• Title/Summary/Keyword: Controlled Rolling

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An Experimental Study of Environmental Effects on the Rolling Resistance of Bearing Surfaces Coated by Soft Metallic Films (연금속 박막이 코팅된 베어링 표면의 구름 저항 거동에 미치는 분위기의 영향에 대한 실험적 고찰)

  • 양승호;공호성;윤의성;김대은
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1998.04a
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    • pp.47-54
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    • 1998
  • An experimental study was performed to discover the effect of environmental conditions on the rolling resistance behavior of pure silver and lead coated 52100 bearing steel. Pure silver and lead coating were produced by a thermal evaporation coating method. Experiments using a thrust ball bearing-typed rolling test-rig were performed under vacuum, dry air and controlled humidity conditions. Results showed that agglomeration of particles were prevented in vacuum environment and as it showed low and stable rolling resistance by shakedown phenomena. Also, humidity relates closely to the agglomeration of particles and increased the rolling resistance after the failure of coated layer.

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Size-controlled Growth of Fe Nanoparticles in Gas Flow Sputtering Process

  • Sakuma, H.;Aoshima, H.;Ishii, K.
    • Journal of Magnetics
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    • v.11 no.3
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    • pp.103-107
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    • 2006
  • In grain oriented electrical steel process, hot band annealing has thought to be essential for obtaining good magnetic properties. New hot rolling method of heavy reduction in early hot rolling stage was applied to obtain good magnetic properties in GO process without hot band annealing. Hot rolling was carried out by varyinghot rolling reduction distribution along hot rolling pass. The heavy hot rolling reduction in rear stand improves the magnetic flux density in the case of no hot band annealing. The hot band specimens of the heavy reduction in front stand shows the elongated hot deformed microstructures in the center layer and strong {001}<110> texture.On the contrary, the heavily reduced specimens in rear stand shows the recrystallization in the center layer of hot band and strong {111}<112> and {110}<001> textures.

Controlled Deformation of Microalloyed Steel by Precipitation and Recrystallization (미량원소첨가강의 석출 및 재결정에 의한 제어변형)

  • 조상현;김성일;유연철
    • Transactions of Materials Processing
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    • v.6 no.2
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    • pp.102-109
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    • 1997
  • The multistage deformation and stress relaxation were carried out to investigate the strain induced precipitation by torsion tests in the range of 1000~80$0^{\circ}C$, 0.05~5/sec for V-microalloyed steel. The starting temperature and time for the initiation of precipitation were determined by stress relaxation tests. The distribution of precipitates increased, as the strain rate increased and the mean size of precipitates was found to be about 10~30nm. The precipitation starting time$(P_s)$ decreased with increasing strain rate and the amount of pre-strain. The effect of deformation conditions on the no-recrystallization temperature$(T_nr)$ was also determined in the multistage deformation. $T_nr$ Tnr decreased with increasing the strain and strain rate. In the controlled rolling simulation, grain refinement and precipitation hardening effects could be achieved by the alternative large pass strain at the latter half pass stage under the condition of low temperature and high strain rate.

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Evolution of temperature gradients during rolling of $Cu_{54}Ni_6Zr_{22}Ti_{18}$ bulk metallic glass in the super cooled liquid region (Cu기 비정질 합금의 과냉각 액상구간에서 온간 압연시 Roll 온도의 영향)

  • Park, E.S.;Lee, J.H.;Kim, H.J.;Bae, J.C.;Huh, M.Y.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2006.05a
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    • pp.409-412
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    • 2006
  • Bulk metallic glass (BMG) strips of $Cu_{54}Ni_6Zr_{22}Ti_{18}$ were produced by warm rolling of the amorphous powder canned with copper. Controlling of temperatures of the rolled sample and rolls was essential for the successive rolling process. Because improper controlling of the sample temperature gave rise to the crystallization of BMG loading to the catastrophic fracture of BMG strips, the temperature of rolls should be properly controlled for achieving successful powder rolling of BMG. The variations of the strain state and temperature in the roll gap was simulated by the finite element method(FEM) using various roll temperatures.

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Structural Formulation of As-grown Vertically Aligned Nanostructures to Multifunctional Thin-Film Frameworks through Controlled Mechanical Rolling (기계적 롤링을 통한 수직배향 나노구조의 다용도 박막 프레임워크 변환)

  • Park, Tae Jun;Choi, Seok Min;Youn, Do Kyung;Lee, Seungjo;Park, Jaekyu;Lee, Jae Hyuk;Kim, Jeong Dae;Lee, Han Kil;Ok, Jong G.
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.25 no.4
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    • pp.266-270
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    • 2016
  • We present a useful and practical manufacturing technique that enables the structural conversion of delicate as-grown nanostructures to more beneficial and robust thin-film frameworks through controlled mechanical rolling. Functional nanostructures such as carbon nanotubes grown through chemical vapor deposition in a vertically aligned and very loosely packed manner, and thus difficult to manipulate for subsequent uses, can be prepared in an array of thin blades by patterning the growth catalyst layer. They can then be toppled as dominos through precisely controlled mechanical rolling. The nanostructures formulated to horizontally aligned thin films are much more favorable for device applications typically based on thin-film configuration. The proposed technique may broaden the functionality and applicability of as-grown nanostructures by converting them into thin-film frameworks that are easier to handle and more durable and favorable for fabricating thin-film devices for electronics, sensors, and other applications.

The Rolling Error Caused by the Centrifugal Force on the Ship's Gyro Compass (원심력에 의한 Gyro Compass의 동요오차)

  • 정태권;이상집
    • Journal of the Korean Institute of Navigation
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    • v.3 no.1
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    • pp.19-28
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    • 1979
  • There are two different assertions on the rolling error in the solid-controlled gyro compass which contains two rotors in its inner gyro sphere. One assertion is that there is a rolling error and the other is that there is no rolling error. This paper examines the rolling error caused by the centrifugal force by the experiment to reveal that the first assertionis reasonable, and it also attempts to explain qualitatively how the rolling error occurs. The Hokushin-Plath gyro compass is chosen as a model. The rolling error is examined by the swing test in various periods. From the tests, the following results are obtained. As long as the swing is continued under the fixed condition of the ship's heading, the swinging period and the amplitude, no error appears. In case the gyro compass is affected by the swingings except those of the cardinal planes, the error starts to appear only after the swing is finished and it is increasing slowly. It takes about 20 minutes for the error to reach its maximum value. The type of this error is a quadrantal one which makes the ship's heading high in the first and third quarters and low in the second and fourth quarters. But in each case the experimental maximum error is greater than the theorectical one.

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A Study on Rolling Friction Characteristics of Magneto-Rheological Elastomer under Magnetic Fields (자기장 영향에 따른 자기유변탄성체의 구름 마찰 특성 연구)

  • Lian, Chenglong;Lee, Kwang-Hee;Kim, Cheol-Hyun;Lee, Chul-Hee
    • Tribology and Lubricants
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    • v.30 no.4
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    • pp.234-239
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    • 2014
  • Magneto-rheological elastomer (MR elastomer) is a smart material, because it has mechanical properties that change under a magnetic field. An MR elastomer changes its stiffness characteristics when the inner particles (iron particles) align along the direction of a magnetic field. There has been much research to make use of this characteristic to control vibration issues in various mechanical systems, such as for mounting systems in the automotive field, home appliances, etc. Furthermore, the friction and wear properties of MR elastomer have been studied, as these relate to the durability of the material needed to meet engineering requirements. Rolling friction (or rolling resistance) is one of these friction properties, but has not yet been studied in the context of MR elastomers. In this study, an MR elastomer is fabricated in the shape of a hollow cylinder to evaluate the rolling friction characteristic under a magnetic field. The test apparatus is setup and a strain gauge is used to calculate the rolling resistance under test conditions. Permanent magnets are used to supply the magnetic field during tests. The load and rolling speed conditions are also considered for the tests. The test results show that rolling friction characteristic has a different trend under different magnetic field, load, and rolling speed conditions. It is assumed that the stiffness change of an MR elastomer under a magnetic field has an effect on the rolling friction characteristic of the MR elastomer. For the future work, the rolling friction characteristics of MR elastomers will be controlled by adjusting the strength of the magnetic field using electromagnets.

Analysis of Residual Stress and Etching Curl of Cold Rolled Sheet in Shadow Mask (Shadow Mask용 냉간 압연박판의 잔류응력과 변형 해석)

  • 정호승;조종래;문영훈;김교성
    • Transactions of Materials Processing
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    • v.12 no.2
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    • pp.123-127
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    • 2003
  • The cold rolling conditions for the ultra thin steel for tension mask are very important because the residual stress that affects the flatness of strip is generate during the cold rolling. The residual stress in the sheet causes etching curls when it suffers perforation process. The residual stress through the thickness. To estimate the residual stress and deformation due to etching curl. FEM analysis is performed. Numerical simulation employ a ANSY5 5.6 and an elastic-plastic constitutive equation. The simulation results indicate the distribution of residual stress in the rolled sheet can be controlled by selecting the rolling conditions properly.

The Production Technology of High-Strength Round Bar by QST Rolling (QST압연법에 의한 고장력봉강 제조기술)

  • 신정호;한철호;이종수;장병록
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1997.03a
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    • pp.240-243
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    • 1997
  • The Quenching and Self Tempering (QST) rolling is treated in terms of an advance process on Controlled Rolling and Cooling Technology (CRCT). In the analysis, the effect of this process is governed by both quenching and finishing conditions in the related with temperature. The objective of the QST model is to simulate the temperature gradient of the stock being rolled in the rolling mill. A comparison of computer simulated and manufactured micro structure as well as mechanical properties shows a good consistency. The micro structure of this high-strength round bar consists of tempered martensite and ferrite + pearlite phases.

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A Behavior of Rolling Contact Fatigue on Retained Austenite in High-Carbon Chromium Bearing Steel (고탄소 크롬 베어링 강에서의 잔류 오스테나이트 변화에 따른 회전접촉 피로거동)

  • Jin, Jai Koan;Kim, Dong Keon
    • Journal of the Korean Society for Heat Treatment
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    • v.7 no.3
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    • pp.190-198
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    • 1994
  • In order to study the effect of retained austenite on rolling contact fatigue in high-carbon chromium bearing steel, retained austenite was controlled by only tempering temperature, individually 200, 220 and $240^{\circ}C$. Among various microstructural alteration during rolling contact fatigue test, plate-like carbide most related to the flaking at sub-surface of contact pressure. The plate-like carbides formed during rolling contact fatigue test decrease with increasing tempering temperature, and fatigue life is much more improved. The retained austenite was decreased with the tempering temperature, and that decreased plate-like carbide formation. Therefore fatigue life is much more improved with decreasing retained austenite.

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