• Journal of Advanced Marine Engineering and Technology
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• v.35 no.4
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• pp.451-459
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• 2011

Austenitic stainless steels of 300 series are widely used as the structural material due to excellent their cryogenic mechanical properties at cryogenic temperature. There are 316 steel which molybdenum is added to improve the austenitic stability, 316L which carbon contents is reduced to decrease the grain boundary precipitation during welding process, and 316LN which nitrogen is added to improve the austenitic stability and the mechanical strength. But material researches for the welding conditions and mechanical properties at the cryogenic temperature were insufficient so far. In this paper, the characteristics of mechanical properties considering the effect of welding conditions and cryogenic temperature are studied.

• Journal of Adhesion and Interface
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• v.7 no.4
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• pp.10-12
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• 2006

The successful use of adhesively bonded parts depends on the defect-free bond of the components. Therefore it is necessary to detect relevant faults and defects in an early state of the production. A 100% test should be pursued, but especially at complicated structures the detection of defects is not easy. Possible testing methods, which show a high potential for the NDT of adhesively bonded parts, are thermography based NDT methods. At present mainly two different procedures of active thermography are being used: Pulse and Lock-In Thermography. With pulse thermography the examined material is warmed up with a short energy pulse (light, eddy current or ultrasonic pulse) and the heat response is recorded after a certain time. The result is an infrared image which indicates material defects in different depths. This paper presents a variety of images showing the capability of Lock-In Thermography to image subsurface defects. Several examples of adhesives joints qualify the ultrasonic Lock-In-Thermography for the in-process quality control for adhesive bonded components.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.93-93
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• 2010

We developed friction welded bimetallic sleeve for 220kV aluminum conductor XLPE cable. Not only friction welded bimetallic sleeve for Termination(EB-A, EB-G) but also friction welded sleeve for Joint of Al to Cu conductor was developed regardless of this project. Generally, friction welded sleeve used to connect Al conductor cable to Cu conductor cable and used for improvement of mechanical property of terminal by offer the copper side of friction welded bimetallic sleeve at the Termination. Connection method for Al-Cu conductor has mainly used friction welding at the solid state, because it is difficult to connect by using conventional welding method. this investigation introduces development of friction welded bimetallic sleeve by friction welding and test result of 220kV Al conductor XLPE cable and accessories using friction welded sleeve.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.6
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• pp.632-639
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• 2012

A fully coupled thermo-mechanical model is adopted to study the temperature distribution and the material deformation in friction stir welding(FSW) process. Rotational speed is most important parameters in this research. Three dimension results under different process parameters were presented. Result indicate that the maximum temperature is lower than the melting point of the welding material. The higher temperature gradient occurs in the leading side of the workpiece. The maximum temperature can be increased with increasing the tool angular velocity, rpm in the current numerical modeling. In this research ABAQUS Ver.6.7 is to analyze a fully coupled thermo-mechanical model. ALE(Arbitrary Lagrangian-Eulerian) finite element formulation is used for the large deformation in FSW process and using the Mass scaling for the analysis time efficiency.

• Transactions of Materials Processing
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• v.19 no.5
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• pp.277-282
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• 2010

Magnesium alloy has been known as lightweight material in automobile and electronic industry with aluminum alloy, titanium alloy and plastic material. Friction welding is useful to join various metals and nonferrous metals that are difficult to join by such as gas welding, resistance welding and electronic beam welding. In this study, friction joining was performed to investigate mechanical properties of Mg alloy with 20mm diameter solid bar. Also the optimal joining conditions for its application were determined on the basis of tensile test, and hardness survey. The joining parameters were chosen as heating pressure, heating time, upsetting pressure, and upsetting time. Heating and upsetting pressure were executed under the range of 10~40MPa and 20~80MPa, respectively. From the experimental results, optimal joining conditions were determined as follows; rotating speed=2000rpm, heating pressure=35MPa, upsetting pressure=70MPa, heating time=1sec, upsetting time=5sec. Also the hardness of jointed boundary showed as HV50 which was similar to that of base metal at the optimal condition, and it was supposed that zone of HAZ was 8mm. Finally two materials were strongly mixed at interface part to show a well-combined microstructure without particle growth or any defect.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.29-36
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• 2007

The present study examined the mechanical properties of the friction welding of Ni-Cr-Mo to SM45C. Friction welding was conducted at welding conditions of 2,000 rpm, friction pressure of 100MPa, friction time of 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0 seconds, upset pressure of 150MPa, and upset time of 3.0 seconds. When the friction time was 1.6 seconds, the maximum tensile strength of the friction weld happened to be 1,020MPa, which is 120% of the base material's tensile strength(850MPa). At the same condition, the maximum shear strength was 438MPa, which is equivalent to 103% of the base material's shear strength(425MPa). At the same condition, the maximum vickers hardness was Hv490 at Ni-Cr-Mo nearby weld interface, which is higher Hv40 than condition of the friction time 0.8 seconds, and the maximum vickers hardness was Hv305 from weld interface of SM45C, which is higher Hv12 than condition of the friction time 0.8 seconds. The results of microstructure analysis show that the structures of two base materials have fined and rearranged along a column due to heating and axial force during friction, which has affected in raising hardness and tensile strength.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.12
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• pp.477-482
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• 2016

Airtight containers have been widely used in many industries and household. They need a packing for sealing between the inside and outside. Previous packing materials have some drawbacks like stench, stickiness, and difficulty of applying to automated manufacturing systems. So, a new packing material which is harmless and suitable for automation is needed. This study performed a hot plate welding process of thermoplastic elastomer (TPE) as the packing material. The hot plate welding process included a phase change process of solidification and melting. The porosity-enthalpy method was adopted in order to simulate phase change problems. The TPE showed non-Newtonian fluid characteristics during the melting process. Since properties of SEBS are not well-defined, we established TPE properties by observing the melting behavior of TPE. In order to find an optimized condition, a parametric study including packing thickness, shapes, hot plate temperature, and thermal resistance, was conducted.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.399-406
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• 2005

Alloy 625 is used widely in industrial applications such as aeronautical aerospace, chemical, petrochemical and marine applications. Because of a good combination of yield strength. tensile strength, creep strength, excellent fabricability, weldability and good resistance to high temperature corrosion on prolonged exposure to aggressive environments. High qualify weldments for this material are readily produced by commonly used processes. But all of processes are not applicable to this material by reason of unavailability of matching, position or suitable welding filler metals and fluxes may limit the choice of welding processes. Recently, the flux cored wire is developed and applied for the better productivity in several welding position including the vortical position. In this study. the weldability and weldment characteristics of Alloy 625 are evaluated in FCAW weld associated with the several shielding gases($80\%Ar+20\%\;CO_2,\;50\%Ar+50\%\;CO_2.\;100\%\;CO_2$) in viewpoint of welding productivity. The results of the experimental study on corrosive characteristics of Alloy 625 are as follows; There is no remarkable difference among shielding gases. however they has a striking difference among corrosive solutions by results of distinguished density and time of corrosive solution. Generally, the shielding gases($80\%Ar+20\%\;CO_2$) was superior to the other gases on high temperature tensile and a low temperature impact. but all of the shield gases were making satisfactory results on corrosion test.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.5
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• pp.491-497
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• 2019

Dissimilar friction welding were produced using 15 mm diameter solid bar in superalloy(Alloy718) to chrome molybdenum steel(SCM440) to investigate their mechanical properties. Consequently, optimal welding conditions were n=2000 rpm, HP=60 MPa, UP=120 MPa, HT=10 sec and UT=10 sec when the metal loss(Mo) is 3.5 mm. Acoustic Emission(AE) technique was applied to analyze the dissimilar friction welding of Alloy718 and SCM440. The relationship between the AE parameters and dissimilar friction welding of both material was discussed. In the case of heating time of 6 sec, 10 sec, 14 sec and 20 sec, 5 AE events per 0.5 seconds and energy about $2.7{\times}10^{10}$ were exhibited in heating time. In upsetting time, resulting in various numbers of events per second and very low energy. The frequency range of the signal generated during the heating time was about 200 kHz. However, the upsetting time resulted in a wide range of signals from very low frequency to high frequency of 500 kHz due to rapid plasticity of the material.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.1
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• pp.8-14
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• 2022

A computer simulation was performed to investigate the heat source distribution and temperature distribution of a laser having multiple characteristics. To simulate the actual size of a welding specimen, the temperature distributions at 0 s, 1 s, and 2 s were analyzed by increasing the domain size to 50 mm in length and 25 mm in width in a material of the same thickness. As indicated by the results, because of the characteristics of metals with high thermal conductivity, the temperature at the welding center line and the temperature distribution at the offset position were not significant. When the core part was cooled by irradiating with a laser, it cooled at a rate of up to 500 ℃/s. In contrast, when the laser was irradiated to the ring part, the cooling proceeded at a rate of over 1800 ℃/s. Comparing the relative numerical values rather than the absolute values, it was found that the cooling rate was approximately 3.6 times faster when the laser was irradiated through the ring than when the laser was irradiated through the core. As a result of irradiating with the same heat source (at 100 W) into the core, ring, and ring + core, it was confirmed that the highest temperature was irradiated to the ring part and the lowest temperature was irradiated to the core part.