• 한국군사과학기술학회지
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• 제3권2호
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• pp.231-243
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• 2000

This paper describes a simulation of secondary motion of piston assemblies using PISDYN by Ricardo. Motions of the piston, pin, rod and skirt are separately calculated, by integrating equations of motion for individual components and dynamic degrees of freedom. The effects of engine speed at full load and pin offsets on the piston assembly secondary motions, forces and friction were investigated in parametric study for 4-cylinder gasoline engine. Results show that lateral displacement and friction loss of the piston increase as a function of engine speed. The lateral motion of the piston is affected by the change in pin offset. The minimum friction loss for the condition of 4800rpm WOT occurs at a pin offset of 1.6mm.

• 한국세라믹학회지
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• 제35권7호
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• pp.721-725
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• 1998

본 연구에서는 Boron과 Carbon black이 소결조재로 첨가된 탄화규소 분말을 $1950^{\circ}C$에서 상압소결 방법으로 시편을 제조하고 꺽임강도, 파괴인성, 비마모량을 측정하고 파단면 및 마찰마모면의 미세구조를 SEM으로 관찰하여 마찰마모특성과 미세구조와의 관계를 규명하였다. 또한 마모상대재료로서 SiC pin과 $Al_{2}O_{3}$ pin을 사용하였을때 마찰마모특성과 미세구조와의 관계도 비교 검토하였으며 다음과 같은 결론을 얻었다. 1. SiC pin을 사용한 경우 소결시편의 비마모량은 $Al_{2}O_{3}$ pin을 사용한 경우보다 많았으나, 가압하중이 증가하면 $Al_{2}O_{3}$ pin을 사용한 경우가 SiC pin을 사용한 경우보다 비마모량의 증가율이 6.5배로 되었다. 2. Pin의 비마모량은 SiC pin의 경우가 $Al_{2}O_{3}$의 경우보다 많았으나 가압하중이 증가하면 $Al_{2}O_{3}$ pin의 경우가 SiC pin의 경우보다 비마모향의 증가율이 약4배로 되었다. 3. 마모상대재료의 마찰계수가 작은 경우에는 마모면의 미세구조가 평활하면서 crack이 나타나지 않았으나, 마찰계수가 큰 경우에는 마모면이 평활치 못하고 crack의 전파현상이 크게 나타났다. 4. 사용된 Pin의 마찰계수가 큰 경우에는 고상소결한 SiC 시편도 액상소결한 시편과 마찰마모 특성이 유사하였다.

• 한국전산유체공학회지
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• 제13권2호
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• pp.20-26
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• 2008

A numerical study is carried out to analyze the steady three-dimensional turbulent flow and convective heat transfer in a staggered pin-fin array with diamond shaped elements at various geometrical configurations. Steady Reynolds-averaged Navier-Stokes equations and energy equation are solved using a finite volume based solver. Shear stress transport (SST) model is used as turbulence closure. The computational domain is composed of one pitch of pin-fin displacement with periodic boundary conditions on the surfaces normal to the streamwise direction and the cross-streamwise direction. The numerical results for Nusselt number and friction factor are validated with experimental results. The effects of pin angle, pin height and pitch on Nusselt number, friction factor and efficiency index are investigated.

• 대한치과의사협회지
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• 제15권11호
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• pp.763-766
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• 1977

The Purpose of this study was to observe force required to remove some kinds of pin from dentin. The teeth were embedded within a resin cylinder and the occlusal surface was sectioned at a right angle to the axis of the cylinder to expose dentin surface. Thread mate system pin (minim and regular), friction Iocked pin and cemented pin were tested Pin holes were drilled by handpiece and depths of pin holes were tested 1,2 and 3mm. After insertion of the pins into pinhole, tensile loading was performed on the Instron testing machine at the speed of 0.5 inch/min. Results were follewed: 1. In retention, the cemented pins are the least, the friction locked pins intermediate and the self threading pins the greatest in all pins. In self threading pins, regalar pin has greater retention than minim pin 2. The deeper the depth of the pin hole is, the more the retention of the pin increases.

• 소성∙가공
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• 제22권2호
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• pp.86-92
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• 2013

When stamping ultra-high-strength steel (UHSS), the phenomenon of galling, which corresponds to a transfer of material from the sheet to the tool surface, occurs because of the high contact pressure between tool and workpiece. Galling leads to increased friction, unstable interface conditions, scratches on the sheet and the tool surfaces and, eventually, premature tool surface failures. Therefore, a simple and accurate evaluation method for tool scratching is necessary for the selection of tool material and coating, as well as for a better optimization of process conditions such as blank holder force and die radius. In this study, the pin-on-disc (PODT) and pin-on-flat surface (POFST) tests are conducted to quantitatively evaluate scratch-related tool life for stamping of UHSS. The variation of the friction coefficient is used as an indicator of scratch resulted from galling. The U-channel ironing test (UCIT) is performed in order to validate the results of the friction tests. This study shows that the POFST test provides a good quantitative estimation of tool life based on the occurrence of scratch.

• Journal of Welding and Joining
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• 제35권3호
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• pp.44-51
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• 2017

In the present study, AA 5083-O plates are joined by friction stir welding technique. A universal milling machine was used to perform the welding process of the work-pieces which were fixed on the proper position by a vice. The joints were friction stir welded by two tools with different pin profiles; cylindrical threaded pin and tapered smooth one at different rotational speed values; 400 rpm and 630 rpm, and different welding speed values; 100 mm/min and 160 mm/min. During FSW of each joint, the temperature was measured by infra-red thermal image camera. The welded joints were inspected by visually as well as by the macro- and microstructure evolutions. Furthermore, the joints were tested for measuring the hardness and the tensile strength to study the effect of changing the FSW parameters on the mechanical properties. The results show that increasing the rotational speed results in increasing the peak temperature, while increasing the welding speed results in decreasing the peak temperature for the same tool pin profile. Defect free welds were obtained at lower rotational speed by the threaded tool profile. Moreover, the threaded tool pin profile gives superior mechanical properties at lower rotational speed.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.629-630
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• 2006

To investigate sliding friction and wear behaviors of WC-Co/WC-Co pairs containing different WC grain sizes, the ball-on-disc test in air were carried out, where WC grain sizes a $0.5\;{\mu}m$ (F.G.) and $1.5\;{\mu}m$ (C.G.). The wear volume of F.G. pin for F.G. pin/C.G. disc is larger than that of F.G. pin for F.G. pin/F.G. disc due to higher friction coefficient, and the surfaces after wear test are richer in oxygen compared to those before test. Furthermore, the wear debris, which is composed of nona-scale grain, after the wear test are remarkably richer in oxygen than to those before test.

• Tribology and Lubricants
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• 제16권6호
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• pp.409-414
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• 2000

The friction and wear behaviors of MoS$_2$ coatings were investigated by using a pin and disk type tester. The experiment was conducted by using silicon nitride as pin material and MoS$_2$-on-bearing steel as disk material under different operating conditions that include linear sliding velocities in the range of 22-66 ㎜/sec, normal loads varying from 9.8 N to 29.4 N, corresponding to maximum contact pressures of 1.18-2.83 GPa and atmospheric conditions of high vacuum, medium vacuum, ambient air. The results showed that low friction coefficient of the coating has been identified in high vacuum and that friction coefficient and wear volume increased with increasing normal load. Also at high load conditions, the friction coefficient and wear volume increased with increasing sliding velocity.

• KSTLE International Journal
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• 제1권2호
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• pp.91-94
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• 2000

The friction and wear behavior of MoS$_2$coatings was investigated using a pin and disk type tester. The experiment was conducted with silicon nitride as the pin material and MoS$_2$-on-bearing steel as the disk material under different operating conditions that included linear sliding velocities within a range of 2266 mm/sec, normal loads varying from 9.829.4 N, corresponding to maximum contact pressures of 1.782.83 Gpa, and high vacuum, medium vacuum, and ambient air atmospheric conditions. The results showed a low friction coefficient far the coating in a high vacuum, plus the friction coefficient and wear volume increased with an increased normal load. Furthermore, under high load conditions, the friction coefficient and wear volume also increased with an increased sliding velocity.

• Journal of Welding and Joining
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• 제20권4호
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• pp.534-537
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• 2002

In the various industry such as shipbuilding and automobile, etc., Al-alloys are used to reduce weight and improve economical efficiency, and they are mainly utilized in the process of Friction Stir Welding (FSW). A number of studies have been carried out on the metallurgical characteristics of friction stir welding In Al-alloys. However, research on the thermal behavior of FSW by using numerical analysis is not sufficient in the domestic and abroad. In this paper, therefore, numerical simulation was used to find out thermal behaviour of FSW by finite element method. We considered heat source that occurred by friction between tool shoulder including pin and base metal. To confirm the result of simulation, macrostructure is examined and compared after welding. The result of numerical simulation shows that Al-alloy is welded under a melting point of Al around pin by FSW.