• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2001.04a
• /
• pp.119-124
• /
• 2001

Currently knowledge of strain in welds has mainly been obtained form strain gaging method:; that is directly attaching most of the material to the gate. The very few non-contact method are still in the early stage. One of the non-contact methods is by the use of the laser that has high-level of the accuracy for the measurement, and this laser also has excellent characteristics on which many studies for its applications are focused throughout the many fields. The dissertation is on the measurement of the strain caused by the characteristics and the temperature changes of the TIG welded zone which is used with 3D ESPI system that is functionally modified through the laser ESPI system. This system employed the aluminum sheet-metal which are mainly used for the steel plate such as for the electronics, chemisry, food instrument and electronic appliances.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2001.04a
• /
• pp.155-161
• /
• 2001

Currently knowledge of strain in welds has mainly been obtained from strain gaging method; that is directly attaching most of the material to the gage. The very few non-contact method are still in the early stage. One of the non-contact methods is by the use of the laser that has high-level of the accuracy for the measurement, and this laser also has excellent characteristics on which many studies for its applications are focused throughout the many fields. The dissertation is on the measurement of the strain caused by the characteristics and the temperature changes of the TIG welded zone which is used with 3D ESPI system that is functionally modified through the laser ESPI system. This system employed the aluminum sheet-metal which are mainly used for the steel plate such as for the electronics, chemistry, food instrument and electronic appliances.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.989-992
• /
• 1997

The objective of this study is to develop stencil cutting process and determine optimal conditions which make good-quality stencil by using a Nd:YAG laser. The effects of process parameters such as laser power, type of mask, gas pressure, cutting speed and pulse width on the cut edge quality were investigated. In order to analyze the cut surface characteristics(roughness, kerf width, dross) optical microscopy, SEM photography and roughness test were used. A a results, the optimal conditions of process parameters were determined, and the practical feasibility of the proposed system is also examined by using a commercial gerber file for PCB stencil manufacturing.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.8 s.173
• /
• pp.17-26
• /
• 2005

Dissimilar-metal welds(DHWs) are used widely in various industrial applications due to the pratical importance from the technical and economic aspect. However, DMWs have several fabricative and metallurgical drawbacks that can often lead to in-service failures. For example, the most pronounced fabrication faults are hot cracks. Recently, DMWs have used the various of heat source to decrease such as faults. In this paper, the weldability on dissimilar metal welds of Austenite stainless steel and Low carbon steel using a continuous wave Nd:YAG laser was experimentally investigated. Experiments were conducted to determine effects of welding parameters, on eliminating or reducing the extent welding zone formation at dissimilar metal welds and to optimize those parameters that have the most influence parameters such as focus length, power, beam speed, shielding gas, and wave length of laser.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.54 no.3
• /
• pp.103-108
• /
• 2005

ZnO thin films on (001) sapphire substrates have been deposited by pulsed laser deposition(PLD) technique using an Nd:YAG laser with a wavelength of 266nm. Before post-annealing treatment in the oxygen ambient, the experiment of the deposition of ZnO thin films has been performed for substrate temperatures in the range of $300\~450^{\circ}C$ and oxygen gas flow rate of $100\~700\;sccm$. In order to investigate the effect of post-annealing treatment of ZnO thin films, films have been annealed at various temperatures after deposition. After post-annealing treatment in the oxygen ambient, the structural properties of ZnO thin films were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM) and the optical properties of the ZnO were characterized by photoluminescence(PL).

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.03a
• /
• pp.251-256
• /
• 2004

A concept in which laser-sustained plasmas (LSPs) are combined with inductively coupled plasmas (ICPs) is proposed. The concept is aiming at extensions of operative conditions of a CW laser thruster due to the fact that the ICP has some characteristics which are in contrast to those of LSPs. An estimation confirmed that the concept would effectively work. And a fundamental experiment was conducted. The results showed that the radio frequency magnetic field induced by a alternate current of 13.56 MHz coupled inductively with LSPs, resulting in the enlargement of the plasma region and the attainment of the enthalpy. It is expected that some improvements will enable to transfer the RF power to the work gas more effectively and to demonstrate the synergy effect between the LSPs and the ICPs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.1
• /
• pp.75-78
• /
• 2002

Si thin films on p-type (100) Si substrate have been prepared by a pulsed laser deposition technique using a Nd:YAG laser. The pressure of the environmental gas during deposition was 1 Torr. After deposition, Si thin film has been annealed again at 400-840$^{\circ}C$ in nitrogen ambient. Strong blue photoluminescence (PL) have been observed at room temperature. We report the PL properties of Si thin films with the variation of the annealing temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.430-431
• /
• 2006

This letter reports the fabrication of polycrystalline silicon thin-film transistors (poly-Si TFT) on flexible plastic substrates using amorphous silicon (a-Si) precursor films by sputter deposition. The a-Si films were deposited with mixture gas of argon and helium to minimize the argon incorporation into the film. The precursor films were then laser crystallized using XeCl excimer laser irradiation and a four-mask-processed poly-Si TFTs were fabricated with fully self-aligned top gate structure.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.1016-1019
• /
• 2005

In the cutting of plate steel, the quality of the cut surfaces is strongly dependent on the cutting condition such as cutting speed, plate thickness, power, kerf width and gas pressure etc. The cutting tests of Steel Automobile Press Hot were carried out using $CO_2$ Laser cutting machine. The kerf width and surface roughness of a section are examined at various cutting conditions. This paper deals with cutting characteristics of Steel Automobile Press Hot(SAPH400) using $CO_2$ Laser Cutting Machine.

• Korean Journal of Optics and Photonics
• /
• v.1 no.1
• /
• pp.28-32
• /
• 1990

We have constructed and operated a discharge heated copper vapor laser which generated green (510.6 nm) and yellow (578.2 nm) light. The plasma tube was made of high purity (99.8%) alumina tube which has an inner diameter 25 mm and a length 106 cm. The electrodes, made of molybdenum sheet, were separated 108 cm apart. The laser gave an average power of 10 W at repetition rate of 5 kHz, charging voltage of 10 kV, Ne buffer gas pressure of 40 mbar, and the laser tube temperature of $1500^{\circ}C$..