• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.11
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• pp.1124-1130
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• 2007

This paper presents a new way for fabricating sandwich plates with tetrahedral truss cores. The tetrahedral truss cores are manufactured through metal expanding and bending process and then brazed with solid face sheets. The properties of sandwich plates with the tetrahedral truss cores composed of a wrought steel SS41 under compression and shear loading have been investigated. Good agreement is observed between the measured and predicted peak strengths. Comparisons with normalized compressive strength for other cellular metals have indicated that the tetrahedral truss structures outperform aluminum open cell forms and woven core sandwich plates.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1481-1486
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• 2007

Frictional laws are criticized with emphasis on their application to bulk metal forming simulation in this paper. Coulomb frictional law and constant shear frictional law are investigated in detail in terms of their effect on metal forming process. A friction sensitive bulk metal forming process, a long-pipe simultaneously shrinking and expanding process, is introduced and the problems of the constant shear frictional law are revealed comparing the predictions obtained by the Coulomb frictional law and the constant shear frictional law with the experiments. It is shown that the constant shear frictional law is improper in the case that the normal stress varies very much from position to position and that the normal stress is low compared with flow stress of the adjacent material. It is also shown that the Coulomb frictional constant is more or less affected by the normal stress.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.5
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• pp.435-441
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• 1984

The matrix method, as an effective FEM formulation for the analysis of rigid-plastic deformation, was applied to the bore expanding of anisotropic sheet metal. The effect of planar anisotropy on sheet metal deformation was studied for bore expanding process under the uniform radial stretching condition, and the results were compared with isotropic and normal anisotropic solutions. Experiments were carried out using a flat punch for cold-rolled sheet metal. The experimental results were compared with computations from the matrix method with the boundary conditions corresponding to actual experiment. Both in theory and experiment, it is found that the maximum thinning which results in necking occurs in the direction of the minimum R-value. The results also suggest that the matrix method is efficient for analyzing planar anisotropic sheet metal. The comparison between theory and experiment suggests that Hill's theory of planar anisotropy is somewhat exaggerated. However, the theoretical predictions are in qualitative agreement with the experimental results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.10
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• pp.1025-1030
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• 2007

Three kinds of metallic sandwich panels with quasi-Kagome truss cores have been analyzed on their mechanical behaviors subjected to bending load. According to the results of previous work on the optimal design, they were designed to have similarly high strength per weight with the identical overall sizes, i.e., the total length, the width, the core height. Differences were in the face sheet thickness and/or the thickness of the metal sheet from which the core was fabricated through expanding and bending processes. Under the bending load, they performed well as designed, as far as the maximum load is concerned. However, after the maximum load, the load-displacement curves were different each other depending on the slenderness ratio of the truss elements composing the quasi-Kagome truss cores and the face sheet thickness. Namely, the slenderness ratio and the face sheet thickness governed stability of the elastic and plastic buckling. Therefore, if energy absorption characteristics or structural stability as well as the maximum load capacity are to be achieved, the sandwich panel with thick truss members and thick face sheet should be selected.

• Design & Manufacturing
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• v.10 no.2
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• pp.39-43
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• 2016

Most of automobile parts manufactured through sheet metal forming are mass-produced by using press mold. In recent years, automation and speeding up of press lines have been expanding to maximize product productivity using a press die. The proportion of the moving time in the press line is high, and therefore requires high-speed and automated equipment for the moving process. In this paper, to provide the double-moving system can be the moving time reduction and increased productivity. Developed transport system consists of the material supply, the material feeding device and the PLC controller and the devices are positioned between each of the pressing process. In this paper, the double-moving system including developed units using a multi-axial single-acting through this reduced the C/T(cycle time) and improved the productivity.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.7
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• pp.179-185
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• 2001

Porthole die extrusion is profitable to manufacture long tube with hollow section. The material through portholes is gathered within chamber and welded under high pressure. This weldability which classifies the quality of tube product is affected by several variables and die shape. But, porthole die extrusion has been executed on the experience of experts due to the complicated die assembly and complexity of metal flow. Analytic approaches that are useful in profitable die design and in the improvement of productivity are inevitably demanded. Therefore, the objective of this study is respectively to analyze the behavior of metal flow and to determine welding pressure of hot extrusion product according to the various billet temperature, bearing length and tube thickness by FE analysis and its results are compared with tube expanding tests.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.3
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• pp.36-41
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• 2003

This paper describes a numerical analysis of a non-steady state porthole die extrusion, which is useful for manufacturing long tubes with a hollow section. Materials divided through several portholes are gathered within a chamber and are then welded under high pressure. This weldability classifies the quality of tube products and is affected by process variables and die shapes. However, porthole die extrusion has been executed based on the experience of experts, due to the complicated die assembly and the complexity of metal flow. In order to better assist the design of die and to obtain improvement of productivity, non-steady state 3D FE simulation of porthole die extrusion is required. Therefore, the objective of this study is to analyze the behavior of metal flow and to determine the welding pressure of hot extrusion products under various billet temperatures, bearing length, and tube thickness by FE analysis. The results of FE analysis are compared with those of experiments.

• Journal of the Korean Electrochemical Society
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• v.15 no.3
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• pp.135-148
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• 2012

Ionic liquids are steadily attracting interests throughout a recent decade and their application is expanding into various fields including electrochemistry due to their unique properties such as non-volatility, inflammability, low toxicity, good ionic conductivity, wide electrochemical potential window and so on. These features make ionic liquids become an alternative solution for electrodeposition of metals that cannot be electroplated in aqueous electrolytes. In this review, we classify investigated metals into three categories, which are light (Li, Mg), refractory (Ti, Ta) and noble (Pd, Pt, Au) metals, rather than covering the exhaustive list of metals and try to update the recent development in this area. In electrodeposition of light metals, granular fine Li particles were successfully obtained while the passivation of electrodeposited Mg layers is an obstacle to reversible deposition-dissolution process of Mg. In the case of refractory metals, the quality of Ta and Ti deposit particles was effectively improved with addition of LiF and pyrrole, respectively. In noble metal category, EMIM TFSA ionic liquid as an electrolyte for Au electrodeposition was proven to be effective and BMP TFSA ionic liquid developed a smooth Pd deposit. Pt nanoparticle production from ionic liquid droplet in aqueous solution can be cost-effective and display an excellent electrocatalytic activity.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.268-275
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• 2023

This paper delves into the crucial realm of support structures in metal additive manufacturing (AM) processes and their direct impact on the stiffness of printed components. With the continuous evolution of AM technologies, optimizing support structures has become imperative to enhance the overall quality and performance of manufactured metal parts. Therefore, in this study, tensile specimens were manufactured using various representative support design variables such as support type, spacing, and penetration depth, and the differences in displacement-load curve were analyzed though tensile test. Using additively manufactured support shaped tensile specimen, the paper presents a comprehensive examination of the effect of support parameters on their stiffness. The findings contribute to advancing the understanding how to design supports to suppress thermal deformation of metal parts during AM process, thereby paving the way for enhanced design freedom and functional performance in the ever-expanding field of AM.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.5
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• pp.479-483
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• 2011

The automation of production process is actively expanding for the purpose of the cost reduction and quality assurance. Among these, automatic tracking of the product along the whole process of the production is also important topic. Typically this is done by adopting OCR technology. Conventional OCR technology operates well on the rather good quality of the image like as printed characters on the paper. In industrial application, IDs are marked on the metal surface, and this cause the height difference between background material and character. Illumination systems that guarantee an image with good quality may be a solution, but it is rather difficult to design such an illumination system. This paper proposes an algorithm for the recognition of vehicle's ID characters using edge projection and PCA (Principal Component Analysis). Proposed algorithm robustly operates under illumination change using the same parameters. Experimental results show the feasibility of the proposed algorithm.