• Title/Summary/Keyword: YAG-Laser

검색결과 1,154건 처리시간 0.026초

Nd:YAG 레이저 맞대기 용접의 비드형상 예측에 관한 유한요소해석 (Finite element analysis for prediction of bead shape of Nd:YAG laser butt welding)

  • 김관우;남기정;이제훈;서정;조해용
    • Journal of Advanced Marine Engineering and Technology
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    • 제32권1호
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    • pp.137-146
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    • 2008
  • Nd:YAG pulse laser welding of stainless steel plate was simulated to find welding condition by using commercial finite element code MARC. Due to geometric symmetry, a half model of AISI 304 stainless steel plate was considered and user subroutines were applied to boundary condition for the heat transfer. Material properties such as conductivity, specific heat, mass density and latent heat were given as a function of temperature. As results, Three dimensional heat source model for pulse laser beam conditions of butt welding has been designed by the comparison between the finite element analysis results and experimental data on AISI 304 stainless steel plate. Nd:YAG laser welding for AISI 304 stainless steel was successfully simulated and it should be useful to determine optimal welding condition.

CW Nd:YAG레이저를 이용한 금형 재료의 표면열처리 (Surface Heat treatment of Die material by means of CW Nd:YAG Laser)

  • 유영태;신호준;장우양
    • 한국공작기계학회논문집
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    • 제13권5호
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    • pp.67-74
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    • 2004
  • Laser heat treatment is an effective technique used to improve the tribological properties and also to increase the service life of automobile components such as camshafts, crankshatfs, lorry brake drums and gears. High power $CO_2$ lasers and Nd:YAG lasers are employed for localized hardening of materials and hence are of potential application in the automobile industries. The heat is conducted rapidly into the bulk of the specimen causing self-quenching action to occur and the formation of matrensitic structure. In this investigation, the microstructrual features occurring in Nd:YAG laser hardening SM45C and $STD_11$ steel are discussed with the use of optical microscopic and scanning electron microscopic analysis. Moreover, This paper describes the optimisation of the processing parameters for maximum hardened depth of SM45C and $STD_11$ steel specimens of 10mm thickness by using CW:YAG laser.

A comparative evaluation of $CO_2$ and erbium-doped yttrium aluminium garnet laser therapy in the management of dentin hypersensitivity and assessment of mineral content

  • Belal, Mahmoud Helmy;Yassin, Abdulaziz
    • Journal of Periodontal and Implant Science
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    • 제44권5호
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    • pp.227-234
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    • 2014
  • Purpose: Dentin hypersensitivity is a potential threat to oral health. Laser irradiation may provide reliable and reproducible treatment but remains controversial. The present study aimed to evaluate the effects of $CO_2$ or erbium-doped yttrium aluminium garnet (Er:YAG) laser therapy, and to assess mineral content. Methods: Eighteen human single-rooted teeth affected with advanced periodontitis were obtained. Buccal and lingual surfaces were planed to form 36 specimens. Ethylenediaminetetraacetic acid gel (24%) was applied to remove the smear layer and simulate hypersensitive teeth. The experimental groups were: group 1, control (no irradiation); group 2, $CO_2$ laser (repetitive pulsed mode, 2 W, $2.7J/cm^2$); and group 3, Er:YAG laser (slight contact mode, 40 mJ/pulse and 10 Hz). To evaluate dentinal tubule occlusion, six specimens per group (2-mm thickness) were prepared and observed using scanning electron microscopy (SEM) for calculation of the occlusion percentage. To evaluate the mineral content, six specimens per group (0.6-mm thickness) were used, and then the levels of Ca, K, Mg, Na, and P were measured by inductively coupled plasma-atomic emission spectrometry. In addition, the surface temperature of the specimens during laser irradiation was analyzed by a thermograph. Results: The SEM photomicrographs indicated melted areas around exposed dentinal tubules and a significantly greater percentage of tubular occlusion in the $CO_2$ and Er:YAG laser groups than the control, and in the Er:YAG group than the $CO_2$ laser group. In addition, no significant differences were noted among the experimental groups for the mineral elements analyzed. The $CO_2$ laser group showed an evident thermal effect compared to the Er:YAG group. Conclusions: $CO_2$ and Er:YAG laser are effective in treating dentin hypersensitivity and reducing its symptoms. However, the Er:YAG laser has a more significant effect; thus, it may constitute a useful conditioning item. Furthermore, neither $CO_2$ nor Er:YAG lasers affected the compositional structure of the mineral content.

Immediate effect of Nd:YAG laser monotherapy on subgingival periodontal pathogens: a pilot clinical study

  • McCawley, Thomas K.;McCawley, Mark N.;Rams, Thomas E.
    • Journal of Periodontal and Implant Science
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    • 제52권1호
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    • pp.77-87
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    • 2022
  • Purpose: This pilot study assessed the immediate in vivo effect of high peak pulse power neodymium-doped yttrium aluminum garnet (Nd:YAG) laser monotherapy on selected red/orange complex periodontal pathogens in deep human periodontal pockets. Methods: Twelve adults with severe periodontitis were treated with the Laser-Assisted New Attachment Procedure (LANAP®) surgical protocol, wherein a free-running, digitally pulsed, Nd:YAG dental laser was used as the initial therapeutic step before mechanical root debridement. Using a flexible optical fiber in a handpiece, Nd:YAG laser energy, at a density of 196 J/cm2 and a high peak pulse power of 1,333 W/pulse, was directed parallel to untreated tooth root surfaces in sequential coronal-apical passes to clinical periodontal probing depths, for a total applied energy dose of approximately 8-12 joules per millimeter of periodontal probing depth at each periodontal site. Subgingival biofilm specimens were collected from each patient before and immediately after Nd:YAG laser monotherapy from periodontal pockets exhibiting ≥6 mm probing depths and bleeding on probing. Selected red/orange complex periodontal pathogens (Porphyromonas gingivalis, Tannerella forsythia, Prevotella intermedia/nigrescens, Fusobacterium nucleatum, Parvimonas micra, and Campylobacter species) were quantified in the subgingival samples using established anaerobic culture techniques. Results: All immediate post-treatment subgingival biofilm specimens continued to yield microbial growth after Nd:YAG laser monotherapy. The mean levels of total cultivable red/orange complex periodontal pathogens per patient significantly decreased from 12.0% pretreatment to 4.9% (a 59.2% decrease) immediately after Nd:YAG laser monotherapy, with 3 (25%) patients rendered culture-negative for all evaluated red/orange complex periodontal pathogens. Conclusions: High peak pulse power Nd:YAG laser monotherapy, used as the initial step in the LANAP® surgical protocol on mature subgingival biofilms, immediately induced significant reductions of nearly 60% in the mean total cultivable red/orange complex periodontal pathogen proportions per patient prior to mechanical root instrumentation and the rest of the LANAP® surgical protocol.

Nd:YAG 레이저 응접기의 국산화개발 및 응용 (Development of a Nd;YAG Welding System and Its Applications)

  • 김철종;이종민
    • 한국광학회:학술대회논문집
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    • 한국광학회 1989년도 광학 및 양자전자학 워크샵
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    • pp.107-115
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    • 1989
  • A 200 W industrial Nd:YAG laser was developed and its weding applications were investigated. The important factors in designing of an industrial Nd:YAG laser were analyzed and special sedign features were explained. Also, the performance of laser weldings of Zircaloy-4, stainless steel and fine thermocouples was presented.

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Nd : YAG LASER 조사가 치과 임플란트의 물성과 온도 상승에 미치는 영향 (EFFECT OF ND : YAG LASING ON TEMPERATURE RISING AND PROPERTIES OF MATTER OF DENTAL IMPLANTS)

  • 이호용
    • 대한치과보철학회지
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    • 제34권3호
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    • pp.489-500
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    • 1996
  • Pulsed Nd : YAG LASER has been applied to various fields in clinical dentistry including the treatment of peri-implantitis. However, LASER can affect properties of matter of dental implants which are important to maintaining the health of peri-implant tissue and can raise its temperature during lasing. So there have been warings of using LASER to treat peri-implantitis. But, the effects of laser on dental implants itself are not certain yet. So we measured the temperature rising, examined matter of properties by SEM and EDX before and after pulsed Nd : YAG lasing various intensity. 7 TPS implants and 7 HPS implants were used and pulsed Nd : YAG LASER was used in 0.3W, 1.0W, and 2.0W. 1. 2.0W LASER made polished neck portion of HPS implants reach $39.2^{\circ}C$ after 5 seconds lasing. 2. LASER made crater-like defects on plasma sprayed surface and surfaces were melted and divided by fragments after lasing. 3. There was no specific evidence of element change after lasing.

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연속파형 Nd:YAG 레이저를 이용한 인코넬 600 합금의 맞대기 용접 특성 연구 (Study of Welding Characteristics of Inconel 600 Alloy using a Continuous Wave Nd:YAG Laser Beam)

  • 송성욱;유영태;신호준
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 춘계학술대회
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    • pp.1154-1159
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    • 2004
  • Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. Experiments are performed for Inconel 600 plates changing several process parameter such as laser power, welding speed, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between plate and plate, etc. The follow conclusions can be drawn that laser power and welding speed have a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted in an increase in weld depth/ aspect ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power . Welding characteristics of austienite Inconel 600 using a continuous wave Nd:YAG laser are experimentally investigated. This paper describes the weld ability of inconel 600 for machine structural use by Nd:YAG laser.

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백서에서 Pulsed Nd : YAG Laser에 의한 치은절제술후의 치유양상 (Wound Healing After Gingivectomy Using Pulsed Nd : YAG Laser In The Rat)

  • 김옥수;정현주
    • Journal of Periodontal and Implant Science
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    • 제26권1호
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    • pp.293-308
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    • 1996
  • Recently, dental laser have been applied for removal of soft tissues, hemostasis and blood coagulation, removal of benign and malignant tumor, treatment of leukoplakia, aphthous ulcer and herpetic lesion, implant second surgery, removal of granulation tissue, frenectomy, clinical crown lengthening, gingivectomy, gingivoplasty, and treatment of dentin hypersensitivity. Even though the frequency of laser treatment is increasing, the research on the healing process after gingivectomy using pulsed Nd : YAG laser is very rare. The purpose of this study was to observe and compare the wound healing after gingivectomy using scalpel and pulsed Nd : YAG laser in the rat. Gingivectomy was performed using pulsed Nd : YAG laser(SUNRISE Technologies, U.S.A., 1.5 Watts, 10 pps) on the buccal gingiva of right maxillary first molar and using scalpel(No.12) on the contralateral side. Those sites treated by surgical scalpel were designated as the control, and by pulsed Nd : YAG laser as the experimental group. Animals were sacrificed at 1, 2, 3, 5, 7, 11 and 14 days postoperatively, and specimens were histologically observed under light microscope. The results were as follows : 1. Clinical observation Normal color and shape were observed at the 5th day ill the control group and the 7th day in the experimental group. 2. Histologic findings 1) In the control group, denser inflammatory infiltration was observed. 2) Epithelialization started at the 2nd day in the control group, similar to the experimental group, and completed at the 11th to the 14th day postoperatively. 3) In the experimental group, connective tissue showed the vacuole formation and degenerative change during early healing period. Healing of connective tissue was slower in the experimental group than in the control group by 2 days. 4) In the both groups, wound healing was completed at the 2nd week. From this study, gingivectomy using pulsed Nd : YAG laser seems to result in a little delayed wound healing process, compared to the gingivectomy using scalpel. Considering the clinical advantages of laser surgery, pulsed Nd : YAG laser might be useful device for gingivectomy.

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반도체 레이저 측면 여기 Nd:YAG 매질에서의 열영향 (Thermal effect at Nd:YAG using a laser-diode side-pumping)

  • 양동옥;김병태
    • 한국광학회지
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    • 제14권1호
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    • pp.44-50
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    • 2003
  • 반도체 레이저 측면 여기시 Nd:YAG 레이저 매질에서 발생하는 열영향에 대해 분석하였다. 열영향을 고감도로 측정하기 위해 편광자와 Nd:YAG 매질 사이에 λ/4판을 삽입하여 여기 파워에 따라 발생하는 depolarization양을 측정하였다. CCD로 는 열영향에 의한 매질 내에서의 탐침광 분포 변화를 측정하고 해석하여 반도체 레이저 측면 여기시 발생하는 열영향을 최소화하기 위한 공진기 설계의 효과적인 방법을 제시하였다.

ZCS공진형 컨버터를 적용한 고반복 대출력 펄스형 Nd:YAG 레이저 전원장치 개발 (Development of high repetition rate and high power pulsed Nd:YAG laser power supply using ZCS resonant converter)

  • 조기연;김은수;변영복;김희제;박점문;이현우
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1996년도 하계학술대회 논문집 A
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    • pp.514-517
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    • 1996
  • Zero current switching(ZCS) series resonant converter is used to control laser power density in a pulsed Nd:YAG laser power supply. The high power and high repetition rate paused Nd:YAG laser is designed and fabricated to control current pulse width and pulse repetition rate in the double elliptical laser oscillator. In order to find out operational characteristics of pulsed Nd:YAG laser, the electrical properties of driving power supply and laser output power are investigated and experimented by changing of the current pulse width from 200uS to 350uS(step 50uS) and pulse repetition rate range of 500pps(pulse per second) to 1150pps. From that result, we obtaind maximum efficiency of 1.83% and maximum laser output or 220W at the condition of 350 uS and 1150pps with one Nd:YAG rod), and obtained that of more than 400W with two laser head connecting series.

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