• Proceedings of the Korean Society of Laser Processing Conference
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• 1998.05a
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• pp.46-47
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• 1998

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.125-128
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• 1995

The remote sleeve repair-welding technology using the pulsed Nd:YAG laser for increasing the lifetime of the steam generator tube in the nuclear power plant has been developed. The laser welding has many advantages on deep penetration depth and narrow heat affect zone(HAZ). The inconel 600 tube and inconel 690 sleeve used high temperature and high pressure service have been welded as round lap welds. It is found that the relation between the connection width and welding parameters. It is found that the shear strength in proportion to the connection width by conducting tensile-shear tests.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.25-26
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• 2005

This study suggested the occurrence source of weld-defects and its solution methods in a welding of Electrolyte injection hole by pulsed Nd:YAG laser. In experiment, the ramp down was used in order that solidification crack was removed. Furthermore, shrinkage stress and heat input were reduced by changing of weld trajectory and defocused distance. As a results of a experiment, a sound weld bead shape and crack-free weld bead can be obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.1053-1057
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• 1997

Laser thin film process with a Q-switch pulsed YAG laser was performed for micro machining. In this research, we performed basic Cr thin film on glass substrates removal machining experiments. Form experiments, it happens not only evaporration of thin film but also spatter and cohesion of melting substance in working region, when machining a Cr thin film by Q-switch YAG laser beam irradiation. Critical energy of surface irradiation type by irradiation direction of laser in a face composing thin film on the glass is higher than that of back irradiation type, but the latter is favorable because of spatter appearance. In case of image formation position when laser beam is irradiated, the defocus is permitted to a certain extent within forcus depth. Ifexceeds focus depth, formation of pattern is vanishing step by step.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.6
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• pp.740-745
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• 2006

This study suggested the occurrence source of weld-defects and its solution methods in a welding of Electrolyte injection hole by pulsed Nd:YAG laser. In experiment, the ramp down was used in order that solidification crack was removed. Furthermore. shrinkage stress and heat input were reduced by changing of weld trajectory and defocused distance. As a results of a experiment, a sound weld bead shape and crack-free weld bead can be obtained. In conclusion this show that the welding stability is greatly affected by modulation of laser pulse shape for the same laser energy and welding parameters.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.223-224
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• 2006

In this study, we have investigated the micromachining of PZT to fabricate interdigitated electrodes of electro active material actuator using Nd:YAG laser We have observed groove shapes of PZT with changing beam power, scanning speed, gas, and so on to find optimum conditions of the laser processing for PZT grooves. As a result, this method has been applied to the laser micromachining for grooves in PZT surface, and we could have optimum parameters of Nd:YAG laser Finally it was shown that the laser micromachining of PZT can substitute fer bonding, etching and deposition processes in fabricating electro active material actuator embedded with interdigitated electrodes.

• The korean journal of orthodontics
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• v.34 no.4 s.105
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• pp.343-349
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• 2004

Laser-aided debonding has advantages in that the heat produced is localized and controlled, the debonding tool is not heated, and it can be used for the removal of various types of ceramic brackets, regardless of their design. However, the range of safe power usage for laser-aided debonding has not vet been confirmed. The Purpose of this study was to evaluate the histologic changes of pulpal tissue in a rabbit's incisor after Nd-YAG laser-aided ceramic bracket debonding at different levels of power. The result were as follows: 1. At 3-5W Nd-YAG laser power level and 3 seconds of exposure time, the ceramic bracket debonding procedure was not easy. At 5W of power a tie-wing fracture occurred on one bracket during debonding using Weingart plier. The histologic section of pulp represented no adverse changes. 2. At 7-13 W power level and less than 5 seconds of exposure time, the debracketing procedure was done easily and bracket facture did not occur. The histologic section of pulp represented mild and reversible changes. All the results were reversible and no pulpal degeneration or necrosis occurred. Considering the results, it appears that the laser-aided debonding technique is a safe method that does not result in irreversible pulpal changes, softens bracket bonding resin within a saie range of power and exposure time, and is useful for ceramic bracket recycling by lowering the tie- wing fracture rate.

• Proceedings of the KWS Conference
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• v.43
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• pp.91-93
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• 2004

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.84-86
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• 2000

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.271-273
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• 2000