• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.421-426
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• 2009

This paper describes on energy loss in a pipe of refuse collecting system. Analysis energy loss in a pipe is the decisive factor in a design for refuse collecting system. From the analysis energy loss, we can determine the capacity of turbo blower. The flow characteristics in the pipe with the refuse bag are analyzed by three-dimensional Navier-Stokes analysis. The refuse bag is modeled using the actual measurement. We obtain friction factor by changing refuse bag's size and mixing ratio and Reynolds number. And From the result we calculate energy loss by using compressible flow analysis.

• Journal of Mechanical Science and Technology
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• v.18 no.9
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• pp.1668-1679
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• 2004

The design of an axial piston pump for electro-hydrostatic transmission systems requires accurate information where and how much the internal friction and flow losses are produced. This study is particularly focused on the friction losses of a bent-axis type hydraulic piston pump, aiming at finding out which design factors influence its torque efficiency most significantly. To this end, the friction coefficients of the pump parts such as piston heads, spherical joints, shaft bearings, and valve plate were experimentally identified by a specially constructed tribometer. Applying the experimental data to the equations of motion for pistons as well as to the theoretical friction models for the pump parts, the friction torques produced by them were computed. The accuracy of the computed results was confirmed by the comparison with the practical input torque of the pump. In this paper, it is shown that the viscous friction forces on the valve plate and input shaft bearing are the primary source of the friction losses of the bent-axis type pump, while the friction forces and moments on the piston are of little significance.

• The KSFM Journal of Fluid Machinery
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• v.18 no.3
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• pp.66-73
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• 2015

This paper deals with a parametric study on boot-shaped ribs in a rectangular cooling channel. Numerical analysis of the flow and heat transfer was performed using three-dimensional Reynolds averaged Navier-Stokes equations with the Speziale, Sarkar and Gatski turbulence model. The parametric study was performed for the parameters, tip width-to rib width, tip height-to-rib height, rib height-to-channel height, and rib height-to-width ratios. To assess the cooling performance and friction loss, Numsselt number and friction factor were defined as the performance parameter, respectively. The results showed that the cooling performance and friction loss were seriously affected by the four geometric parameters.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.3
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• pp.29-35
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• 2020

This paper studies the main parameters of tube-to-bar dissimilar material and shape friction welding for piping materials. The weldability of joint parts was investigated with respect to tensile tests, micro-Vickers hardness, the bond of area, and optical microstructure. The specimens are tested as-welded. Optimal welding conditions are n = 2000 rpm, HP = 50 MPa, UP = 100 MPa, HT = 5 sec, and UT = 10 sec when the metal loss (Mo) is 11 mm. Moreover, the same two materials for friction welding are strongly mixed with a well-combined structure of micro-particles without any molten material, particle growth, or defects. Therefore, the expected result of dissimilar material friction welding includes a reduction of cost and material in the welding process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.88-93
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• 2003

The aim of this paper is to investigate the friction characteristics of piston assembly, which composed of ring pack and piston skirt. The friction force of piston assembly was measured by using the movable liner in the single cylinder engine, and the various parameters were tested. The friction force was suddenly increased at the expansion stroke due to higher cylinder pressure. The viscous friction was dominant at the mid stroke, but the boundary friction was dominant at the top and bottom dead centers. Through the experiment, we could validate previous theoretical study, and confirm that th e radial clearance and ring tension were very effective to reduce friction loss of piston assembly.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.2
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• pp.191-199
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• 2019

In this paper, dissimilar friction welding were produced using 15 mm diameter solid bar in chrome molybedenum steel(SCM440) to stainless steel(STS316L) to investigate their mechanical properties. Consequently, optimal welding conditions were n=2000 rpm, HP=70 MPa, UP=140 MPa, HT=10 sec and UT=10 sec when the metal loss(Mo) is 8.6 mm. In addition, an acoustic emission technique was applied to evaluate the optimal friction welding condition. AE parameters including the cumulative count, amplitude and energy showed a various changes according to the friction condition. A continuous type waveforms and low frequency spectrum was presented in friction time. On the other hand, a burst type waveform and high frequency spectrum was exhibited in pressing time.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.31-38
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• 2006

Cylinder liner rotation is a new concept for reducing piston assembly friction in the internal combustion engine. The purpose of cylinder liner rotation is to reduce the occurrence of boundary and mixed lubrication friction in the piston assembly. This paper reports the results of experiments to quantify the potential of the rotating liner engine. A GM Quad-4 SI engine was converted to single cylinder operation and modified for cylinder liner rotation. The hot motoring method was used to compare the friction loss between the baseline engine and the rotating liner engine. Additionally, tear-down tests were used to measure the contribution of each engine component to the total friction torque. The cycle-averaged motoring torque of the RLE represents a $23\~31\%$ friction reduction compared to the baseline engine for hot motoring tests. Through tear down tests, it was found that the piston assembly friction of the baseline engine is reduced from $90\%$ at 1200 rpm to $71\%$ at 2000 rpm through liner rotation.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.91-96
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• 2011

In this paper, friction welded joints were constructed to investigate the mechanical properties of welded 15-mm diameter solid bars of Mg alloy (AZ31B). The main friction welding parameters were selected to endure reliable quality welds on the basis of visual examination, tensile tests, impact energy test, Vickers hardness surveys of the bonds in the area and heat affected zone (HAZ), and macrostructure investigations. The study reached the following conclusions. The tensile strength of the friction welded materials (271 MPa) was increased to about 100% of the AZ31B base metal (274 MPa) under the condition of a heating time of 1 s. The metal loss increased lineally with an increase in the heating time. The following optimal friction welding conditions were determined: rotating speed (n) = 2000 rpm, heating pressure (HP) = 35 MPa, upsetting pressure (UP) = 70 MPa, heating time (HT) = 1 s, and upsetting time (UT) = 5 s, for a metal loss (Mo) of 10.2 mm. The hardness distribution of the base metal (BM) showed HV55. All of the BM parts showed levels of hardness that were approximately similar to friction welded materials. The weld interface of the friction welded parts was strongly mixed, which showed a well-combined structure of macro-particles without particle growth or any defects. In addition, an acoustic emission (AE) technique was applied to derive the optimum condition for friction welding the Mg alloy nondestructively. The AE count and energy parameters were useful for evaluating the relationship between the tensile strength and AE parameters based on the friction welding conditions.

• Tribology and Lubricants
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• v.23 no.4
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• pp.156-161
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• 2007

The friction test using disk-on-pad type was carried out and regression analysis with friction parameters was applied fur wear loss presumption of motorcycle break disk. The wear loss has an effect on the frictional factor such as applied load, sliding speed, and number of ventilated disk hole. However, it is difficult to know the mutual relation of these factors on wear loss of motorcycle break disk. From this study, the result was shown that the regression analysis equation containing 4 elements were constructed and this equation had a trust of 95% in wear loss presumption of motorcycle break disk. It is possible to apply for another automobile parts.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1510-1519
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• 1994

It is important to understand the friction characteristics between piston-ring assembly and cylinder wall for the friction loss reduction as well as the solution of problem such as scuffing wear and oil consumption. A new system was developed for the piston-ring assembly friction force measurement. This system was applied to the friction force measurement to find its functional relationship with variables such as engine speed, oil viscosity, and engine load. The friction mean effective pressure(fmep) was found to have a linear relationship with$(\vpsilon{U})^{0.42}$ under motering and with$(\vpsilon{U})^{0.45}$ under firing operations, where $\vpsilon$ is the kinematic oil viscosity and U is mean piston speed.