_3$ was formed on both friction surfaces.

• Tribology and Lubricants
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• 제20권5호
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• pp.272-277
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• 2004

This study deals with the friction and wear characteristics of C-N coated spur gear. The PSII apparatus was built and a SCM415 test piece and test gear with steel substrate was treated with carbon nitrogen by this apparatus. The composition and structure of the surface layer were analyzed and compared with that of PVD coated TiN layer. It was found that both of friction coefficient of C-N coating and TiN coating decreased with increasing load, however, C-N coating showed relatively lower friction coefficient than that of TiN coating. We was investigated the effect of C-N coating on hardness, friction and wear. The TiN coated gear showed a more serious friction phenomena than that of C-N coated gear. It was considered that coating of TiN, which was conducted at a vacuum chamber at about 500$^{\circ}C$, results in a tempering of base material that causes microstructural change, which in turn resulted in decreasing of hardness. The C-N coated gear and pinion had higher wear resistance that of TiN coated gear and pinion. C-N coating significantly improved the friction and wear resistance of the gear.

• 한국표면공학회지
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• 제44권6호
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• pp.233-238
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• 2011

The friction and wear characteristics of CrN and TiN coatings on SKD61 which is mold material using for extrusion of AZ80 magnesium alloy were investigated. The coatings were deposited by the arc ion-plating method, and the thickness were about $3.59{\mu}m$ and $3.28{\mu}m$, respectively. Reciprocating friction wear tests were conducted by varying pin load and temperature of counter substrate at un-lubricated condition. The pin loads were 11, 15 and 19 kgf, and the substrate temperatures were room temperature and $120^{\circ}C$. CrN coating which has a lower friction coefficient and a smaller adhesive wear with AZ80 magnesium alloy showed better wear resistance than TiN coating.

• Tribology and Lubricants
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• 제22권1호
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• pp.1-7
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• 2006

The sliding friction and wear properties of mineral fiber reinforced composite(MF) and glass fiber reinforced composites(GF) are investigated to clarify their field of use and the role of each fiber in friction material. Friction and wear test reveals that GF composite has better wear resistance even though with low friction coefficient, comparing with MF composite. Glass fiber strengthen effectively the matrix and may absorb friction energy to convert it into the fracture energy of them, as well as its lubricative role. However, mineral fiber in MF composite is too small to strengthen the matrix. Then MF composite are easily plowed and worn out by asperity on counter material. Friction coefficient of MF composite is higher friction coefficient than that of GF composite and varied widely with test.

• Tribology and Lubricants
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• 제30권3호
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• pp.146-155
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• 2014

In this study, we conduct fretting corrosion tests on tin-plated brass coupons to investigate the effect of temperature on fretting corrosion for various span amplitudes. We prepare a coupled fretting corrosion specimens using a tin-plated brass coupon with a thickness of $10{\mu}m$. One specimen is a flat coupon and the other specimen is a coupon with a protuberance in 1 mm radius, which is produced using 2 mm diameter steel ball. We conduct fretting corrosion tests at $25^{\circ}C$, $50^{\circ}C$, $75^{\circ}C$, $100^{\circ}C$ by rubbing the coupled coupons together at the contact between the flat and protuberance coupons. We measure electric resistance of the contact during the fretting corrosion test period. There is increase in resistance with fretting cycles. It is found that rate of increase in electric resistance becomes faster with increase in testing temperature. Magnitude of friction coefficient increases with fretting span amplitudes. And, change in friction coefficient becomes desensitized to the increment in span amplitude. Assuming that failure cycle is the cycle with an electric resistance of $0.01{\Omega}$, we find that failure lifetime ($N_f$) decreases with increase in testing temperature. Furthermore, based on the assumption that the damage rate of the connector is inversely related to the failure cycle, we calculate the activation energy for fretting damage to be 13.6 kJ/mole by using the Arrhenius equation. We propose a method to predict failure cycle at different temperatures for span amplitudes below $30{\mu}m$. Friction coefficients generally increase with increase in span amplitude and decrease in testing temperature.

• 대한금속재료학회지
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• 제50권11호
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• pp.809-815
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• 2012

Recently, as the interest in improving energy efficiency has grown, the demand for vehicle and machine parts that are resistant in high temperature corrosive conditions and abrasive environments has increased. Pack chromizing treatment of sintered steels is a profitable method that satisfies both corrosion resistance and low friction properties. Since austenitic stainless steels have good corrosion resistance but low mechanical hardness, if they are replaced by sintered steel parts with pack chromizing treatment, all the desirable properties such as low price, easy molding, high hardness, low frictional coefficient, and high corrosion resistance, can be obtained. The higher corrosion resistance of the chromized parts over that of the austenitic stainless steels was acquired by coating chromium carbides and a thin chromium oxides layer on the surface. Moreover, the surface morphology of chromized parts, which were composed of chromium rich phases and hardened chromium carbides by diffusing and alloying, had a peak-and-valley shape so that the dimple effect by the wrinkled morphology and high hardness induced a low friction coefficient.

• 소성∙가공
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• 제1권1호
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• pp.75-86
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• 1992

Coated sheet steels have been increasingly used in automotive industry for improving corrosion resistance. One of the arised concerns is frictional behavior of coated sheet steel in stamping process. But analyses of the frictional behavior are complex and difficult. A tensile strip test has been developed for evaluating friction under the condition which simulate the stretching of sheet. Tests are conducted under different die radius and lubrication conditions. Electro-galvanized steel sheets show a lower coefficient of friction than bare steel sheets whose coated layers have been chemically removed. The coefficients of friction are independent of die radius.