• Proceedings of the KWS Conference
• /
• 1998.10a
• /
• pp.71-72
• /
• 1998

• Journal of Welding and Joining
• /
• v.21 no.6
• /
• pp.20-25
• /
• 2003

Various welding methods such as Gas Tungsten Arc Welding(GTAW), magnetic force electrical resistance welding and Laser Beam Welding(LBW) are now available for end cap closure of nuclear fuel rods. Even though the resistance and GTA welding processes are widely used in manufacturing commercial fuel rods, they can not be recommended for the remote seal welding of fuel rods in the hot cell Facility due to the complexity of the electrode alignment, the difficulty in replacing parts in a remote manner and the large heat input for the thin sheath. Therefore, the Nd:YAG laser system using optical fiber transmission was selected for the end cap welding of irradiation fuel rods in the hot cell. The remote laser welding apparatus in the hot cell Facility was developed using a pulsed Nd:YAG laser of 500 watt average power with an optical fiber transmission. The weldment quality such as microstructure and mechanical strength was satisfactory. The optimum conditions of laser welding for encapsulating irradiation fuel rods in the hot cell were obtained.

• Journal of Welding and Joining
• /
• v.15 no.6
• /
• pp.85-95
• /
• 1997

This study is to investigate the optimum conditions of Nd:YAG laser beam welding for Zircaloy-4 end cap closure by optical fiber transmission. Laser welding parameters which affect the penetration depth and bead width were experimentally examined using the various beam radius by the beam quality analyzer, joint geometries of end cap and the laser parameters which mean pulse width, repetition rate and pulse energy. Also, an optimum welding speed and the effect of assistant gas with varying the flow rate of He were investigated. We found that the laser average power for the end cap welding will be 230W and rotation speed must not exceed 8 RPM, the best position of focus using optical fiber with 600.mu.m will be 2 to 3mm below the surface of the material.

• Proceedings of the KWS Conference
• /
• 1998.05a
• /
• pp.246-248
• /
• 1998

• Proceedings of the KWS Conference
• /
• 1994.05a
• /
• pp.136-141
• /
• 1994

• Korean Journal of Metals and Materials
• /
• v.47 no.7
• /
• pp.447-453
• /
• 2009

Isotropic conductive adhesives (ICAs) have been used or considered as an interconnect material for radio frequency identification (RFID) inlays or other flip chip assemblies due to the advantages of having a low temperature and high-speed bonding. In this work, the curing properties of commercial ICAs for the RFID tag application and the signal transmission in conductive lines that contained the ICA joints were evaluated as a function of the degree of cure at 900 MHz frequency range. The ICAs showed adequate signal transmission only after the curing process passed over the critical time. It was also found that the insertion loss of signal was more dependent on the contact states of Ag fillers in the bondline in preference to the electrical resistance of the ICA itself.

• Journal of Welding and Joining
• /
• v.33 no.2
• /
• pp.8-13
• /
• 2015

This study was carried out to evaluate mechanical properties of the jointed Al6061/HT590 alloys by friction stir welding (FSW). FSW was conducted under the conditions with tool rotating speed of 500 RPM and traveling speed of 300 mm/min., where Ar gas was introduced to prevent the materials from corrosion during the welding process. Electron back-scattering diffraction (EBSD) was used to characterize microstructures such as grain size, misorientation angle and crystal orientation. Evolution of intermetallic compounds in Al6061 during the process were examined in terms of morphology, size and aspect ratio at three distinct zones Al base material, heat affected zone and stir zone, where transmission electron microscope (TEM) was used. It was revealed that FSW gave rise to refinement of grains as well as growth of intermetallic compounds in Al6061. The morphological changes of intermetallic compounds exerted an influence on mechanical properties, resulting in occurrence of fracture in the part of the base material instead of the jointed parts (heat affected zone and stir zone). This study systematically evaluated the microstructural evolutions during the FSW for joining Al6061 with HT590 and their effect on mechanical properties.

• Proceedings of the KWS Conference
• /
• 2005.06a
• /
• pp.43-45
• /
• 2005

A precise bonding technique, transmission laser bonding using energy transfer, for polymer micro devices is presented. The irradiated IR laser beam passes through the transparent part and absorbed on the opaque part. The absorbed energy is converted to heat and bonding takes place. In order to optimize the bonding quality, the temperature profile on the interface must be obtained. Using optical measurements of the both plates, the absorbed energy can be calculated and heat transfer model was applied for obtaining the transient temperature profile. The transmission laser bonding has a potential in the local precise bonding in MEMS or Lab-on-a-chip.

• International Journal of Korean Welding Society
• /
• v.3 no.2
• /
• pp.29-39
• /
• 2003

The durability and reliability of thermal barrier coatings (TBCs) play an important role in the service reliability, availability and maintainability (RAM) of hot­section components in advanced turbine engines for aero and utility applications. Photostimulated luminescence spectroscopy (PSLS) and electrochemical impedance spectroscopy (EIS) are being concurrently developed as complimentary non­destructive evaluation (NDE) techniques for quality control and life­remain assessment of TBCs. This paper overviews the governing principles and applications of the luminescence and the impedance examined in the light of residual stress, phase constituents and resistance (or capacitance) in TBC constituents including the thermally grown oxide (TGO) scale. Results from NDE by PSLS and EIS are discussed and related to the microstructural development during high temperature thermal cycling, examined by using a variety of microscopic techniques including focused ion beam (FIB) in­situ lift­out (INLO), transmission and scanning transmission electron microscopy (TEM and STEM).

• Polymer(Korea)
• /
• v.37 no.6
• /
• pp.753-763
• /
• 2013

Laser transmission welding of polymers is now used in a very wide range of industries due to its advantages. If the joining between polypropylene (PP) and polycarbonate (PC) occurs by laser transmission welding, the automotive headlight will get a large profit. However, PP/PC have poor miscibility. In the laser transmission welding results, the adhesion strength between PP and PC was very weak. In this study, PP was modified by grafting of glycidyl methacrylate (GMA). The adhesion strength of PC and PP-g-GMA as a reactive compatibilizer was observed. The adhesion strength was investigated by compatibility with PC, mechanical properties and laser transmission welding.