• Journal of Welding and Joining
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• v.19 no.4
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• pp.379-383
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• 2001

Resistance spot welding has been widely used in the sheet metal joining processes because of low cost, high productivity and convenience. Recently, automobile and aerospace industries are trying to replace partly steel sheets with aluminum alloy sheets. But in the case of dissimilar materials, to apply resistance spot welding has been known to be very difficult owing to the effect of melting temperature. On this study, an effort was made to apply spot welding of dissimilar sheet metals, 2024 aluminum alloy and zinc coated steel sheet, evaluate the spot weld quality with tensile-shear strength test and nondestructive evaluation technique, C-scan image methodology. In this study results, as the current below 11 kA, melting of materials is not achieved well. Also as the current exceeds to 13.5 kA, the more spatters happen at welded zone and tensile-shear strength lowered. So, the feasibility of C-scan image technique proposed in the study is found to be suitable evaluation method for resistance spot weldability.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.247-249
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• 2005

Evaluation and prediction of fatigue crack initiation life in EZNCEN(Galvanized steel sheet) and HS40R(High strength steel sheet) tensile-shear spot weldment were studied by using DCPDM(DC Potential Drop Method)

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.92-97
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• 2008

To survive in outdoor environments, photovoltaic modules rely on packaging materials to provide requisite durability. We analyzed the properties of encapsulant materials that are important for photovoltaic module packaging. The properties of Ethylene Vinyl Acetate(EVA) sheet in photovoltaic encapsulant materials have to meet conditions that are high optical transmittance, good adhesion and high cross-linking rate. The objective of this paper is to understand the property evaluation methods of EVA sheet. Through this research, we could confirm that properties of EVA sheet have an effect on durability and operating efficiency of photovoltaic module.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.235-236
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• 2007

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.440-443
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• 2005

Recently the usage of galvanealed steel sheet was increased in order to protect corrosion in automobile industry. So, the alternative of steel sheet was investigated in a point of formability. Generally it was known that uncoated steel sheet has better mechanical properties than coated steel sheet. But, contrary results were sometimes occurred in workplace. This reason is the effect of friction. In this study, the formability of steel sheet considering friction characteristics was investigated with tensile test, cup drawing test and finite element method.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.4
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• pp.142-150
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• 2001

Automotive manufactures have taken more interests in tailored sheet metals for improving the rigidity, weight reduction, crash durability, and cost savings so that their application to auto-bodies has been increased. However, since the tailored sheet metals do not behave like un-welded sheet metals in press forming operations, the stamping engineers no longer rely only on conventional forming techniques. Futhermore, there is no clear understanding of the characteristics of welded metal which influence the overall press formability of tailored sheet metals. Recently, the computer simulations are prevailing for the evaluation of the formability. Unfortunately, the mechanical property of tailored sheet metal has to be quantitatively defined in the simulation. In this study, the analytical equations are formulated in order to find the mechanical properties of the welded metal in the tailored sheet metal welded by co$_2$laser. Based on force distribution assumption, the constitutive behavior of the welded metal is investigated using uniaxial tensile test results of base metals and tailored sheet metal. Then, the strength coefficient, work-hardening exponent, and plastic strain ratio of laser-welded metal are calculate from those of base metals and tailored sheet metal. In addition, the existence of weld defects in the welded metal is indirectly detected by examining the slop of strength coefficient of the welded metal.

• Proceedings of the Korean Institute of Building Construction Conference
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• v.y2004m10
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• pp.39-44
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• 2004

A heat and room temperature construction method of asphalt have been mainly applying to rooftop waterproofing in concrete structure, and the rest construction method are sheet, membrane and mortar waterproofing construction method. In particular, joint method in sheet waterproof method is as overlap joint which on being reinforced with fiber and tape, have been applying for job site to mechanical fix using protection disk and anchorage and metal ironwork on the end of sheet. These construction method cause cutting off joint of sheet as behavior of structure according to repairs of sheet itself and thermal conduct, outdoor air environment. In conclusion, we analyzed and examined the application of various sheets and piece ashes about superior 'I' joint which divide from one and the other sheet and progressed about joint construction method of fixing method for overlap.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.130.1-130.1
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• 2011

Nowadays, the number of PV module corporation is increasing due to demand growth of silicon solar module. However almost study of module is research about increasing of efficiency for it. This study is evaluation and development for process of module using the silicone encapsulation material instead of existing EVA sheet. We are changed adding material ratio on silicone and thickness of silicone. So we get better efficiency than EVA sheet through the evaluation for silicone liquid and modulation. Also, we are test after establishing manufacture system being able to quicker than existing modules line. The result of EVA sheet is average 207.47W and silicone material is 211.32W so we think that silicone is better than EVA sheet.

• Transactions of The Korea Fluid Power Systems Society
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• v.5 no.2
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• pp.8-13
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• 2008

Shell-and-tube type heat exchangers are generally classified with fixed tube-sheet and floating tube-sheet heat exchangers. In this paper, we employed the fixed tube-sheet heat exchangers. We theoretically investigated the safety evaluation of our shell-tube heat exchanger by axial, bending and equivalent stress of fin tubes, tube plates, channels and shell. Design pressure ranges were chosen pressure($0.6{\sim}2\;MPa$) on tube side and 200 %(3 MPa) of Maximum pressure on shell side for safety evaluation of heat exchangers. This research will be useful for fabrication of heat exchangers to prevent against damage hazard of heat exchangers in operation.

• Transactions of Materials Processing
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• v.11 no.6
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• pp.503-512
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• 2002

The drawbead is used to control material flow into the die during the binder wrap process and the stamping process in the sheet metal forming process. Since the dimension of drawbead is relatively small in comparison with the typical dimensions, it is difficult to include drawbeads in finite element analysis of the sheet metal forming process. It is because the mesh system has to be fine enough to describe the drawbead and the computation time is drastically increased. In this paper, simulation of drawbead forming has been carried out to obtain the equivalent boundary conditions in the binder wrap process and the stamping process. In order to investigate the effect of various die geometries, parameter studies are performed with the variation of parameters such as the blank length, the drawbead depth, the drawbead radius, the inclination of die and the friction coefficient.