• 한국생산제조학회지
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• 제5권4호
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• pp.38-46
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• 1996

This paper discusses the feasibility of Ultrasonic Nondestructive Evaluation (UNDE) technique for sport weld quality. Ultrasonic c-scan image assisted by image processing technique was used for Nondestructive Evaluation(NDE) of spot weld quality. Ultrasonic testing results obtained were confirmed and compared by Optical Microscope and SAM(Scanning Acoustic Mircroscope) observation of the spot-weld cross section, The results show that the nugget dinameter can be successfully measured with the accuracy of 0.5mm. It was ascertained that ultrasonic c-scan technique is very effective method for the sake of the approach to the quantitative measurement of nugget diameter and the discrimination of the corona bond from nugget. Additional support for the above conclusions is provided by the results for galvanized steel. The ultrasonic results for galvanized welds generally correspond to the results for uncoated steel. Finally, it was found that the above-mentioned technique can be sufficiently applied to NDE method for securing the Quality Assurance(QA) of spot welded products in production line.

• 한국디지털건축인테리어학회논문집
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• 제8권1호
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• pp.57-64
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• 2008

There are many problems in present truss-deck slab system for example welding defect, segregation, water leakage, rust and tarnish etc. These problems may be caused by spot welding thin galvanized steel plate and lattice bar. The TOX Joining Systems is to join metal sheets of different material and thickness with and without coating or painting without adding heat or a joining part. Newly developed TOX-deck slab system using non-welding joint is free from above mentioned problems. The objects of this study are suggestion of design strength of TOX joint by experimental and statistical analyses and development of window based program to design the TOX-deck slab system.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1992년도 특별강연 및 추계학술발표 개요집
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• pp.91-95
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• 1992

The resistance spot welding process has been extensively used for joining of sheet metals, which are subject to variation of many process variables. Many qualitive analyses of sampled process variables have been attempted to predict nugget size. In this paper, dynamic resistance and electrode movement signal which is a good indicative of the nugget size was examined by introducing an artificial neural network estimator. An artificial neural feedforward network with back-propagation of error was applied for the estimation of the nugget size. The prediction by the neural network is in good agreement with the actual nugget size for resistance spot welding of galvanized steel. The results are quite promising in that the quantitative estimation of the invisible nugget size can be achieved without conventional destructive testing of welds.

• 한국표면공학회지
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• 제32권1호
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• pp.21-30
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• 1999

Coating adherance behavior of low carbon steels, produced by POSCO, Korea, was studied in order to study the characteristics of hot rolled galvanized iron(HGI) manufactured without pickling line and the development of its process. Galvanizing experiments were carried out in zinc pot with 0.2wt% Al after hot rolled plates with scale were reduced at $550~750^{\circ}C$ in 10~30% hydrogen gas atmosphere during 60~400seconds. The reduced plates and coated products were examined by SST, XRD, SEM and EPMA on their surfaces and cross sections. Coating layer of HGI manufactured with pickling line was composed of retained scale, Fe-Zn-Al compound, Fe-Zn compound ($\delta_1\;and\;\zeta$ Phase) and pure zinc. It was superior to HGI in coating adhesion. It seems to be due to forming of Fe-Zn-Al compound in interface of matrix and retained porous scale.

• 한국표면공학회지
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• 제33권4호
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• pp.233-240
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• 2000

A novel electrostatic spraying method to solidify molten zinc coating layer was studied by SEM and measurement of sample's temperature. The sprayed droplets also served as nucleation sites in the solidification reaction of molten zinc but might leave the pitting mark by impinging on its surface especially at high spray pressure. Our experimental results showed that electric field could change the sprayed particle trajectories and assist the fine droplets to attach on the surface. Thus, by reducing the spray pressure and by applying the electric voltage higher than -20 KV to charge the droplets electrostatically, we could produce the spangle free galvanized coating layer without pitting.

• 한국표면공학회지
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• 제32권1호
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• pp.31-42
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• 1999

The effect was investigated that aluminium in the zinc bath has on the coating adhesion of Hot-rolled Galvanized Iron(HGI) manufactured without pickling process. It is thought that the coating adhesion of HGI manufactured without pickling process is good due to the fact that increasing aluminium content in the zinc bath makes zinc and aluminium diffuse to the cracks or pores in the scale formed through the reduction heat treatment, and Fe-Zn-Al compound with good ductility is formed in the scale layer and plays a role of anchor between zinc coating and substrate. It is possible that HGI with the good coating adhesion was produced without pickling treatment in the zinc bath with more that 3wt% of Al content even at the $550^{\circ}C$ of conventional reduction heating temperature. In creasing the temperature of heating section and aluminium content in the zinc bath prevents the Zn-Fe alloy. The corrosion resistance of HGI manufactured without pickling process is excellent because of the mixed reaction of zinc sacrifice and aluminium passivity film.

• 한국표면공학회지
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• 제36권6호
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• pp.466-474
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• 2003

To develop a method of detecting dross in coating layer on hot-dip galvanizing steel, chemical etching behavior of the artificial coating layers with top and bottom dross were investigated. After chemical etching with the mixture of picric acid and sodium thiosulfate, each of the top and bottom dross take its distinct color, and alloy layer in coating is also observed. Defects in the coating layers of HGI(hot rolled galvanized iron), CGI(continuous galvanized steel sheet) and GA(galvannealed steel) were analysed, and methods of dross detection which can be applied to inspection process in manufacture were suggested.

• 한국표면공학회지
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• 제16권4호
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• pp.153-159
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• 1983

The growth rate equation of Fe-Zn alloy layer was represented by x = Kt, and hence the growth of alloy layer was considered to be controlled by diffusion process. The constituent of alloy layer formed on the steel surface was identified to be intermetallic compound of Fe3Zn10 and FeZn10. The ultimate tensile strength and elongation of galvanized steel showed a nearly constant value at the thickness below about 30$\mu\textrm{m}$, and both properties decreased with increasing thickness above about 30$\mu\textrm{m}$. In the case of galvanied steel with a great thickness of alloy layer, crack was formed below yield point of base metal, which is considered to be attributed to the alloy layer failure.

• Advances in concrete construction
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• 제8권2호
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• pp.91-100
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• 2019

In this paper three damaged exterior RC beam-column joints made of recycled aggregate concrete (RAC) were repaired. The aim of the study was to restore back the lost capacity of the beam-column joint to the original state or more. A relatively cheap material locally available galvanized steel welded wire mesh (GSWWM) of grid size 25 mm was used to confine the damaged region and then jacketed with cement mortar. Repaired specimens were also subjected to similar cyclic displacement as those of unrepaired specimens. Seismic parameters such as load carrying capacity, ductility, energy dissipation, stiffness degradation etc. were analyzed. Results show that repaired specimens exhibited better seismic performance and hence the adopted repairing strategies could be considered as satisfactory. These findings would be helpful to the field engineers to adopt a suitable rapid and cost efficient repairing technique for restoring the damaged frame structural joints for post earthquake usage.

• 설비공학논문집
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• 제17권6호
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• pp.605-610
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• 2005

The purpose of this experiment is to study the radiant cooling effects by a plate directly viewing the nighttime sky. The measurements are performed on a rooftop of the Engineering building at the Dongguk University in Seoul during the month of August in 2004. The radiant cooling effects are compared using three different types of plate sufaces, namely, galvanized iron, black painted, and aluminum film coated galvanized iron plate. Among these plates, the black Painted surface showed the lowest temperature that is lower than the ambient temperature. The maximum radiant cooling temperature difference, which is ambient temperature minus plate temperature, observed is about 5 K.