• Fire Science and Engineering
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• v.24 no.4
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• pp.104-108
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• 2010

This paper describes electrical fire on electric pad using carbon type hot wires. A carbon type hot wires electric pad is virtually impossible to connect hot wire as a method of electrical welding or soldering. In order to connect between hot wires, that has to splice carbon type material connector. If junction of hot wires was occurrence of poor connection on electric pad, it increase contact resistance on this junction point. With increasing contact resistance, junction of hot wires on electric pad generates local heating and finally leads to electrical fire. In this paper, we analyzed shape of damage in hot wires caused by electrical local heating and investigated fire cause on electric pad using by carbon type hot wires.

• Journal of Ocean Engineering and Technology
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• v.1 no.2
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• pp.113-122
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• 1987

Ships and offshore strrctures are exposed to the corrosive surroundings, and the extablishment of the design criteria and the elucidation on the influence by this environment are requested to maintain the safety and to demonstrate the function of the structure. In this paper, the fatigue-crack-growth behavior on the compact tension specimens of quenched, tempered HT80 grade steels and RA36 high tensile steels having a single edge fatigue cracked notch respectively, were investigated under the repeated tensile stress with constant stroke in sea water for the welded parts by shielded metal arc welding. Main results obtained are summerized as follows; 1. The fatigue-crack-growth rates da/dN in sea water appeared to be greater behavior than those in air environment at the same stress intensisy factor range $\DeltaK$. 2. The correlation data of da/dN$\DeltaK$ of the two kinds of high tensile steels in sea water showed no great difference, however, the correlation data of da/dN$\DeltaK/\sigma_y$($\sigma_y$ stands for yield strength of the material) showed that the fatigue-crack-growth behavior of RA36 plate is affected by active path corrosion(APC) mechanism, while that of HT80 grade plate is mainly affected by hydrogen embrittlement mechanism.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.5 no.4
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• pp.7-12
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• 2006

Galvanized steel pipe, copper pipe and stainless steel pipe, which is being used in waterworks piping materials. In case of galvanized steel pipe, the precipitation of a product is being generated due to the pollution of the tap water, a white water phenomenon, and various corrosion reaction because a zinc ion is melted by tap water. And in case of a cupper pipe, many problems which is harm in sanitation appeared because of a inflow of harmfulness substance by a frequent accident of a water leakage. So, to prevent these problems, it is substituted for stainless steel pipe. However, those problems is still occurring because of badness of welding, a problem of a water leakage in connection part, and a increment of construction expenses. Therefore, this research has examined the laying period according to each piping thickness and a corrosion shape according to each laying depth after laying in various soils(sandy loam, loamy, clay loam, clay) using galvanized steel pipe, copper pipe, and stainless steel pipe. That is, we has studied the data which is necessary for a rational method of preserving the quality of water by examining the corrosion properties of piping materials in the soil environment which waterworks piping materials is being used.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.6
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• pp.93-100
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• 2013

This paper presents the development process for a bicycle monocoque frame using bolt fastening. Traditionally, bicycle frames have been constructed with metal tubes joined at their ends by welding. These frames have been brazed or soldered onto metal lugs, forming the frame. Because stress loads become greatest at the joint of the bicycle tube frame, joint construction strongly influences frame design and construction. To avoid the inherent problems of material discontinuity at frame joints, numerous designers have attempted to reduce or eliminate the number of joints in tube frames. Nevertheless, the manufacture of high quality, reliable, one-piece and jointless frames has proven difficult and expensive. In this study, a new monocoque frame adapted to a hybrid bike is proposed. The advantage of the monocoque frame, is theat is has a rechargeable battery system that is built into the frame; as a result, the emotional quality for the customer is improved. In order to estimate the design compatibility compared with that of tube frames, structural analysis is performed using finite element method. A prototype based on a modified design has also been made and stability testing has been carried out.

• International Journal of Ocean System Engineering
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• v.1 no.1
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• pp.46-51
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• 2011

In a line heating process for hull forming, the phase of the steel transforms from austenite to martensite, bainite, ferrite, or pearlite depending on the actual speed of cooling following line heating. In order to simulate the water cooling process widely used in shipyards, a heat transfer analysis on the effects of impinging water jet, film boiling, and radiation was performed. From the above simulation it was possible to obtain the actual speed of cooling and volume percentage of each phase in the inherent strain region of a line heated steel plate. Based on the material properties calculated from the volume percentage of each phase, it should be possible to predict the plate deformations due to line heating with better precision. Compared to the line heating experimental results, the simulated water cooling process method was verified to improve the predictability of the plate deformation due to line heating.

• Journal of Power System Engineering
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• v.17 no.4
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• pp.86-93
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• 2013

This paper deals with the effects of driving force and material properties on statistical distribution of fatigue crack growth rate (FCGR) for the friction stir welded joints of Al 7075-T651 aluminum plate. In this work, the statistical probability distribution of fatigue crack growth rate was analyzed by using our previous constant stress intensity factor range controlled fatigue crack growth test data. As far as this study are concerned, the statistical probability distribution of fatigue crack growth rate for the friction stir welded (FSWed) joints was found to evaluate the variability of fatigue crack growth rate for base metal (BM), heat affected zone (HAZ) and weld metal (WM) specimens. The probability distribution of fatigue crack growth rate for FSWed joints was found to follow well log-normal distribution. The shape parameter of BM and HAZ was decreased with increasing the driving force, however, the shape parameter of WM was decreased and increased with increasing the driving force. The scale parameter of BM, HAZ and WM was increased with the driving force.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.5 s.170
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• pp.152-158
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• 2005

Inner structured and bonded panel, or ISB Panel, as a kind of sandwich type panel, has metallic inner structures which have low relative density, due to their dimensional shape of metal between a pair of metal skin sheets or face sheets. Previous works showed that ISB panels containing inner structures formed as repeated pyramidal shapes saved weight up to $60\%$ in condition of same stiffness comparing with solid sheet. In this work, woven metal is adapted to inner structures replacing pyramidal structures. The test specimens of ISB panel containing woven metal made by multi-point electric resistance welding and 3-point bending test have been carried out. The results of experiments and comparisons of process parameters, stiffness and failure mode are discussed.

• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.280-284
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• 2012

In this study, we prepared a sample of AISI 409L weld metals using automotive exhaust manifolds and evaluated their corrosion properties by conducting an anodic polarization test after 10 minute of heat treatment at $900^{\circ}C$. The specimens of AISI 409L transformed fully ferrite. Weld metal was refined more than base metal. Specimen of heat treatment at $900^{\circ}C$ and as weld specimen was formed precipitation. However heat treatment specimen was bulkly formed and coarser than the as weld specimen. The strength measured by 10 Hv highly at heat treatment specimens in comparison with as weld. The increase in strength is attributed to the precipitation of Ti. The result of heat treatment suggest that there was a decrease of current density and high corrosion potential. Following heat treatment process produced Ti precipitation and for this reason, it can restrain Cr-carbide so that steel will have more corrosion resistance.

• Steel and Composite Structures
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• v.25 no.2
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• pp.245-255
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• 2017

The performance of an Industrialised Building System (IBS) consists of prefabricated reinforced concrete components, is greatly affected by the behaviour of the connection between beam and columns. The structural characteristics parameters of a beam-to-column connection like rotational stiffness, strength and ductility can be explained by load-rotation relationship of a full scale H-subframe under gravitational load. Furthermore, the connection's degree of rigidity directly influences the behaviour of the whole frame. In this research, rotational behaviour of a patented innovative beam-to-column connection with unique benefits like easy installation, no wet work, no welding work at assembly site, using a hybrid behaviour of steel and concrete, easy replacement ability, and compatibility with architecture was investigated. The proposed IBS beam-to-column connection includes precast concrete components with embedded steel end connectors. Two full-scale H-subframes constructed with a new IBS and conventional cast in-situ reinforced concrete system beam-to-column connections were tested under incremental static loading. In this paper, load-rotation relationship and ratio of the rigidity of IBS beam-to-column connection are studied and compared with conventional monolithic reinforced concrete connection. It is concluded that this new IBS beam-to-column connection benefits from more rotational ductility than the conventional reinforced concrete connection. Furthermore, the semi-rigid IBS connection rigidity ratio is about 44% of a full rigid connection.

• Corrosion Science and Technology
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• v.20 no.2
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• pp.69-76
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• 2021

In this work, we have performed a corrosion failure analysis of a leaking tube connected to an upper header of a condensate pre-heater in a heat recovery steam generator. It was revealed that the leakage position in the tube was the location where the materials were easily vulnerable due to tensile residual stresses induced by the material manufacturing process and welding process. In addition to an imbalance in the module induced by temperature difference during operation of the pre-heater, the weight of the modules and thermal fatigue provoked a type of stress of tensile-tensile fatigue on the tube. Thus, the leakage position of the pre-heater was exposed to the tensile stress on the inner surface of the tube facing the gas, which rendered the unstable oxide layer susceptible to corrosion and the formation of pits on the water side. The cracks propagated along with the degraded microstructure in a transgranular cracking mode under fatigue loading and finally resulted in water leakage.