• Proceedings of the KWS Conference
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• 2005.06a
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• pp.226-228
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• 2005

Of typical welding techniques, to employ the heat for joining process is the most commonly used welding process. But there arise difficulties when this process is applied to light weight alloys such as Aluminium alloy. In this respect, Friction Stir Welding(FSW), a solid-state joining process, is the most effective welding technique with significant potential for various industrial applications. In this study, the characteristics of lapping FSW Al 5052 alloy are shown under a variety of welding parameters such as the rotation speed of FSW tool and welding velocity. Conclusively, the welding properties of lapping FSW Al 5052 were found to be dominated by the deformation of non-joining area near the welding nugget rather than other factors such as the thermal input.

• Journal of Welding and Joining
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• v.21 no.1
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• pp.107-113
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• 2003

Joining of $Si_3N_4$ to $Si_3N_4$ with crystallized glass solder was studied. $SiO_2-Al_2O_3-MgO$ glass with $P_2O_5$ as a crystallizing reagent was used as a solder. To improve the hish temperature toughness of joined specimen, two stage heat treatment was applied to Joined sample for the crystallization of joined layer, Two factors, i.e. thickness of soldered layer and crystallization were taken and thier effects on joining strength were investigated by a SEM-EDX observation of joined interface and bending strength both at room and elevated temperatures. Obtained results are summarized as follows: (1) Nitrogen diffused from $Si_3N_4$ to solder during the Joining process. Average amount of nitrogen in soldered layer depended on the thickness of the soldered layer and increased with decrease of the thickness. (2) Joining strength of the specimen having a thinner soldered layer was stronger than that of thicker layer. This can be mainly attributed to the difference of the nitrogen content in the soldered layer. (3) Higher content of nitrogen in solder brought forth higher viscosity of the solder. Hence the crystallization of the solder become more difficult in thinner layer of the solder than thicker one. (4) Thus, the effect of crystallization was evaluated mostly by the thicker layer specimen. Crystallization of soldered layer improved markedly the fracure strength of joining at higher temperatures than the softening temperature of glass solder.

• Journal of Welding and Joining
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• v.30 no.6
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• pp.80-85
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• 2012

Fatigue cracks in structural components are the most common cause of structural failure when exposed to fatigue loading. In this respect, fatigue crack detection and structural health assessment are very important. Currently, various smart materials are used for detecting fatigue crack and measurement of SIFs(Stress Intensity Factors). So, this paper presented a measurement of SIFs using MFC(Micro Fiber Composite) sensor which is the one of the smart material. MFC sensor is more flexible, durable and reliable than other smart materials. The SIFs of Mode I(K I) as well as Mode II(K II) based on the piezoelectric constitutive law and fracture mechanics are calculated. In this study, the SIF values measured by MFC sensors are compared with the theoretical results.

• Journal of Welding and Joining
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• v.22 no.4
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• pp.73-81
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• 2004

Failure mechanisms of welded joints under fatigue loads are interpreted that multiple collinear surface cracks initiating randomly along the weld toes propagate under the mutual interaction and coalescence of adjacent two cracks. To estimate fatigue crack propagation life for three types of the representative welded joints, i.e. non-load carrying cruciform, cover plate and longitudinal stiffener joint, the stress intensity factors at the front of the surface cracks have to be calculated, which are influenced strongly by the geometry of attachments, weld toes and the crack shapes. For the effective calculation of the stress intensity factors the Mk-factor was introduced which can be derived by a parametric study performed by FEM considering influence of the geometrical effects. The fatigue life of the cruciform joint was estimated by using the Mk-factors and the method considering the propagation mechanisms of the multiple surface cracks. Analysis results for the fatigue life had a good agreement with that of experiment.

• Korean Journal of Metals and Materials
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• v.48 no.12
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• pp.1056-1063
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• 2010

We present a new joining method for Pd-Cu membrane foils used as permeation tubes to collect $CO_2$. Since foils have poor mechanical strength, joining should be done at low temperatures to reduce residual stresses and without joining pressure. This contradicts the well known conditions for good contact between base materials that determines joint qualities. We selected Sn-Ag-Cu alloys that are highly reactive with Pd and Cu as a filler metal. As the filler melts at joining temperatures as low as $220{\sim}280^{\circ}C$, Pd and Cu are dissolved into the melt and react with the filler elements, which raises the melting temperature of the filler based on eutectic structures among the elements. Then, isothermal solidification progresses for the rest of the joining time. Intermetallic compounds (IMC) in the joints, one of the main factors for brittle joints, are inevitably formed. However, by optimizing both joining time and temperature, we balanced the wettability with IMC. Sealing test results confirmed that the joints are mechanically reliable during operation.

• Proceedings of the KWS Conference
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• 1999.05a
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• pp.180-182
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• 1999

• Journal of Welding and Joining
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• v.24 no.5
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• pp.62-66
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• 2006

Panel line is an important process occupying the largest work amount in shipbuilding. In this research product simulation has been carried out to establish the optimal production scheduling. For this purpose a web-based panel line simulator was developed using an object modeling technology and C# language. The balance of work-load and increase in the productivity by the improvement of production facilities and process are the key factors for a good scheduling. In this study SPRT(Shortest Remaining Process Time) rule was applied for the work-load balancing and a good result achieved. To increase the productivity in the stiffener welding stage which is a bottleneck; process, more welding heads and higher welding speed were tested using the developed simulator. The simulation results showed that either more welding head or higher welding speed decreased the total work time. Use of both, however, deteriorated the productivity because of the bottleneck in the following stage. This result points out that the improvement of production facilities and/or process should be evaluated with their influences on the leading and following processing stage.

• Journal of Digital Convergence
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• v.20 no.4
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• pp.689-697
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• 2022

The purpose of this study is to analyze the difference before and after and the influencing factors health status according to the change in the timing of joined in the healthy city area, centering on the metropolitan area. The subjects of this study were divided into two areas. Using the Seoul Survey on Household Members, difference tests and multiple regression analyses were conducted to analyze differences according to timing changes and influencing factors on health status as of 2020. The difference in variables between regions 4 to 5 years and 1 year after joining the healthy city was different, and the factors affecting their health status were also different between regions 4 to 5 years after joining and regions 1 year after joining, so it is necessary to implement policies in consideration.

• Journal of Welding and Joining
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• v.2 no.1
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• pp.25-29
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• 1984

In order to investigate the predominant factors which determine penetration depth and bead width in electron beam welding, bead-on-plate welding was carried out using 7075-T6 Al alloy. The results obtained from the present experiments can be summarized as follows; 1) With increasing accelerating voltage, bead width (B.W) decreases but penetration increases remarkably. 2) Increasing beam current results in increase of bead width and penetration respectively, and decrease of the ratio of penetration increment to beam current increment. 3) With increasing welding speed penetration decreases remarkably, while bead width creases.

• Journal of Welding and Joining
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• v.3 no.2
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• pp.10-15
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• 1985

Roughness of the surface to be welded is one of the important factors affecting the weldabilities on the pressure welding. The purpose of this study is to investigate the influences of the surface roughness upon the welding process and the weldability of pressure welds, using Aluminium AA1050 plates treated by various surface polishing The results obtained are as following. 1. The optimum welding deformation is about 38(%)-42(%) in cold pressure weld. 2. The grinding work on the weld surface is superior to milling and paper polishing. 3. Weld pressure must be beyond $0.5kg/mm^2$ in order that the bond may be achieved.