• Title/Summary/Keyword: Effect of rolling direction

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Relationship between Rolling Motion and Microstructural Change in Rolling Element (구름계의 미소조직 변화와 구름운동의 상호관계)

  • 차금환;김대은
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1996.10a
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    • pp.163-167
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    • 1996
  • The life of rolling elements depends on various factors such as operating conditions and material properties. In this work, the effect of microstructure on the rolling behavior is investigated. Specially, the deformations in the substrate regions before and after rolling are compared. It is found that rolling action causes severe flow of material in the direction opposite to the rolling direction in the case of dry rolling direction. With lubrication, the deformation is more severe at the subsurface region rather than at the surface.

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Effect of Initial Texture on the Twinning Formation of AZ31 Mg Alloy (AZ31 Mg 합금의 쌍정 형성에 미치는 Initial Texture의 영향)

  • Lee, Byoung-Ho;Kim, Yong-Woo;Lee, Chong-Soo
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2007.05a
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    • pp.114-117
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    • 2007
  • In the present study, the effects of initial texture on the twinning formation of AZ31 Mg rolled sheet was investigated. Uniaxial compression tests were performed on samples cut along the normal direction and rolling direction of rolled AZ31 Mg alloy sheet at various temperatures (RT, 200, 250, 300, 350, $400^{\circ}C$) with the 0.01/s strain rate. Pole figure of rolling planes showed that basal planes of most gain were located parallel to the rolling direction. After compression test, microstructures and stress-strain curves results indicated that active deformation twining occurred only at the specimen cut along the rolling direction. The slip-twin transition with the increase of temperature was also investigated.

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A Study on the Development of Hot Rolling Process for 18Cr-10Mn-0.44N2 (18Cr-10Mn-0.44N2 고질소강의 열연공정개발에 관한 연구)

  • Kim, Y.D.;Cho, J.R.;Lee, J.W.;Bae, W.B.
    • Transactions of Materials Processing
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    • v.20 no.4
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    • pp.296-302
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    • 2011
  • The objective of this paper is to determine the effect of process parameters on the behavior of a 18Cr-10Mn-$0.44N_2$ nitrogen steel sample deformed by hot rolling. Compression tests were carried out at high temperatures to determine the flow stresses needed for a finite element(FE) analysis. The strain rate, ranging from 0.1 to $1.0s^{-1}$, significantly affected the flow stress at temperatures higher than $1,000^{\circ}C$. Non-isothermal rolling simulations and laboratory rolling tests were performed with plate specimens 14.5mm thick, 135mm wide and 226mm long. A rolling reduction of 15% per pass leading to a cumulative rolling reduction of 60% was determined as optimal. The extension ratio of 176.5% in the length direction was about 30.4 times greater than the extension ratio of 5.8% in the width direction. Isotropic properties for tensile strength, microstructure and grain size were measured after mock-up hot rolling tests. The results from the mockup tests were found to be in good agreement with those of the simulations.

Evolution of strain states during Cross-roll rolling in AA 5052 sheet for varying cross-roll angle using FEM (유한요소 해석을 통한 AA 5052 판재의 Cross-roll 압연시 Cross angle에 따른 변형을 상태의 변화)

  • Kim, S.H.;Kang, H.G.;Kim, D.G.;Lee, J.S.;Huh, M.Y.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.10a
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    • pp.95-98
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    • 2008
  • In the present work, cross-roil rolling was rallied out using a rolling mill in which the roll axes are tilted by $5^{\circ},\;7.5^{\circ},\;10^{\circ}$ towards the transverse direction of the roiled sample. The evolution of strain states during cross-roll rolling was investigated by three-dimensional finite element method (FEM) simulation. Parallel to cross-roll rolling, normal-rolling using a conventional rolling mill was also carried out in the same rolling condition for clarifying the effect of cross-roll rolling. It turned out that three shear rate components were all introduced to the rolled sample by the cross-roll rolling process, while only one shear rate component operated during normal-rolling.

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Evolution of strain states during Cross-roll rolling in AA 5052 sheet using Finite Element Method (유한요소 해석을 통한 AA 5052 판재의 Cross-roll 압연시 변형율 상태의 변화)

  • Kim, S.H.;Kim, D.G.;Park, E.S.;Lee, J.S.;Huh, M.Y.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.05a
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    • pp.404-407
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    • 2008
  • In the present work, cross-roll rolling was carried out using a rolling mill in which the roll axis is tilted by $7.5^{\circ}$ towards the transverse direction of the rolled sample. The evolution of strain states during cross-roll rolling was investigated by three-dimensional finite element method (FEM) simulation. Parallel to cross-roll rolling, normal-rolling using a conventional rolling mill was also carried out in the same rolling condition for clarifying the effect of cross-roll rolling. It turned out that three shear rate components were all introduced to the rolled sample by the cross-roll rolling process, while only one shear rate component operated during normal-rolling.

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Effect of loading direction on the low cycle fatigue behavior of rolled AZ31 Mg alloy (AZ31 Mg 합금 압연 판재에서 하중방향에 따른 저주기 피로특성)

  • Park, S.H.;Hong, S.G.;Lee, B.H.;Lee, C.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.10a
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    • pp.77-80
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    • 2008
  • Low-cycle fatigue (LCF) tests were carried out to investigate the effect of loading direction on the cyclic deformation behavior and fatigue resistance of rolled AZ31 magnesium alloy. The as-received alloy showed a strong basal texture indicating that the most of basal planes of hexagonal close-packed structure were located parallel to the rolling direction. Two types of specimens whose loading directions were oriented parallel (RD) and vertical (ND) to the rolling direction. respectively, were used for the comparison. It was found that RD specimens yielded at much lower stresses during compression, while vice versa for the ND specimens, which was mainly attributed to the formation of primary twins. This anisotropic deformation behavior resulted in the different mean stresses during the cycling of RD and ND specimens, affecting the fatigue resistance of two specimens. The ND specimen showed a superior fatigue resistance as compared to the RD specimen under strain-controlled condition.

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Strength and fracture toughness of reduced - activation ferritic steel (JLF-1) for fusion reactor application (핵융합로용 저방사화 철강재료(JLF-1)의 강도와 파괴인성)

  • Yun, Han-Gi;Kim, Dong-Hyeon;Lee, Sang-Pil;Park, Lee-Hyeon;Gong, Yu-Sik;Katoh, Y.;Kohyama, A.
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.13-18
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    • 2003
  • Reduced activation ferritic steel, JLF-1 steel (Fe-9Cr-2W-V-Ta), is one of the promising candidate materials for fusion reactor applications. Fracture toughness ($J_IC$) and tensile tests were carried out at room temperature and elevated temperature ($400^{\circ}C$). Two types of CT specimen were prepared to examine the effect of rolling direction on the fracture toughness of JLF-1 steel. Four types of tensile specimen were also prepared to investigate the property by the rolling direction and welding. The Micro Vickers hardness was measured at various distances of a cross section of the TIG joints of JLF-1 steel according to the heating history of each position. Finally, the fracture surface was observed by scanning electron microscopy (SEM).

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Study on the Mechanical Properties of Laser Welded AZ31 Magnesium Alloy (AZ31 마그네슘 합금 레이저 용접부의 기계적 성질에 관한 연구)

  • Lee, M.Y.;Jeong, B.H.;Jeong, S.M.;Park, H.J.
    • Laser Solutions
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    • v.9 no.1
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    • pp.25-29
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    • 2006
  • This study aimed to investigate the change of mechanical properties with the rolling direction and shielding condition during laser welding of AZ31 magnesium alloy. AZ31 magnesium alloy sheets of 1mm thickness were welded using a continuous wave Nd:YAG laser with and without Ar shielding gas. The effect of Ar shielding gas and rolling direction on the mechanical properties were investigated using Vickers hardness, transverse-weld tensile. Porosity in the weld metals was investigated using an optical microscope. The experimental results showed that mechanical properties of AZ31 magnesium alloy laser welds were upgraded compared to those of base metal. Mechanical properties of AZ31 magnesium alloy laser welds were not substantially changed when Ar shielding gas was supplied.

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Fundamental Study on Mechanism of Strip Pinching in Rolling (압연 공정에서 꼬임 발생 메커니즘에 대한 기초 연구)

  • Lee Chang Woo;Shin Kee Hyun;Hong Wan Kee;Jung Dong Taek
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.12
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    • pp.127-132
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    • 2004
  • It is very important to find out causes of strip pinching for the high quality of products and fer the stable operation of rolling system. We have examined the strip pinching from three points of view to find out the causes of strip pinching in rolling system: strip shape, rolling operation conditions, and behavior of strip. Wedge, off center, and difference of rolling force through CMD(Cross machine direction) are found to possibly provide major initial causes of strip pinching. Generally strip pinching occurred in the tail of strip. Thus, computer simulations by using a FEM code were also carried out to find out the initial mechanism of strip pinching depending upon the force and geometric boundary conditions at the time of strip tail rolling. The strong compression force effect due to the sudden release of strip tail from the work roll and non-uniform strip tail shape (ex. Fish tail) across the CMD were found to provide possible major causes of strip pinching.

A Study on Change of Texture During Thermal Cycling in Cu-Zn-AI Shape Memory Alloy (Cu-Zn-AI 형상기억 합금의 열사이클에 따른 집합조직의 변화에 관한 연구)

  • Hong, D.W.;Park, Y.K.
    • Journal of the Korean Society for Heat Treatment
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    • v.5 no.3
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    • pp.179-185
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    • 1992
  • The shape memory effect results from the martensite transfomation of each individual grain. Thus it is necessary to study the texture and its variation. In this study the change of texture during thermal cycling and it's effect on shape memory ability are investigated. The major component of the rolling texture in the parent phase is identified (001) [110], and minor components are (112) [110], (111) [112], {hkl}<100> fiber texture is developed at $45^{\circ}$ from rolling direction. In the case of martensite phase, it is estimated that the major component is (011) [100] and the minor components are (105) [501], (010) [101] and (100) [001]. According to thermal cycling. severity of texture, especially (001) [110] component in parent phase and (011) [100] component in martensite phase are increased. The shape memory ability is increased with increase of thermal cycles and also increased as the direction of specimen approach to $45^{\circ}$ from rolling direction. After first thermal cycling the temperature of transformation can be define clearly and Ms and As are raised by thermal cycling.

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