• 한국건축시공학회지
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• 제3권4호
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• pp.73-78
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• 2003

In this Study, we examined the influence of characteristics of rolling loads by casters on separation resistance of substrate concrete and synthetic resin floor coating. In the experiment, we first prepared floor samples having substrate concrete of various compressive strength, surface hardness and surface configurations, then put the coated samples to the test of separation resistance with Rolling Caster Loading Machine. Three loading conditions consisted of different kinds of casters, rolling conditions, and coating materials. Consequently, we clarified that the grade of separation resistance varied widely according to the characteristics of substrate concrete and rolling loads.

• Tribology and Lubricants
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• 제7권1호
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• pp.40-45
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• 1991

Wear performances for dibutyl 3,5-di-t-butyl 4-hydroxy benzyl phosphonate (DBP) were invesitigated using the four ball test machine under sliding and also rolling contact conditions, and compared with ZDDP. DBP showed excellent antiwear performace compared with ZDDP under severe sliding contact. Also, DBP achieved a longer fatigue life than ZDDP under rolling contact conditions. The surface of the worn balls was observed using an optical microscope, and the wear derbis generated was measured using the Particle Quantifier (PQ).

• Tribology and Lubricants
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• 제17권6호
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• pp.417-426
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• 2001

The effect of silver particle introduction on the rolling friction of AISI 52100 steel pairs has been investigated. Experiments ware performed in dry conditions using a thrust bearing-type rolling test rig at a load range of 12-960 N and a sliding velocity range of 8-785 mm/sec with pure (99.99%) silver particles. Results showed that introduced silver particles formed transfer layers, which protected the virgin bearing surfaces and resulted in the low lolling friction. By changing the quantity of silver particles, transitions in the rolling friction were found. Results also showed that the variations in normal load and rolling speed also affected the rolling friction behavior. Analyses of SEM and EPMA showed that the formation the transfer layer was mainly governed by the silver particle quantity, normal load and rolling speed, and this resulted in the different behavior of rolling friction. In this study, it was found that the low and stable rolling friction was resulted from the, shakedown phenomena occurred at the silver transfer layer.

• 소성∙가공
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• 제18권5호
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• pp.377-384
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• 2009

The shape of edge cracking in rolling process generally occurred "V" shape. This cracking is successively generated at width edge of strip. The edge cracking is developed to center of strip during rolling process. In the results, the strip is occurred fracture, and the productivity is gone down because of the extensive production time. Accordingly, we need to control crack propagation during rolling process. But, the control of cracking is very difficult in rolling process. Previously the studies of edge cracking were mainly performed on hot rolling process. In this paper, the shape of the edge cracking in rolling was estimated according to process conditions such as initial edge crack size, reduction ratio and tension using FE-simulation and the simplicity experiments on cold rolling process.

• 소성∙가공
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• 제19권3호
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• pp.160-166
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• 2010

In this paper, the process parameters of thread rolling were designed based on the numerical analysis results. Firstly, the effective analysis conditions that guarantee the reliability of the analysis results were found. To find the effective analysis conditions, the analyses were carried out for various numbers of teeth. And then, the effects of the process parameters such as tool shape and temperature on the thread rolling performance were investigated. The formability in thread rolling process was evaluated in terms of Cockcroft-Latham damage value. In order to evaluate formability, Cockcroft-Latham damage value was normalized by the critical damage value which was obtained from the analysis of uniaxial tensile test. The analyses were carried out using DEFORM-3D. The results showed that the flank angle and crest round had an effect on the thread rolling load. It was also shown that temperature had significant effects on the effective strain distribution, rolling load, and damage. With the reduced formability of stainless steel at higher temperature, it was shown that the normalized damage values increased as the process temperature.

• Journal of Mechanical Science and Technology
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• 제16권10호
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• pp.1296-1302
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• 2002

A mathematical model for cold rolling and temper rolling process of thin steel strip has been developed using the influence function method. By solving the equations describing roll gap phenomena in a unique procedure and considering more influence factors, the model offers significant improvements in accuracy, robustness and generality of the solution for the thin strip cold and temper rolling conditions. The relationship between the shape of the roll profile and the roll force is also discussed. Calculation results show that any change increasing the roll force may result in or enlarge the central flat region in the deformation zone. Applied to the temper rolling process, the model can well predict not only the rolling load but also the large forward slip. Therefore, the measured forward slip, together with the measured roll force, was used to calibrate the model. The model was installed in tile setup computer of a temper rolling mill to make parallel setup calculations. The calculation results show good agreement with the measured data and the validity and precision of the model are proven.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1996년도 제24회 추계학술대회
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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.

• 대한전기학회논문지
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• 제38권4호
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• pp.307-315
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• 1989

본 논문에서는 열간압연공정중 소재가 가열로에서 추출되어 조압연 공정을 마치기 까지 소재인 slab의 온도변화추이를 해석키 위하여 rolling process 상에서 온도에 영얄을 미치는 인자인 1) 대기중 복사 및 대류에 의한 냉각 2) 소성가공발열 3) descaling water에 의한 수냉각 4) rolling roll, 운반 roll과의 접촉냉각등 제요인에 관한 사항을 rolling process 상에서의 문제로 평가도입하여 해석하고저 하는 slab 표면에서의 경계조건 설정과 관련한 적용기법을 정립하였고 소재의 냉각 현상을 two dimensional transient heat flow문제로 취급, 유한차분방정식을 이용하여 해석하는 과정과 관련 rollinh작업을 sequence화 하여 적용하는 기법을 제시하였다. simulation 결과 계산치와 실계측편차 (${\pm}18^{\circ}C$)범위내에서 일치함을 제시하였고 또한 rolling event 별로 나타나는 온도하강 pattern이 실제의 압연상황과 잘 일치함을 제시하므로서 본 computer simulation 과정에서 적용한 가정, 조건, 물성치 등의 적정성 등을 입증하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.117-120
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• 2001

In hot roiling process, new rolling mills have been apapted to strip rolling but we can usually experience the problem of snaking of strip. This phenomenon was arisen by nonsymmetric rolling and on-centering and cambering of a strip and other mill conditions. Three dimensional analysis for strip rolling predicted the influence of nonsymmetric rolling, off-centering and pair crossing system This study evaluated the fundamental characteristics of snaking of a strip to optimize the operating condition for trouble free rolling.

• 조명전기설비학회논문지
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• 제27권11호
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• pp.47-56
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• 2013

Rolling speed, roll gap, and cooling pattern in hot strip finishing mill process should be determined before inserting strip into roll. Such parameters are initially calculated by a mathematical set-up model. The technique to find adequate roll speed via a mathematical model has inherently limit because required working conditions are various and rolling process is nonlinear. To improve the accuracy of initial rolling speed for a finishing mill, this paper suggests a correction technology for initial rolling speed. The proposed method was implemented in hot strip mill process. As the results, the magnitude of width error in strip head-end part caused by excessive strip tension was decreased remarkably.