• Title, Summary, Keyword: Argon laser

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A STUDY ON THE PHYSICAL PROPERTIES OF A COMPOSITE RESIN INLAY BY CURING METHODS (중합방법에 따른 복합레진 인레이의 물리적 성질에 관한 연구)

  • Cho, Sung-A;Cho, Young-Gon;Moon, Joo-Hoon;Oh, Haeng-Jin
    • Restorative Dentistry and Endodontics
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    • v.22 no.1
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    • pp.254-266
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    • 1997
  • This study was to know the usefulness of argon laser for composite resin, to prove the polymerized effect of heat treatment of composite resin inlay and to get the curing method for optimal physical properties of composite resin inlay. In this study we used four light curing units and one heat curing unit: Visilux $II^{TM}$, a visible light gun: $SPECTRUM^{TM}$, an argon laser: Unilux AC$^{(R)}$ and Astorn XL$^{(R)}$, visible light curing unit: CRC-$100^{TM}$ for heat treatment. Compared to a control group, we divided the experemental groups into five as follows: Control group: Light curing(Visilux $II^{TM}$) Experimental group 1 : Light curing(Visilux $II^{TM}$) + Light curing(Unilux AC$^{(R)}$) Experimental group 2: Light curing(Visilux $II^{TM}$) + Light curing(Astron XL$^{(R)}$) + Heat treatment(CRC-$100^{TM}$) Experimental group 3 : Laser curing($SPECTRUM^{TM}$) Experimental group 4 : Laser curing($SPECTRUM^{TM}$) + Light curing(Unilux AC$^{(R)}$) Experimental group 5 : Laser curing($SPECTRUM^{TM}$) + Light curing(Astron XL$^{(R)}$) + Heat treatment (CRC-$100^{TM}$) According to the above classification, we made samples through the curing of Clearfil CR Inlay$^{(R)}$, which is a composite resin for inlay, in a separable cylindrical metal mold and polycarbonate plate. And then, we measured and compared the value of compressive strength, diametral tensile strength and the surface micro hardness of each sample. The results were as follows : 1. Among the experimental groups, group 5 showed the highest value of compressive strength, $157.50{\pm}10.24$ kgf and control group showed the lowest value of compressive strength, $103.93{\pm}21.93$ kgf. Control group showed significant difference with the experimental groups(p<0.001). Group 2 which was treated by the heat showed higher compressive strength than that of group 1 which was not, and there was significant difference between group 1 and group 2(p<0.001). Group 5 which was treated by heat showed higher compressive strength than group 4 which was not, and there was significant difference group 4 and group 5(p<0.001). 2. Among the experimental groups, group 5 showed the highest value of diametral tensile strength, $95.84{\pm}1.97$ kgf and control group showed the lowest value of diametral tensile strength, $81.80{\pm}2.17$ kgf. Control group which was cured by visible light showed higher diametral tensile strength than group 3 which was cured Argon Laser. Group 2 which was treated by heat showed higher compressive strength than that of group 1 which was not, and there was significant difference between group 1 and group 2(p<0.001). Group 5 which was treated by heat showed higher compressive strength than group 4 which was not, and there was a significant difference group 4 and group 5(p<0.001). 3. Among the experimental groups, group 5 showed the highest value of microhardness of top surface, $148.42{\pm}9.57$ kgf and control group showed the lowest value of microhardness, $111.43{\pm}7.63$ kgf. In the case of bottom surface, group 5 showed the highest value of $146.19{\pm}7.62$ kgf, and control group showed the lowest, $104.03{\pm}11.05$ kgf. Group 3 which was cured by Argon Laser showed higher diametral tensile strength than control group which was cured only with a visible light gun. Group 2 which was treated by heat showed higher compressive strength than that of group 1 which was not, and there was a significant difference between group 1 and group 2(p<0.001). Group 5 which was treated by heat showed higher compressive strength than group 4 which was not, and there was a significant difference group 4 and group 5(p<0.001). 4. According to the above results, we took a conclusion that argon laser can be used as a useful unit for curing the composite resin and heat treatment can improve the physical properties of the composite resin inlay.

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Study of variables influencing on the metal transfer in GMAW (GMAW의 금속이행에 영향을 주는 변수연구를 위한 계측 시스템과 조건해석)

  • 이세헌
    • Journal of Welding and Joining
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    • v.11 no.1
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    • pp.73-79
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    • 1993
  • The phenomenon of metal transfer has been investigated for different transfer modes using a digital high speed motion analyzer and an arc shadow-graphing system based on a laser source and related optical system. It was observed that the pinch instability phenomenon did not occur for the globular transfer mode, since the liquid globule was then spherical rateher than a cylindrical liquid bar. On increasing the ratio of carbon dioxide to argon, the transition current from globular to spray transfer generally increased, but it is interesting that the transition was observed to occur at the lowest current in a 5% CO$_{2}$-95% argon gas mixture. For pure carbon dioxide and helium shielding gases, the drop frequency increased slowly with increasing current. At high currents or an argon based shielding gas, the length of liquid bar decreased as the carbon dioxide content increased. The acceleration of a droplet within the arc was determined using the gas drag force theory and was found to be greater than the experimental results.

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Fabrication of Micro Carbon Structures and Patterns with Laser-assisted Chemical Vapor Deposition (레이저 국소증착을 통한 미세 탄소구조물 및 패턴 제조)

  • 정성호;김진범;이선규;이종현
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.914-917
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    • 2002
  • Fabrication of micro carbon structures and patterns using laser-assisted chemical vapor deposition is studied. Argon ion laser and ethylene were used to grow micro carbon rod through pyrolytic decomposition of the reaction gas. The influence of reaction gas pressure and incident laser power on the diameter and growth rate of the micro carbon rod was experimentally investigated. The diameter of micro carbon rods increases linearly with respect to the laser power but is almost independent of the reaction gas pressure. Growth rate of the rod changes little with gas pressure when the laser power remains below 1W. When the carbon rod was grown at near threshold laser power, a very smooth surface is obtained on the rod. By continuously moving the focusing lens in the direction of growth, a micro carbon rod with a diameter of 28 ${\mu}{\textrm}{m}$ and aspect ratio of 100 was fabricated.

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LASER-Crosslinking Behavior of PVA Emulsion for Textile Printing Screen (날염 제판용 PVA 유제의 레이저 가교거동)

  • 이재환;박상원
    • Textile Science and Engineering
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    • v.33 no.9
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    • pp.785-789
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    • 1996
  • For the development of economic, automated, and computer-aided manufacturing process of textile printing screen, photocuring of PVA emulsion by argon LASER was studied. The crosslinking-degree of PVA, photosensitized by diazonium salt, was analyzed by gravimetric and IR-spectroscopic method. The exposure time was longer than 4 $\mu$s with 1 W power and 50 $\mu$m spot size for processable crosslinking. The crosslinking behavior of PVA showed typical S-shape kinetics against the cumulative exposure time.

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Establishment of Laser Sintering Technique for Titanium Powder

  • Miura, Hideshi;Takemasu, Teruie;Uemura, Makoto;Otsu, Masaaki
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.244-245
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    • 2006
  • This paper investigates the characteristic of single-layered and multi-layered compacts made by selective laser sintering using titanium powder (TILOP45 and TILOP150, Sumitomo Titanium Corp.) There were few defects in smooth surface of laser sintered specimen in vacuum as compared to the laser sintered specimen in argon. Maximum tensile strength of singlelayered compact was about 200MPa. Multi-layered compacts show the density of around 75% and the adhesive bonding was not observed between layers, resulted in 70MPa of maximum bending strength and 50MPa of maximum tensile strength.

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Effect of Assist Gas on Laser Induced Plasma and Bead Formation in Welding of Structural Steel by CW Nd:YAG Laser (철강재료 용접에서 보조가스가 레이저플라즈마와 용입특성에 미치는 영향)

  • 김기철;신현준
    • Journal of Welding and Joining
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    • v.20 no.3
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    • pp.109-115
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    • 2002
  • In this study high power Nd:YAG laser welding of structural steel was investigated. For the test steel blocks of $50{\times}50{\times}200mm$ were cut and machined, and bead-on-plate weld was made on the machined surface. Argon, nitrogen, helium, dry air or mixed gases were used to find the effect of shielding conditions on the bead formation. Results demonstrated that there were Fe I rich region and Fe II rich region in the laser induced plasma column based on the spectral analysis with S-2000 field spectrometer The Fe I region was located at the root of the column near keyhole opening. On the other hand, Fe II region was found at the middle of the plasma column. In the Nd:YAG laser welding, Fe I region emitted continuum which had peak value at wave length of around 710nm, and Fe II region had the peak at 580nm. In the welding of steel by $CO_2$ laser, however, no continuum was observed. There showed two groups of strong spikes in the $CO_2$ laser welding; the first group was displayed at the wave band of 450-560nm. This spike group emitted stronger intensity of light and sharper peaks than those group at 680-800nm.

Effect of Process Parameters on Forming Characteristics of Selective Laser Sintered Fe-Ni-Cr Powder (Fe-Ni-Cr 분말의 선택적 레이저 소결 적층시 공정변수에 따른 조형특성)

  • Joo, B.D.;Jang, J.H.;Yim, H.S.;Son, Y.M.;Moon, Y.H.
    • Transactions of Materials Processing
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    • v.18 no.3
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    • pp.262-267
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    • 2009
  • Selective laser sintering is a kind of rapid prototyping process whereby a three-dimensional part is built layer wise by laser scanning the powder. This process is highly influenced by powder and laser parameters such as laser power, scan rate, fill spacing and layer thickness. Therefore a study on fabricating Fe-Ni-Cr powder by selective laser sintering has been performed. In this study, fabrication was performed by experimental facilities consisting of a 200W fiber laser which can be focused to 0.08mm and atmospheric chamber which can control atmospheric pressure with argon. With power increase or energy density decrease, line width was decreased and line surface quality was improved with energy density increase. Surface quality of quadrangle structure was improved with fill spacing optimization.

A Study of the Effect of Magnetic Fields Using Welding Process (용접 공정에서 자기력의 효과에 대한 연구)

  • Cho, Hong Seok;Park, Ik Keun;Lee, Wooram
    • Journal of Welding and Joining
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    • v.32 no.5
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    • pp.32-43
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    • 2014
  • Welding and joining technology has become a core field. Therefore it is more widely applied to nonferrous metals, inorganic and polymeric materials. That is because the high performance, high function and diversification trend of materials used as industrial technology develops. In the laser welding process, STS 304 and SCP1-S were used as the base materials, the output density was fixed $7MW/cm^2$, the protective gas was argon(Ar) and the transfer rate was fixed 5 mm/sec. and it was progressed while the magnetic field is gradually increasing by 100 mT ranging 0 to 400 mT. The tensile test showed in average about 6 % tensile strength improvement in the case of the laser welding process using the magnetic fields. In the shielded metal arc welding process using SPHC only or the combination of SPHC+STS304 as base materials. The electric current was set at 80 Amperes and the protective gas used argon(Ar) the same as the laser welding process and the strength of magnetic fields. In the shielded metal arc welding process using the magnetic fields, the tensile tests showed about 5 % tensile strength improvement in the case of using SPHC only, 3 % tensile strength improvement in the case of using the combination of SPHC+ STS304. In comparing the results of numerical analysis to the results of experimental tests, it was revealed that the temperature, thermal stress distribution and the behavior of molten pool were similar to those of real tests. Consequently, it may be considered that the numerical assumption and the analytical model used in this study were reasonable.

Laser- Plume Effects on Radiation Energy Transfer in Materials Processing (레이저 가공시 에너지 전달과 Plume 효과)

  • Kang, Kae-Myung;Kim, Kwang-Ryul
    • 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.

Effect of Process Parameters on Bead Formation in Nd:YAG Laser Welding of Thin Steels (저탄소 박판 강재의 Nd:YAG 레이저 용접부 형성에 미치는 공정변수의 영향)

  • 김기철;허재협
    • Journal of Welding and Joining
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    • v.19 no.3
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    • pp.317-324
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    • 2001
  • This study deals with high power Nd:YAG laser welding of thin steels for small pressure vessels. Full penetration welding at the overlap joint was performed so as to assure sufficient weld strength. Results showed that mid-depth weld size reduced drastically with increasing the travel speed. Position of focus had little effect on the bead formation even though short focal system was used. However, the shape factor and the bead width had closely related with the position of focus. Based on the microstructural inspection, acceptable weld was obtained when the overlap clearance was controlled up to 20% of the base metal thickness. In the case that the joint contained more clearance than the critical value, both the tensile shear strength and the tear strength were reduced. Results also demonstrated that shielding gases were proved to play a key role as far as the bead formation characteristics was taken into consideration. Blowing dry air through 5mm in diameter nozzle produced narrower bead cross-section than that of argon or nitrogen shielding.

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