• Laser Solutions
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• v.8 no.1
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• pp.19-25
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• 2005

Pulse laser welding of AISI 304 stainless steel plate was simulated to optimize welding conditions by using commercial finite element code MARC. Due to geometric symmetry, a half model of AISI 304 stainless steel plate was considered. for the heat transfer analysis, user subroutines were applied to boundary condition. The material properties such as conductivity, specific heat, and mass density were given as a function of temperature and the latent heat associated with a given temperature range was considered. A moving heat source was designed on the basis of experimental data. As a result, Nd:YAG laser welding for AISI 304 stainless steel was successfully simulated and it should be useful to determine optimal welding condition.

• Laser Solutions
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• v.14 no.1
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• pp.19-24
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• 2011

This work reports the results for laser shock peening of duplex stainless steel (22% Chromium - 5% Nickel) using a pulsed Nd:YAG laser (wavelength = 532nm, pulse width = 8ns). for the application to high-capacity pumps for seawater desalination plants. By properly selecting the process parameters such as laser intensity of 10GW/$cm^2$, laser pulse density of 75pulse/$mm^2$, and $100{\mu}m$ thick aluminum foil as an absorbent coating layer, the surface hardness of duplex stainless steel could be enhanced by 26%, from 256HV to 323HV with little changes in surface morphology and roughness. The depth of laser shock peened layer was measured to be around 2mm. The large enhancement of surface hardness is considered to have high practical importance in minimizing abrasive and corrosive deterioration of pump parts.

• Laser Solutions
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• v.13 no.1
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• pp.11-15
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• 2010

Indium tin oxide (ITO) provides high electrical conductivity and transparency in the visible and near IR (infrared) wavelengths. Thus, it is widely used as a transparent electrode for the fabrication of liquid crystal displays (LCDs) and organic light emitting diode displays (OLRDs), photovoltaic devices, and other optical applications. Lasers have been used for removing coating on polymer substrate for flexible display and electronic industry. In selective removal of ITO layer, laser wavelength, pulse energy, scan speed, and the repetition rate of pulses determine conditions, which are efficient for removal of ITO coating without affecting properties of the polymer substrate. ITO coating removal with a laser is more environmentally friendly than other conventional etching methods. In this paper, pattering of ITO film from polymer substrates is described. The Yb:KGW femtosecond laser processing system with a pulse duration of 250fs, a wavelength of 1030nm and a repetition rate of 100kHz was used for removing ITO coating in air. We can remove the ITO coating using a scanner system with various pulse energies and scan speeds. We observed that the amount of debris is minimal through an optical and a confocal microscope, and femtosecond laser pulses with 1030nm wavelength are effective to remove ITO coating without the polymer substrate ablation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.425-429
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• 2011

The development of metal plasma generated by high laser irradiance and its effect on the surrounding air using shadowgraph images after laser pulse termination are studied; hence the formation of laser supported detonation and combustion processes has been investigated. The core of the paper is in detecting chemical reaction using X-Ray Diffraction (XRD) between ablated aluminum plasma and oxygen from air by inducing high power laser pulse (>1000 mJ/pulse) and conduct a quantitative comparison of chemically reactive laser initiated waves with the classical detonation of exploding aluminum (dust) cloud in air. This study may suggest a new approach of initiating detonation from metal sample in its bulk form without the need of mixing nano-particles with oxygen for initiation.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.102.2-102
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• 2001

In this study, a solid-state laser system adopting a new real time multi-discharge (RTMD) method in which three flashlamps are turned on consecutively was designed and fabricated to examine the pulse width and the pulse shape of the laser beams depending upon the changes in the lamp turn-on time. That is, this study shows a technology that makes it possible to make various pulse shapes by turning on three flashlamps consecutively on a real-time basis with the aid of a PIC one-chip microprocessor, With this technique, the lamp turn-on delay time can be varied more diversely from 0 to 10 ms and the real-time control is possible with an external keyboard, enabling various pulse shapes. In addition, longer pulses can be more widely used for industrial processing and lots of medical purposes.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1807-1809
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• 2002

In this study, asolid-state laser system adopting a firing time control(FTC) method in which three flashlamps are turned on consecutively was designed and fabricated to examine the pulse width and the pulse shape of the laser beams depending upon the changes in the lamp turn-on time. That is, this study shows a technology that makes it possible to make various pulse shapes by turning on three flashlamps consecutively on a real-time basis with the aid of a PIC one-chip microprocessor With this technique, the lamp turn-on delay time can be varied more diversely from 0 to 10 ms and the real-time control is possible with an external keyboard enabling various pulse shapes. In addition longer pulses can be more widely used for industrial processing and lots of medical purposes.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1864-1866
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• 1997

In this study, we designed the pulse superposition network consisting of a six-mesh and a three-mesh network, and fabricated the electrical power supply and the single elliptical resonator. We have developed a tec.bnique forming the step-pulse shape of pulsed Nd:YAG laser by using one shot multivibrater and have studied on the effect of two pulses superposition for the output and efficiency improvement of pulsed Nd:YAG laser by superposing a sinusoidal pulse on a main pulse.

• The Journal of the Korea Contents Association
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• v.8 no.4
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• pp.63-70
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• 2008

This paper presents a method of PRI do-interleaving for LASER pulse signals. When the PRI of LASER pulse is periodically changed, the first deviation and the second deviation of TOA is used to calculate the PRI pattern of input LASER signals of receiver. If the standard deviation of the first difference of TOA is less than 5% of the average of the first difference of TOA, the PRI pattern of LASER signal is fixed or jittered type. If the standard deviation is larger than 5% of the average, those are triangular PRI patterns or sawtooth PRI patterns.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.519-524
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• 2001

These days, $Al_[2}O_{3}$ ceramic use all over the industry because dynamic function and special properties to compare traditional material. But $Al_[2}O_{3}$ ceramic is high hardness and brittleness materials. For this reason, it is very difficult to process. Therefor, In this paper, it was investigated that laser process parameter, which can produce appropriate quality of $Al_[2}O_{3}$ ceramic microhole machining utilized Nd:YAG laser and Excimer laser.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04a
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• pp.76-78
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• 2002

The influence of laser annealing on gaint magnetoimpedance effect of glass-covered Co-based amorphous microwires is investigated by illuminating pulse Nd:YAG laser on the etched microwires. The maxium GMI ratio reaches maximum of around 85 % at the frequency of 5 MHz for the sample iluminated by the pulse with laser energy fo 132 mJ/pulse.