• 소성∙가공
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• 제20권4호
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• pp.284-290
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• 2011

The front end bending(FEB) behavior of material that usually occurs in plate rolling is investigated. In this paper, a rollbite profile map approach that systematically predicts the FEB slope is presented. It is based on the concurrent use of shape factors and reduction ratios to ensure an accurate value of the FEB and its slope. In order to obtain the unit roll-bite profile map, the FEB slope model was decomposed into a temperature deviation component and a roll-velocity deviation component. By mapping the results of a series of finite element analyses to the unit functions of the roll-bite profile map, it was possible to obtain a realistic prediction of the FEB slope applicable to an actual plate rolling process. Thereby, the usefulness of the present approach is clearly demonstrated.

• 소성∙가공
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• 제28권4호
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• pp.190-196
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• 2019

The capability of accurately predicting the roll force profile across a strip in the bite zone in cold rolling process is vital for the calculation of strip profile. This paper presents a derivation of a precision mathematical model for predicting variations in the roll force across a strip in cold rolling. While the derivation is based on an approximate 3-D theory of rolling, this mathematical model also considers plastic deformation in the pre-deformation region which is located close to the roll entrance before the strip enters the bite zone. Finally, the mathematical model is expressed as a boundary value problem, and it predicts the roll force profile and tension profile in addition to lateral plastic strain profile.

• 대한치과교정학회지
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• 제53권4호
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• pp.254-263
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• 2023

Objective: The evidence on the accuracy of bite registration using intraoral scanners is sparse. This study aimed to develop a new method for evaluating bite registration accuracy using intraoral scanners. Methods: Two different types of models were used; 10 stone models and 10 with acrylic resin teeth. A triangular frame with cylindrical posts at each apex (one anterior and two posteriors) was digitally designed and manufactured using three-dimensional (3D) printing. Such a structure was fitted in the lingual space of each maxillary and mandibular model so that, in occlusion, the posts would contact their opposing counterparts, enforcing a small interocclusal gap between the two arches. This ensured no tooth interference and full contact between opposing posts. Bite registration accuracy was evaluated by measuring the distance between opposing posts, with small values indicating high-accuracy. Three intraoral scanners were used: Medit i500, Primescan, and Trios 4. Viewbox software was used to measure the distance between opposing posts and compute roll and pitch. Results: The average maximum error in interocclusal registration exceeded 50 ㎛. Roll and pitch orientation errors ranged above 0.1 degrees, implying an additional interocclusal error of around 40 ㎛ or more. The models with acrylic teeth exhibited higher errors. Conclusions: A method that avoids the need for reference hardware and the imprecision of locating reference points on tooth surfaces, and offers simplicity in the assessment of bite registration with an intraoral scanner, was developed. These results suggest that intraoral scanners may exhibit clinically significant errors in reproducing the interocclusal relationships.

• 소성∙가공
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• 제8권6호
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• pp.583-590
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• 1999

New forward slip model has been developed for the precise prediction of rolling speed in the hot strip finishing mill. Besides those influential factors such as neutral point, work roll diameter, friction coefficient, bite angle and the thickness at each side of entry and delivery of the rolls, roll torque was specifically taken into account in this study. To consider the effect of width change on forward slip, calibration factors obtained from rolling torque has been added to new prediction model and refining method has also been developed to reduce the speed unbalance between adjacent stands. The application of the new model showed a good agreement in rolling speeds between the predictions and the actual measurements, and the standard deviation of prediction error has also been significantly reduced.

• 소성∙가공
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• 제19권6호
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• pp.344-351
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• 2010

This paper presents a precision on-line model for the prediction of the roll force and tension distributions across the strip in hot strip rolling. The approach is based on an approximate 3-D theory of rolling, and in particular, considers the effect of pre-deformation of the strip, which occurs near the roll entrance before the strip enters the bite zone. The prediction accuracy of the proposed model is examined through comparison with the predictions from the 3-D finite element models.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1068-1071
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• 1996

Good shape on flat rolled product is necessary to meet today's customer quality requirement. To meet the increasing demand in quality of strip shape from downstream customers, POSCO has replaced the Automatic Shape Control(ASC) system with the existing one that had used noncontact type measuring system at No.2 Cold Rolling Mill, Pohang works in October, 1995. The strip shape is influenced by the profile, roll crown, bending control, skew control system, as well as work roll cooling system. We have used ASC to adjust those factors in Cold Rolling Mill that could get a satisfactory result, almost less than .+-.5 1-unit deviation from the target shape. However, the downstream customer(i.e. Continuos Annealing Line) wants a good shape not only at the moment of exit of roll bite, but after rolling without tension. In this investigation, the difference will be discussed and how deal with this problem.

• Journal of Mechanical Science and Technology
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• 제18권5호
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• pp.762-769
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• 2004

An analytical approach is presented to investigate the deformation characteristics of billets in a continuous billet mill using power driven horizontal stands and idle vertical stands. The analysis is validated by comparison to the experimental results in a previously published work. The analytical results have shown that, apart from the problems of slip and buckling of billet, there are some shortcomings involved in this method. Compared to conventional rolling with all driven stands, the roll load for idle vertical stands and the rolling torque for horizontal stands are almost doubled. The billet is severely stressed within the roll-bite of idle vertical stands and the overall rolling power has increased by one third of that for conventional rolling. Theseshortcomings impair the feasibility of industrial application of idle vertical stand rolling method.

• 한국소음진동공학회논문집
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• 제15권1호
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• pp.20-28
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• 2005

이 논문에서는 기존의 6-축 혹은 9-축 머리진동 측정장치(bite-bar)를 이용한 머리진동 측정에서 직면하는 불확도 인자들에 대한 문제점을 우선 소개한다. 이들 불확도 인자들은 머리의 6-자유도 운동 성분의 추정에 필요한 모든 측정 요소들을 측정하지 않았다는 한계점에서 유발함을 보인다. 이러한 문제점을 극복하기 위하여 4개의 3축 가속도 센서로 구성된 새로운 머리진동 측정장치(12-axis bite-bar)의 모델을 제안한다. 본 모델은 측정 기준점에서의 선형 3축 가속도 뿐 아니라 3축 각 가속도와 함께 6 종의 2차 각속도 성분들의 추정 또한 가능하게 한다. 이러한 12 성분의 추정 모델로부터 비로소 머리의 임의 점에서 6-자유도 운동 성분의 계산이 가능함을 이론적으로 규명한다. 이러한 이론적 배경에 기반을 두고 설계 제작된 12-축 머리진동 장치(12-axis bite-bar)를 소개한다. 본 장치를 이용하여 얻어진 실험 결과 소개 뿐 아니라 기존의 측정장치의 측정 결과와 비교 분석 내용을 소개한다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.158-163
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• 2003

Several simulation techniques have been developed which are not practical deformation processes but are designed to embody specific tribological aspects. Sliding rolling type friction test machine (Cold rolling tribosimulator) was developed to simulate the tribological phenomena at the roll bite in real mill by laboratory scale. A rolled material is fed at a low speed of Max. 1/20 to that of roll speed, so as to obtain simultaneous plastic deformation in the material during rotation of the rolls in simulator. New cold rolling tribe-simulator is effective for evaluation of the lubricity of lubricant in cold rolling process.

• 대한기계학회논문집
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• 제15권1호
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• pp.145-153
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• 1991

본 연구에서는 Toh가 개발하여 stretchforming에 응용한 강소성 대변형 이론 을 압연문제에 적용하여 강소성 대변형 유한요소 프로그램을 개발하는데 있다.