• Title/Summary/Keyword: 어블레이션 특성

Search Result 21, Processing Time 0.027 seconds

Simulations for Internal Defect Inspection Using Laser Generated Ultrasonic Wave in Ablation Regime (어블레이션 영역 레이저 초음파의 시뮬레이션과 내부결함 검사)

  • Kim, Jin-Gyum;Choi, Sungho;Jhang, Kyung-Young
    • Journal of the Korean Society for Nondestructive Testing
    • /
    • v.34 no.3
    • /
    • pp.226-232
    • /
    • 2014
  • In the present study, the characteristics of laser ultrasound in the ablation regime are investigated using simulations and experiments. The laser ultrasonic technique has been recognized as a noncontact method in the field of nondestructive tests (NDTs). In hostile environments (such as hot temperatures), this method has various advantages over the conventional contact ultrasonic method. In particular, in the ablation regime, the laser ultrasonic technique is suitable for inspecting internal defects because of the high amplitude and directivity of the longitudinal wave. In this paper, a simulation model for laser ultrasound in the ablation regime was developed. This model was subsequently applied to a defective specimen using the B-scan method to locate defects. Finally, we performed an experimental test to verify the simulation results. Consequently, the simulation demonstrated good agreement with the experimental test.

Growth and characterization of amorphous GaN film using a pulsed-laser ablation (펄스 레이저 어블레이션을 이용한 비정질 GaN박막의 성장 및 특성분석)

  • ;;Naoto Koshizaki
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.14 no.1
    • /
    • pp.33-36
    • /
    • 2004
  • Amorphous GaN film was deposited using a laser ablation of the highly densified GaN target. Through the surface morphological and compositional analysis of films deposited under various laser energies and Ar gas pressures, the film deposited under the pressure of 10 Pa were found to be amorphous GaN with the smooth surface. In particular, the film at 200 mJ/pulse showed the enhanced crystallinity and stoichiometric composition, compared with those of the films at relatively lower laser energy. The strong band-gap emission at 2.8 eV was observed from amorphous GaN film in the room temperature photoluminescence spectra, showing the highest efficiency in the film at 200 mJ/pulse under 10 Pa.

Characteristics of the Femto-second Pulsed Laser Ablation according to Feed Velocity on the Invar Alloy (펨토초 레이저의 이송속도에 따른 Invar 합금의 어블레이션 특성)

  • Chung, Il-Young;Kang, Kyung-Ho;Kim, Jae-Do;Sohn, Ik-Bu;Noh, Young-Chul;Lee, Jong-Min
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.26 no.3
    • /
    • pp.25-31
    • /
    • 2009
  • Femto-second laser ablation with the various feed velocities of the Invar alloy and the micro surface milling for the processing condition were studied. We used a regenerative amplified Ti:sapphire laser with a 1kHz repetition rate, 184fs pulse duration time and 785nm wavelength. Femto-second laser pulse was irradiated on the Invar alloy with the air blowing at the condition of various laser peak powers and feed velocities. An ablation characteristic according to feed velocity of the Invar alloy was appeared as the non-linear type at different zone of energy fluence. The micro surface milling of the Invar alloy using a mapping method was investigated. The optimal condition of micro surface milling was laser peak power of 22.8mW, feed velocity of 1 mm/s, beam gap of $1{\mu}m$. With the optimal processing condition, the fine rectangular shape without burr and thermal damage was achieved. Using the femto-second laser system, it demonstrates excellent tool for micro surface milling of the Invar alloy without heat effects and poor edge.

Comparative Study on Ablation Characteristics of Ti-6Al-4V Alloy and Ti2AlN Bulks Irradiated by Femto-second Laser (펨토초 레이저에 의한 티타늄 합금과 티타늄질화알루미늄 소결체의 어블레이션특성 비교연구)

  • Hwang, Ki Ha;Wu, Hua Feng;Choi, Won Suk;Cho, Sung Hak;Kang, Myungchang
    • Journal of the Korean Society of Manufacturing Process Engineers
    • /
    • v.18 no.7
    • /
    • pp.97-103
    • /
    • 2019
  • Mn+1AXn (MAX) phases are a family of nano-laminated compounds that possess unique combination of typical ceramic properties and typical metallic properties. As a member of MAX-phase, $Ti_2AlN$ bulk materials are attractive for some high temperature applications. In this study, $Ti_2AlN$ bulk with high density were synthesized by spark plasma sintering method. X-ray diffraction, micro-hardness, electrical and thermal conductivity were measured to compare the effect of material properties both $Ti_2AlN$ bulk samples and a conventional Ti-6Al-4V alloy. A femto-second laser conditions were conducted at a repetition rate of 6 kHz and laser intensity of 50 %, 70% and 90 %, respectively, laser confocal microscope were used to evaluate the width and depth of ablation. Consequently, the laser ablation result of the $Ti_2AlN$ sample than that of the Ti-6Al-4V alloys show a considerably good ablation characteristics due to its higher thermal conductivity regardless of to high densification and high hardness.

A Study on the Removal Characteristics of a Radioactively Contaminated Oxide Film from the irradiated Stainless Steel Surface using Short Pulsed Laser Ablation (초단 펄스레이저 어블레이션에 의한 스테인리스강 표면의 오염산화막 제거 특성)

  • Kim, Geun-Woo;Yoon, Sung-Sik;Kim, Ki-Chul;Lee, Myung-Won;Kang, Myungchang
    • Journal of the Korean Society of Manufacturing Process Engineers
    • /
    • v.19 no.10
    • /
    • pp.105-110
    • /
    • 2020
  • Radioactive Oxides are formed on the surface of the primary equipment in a nuclear power plant. In order to remove the oxide film that is formed on the surfaces of the equipment, chemical and physical decontamination technologies are used. The disadvantage of traditional technologies is that they produce secondary radioactive wastes. Therefore, in this study, the short-pulsed laser eco-friendly technology was used in order to reduce production of the secondary radioactive wastes. They were also used to minimize the damages that were caused on the base material and to remove the contaminated oxide film. The study was carried out using a Stainless steel 304 specimen that was coated with nickel-ferrite particles. Further, the laser source was selected with two different wavelengths. Furthermore, the depth of the coating layer was analyzed using a 3D laser microscope by changing the laser ablation conditions. Based on the analysis, the optimal conditions of ablation were determined using a 1064nm short-pulsed laser ablation technique in order to remove the radioactively contaminated oxide film from the irradiated stainless steel surface.

Bonding and Physical Characteristics of Diamond-like Carbon Films Prepared by Laser Ablation (레이저 어블레이션에 의해 증착된 비정질 다이아몬드 박막의 결합및 물리적 특성)

  • Park, Hwan-Tae;Hong, Young-Kyu;Kim, Jae-Ki;Kim, Jin-Seung;Park, Chan
    • Journal of the Korean Vacuum Society
    • /
    • v.5 no.1
    • /
    • pp.1-5
    • /
    • 1996
  • Noncrystalline films of diamond-like carbon (DLC) have been prepared by laser ablation technique at room temperature. A Q-switched Nd-YAG laser beam with wavelength of 1064 nm and pulse duration of 10 ns was focused onto a graphite target with power densities of about $10^9 W/\textrm{cm}^2$. The physical properties of the resulting films were analyzed with density, hardness, and resistivity measurements. The surface and bonding structure were investigated by atomic force microscopy (AFM), Raman spectroscopy, electron energy loss spectroscopy (EELS).

  • PDF

Characteristic of FS-laser ablation of metal thin film with respect to the variation of material and substrate (펨토초 레이저를 이용한 박막 재료 및 기판 변화에 따른 가공 특성에 관한 연구)

  • Kim B.H.;Shin H.G.;Lee J.G.;Jeong S.C.
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 2006.05a
    • /
    • pp.671-672
    • /
    • 2006
  • We have investigated the behavior of the ultrafast laser ablation of chromium films (200nm) on the silicon and pyrex-glass(corning 7740) substrate with respect to the laser fluence and the number of laser pulses. In addition, several experiments about ITO thin film were carried out with femto-second Ti:Sapphire laser (150fs). Finally, we introduce the ablation characteristic in accordance with materials of thin film and substrate.

  • PDF

Micro-machining of nickel by picosecond laser ablation (피코초 레이저를 이용한 니켈의 미세가공 특성)

  • Shin D.S.;Lee J.H.;Suh J.;Noh J.W.;Chung Y.W.;Kim J.C.
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 2006.05a
    • /
    • pp.653-654
    • /
    • 2006
  • In case of ultrashort laser ablation of metals, the transfer of energy from the electronic system causing strong absorption of laser light to the lattice needs relaxation times of the order of some picoseconds. Under the above theoretical background, nickel was ablated using femtosecond, picosecond and nanosecond laser. As a result, nickel ablation by picosecond laser and femtosecond laser, which are called ultrashort laser, has similar machinability because of relaxation time of metals, whereas nanosecond Nd:YAG laser has lower absorption, higher thermalization effect in comparison with ultrashort laser.

  • PDF