• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.863-868
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• 2004

Reheating furnace is an essential facility of a rod mill plant where a billet is heated to the required rolling temperature so that it can be milled to produce wire. Sometimes, it is also necessary to control a transient billet temperature pattern according to the material characteristics to prevent a wire from breaking. Though it is very important objective to obtain a correct information of a billet temperature during furnace operation. Consequently, a billet temperature profile must be estimated. In this paper, a billet heat transfer model based on FEM (Finite Element Method) with spatially distributed emission factors is proposed and a measurement is also carried out for two different furnace operation conditions. Finally, the difference between the model outputs and the measurements is minimized by using the new optimization algorithm named uDEAS(Univariate Dynamic Encoding Algorithm for Searches) with multi-step tuning strategy. Hence, the information of billet temperatures can be obtained by using proposed model on various furnace operation conditions.

• International Journal of Control, Automation, and Systems
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• v.5 no.1
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• pp.43-50
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• 2007

Reheating furnace is an essential facility of a rod mill plant where a billet is heated to the required rolling temperature so that it can be milled to produce wire. Although it is very important to obtain information on billet temperatures, it is not feasible during furnace operation. Consequently, a billet temperature profile should be estimated. Moreover, this estimation should be done within an appropriate time interval for an on-line application. In this paper, a billet heat transfer model based on 2D FEM(Finite Element Method) with spatially distributed emission factors is proposed for an on-line billet temperature estimation and also a measurement is carried out for two extremely different furnace operation patterns. Finally, the difference between the model outputs and the measurements is minimized by using a new optimization algorithm named uDEAS(Univariate Dynamic Encoding Algorithm for Searches) with multi-step tuning strategy. The obtained emission factors are applied to a simulation for the data which are not used in the model tuning for validation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.333-336
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• 2006

A new forming method for metal/ other metal two-layer tubes by multi-billet extrusion (MBE) is introduced. The forming possibilities of two-layer tubes CDA 365(inner)/Al 1100(outer) and Al 2014(inner)/Al 1100(outer) by MBE are investigated according to the given frictional condition and die profile. The results show that two-layer tube composed by two types tube as abovementioned can be manufactured by MBE. Some stated variables in the forming process such as effective stress and normalized pressure at welding surface are analyzed by FEM code ($DEFORM^{TM}$-3D)

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.199-202
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• 1999

Many processing times for fabricating complex shaped parts by near net shape process such as thixoforming or semi-solid forming, are required due to the time for die design, induction heating and forming process. Therefore, for the thixoforming process, multi-capacity induction heating process is very important due to the reduction of the processing time and cost. It is indispensable to adopt a power-time heating pattern which manages to conciliate complete eutectic melting at the core with limited overheating at the periphery. The total reheating time is thus dependent on billet diameter; in inches$(pm20%)$. Typically, high frequency is used for the rapid reheating of the billet to the eutectic temperature range and low frequency for the remelting of the desired fraction of liquid and for the radial homogeneization of the liquid fraction. So in this study, the multi-capacity induction heating conditions of ALTHIX 86s alloy to reduce the processing time and cost would be proposed. The suitability of multi-capacity induction heating conditions would be verified through the comparison to Garat's data.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.208-211
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• 2001

In the drawing from round billet to non-circular section there are two different processes through solid hole die(HD) and the other cassette roller dies(CRD). The CRD process has several cassette type rollers and a billet is able to move through the given gaps between two profiled rollers. The objective of this study is based on the analysis and evaluation of two aforementioned processes using experiments and finite element simulation. In order to simulate the multi-stage drawing process from circular sectioned billet to rounded square section, the finite element analysis is applied to the process using a commercially available DEFORM-3D code. Two types of experimental drawing tests through designed and manufactured dies for pure copper and aluminum alloy are carried out at room temperature. The analysis included comparison of material properties before and after drawing of each process and also provide some useful information by a FEM simulation.

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.812-818
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• 2003

The aim of this study is to investigate the fabrication processes on the microstructual changes and mechanical properties of large 7175 aluminum die forgings. The billets range from 370 to 720 mm in diameter were homogenized and hot forged after direct chill casting. The strength and elongation of the homogenized cast billets were revealed nearly same level independent of the billet diameter. However, these properties of ø370 mm cast billet were superior to those of $\Pie720$ mm billet under$ T_{6}$ / condition. The tensile strength of die forged specimens under $T_{6}$ condition increased up to 20% than that of solution treatment, however, the elongation was reduced to 50%. The fracture toughness of die forged specimens under $T_{6}$ condition was 35.6∼39.0 MPa$.$$m^{1}$2 irrespective of the billet size and free forging processes, but this property increased up to 10% by$V_{74}$ treatment. The fracture toughness of die forged specimen manufactured with ø370 mm cast billet showed nearly same level of ø720 mm billet which was processed using MF or Cog free forging followed by die forging.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.359-362
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• 2003

The bending phenomenon has been known to be occurred by the different of velocity at the die exit. The difference of velocity at the die exit section can be obtained by the different velocity of billets through the multi-hole container and by the cohesion of billet inside the porthole die chamber. The bending phenomenon can be controlled by the different hole diameter. The experiments using aluminium material for the curved tube product had been done. The results of the experiment show that the curved tube product can be formed by the extru-bending process without the defects such as the distortion of section and the thickness change of the wall of tube and the folding and wrinkling. It is known that the welding and extruding of each billet has done simultaneously although the curved tube is extruded with four billets.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.4
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• pp.29-35
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• 2007

The main objective of this paper is to propose the optimal design method of forging process using genetic algorithm. Design optimization of forging process was doing about one stage and multi stage. The objective function is considered the filling of die. The chosen design variables are die geometry in multi stage and initial billet shape in one stage. We performed FE analysis to simulated forging process. The optimized preform and initial billet shape was obtained by genetic algorithm and FE analysis. To show the efficiency of GA method in forging problem are solved and compared with published results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.285-288
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• 2003

The bending phenomenon during extruding one product using four billets can be obtain by the difference of hole diameters in the multi-hole container. The difference of hole diameter caused the difference of billet amount inserted in the die cavity. As results, it can bend during extruding products by the different amount of two billets and by the cohesion of billets in the porthole dies cavity. And the bending curvature can be controlled by the size of holes and billets. The experiments using aluminium material had been done for the rectangular and square curved tube product. The results of the experiment show that the curved aluminum tube product can be bended by the extru-bending process without the defects such as the distortion of section and the thickness change of the wall of tube and the folding and wrinkling. The curvature of product is affected by shape of cross section and the difference of billet diameters. It is known that the welding and extruding and bending can be done simultaneously in the die cavity when a rectangular hollow curved tube would be extruded by porthole dies using four different size billets made of aluminum material.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.10a
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• pp.141-148
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• 1994

In order to improve the productivity of cold forging at low production cost, an integrated system's approach is necessary in handling the material preparation and the optimum process design, considering the forming machines, tooling, and operation including quality control. As the first step toward this approach, an expert system for multi-stage cold forging process design for fasteners with various head geometries is developed using Prolog language on IBM 486 PC. For effective representation of the complex part geometries, the system uses the multiple element input, and the forward inference scheme in determination of the initial billet size and intermediate forging steps. In order to determine intermediate steps, the basic empirical rules for extrusion, heading, and trimming were applied. The required forming loads and global strain distributions at each forging step were calculated and displayed on the PC monitor. The designed process sequence drawing can be obtained by AutoCAD. The developed system will be useful in reducing trial and error of design engineers in determining the diameter and height of the initial cylindrical billet from the final product geometry and the intermediate necessary sequences.