• 열처리공학회지
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• 제33권6호
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• pp.284-289
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• 2020

Since the dissimilar bonded interface usually consists of intermetallic compounds (IMCs) layer and cracks, their mechanical and electrical properties can be influenced by microstructure at interface between two different metals. In this study, the friction welded Cu-Al busbar, which is widely used to connect a secondary battery and their component, is selected to analyze the influence of interfacial characteristic on their tensile strength and electric conductivity. Then, the electrical characteristics of Cu busbar and Cu-Al busbar were investigated by thermal flow analysis and temperature rise test. In addition, the relationship between the maximum saturation temperature and the electrical conductivity were discussed in terms of interfacial characteristics of the friction welded Cu-Al busbar.

• Tribology and Lubricants
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• 제33권1호
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• pp.15-22
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• 2017

Because the running speed of vehicles is increasing and a shorter braking distance is required, high heat-resistant brake pads are needed to satisfy the requirements of customers and car makers. In the near future, hazardous materials such as Cu, Cr, Zn, and Sb will be restricted from use in friction materials. Ceramic composites reinforced by carbon fibers are good candidates for eco-friendly friction materials. In this study, we develop ceramic composite friction materials. The friction materials are composed of carbon fibers, Si, SiC, graphite, and phenol resin and are prepared by hot forming and heat treatment at high temperatures. The density, void ratio, and compressive strength are $1.59-1.66g/cm^3$, 16.6-20, and 70-90 MPa, respectively. Friction and wear tests are performed using a pin-on-plate-type reciprocating friction tester at 25, 100, and $200^{\circ}C$. The counterpart material is a CrMoV steel extracted from a KTX brake disc. Friction coefficient, wear amount, and wear mechanism are measured and examined. We determine that the friction coefficients depend on the temperature and the fluctuation of the friction coefficients is larger at higher temperatures. The amount of wear increases with the surface temperatures of the specimens. The tribological properties of the developed composites are similar to those of a Cu-based sintered friction material. Through this study, it is confirmed that ceramic composite materials can be used as friction materials.

• 한국생산제조학회지
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• 제21권6호
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• pp.932-937
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• 2012

In the presented study, SM45C carbon steel parts were joined by friction welding. The welding process was carried out under optimized conditions using statistical approach. The study of SM45C is conducted with various combinations of process parameters. Parameter optimization, microstructure and mechanical property correlation are the major contribution of the study. The welded joints were produced by varying spindle revolution speed, friction pressure, upset pressure and burn-off length. Tension tests were applied to welded parts to obtain the strength of the joints. Fracturs properties were additionally obtained experimentally under fluctuated tensile loads. Microstructures using microphotographs were examined in the weld interface and weld region and heat affected zone and base metal and flash zone of welded parts. Finally, Hardness variations in welding zone and base metal were also obtained. Through these tests, the optimum conditions of parameters for ${\phi}20$ SM45C in friction welding were obtained when the friction spindle revolution was 1,950 rpm, the friction pressures was 30 MPs, upset pressures was 50 MPs.

• Tribology and Lubricants
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• 제36권5호
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• pp.274-278
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• 2020

This study investigates the possibility of reducing squeal noise generated at the contact point between an elastomer and glass by using the properties of a magneto-rheological elastomer (MRE) whose stiffness changes with the application of a magnetic field. Previously, squeal noise was mainly observed in the unstable section caused by the weakening of friction due to velocity. Previous studies have shown that squeal noise decreases as the stiffness increases. Accordingly, this study is conducted to control the unstable area of the friction curve and to reduce the noise by inducing the stiffness change of the MRE by applying a magnetic field. The friction, vibration, and noise characteristics are measured using a reciprocating friction tester. The frequency ranges of vibration and noise measured with the accelerometer and sound sensor show similar results. When a magnetic field is applied to the MRE, there is significantly lower noise compared with the case without the application of the magnetic field. The average coefficient of friction decreases with the application of the magnetic field. The maximum coefficient of friction increases rapidly at the turning point and decreases when the magnetic field is applied. This shows that the mechanical properties of the MRE change due to the magnetic field, and the noise and friction coefficient also decrease.

• 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.

• 한국세라믹학회지
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• 제34권4호
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• pp.380-386
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• 1997

The tribological properties of ceramics are very important in the application to engineering ceramic parts such as seal rings, pump parts, thread guides, and so on. In this study, the effects of graphite addition on the mechanical and tribological properties of alumina/graphite composites were investigated. The composites were prepared by the adding of graphite powder to the mixture of Al2O3, talc and calcium carbonate. Bending strength, water absorption, friction coefficient, the amount of worn out material at a certain time, and maximum surface roughness(Rmax) of the prepared composites were measured. Crystalline phases and microstructure were examined with XRD and SEM. The melt of Al2O3-CaO-MgO-SiO2 system was shown over 10 vol% graphite composition. As the amount of the graphite is increased, needle like crystals of mullite were formed and grown. We obtained the good properties of friction coefficients and wear resistance at the powder composition containing 15 vol% of graphite.

• Journal of Advanced Marine Engineering and Technology
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• 제24권6호
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• pp.139-146
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• 2000

The development of high performance materials is very important subject in order to enhance the properties of bearings whose role is to transfer energy harmoniously by reducing the problem of friction and wear down, etc. between the interacting solid surfaces in relative motion under high loads in comply with mechanical operating mechanism of engines. In this study, several (100-x)Al-xSn coating films (where x=85, 75, 65 atomic % at Al) on substrates which are abt. 2mm thickenss of Kelmet layer sintered back steel were prepared by using RF sputtering system. These coating films were observed the morphology by SEM(Scanning Electron Microscope) and investigated the crystal structure by XRD(X-ray Diffractor) for their properties. And friction coefficient of these films was measured by ball-on-disc tester for their tribological properties. From the experimental results, it was shown that high performance properties of bearing can be improved greatly by controlling the composition and morphology of material surface with effective use of the plasma-assisted sputtering process.

• The Korean Journal of Ceramics
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• 제3권3호
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• pp.169-172
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• 1997

Sintered diamond/(WC-Co) composites were prepared by spark plasma sintering technique. Tribological properties were measured at temperatures from RT to $500^{\circ}C$ in sliding tests with alumina ball. They show coefficient of friction of 0.1 and below at RT and wear of the diamond composites is hardly detected. Effects of diamond grit size, diamond content and test temperature on the coefficient of friction and the wear are discussed. The wear scars were analyzed.

• 한국해양공학회지
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• 제10권3호
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• pp.24-33
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• 1996

Up to now, most of studies on mechanical properties in friction welded components are about tensile and bending strength. However the fatigue studies on the friction-welded components subjected to repeated stress are not available. The purposes of this study are the development of fundamental design and the development of in-process real-time weld quality evaluation technique by acoustic emission for the bar-to-bar dissimilar friction welding of hydraulic valve spool steels.

• 한국생산제조학회지
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• 제9권4호
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• pp.131-136
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• 2000

This study deals with the mechanical properties of STS304-Al351 friction welding zone. Main results are as follows ; under the condition of upset pressure 75MPa, the tensile strength of STS304-al6351 friction weld interface was higher than that of Al6351 base metal, and the highest tensile strength(290MPa) was obtained at upset pressure 125MPa. The hardness profile across the weld interface shows that the hardness of both STS304 and Al6351 is higher around the weld interface, and sharply increased hardness on the STS304 side is related with the plastic deformation of micro volume. As the result of analyzing the tensile fracture, it showed perfect soft fracture.