• Laser Solutions
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• v.8 no.2
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• pp.7-12
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• 2005

The material processing of UV nanosecond pulse laser cannot be avoided the material shape change and contamination caused by interaction of base material and laser beam. Nowadays, ultra short pulse laser shorter than nanosecond pulse duration is used to overcome this problem. The advantages of this laser are no heat transfer, no splashing material, no left material to the adjacent material. Because of these characteristics, it is so suitable for micro material processing. The processing of sapphire wafer was done by UV 355nm, green 532nm, IR 1064nm. X-Y motorized stage is installed to investigate the proper laser beam irradiation speed and cycles. Also, laser beam fluence and peak power are calculated.

• Korean Journal of Materials Research
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• v.12 no.1
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• pp.27-35
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• 2002

In laser materials processing, localized heating, melting and evaporation caused by focused laser radiation forms a vapor on the material surface. The plume is generally an unstable entity, fluctuating according to its own dynamics. The beam is refracted and absorbed as it traverses the plume, thus modifying its power density on the surface of the condensed phases. This modifies material evaporation and optical properties of the plume. A laser-produced plasma plume simulation is completed using axisymmetric, high-temperature gas dynamic model including the laser radiation power absorption, refraction, and reflection. The physical properties and velocity profiles are verified using the published experimental and numerical results. The simulation results provide the effect of plasma plume fluctuations on the laser power density and quantitative beam radius changes on the material surface. It is proved that beam absorption, reflection and defocusing effects through the plume are essential to obtain appropriate mathematical simulation results. It is also found that absorption of the beam in the plume has much less direct effect on the beam power density at the material surface than defocusing does and helium gas is more efficient in reducing the beam refraction and absorption effect compared to argon gas for common laser materials processing.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2001.05a
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• pp.31-34
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• 2001

Laser cladding Processing allows rapid transfer of heat to the material being minimum conduction into base metal. The effects of CO$_2$ laser cladding with high powder were investigated. High viscosity bronze powder consists of bronze powder used at a high temperature. The material has a high viscosity So that it can be substrate. Therefore. Laser cladding can be processed on a curved or slope surface. CO$_2$ laser cladding was designed It consists of the high viscosity bronze powder the shielding gas system and the preheating system The high viscosity powder properly at 0.3g/s and 0.50g/s. Because of the metallic bond between bronze per the hardness of dilution layer was suddenly increased. Experimental as results viscosity mixed powder can be a useful cladding material.

• Laser Solutions
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• v.9 no.3
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• pp.7-13
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• 2006

Auto focusing system to find optimized focal position of laser beam used for material process has been investigated by using fiber confocal method. Wavelength of laser diode (LD) and diameter of single-mode fiber are 780nm and $5.3{\mu}m$, respectively. Intensity distributions of beam reflected from the surface of mirror and silicon bare wafer have been observed in a gaussian form. Experimental results show that focal position obtained by LD is shifted from one observed from surface scribed by laser about $80{\mu}m$. It is due to the difference of wavelength and each divergence of between LD and laser used for material process. It is confirmed that auto focusing control system through position calibration has operated steadily.

• Journal of Welding and Joining
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• v.12 no.3
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• pp.63-70
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• 1994

Laser processing workmen should select the working condition for laser cutting of new materials by the preparatory experiments for that material or from the past experiences in cutting of other similar materials. This paper proposes a criterion to determine how much a material is similar to other materials by using the Sugeno fuzzy integral. With the proposed criterion the laser processing workman can objectify the considered material for his decision. The expert system programmer can give the system a high flexibility by experimenting with some materials in a large range of similarity and can support the laser processing workman by offering the similarity between materials.

• Proceedings of the Korean Society of Laser Processing Conference
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• 1998.05a
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• pp.23-24
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• 1998

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.406-411
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• 2003

This paper deals with the effect of laser material processing on the EMU production technique. Material processing with lasers takes advantage of all the characteristics of laser light. The high energy density and directionality achieved with lasers permits strong localized heat- or photo-treatment of materials with spatial resolution below one micrometer. The pulsed and mono-chromatic light allows the control of depth of heat treatment or selective excitation. The laser beam can be moved to process large areas, is a sterile tool and is no subject to wear and tear. Using laser processing have taken more interests in EMU production for improving the rigidity, weight reduction, crash durability, and cost savings so that their application to auto-bodies has been increased.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2001.05a
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• pp.114-118
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• 2001

• Proceedings of the Korean Society of Laser Processing Conference
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• 1999.11a
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• pp.56-59
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• 1999

• Laser Solutions
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• v.2 no.1
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• pp.22-29
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• 1999

This work was carried out as a fundamental experiment to fabricate a Graded-Boundary Ni/Steel material using a laser beam. A Ni sheet was placed on a steel substrate, and then a series of high power $CO_2$ laser beams were irradiated on the surface in order to produce a homogeneous alloyed layer. The processing parameters were : 4 ㎾ laser power, 2m/min traverse speeds, -2mm defocuing, 17 l/min sheiding gas flow rates. The sequential repetition of the laser surface alloying treatment up to 4 times, resulted in about 5mm thick of fair compositional gradient systems. In order to determine the microstructure, phase and compositional profiles in this material, optical microscopy, XRD and EDS were used. The compositions varied from 66% to 0% for Ni and 34% to 100% for Fe in this material The microstructures were typical morphologies of rapid solidification and solid-state cooling. Since compressive stress was formed in the heat affected region due to martensitic transformation, while relative tensile stress was developed in the alloyed region, cracks were formed between the alloyed region and the substrate region.