• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.774-779
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• 2003

Arc-shaped line array slits have been used for the laser generation of focused Lamb waves. The spatially expanded Nd:YAG pulse laser was illuminated through the arc-shaped line array slit on the surface of a sample plate to generate the Lamb waves of the same pattern as the slit. Then the generated Lamb waves were focused at the point of which distance from the slit position is dependent on the curvature of slit arc. The proposed method showed better spatial resolution than the conventional linear array slit in the detection of laser machined linear defect and drill machined circular defect on aluminum plates of 1mm thickness.

• 비파괴검사학회지
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• 제26권3호
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• pp.181-189
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• 2006

A 2D finite-element numerical simulation has been developed to investigate the generation of ultrasonic waves in a homogeneous isotropic elastic slab under a line-focused laser irradiation. Discussing the physical processes involved in the thermoelastic phenomena, we describe a model for the pulsed laser generation of ultrasound in a metal slab. Addressing an analytic method, on the basis of an integral transform technique, for obtaining the solutions of the elastodynamic equation, we outline a finite element method for a numerical simulation of an ultrasonic wave propagation. We present the numerical results for the displacements and the stresses generated by a line-focused laser pulse on the surface of a stainless steel slab.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.55-58
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• 1997

In automotive industries, stamping of laser-welded blank gives many merits which brings about dimensional accuracy, strong body assembly and high productivity. However the welding of blanks with different thickness or/and different strength materials introduces many challenging formability problems for process development and tool design. In this paper, the deformation characteristics for deep drawing process of laser-welded blank with different thickness sheets are investigated by experiment and FEM simulation. And also the optimal location of weld line in laser-welded blank with different thickness sheets is calculated to compensate for the movement of weld line on deep drawing process. In addition, the effect of location of weld line is clarified using FEM simulation.

• International Journal of Korean Welding Society
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• 제2권2호
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• pp.57-60
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• 2002

Generally, the laser vision sensor makes it possible design a highly reliable and precise range sensor at a low cost. When the laser vision sensor is applied to lap joint welding, however. there are many limitations. Therefore, a specially-designed hardware system has to be used. However, if the multi-lines are used instead of a single line, multi-range data .:an be generated from one image. Even under a set condition of 30fps, the generated 2D range data increases depending on the number of lines used. In this study, a laser vision sensor with a multi-line pattern is developed with conventional CCD camera to carry out high speed seam tracking in lap joint welding.

• KIEE International Transactions on Electrophysics and Applications
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• 제5C권4호
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• pp.152-154
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• 2005

We demonstrate a simple $CO_2$ laser by controlling firing angle of a TRIAC switch in ac power line. The power supply for our laser system switches the voltage of the AC power line (60Hz) directly. The power supply does not need elements such as a rectifier bridge, energy-storage capacitors, or a current-limiting resistor in the discharge circuit. In order to control the laser output power, the pulse repetition rate is adjusted up to 60Hz and the firing angle of TRIAC gate is varied from $45^{circ}$ to $135^{circ}$. A ZCS(Zero Crossing Switch) circuit and a PIC one-chip microprocessor are used to control the gate signal of the TRIAC precisely. The maximum laser output of 40W is obtained at a total pressure of 18 Torr, a pulse repetition rate of 60Hz, and a TRAIC gate firing angle of $90^{circ}$.

• 한국기계가공학회지
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• 제9권5호
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• pp.70-75
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• 2010

In this paper, laser marking systems dedicated to cylinderical parts was developed. We first develop the marking device which consists of Nd-Yag laser, galvano scanner and additional rotational axis, then develop algorithm for supporting the digital image with bmp data format. Additional rotational axis is so attached as to rotate the cylinderical parts for marking its whole surface. The image is separated into line by line and the separated line image is sent to galvano scanner while rotating the additional axis simultaneously. CxImage library, famous open source code, is employed for the image processing. The developed method was tested with various images and shows that it reduces marking time significantly without reducing marking quality.

• 비파괴검사학회지
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• 제22권6호
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• pp.637-642
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• 2002

An arc-shaped line array slit has been used for the laser generation of focused Lamb waves. The spatially expanded Nd:YAG pulse laser was illuminated through the arc-shaped line array slit on the surface of a sample plate to generate the Lamb waves of the same pattern as the slit. Then the generated Lamb waves were focused at the focal point of which distance from the slit position is dependent on the curvature of slit arc. The proposed method showed better spatial resolution than the conventional linear array slit in the detection of laser machined linear defect and drill machined circular defect on aluminum plates of 2mm thickness. Using the focused waves, we could detect the linear defect and the circular defect with the improvement of spatial resolution. The method can also be combined with the scanning mechanism to get an image just like by the scanning acoustic microscope(SAM).

• 반도체디스플레이기술학회지
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• 제19권4호
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• pp.51-58
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• 2020

Many types of optical plastic films are essential in optoelectronics display unit fabrication and it is important to develop high precision laser cutting methods of optical films with extremely low level of film surface contamination by fume particles. This study investigates the effects of suction and blowing air motions with air flow misalignment in removing fume particles from laser cut line by employing random particle trajectory simulation and probabilistic particle generation model. The computational results show fume particle dispersion behaviors on optical film under suction and blowing air flow conditions. It is found that suction air flow motion is more advantageous to blowing air motion in reducing film surface contamination outside designated target margin from laser cut line. While air flow misalignment adversely affects particle dispersion in blowing air flows, its effects become much more complicated in suction air flows by showing different particle dispersion patterns around laser cut line. It is required to have more careful air flow alignment in fume particle removal under suction air flow conditions.

• 한국인터넷방송통신학회논문지
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• 제14권2호
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• pp.147-152
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• 2014

2단으로 구성된 DFB 레이저의 정적 및 동적 작용을 분석하기 위하여 종방향 모드 전송선로 이론 (L-MTLT)을 이용하였다. 활성영역을 갖는 DFB 구조의 특성 임피던스와 등가 전파상수를 L-MTLT에 기초하여 유도하였다. 2단으로 구성된 DFB 레이저가 전송선로 망으로 유사화 되었으며, 각 단은 그에 대응하는 등가 요소들로 등가화된 전송선로 블록으로 나타내었다. 등가 전송선로 망에 기초한 DFB 레이저의 종방향 공진 조건 (resonance condition)이 레이트 방정식 (rate equation)을 재구성하기 위하여 사용되었으며, 이를 이용하여 활성여역을 갖는 2단 DFB 레이저의 정적 및 동적 작용을 자세하게 분석하였다.

• 한국기계가공학회지
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• 제18권5호
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• pp.74-81
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• 2019

This study reports the CW $CO_2$ laser scribing of soda lime glass. In this study, scribing experiments are carried out at different laser powers, scan speeds, and focal positions to investigate the effect of the process parameters on the interaction characteristics between a laser beam and glass. In particular, the interaction characteristics are analyzed and described with the input laser energy per unit length. According to the experimental results, the damage threshold for the glass surface was found to exist between 0.072 and 0.08 J/mm. The input laser energy in this region induced partial melting of the surface and grain-shaped cracks. These cracks tended to increase as the input laser energy increased. At the laser input energy larger than 1 J/mm, a huge crack propagating along the scan direction was produced, and the volume below the scribed area was fully melted. The growth of this crack finally resulted in the complete cutting of the glass at the input laser energy above 8 J/mm. It was found that both the width and depth of the scribed line increased with increasing input laser energy. For the beam focusing at the rear surface, the width of the scribed line varied irregularly. This could be ascribed to the increased asymmetry of the beam intensity distribution when the laser beam was focused at the rear surface. Under this condition, a large burr was only produced on one side of the scribed line.