• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.5
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• pp.462-468
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• 1984

The variation of thermal diffusivity with respect to rolling reduction is experimentally determined by flash technique. Copper alloy is used as an experimental and specimens are cut from the slab produced by rolling process with different percent reduction in thickness along the rolling direction and with 30.deg. 60.deg. and 90.deg. angle to the rolling direction. It is found that thermal diffusivity is slightly decreased as rolling reduction increased, and it has tendency that thermal diffusivity is increased slightly as its angle approached to 90.deg. at same rolling reduction.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.3
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• pp.464-471
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• 2003

Among various methods to acquire high strength in plain carbon steel, the mettled of grain refinement by controlling thermo-mechanical processing parameters has gained a great attention if steel rolling industries. In the present study, three different rolling pass schedules are proposed to obtain fine grains which are based on combined results of recrystallization modelling, finite element analysis and experiment. Since meta-dynamic or dynamic recrystallization has been found to be very effective in producing fine grains, reduction ratio and interpass time in the proposed rolling pass schedules were determined in order to invoke such recrystallization as often as possible.

• Korean Journal of Metals and Materials
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• v.49 no.3
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• pp.243-249
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• 2011

This study describes the feasibility of producing high-strength Al alloy sheet with a high solute content using a combined technique of twin-roll strip casting and asymmetric rolling. The Al sheet produced in this study exhibited excellent formability ($\overline{r}$ =1.0, $\Delta$r=0.16) and mechanical properties ($\sigma_{TS}$~305 MPa, $\epsilon$~33%), that, cannot be feasibly obtained via the conventional technique based on ingot casting and rolling. The structural origin of the observed properties, especially enhanced formability, was clarified by examining the evolution of textures associated with strip casting and subsequent thermo-mechanical treatments. Our evaluation of the mechanical properties and formability leads us to conclude that the combination of strip casting and asymmetric rolling is a feasible process for enhancing the formability of Al alloy sheets to the level beyond what the conventional techniques can reach.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2836-2844
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• 2000

Thickness control of hot-rolled strips has become an important issue in recent years because of the need for improving the quality of the hot-rolled strip. In this study, a modifying method of rolling force set-up with consideration of spread was developed to improve the thickness uniformity at the finishing rolling units in hot rolling. Through the analysis of real production data it was found that the accuracy of the rolling force determined from the finishing mill set-up (FSU) model dominantly governed the thickness uniformity in rolled plates at the front. Based on this analysis , several examples were selected to calculate the spread of rolled plate using three dimensional rigid thermo-viscoplastic finite element program. FE analysis results were used to train the neural network system that can predict the spread hot-rolled plate and the rolling force was modified based on the predicted value of spread. The modified rolling forces were closer to the measured rolling force so it can be expected that the accuracy of thickness uniformity of hot-rolled plate will be improved.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1071-1082
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• 1988

Surface rolling is one of the micro plastic processes which yields local deformation of surface, and improves surface roughness, hardness and fatigue strength. With the use of gray cast iron (GC 30) as material for experiment, the changes in surface roughness were investigated. A number of previous theses were refered to the effects of surface rolling for this study. With the use of steel ball of excellent in surface roughness and hardness, and with the applied force 20Kgf, surface rolling was performed. The summary of the experiment is as follows: (1) With the fixed applied force 20Kgf and the ball of 8.726mm in diameter, surface roughness was found to be the most excellent. (2) Increase in hardness was most prominent in the first rolling, but less effective in the succeeding rolling. (3) Reduction on diameter was affected by the previous process before rolling, and about 70 to 90% of reduction was made in the first rolling.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.12
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• pp.2096-2105
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• 1997

A parallel approach using a network of engineering workstations is presented for the efficient computation in the elastoplastic analysis of strip rolling process. The domain decomposition method coupled with the frontal solver for elimination of internal degrees of freedom in each subdomain is used. PVM is used for message passing and synchronization between processors. A 2-D plane strain problem and the strip rolling process are analyzed to demonstrate the performance of the algorithm and factors that have a great effect on efficiency are discussed. In spite of much communication time on the network the result illustrates the advantages of this parallel algorithm over its corresponding sequential algorithm.

• Transactions of Materials Processing
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• v.28 no.2
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• pp.83-88
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• 2019

This paper introduces a new concept - on-line FE model, as applied to metal rolling. The new technology allows for completion of process simulation within a tiny fraction of a second without loss of high-level prediction accuracy inherent to FEM. The three steps of an on-line FE model design namely, process metamorphosis, mesh design, and process variable design, are described in detail. The procedure is demonstrated step by step through designing actual on-line models for the prediction of the dog-bone profile in edge rolling. The validity and prediction accuracy of the on-line FE models are analyzed and discussed.

• Transactions of Materials Processing
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• v.28 no.2
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• pp.89-97
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• 2019

In this paper, we examine the application of a new concept - on-line FE model in various metal rolling processes. This technology allows for completion of process simulation within a tiny fraction of a second without losing the high level of prediction accuracy inherent to FEM. The procedure is systematically demonstrated through the design of actual on-line models for the prediction of the width spread in horizontal rolling of the slab using a dog bone profile and horizontal rolling of the strip with a strip profile. The validity and the prediction accuracy of the on-line FE models were analyzed and discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.11
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• pp.971-978
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• 2016

Recent trends in miniaturization and lightness in portable electronics parts have driven developments in subminiature screws. This study aims to investigate the thread rolling process of a subminiature screw with an outer diameter and pitch of 1.0 and 0.25 mm, respectively. Finite element (FE) analyses were performed for the thread rolling process of symmetric and asymmetric screw threads. Through FE analyses, various process parameters, such as the horizontal and vertical die gap and the rolling stroke, were investigated in terms of the forming accuracy. The material flow characteristics in the thread rolling process of the symmetric and asymmetric screws were also discussed, and the relevant process parameters were determined accordingly. These simulation results were then reflected on real thread rolling processes, from which the symmetric and asymmetric screws could be formed successfully with allowable dimensional accuracy.

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.320-326
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• 2011

Flat rolling of wire is an industrial process used to manufacture electrical flat wire, medical catheters, springs, piston segments and automobile parts, among other products. In a multi-step wire flat rolling process, a wire with a circular crosssection is rolled at room temperature between two flat rolls in several passes to achieve the desired thickness to width ratio. To manufacture a flat wire with a homogeneous microstructure, mechanical and metallurgical properties with an appropriate pass schedule, this study investigated the effect of each pass schedule (1stand ~ 4stand) on the microstructures, mechanical properties and widths of cold rolled high carbon steel wires using four-pass flat rolling process. The evolutions of the microstructures and mechanical properties of the widths of cold rolled wires during three different pass schedules of the flat rolling process of high carbon wires were investigated, and the results were compared with those for a conventional eight-pass schedule. In the width of cold rolled wires, three different pass schedules are clearly distinguished and discussed. The experimental conditions were the same rolling speed, rolling force, roll size, tensile strength of the material and friction coefficient. The experimental results showed that the four-pass flat cold rolling process was feasible for production of designed wire without cracks when appropriate pass schedules were applied.