• Title, Summary, Keyword: Friction pressure

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Effects of Friction Pressure on Bonding Strength and a Characteristic of Fracture in Friction Welding of Cu to Cu-W Sintered Alloy (동-텅스텐 소결합금(Cu-W)과 동(Cu)의 마찰용접에서 마찰압력이 접합강도와 파단특성에 미치는 영향)

  • 강성보;민택기
    • Journal of Welding and Joining
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    • v.15 no.4
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    • pp.90-98
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    • 1997
  • A copper-tungsten sintered alloy(Cu-W) has been friction welded to a tough pitch copper in order to investigate the effect of friction pressure on bonding strength and a charicteristic of fracture. The tensile strength of the friction welded joint was increased up to 90% of the Cu base metal under the condition of friction time 1.2 sec, friction pressure 4.5kgf/$\textrm{mm}^2$ and upset pressure 10kgf/$\textrm{mm}^2$. From the results of fracture surface analysis, the increase of friction pressure could remarkably decrease the force and the time to be normally acted on weld interface. The W particles which were included in the plastic zone of Cu side could induce fracture adjacent to the weld interface because their existance in Cu induces a decrease in available section area and an increase in notch effect. Therefore, the tensile strength was decreased at high friction pressure (6kgf/$\textrm{mm}^2$) because the destruction of W was increased by an increase in mechanical force and crack was formed at weld interface.

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Dynamic Friction of Polyester Air-jet Textured Yarns

  • Rengasamy Raju Seenivasan;Guruprasad Raghavendran;Asis Patnaik
    • Fibers and Polymers
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    • v.6 no.2
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    • pp.146-150
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    • 2005
  • In this paper, friction of air-jet textured yams is investigated. Using a friction measuring apparatus fabricated inhouse, dynamic friction forces of the yams under yarn-to-metal (YM) and yam-to-yam (YY) rubbing modes are measured. The influence of processing variables of air-jet texturing viz., overfeed, air pressure, dry/wet texturing and normal/core-and-effect texturing on dynamic friction is analysed. The results indicate that friction force increases with increasing rubbing speeds and yam input tension. YM dynamic friction decreases initially and then starts to increase at higher overfeeds. YY dynamic friction increases with increasing overfeed. YM dynamic friction decreases with an increase in air pressure while an opposite trend is observed for YY friction. Wet textured yams have higher friction than dry textured yams. Core wetted coreand-effect textured yams have higher friction than normal textured yams.

The study on the measurement for the pressure drop and friction factor of corrugated metal pipes (주름관에서의 압력강하와 마찰손실 계측에 관한 연구)

  • Yun, Young-Sun;Kang, Jun-One;Yoo, Jai-Suk;Kim, Hyung-Jung
    • Journal of the Korean Society of Visualization
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    • v.4 no.2
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    • pp.76-80
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    • 2006
  • The data for friction factor of the pipe correlated by Reynolds number and relative roughness have been reported well as a Moody chart. However, the results for corrugated shapes have been not investigated sufficiently. In this research, therefore, the pressure drop and friction factor are obtained. Flexible metal tubes with corrugations for the measurement are made of stainless steel plates. The kinds of tubes for the measurement are 5 annular types and helical types. The pressure drop & the velocity of the flow are obtained by micromanometer & digital pressure sensor, supplying dry air at several steps. Then the pressure drop is calculated for each tube, using the obtained data. The result shows that the pressure drop is strongly influenced by the viscous dissipation of kinetic energy due to the circulation of flows, rather than a viscous friction loss. The pressure drop increased consistently as the Reynolds number increases.

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고강도 알루미늄 합금 A7075-T6의 마찰용접성에 관한 연구

  • 강성보
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • pp.71-75
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    • 1998
  • This study deals with the friction weldability of A7075-T6 having high specific strength. The friction welding conditions used are rotation speed 2000rpm, friction pressure 40MPa, friction time 1.5sec, upset pressure 40~100MPa, upset time 5sec. First, upset length was measured by displacement transducer. The plastic flow in 7075-T6 weld generates convex lens shaped resion by friction and concave lens shaped resion by axial force. Under the condition of upset pressure 85MPa, the friction welds have tensile strength of 552MPa and shear strength of 262MPa.

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Development of Evaluation and Prediction Model for Concrete High Speed Pumping (고강도콘크리트의 고속펌핑을 위한 압송성평가 및 예측모델에 관한 연구)

  • Kim, Hyung-Rae;Cho, Ho-kyoo;Jeong, Woong-Taek
    • Proceedings of the Korean Institute of Building Construction Conference
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    • pp.201-203
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    • 2012
  • The establishment of the technology for evaluating friction resistance and pipe pressure and the relation of the fluid characteristics and pumpability of concrete is essential for the evaluation of concrete pumping performance for high speed construction of super-tall building. So, this study focuses on quantitative evaluation of concrete fluid characteristics and surface friction resistance under the change of concrete mix proportion and pumping condition. In this study, we measured the rheology of concrete and pipe pressure and surface friction characteristics when pumping. And, relations between the rheology characteristics of concrete and pumping performance was investigated by experiment. As the result of the experiment, high regression between the surface friction and pressure gradient was confirmed. And, prediction model to evaluate the friction resistance coefficient and pipe pressure reduction coefficient was suggested.

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Comparison of Friction and Wear Characteristics of Thin Film Coatings Using Tribotesters at Atmospheric/Vacuum Conditions (대기압/진공 조건의 트라이보 시험기를 이용한 박막 코팅의 마찰/마모 특성 비교)

  • Kim, Hae-Jin;Kim, Dae-Eun;Kim, Chang-Lae
    • Tribology and Lubricants
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    • v.35 no.6
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    • pp.389-395
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    • 2019
  • In various industries, thin film coatings are used to improve friction and wear characteristics. Various types of tribotesters are used to evaluate the friction and wear characteristics of such thin film coatings. In this study, we fabricated a micro-tribotester and Tribo-scanning electron microscopy (SEM) to compare the friction and wear characteristics of copper (Cu) coatings under an atmospheric pressure and a vacuum condition, respectively. The reliability of the different types of tribotesters was evaluated by performing calibrations for the sensor to measure the friction forces and normal loads. Using the two different types of devices, the friction and wear tests are conducted at the same experimental conditions excluding environment conditions such as the atmospheric pressure and vacuum condition. The friction coefficient at the vacuum condition is lower than at the atmospheric pressure. This difference in friction characteristics is due to the fact that wear phenomena occur differently according to the atmospheric pressure and vacuum condition. At the atmospheric pressure, the abrasive wear is the main wear mechanism. At the vacuum condition, the adhesive wear is the main wear mechanism. The reason for the difference in the wear mechanism of the Cu coating at the atmospheric pressure and the vacuum condition is that the oxidation phenomenon, which does not appear at the vacuum condition, occurs at the atmospheric pressure; therefore, the characteristics of the Cu coating change accordingly.

A Study on Friction weldability of Copper-Tungsten Sinterd Alloy to Copper (WCu-Cu 전기접점의 마찰용접 특성 연구)

  • An, Y.H.;Yoon, G.G.;Min, T.K.;Han, B.S.
    • Proceedings of the KIEE Conference
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    • pp.1934-1937
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    • 1999
  • A copper-tungsten sintered alloy(Cu-W) has been friction-welded to a tough pitch copper (Cu) in order to investigate friction weldability. The tensile strength of the friction welded joint was increased up to 87% of the Cu base metal under the condition of friction time 1.0 see, friction pressure 40MPa and upset pressure 100MPa, upset time 5.0 sec. And it is related to upset pressure rather than friction time. Mixed layer was formed in the Cu adjacent weld interface and W particles which were included in mixed layer could induce fracture in the Cu adjacent to the weld interface. Thickness of mixed layer was reduced as upset pressure increase.

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A Study on Friction and Wear Characteristics of Welded Rails Under Various Sliding Environments (레일 용접부의 미끄럼 환경변화에 따른 마찰 및 마멸특성 연구)

  • 김청균
    • Tribology and Lubricants
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    • v.15 no.2
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    • pp.178-183
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    • 1999
  • This paper presents friction and wear related results of thermite and gas pressure welded rails under various environmental contact conditions. A welded rail which was fabricated by thermite welding and gas pressure one has been tested over full range of test conditions in a pin-on-disk wear testing machine. The results show that the friction coefficient and wear rates of a welded rail are heavily dependent on the contact pressures and sliding environments for two welding methods such as thermite and gas pressure weldings.

Effect of Upset pressure on weldability in the Friction Welding of SM45C-Solid and SM45C-Pipe which is used in the Piston-Rod (경량화 피스톤 로드에 사용되는 SM45C/SM45C-Pipe의 마찰용접시 업셋압력이 미치는 영향)

  • Min, Byung-Hoon;Choi, Won-Yong;Min, Taeg-Ki
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.17 no.5
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    • pp.36-43
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    • 2008
  • This research is tendencious to manufacture solid piston-rod of shock absorber as hollow piston-rod using friction welding. The SM45C has been welded to the SM45C-pipe in order to investigate the effect of upset pressure on friction weldability. The friction time and upset pressure was variable conditions under the conditions of spindle revolution of 2,000rpm, friction pressure of 55MPa, and upset time of 2.0seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests were studied of friction weld, and so the results were as follows. When the upset pressure is sufficient, gets the high tensile strength. The optimal welding conditions were n=2,000rpm, $P_1$=55MPa, $P_2$=95MPa, $t_1$=1.5sec, $t_2$=2.0sec when the total upset length is 4.5mm.

A Study on the Pressure Characteristics in Low-Friction Piston Pad (저마찰 피스톤 패드의 압력특성에 관한 연구)

  • 김청균;권영진
    • Tribology and Lubricants
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    • v.8 no.2
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    • pp.73-79
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    • 1992
  • The pressure distribution between the piston pad and the cylinder wall is analyzed to reduce the friction and to get the dynamic stability in the low friction piston. The calculated results indicate that the rectangular pad may reduce the friction in comparison to the square one. And the low friction piston can be stabilized when the pressure difference between the top and bottom of the piston skirt is very small.