Papers by Keyword: Laser

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Authors: Artur Medvid', Pavels Onufrijevs, Edvins Dauksta, Volodymyr Kyslyi
Abstract: The possibility to form “black silicon” on the surface of Si structure by Nd:YAG laser radiation has been shown. The shape and height of micro-cone structure strongly depends on Nd:YAG laser intensity and number of laser pulses. Light is repeatedly reflected between the cones in the way that most of it is absorbed. Si micro-cone structure spectral thermal radiation is close to black body spectral radiance, which makes this structure useful for solar cells application. The micro-chemical analysis performed by SEM has shown that the microstructures contain NiSi2. This was approved by presence of LO phonon line in Raman back scattering spectrum. The control of micro-cone shape and height was achieved by changing the laser intensity and number of pulses.
Authors: Jyotsna Dutta Majumdar
Abstract: Laser as a source of focused energy may be applied for the modification of microstructure and/or composition of the near surface region of a component. The technique may be applied for the development of a ceramic/intermetallics/interstitial compound dispersed metal matrix composite layer on the surface of metallic substrate by melting the substrate with a high power laser and simultaneous addition of alloy powders for the development of metal matrix composite layer by in-situ reactions. In the present contribution, development of metal-dispersed and intermetallic-dispersed matrix composite layer on the surface of metallic matrix has been discussed with a suitable example of its application.
Authors: Bo Yang, Xi Chen Yang, Jian Bo Lei, Yun Shan Wang
Abstract: The physical mathematic model for heat transfer and convection in laser molten pool established. 3D-computer simulation of temperature and fluid fields has been completed with finite difference method. It is shown that in laser molten pool there is a strong fluid flow, which is symmetrical in XY plane and anti symmetric in XZ plane. Due to effects of convection and heat transfer laser molten pool is widen. Surface tension gradient is the main drawing force for convection.
Authors: Yue Han, Zong Ling Yang, Yin Nan Yuan, Bing Dai
Abstract: In actual measurement of particle size distribution by the Shifrin-transform, many noises are easily misread as distribution peaks, and bring serious difficulties to the measurement. The purpose of this paper is to find a method of removing these noises to improve existing technology. By analyzing the source of these noises, we found these noises are mainly caused by the serious large angle data loss, and then propose a compensation function in the Shifrin-transform to remove these noises. Simulations explain that the method has a good effect. The method is actually tested for the sample particles of the unimodal and bimodal distribution by experiments. The result shows that the noises disappear but the number and location of original distribution peaks aren’t affected after using the compensate function. So this method can remove effectively noises and restore accurately original distribution in the measurement.
Authors: Keiji Ogawa, Hirotaka Tanabe, Heisaburo Nakagawa
Abstract: This paper proposes a novel process strategy for micro-cutting edge fabrication. Micro-cutting edges need a hardening process for the ridgeline parts that requires abrasive resistance, as well as edge sharpness and shape accuracy, based on their applications. Micro-cutting edge shapes also vary greatly in ridgeline profile and section. The proposed method is shape fabrication after laser hardening, which easily addresses these issues. In the present paper, effects of the proposed method are discussed and the results of a demonstration test are introduced.
Authors: Ching Yen Ho, Mao Yu Wen, Shih Yu Lin
Abstract: This study has developed a thermal model for laser-assisted cutting of zirconia ceramics. Laser-assisted cutting can increase ceramics removal rates by utilizing a localized heat source to elevate the workpiece temperature prior to material removal with traditional cutting tool. At high temperatures the yield strength of ceramics can decrease below the fracture strength, changing the material deformation behavior from brittle to ductile and enabling the use of a single point cutting tool to remove material at rates approaching those of metal cutting. A thermal model has been developed for the workpiece of ceramics cylinder rotating with a constant speed, which was preheated by a laser and cut by cutting tool. Since the cutting tool followed the moving laser with a fixed distance in the axial direction, i.e. the feed rate of the cutting tool was the same as the moving velocity of the laser, this thermal model has been formulated in a cylindrical coordinate system that moved with the laser beam or cutting tool and therefore, this problem was a quasi-steady-state problem. An analytical solution for this thermal model has been obtained. The results calculated by this model agree with the available experimental data. The temperature field is presented during laser-assisted cutting of ceramics. The effects of feed rate and laser power on temperature field are also discussed in this study.
Authors: Yan Yin, Jin Guo Ta, Rui Hua Zhang, Zhan Chong Wang
Abstract: Laser aided activating TIG welding was called LA-TIG. At first, the surface of weld was melted by the mini power laser protected by oxygen, and then the conventional TIG was used to cover the weld, which achieved the target of the weld with deeper penetration and narrower width. In this article, the weld bead morphology, arc images, microstructures and mechanical properties of laser aided activating TIG welding joint were analyzed. The results shows that the penetration increased significantly, excellent weld appearance and finger shape penetration were gained by laser aided activating TIG welding. It was found that the arc images of the LA-TIG was only the enlarged form compared with which observed in the conventional TIG and the arc constriction was also observed. LA-TIG weld exhibits better mechanical properties than the conventional TIG welding. Thus laser aided activating TIG welding was developed as a novel active welding method.
Authors: Mehdi Soodi, S.H. Masood, Milan Brandt
Abstract: Laser cladding is a thermal process for depositing a metallic alloy on to a parent metal to repair corrosion, erosion, wear or other physical damage. The present work studies the effects of the laser cladding process on the integrity of metal substrates and the bond between the cladding layer and the base metal. It also evaluates some physical characteristics of the cladding layer, in this case grade 420 stainless steel. The research compares the work with Tungsten Inert Gas (TIG) welding and concludes that, due to the small size of the heat-affected zone, this laser cladding process does not adversely affect the physical properties of the metallic substrates.
Authors: Mehdi Soodi, Milan Brandt, Syed H. Masood
Abstract: This paper presents an investigation on the microstructure and surface hardness of the parts fabricated by laser assisted Direct Metal Deposition (DMD) technology. A series of engineering metallic alloy powders were used in the DMD process to produce simple 3D geometric structures. The alloy powders investigated include: 316L stainless steel, 420 Stainless Steel, Stellite(R) 6, tool steel (H13), Cholmoloy (Ni Based alloy), and Aluminium Bronze. These were chosen due to their frequent application in engineering parts and components. The microstructure and hardness values have been compared to those of the wrought products (as annealed) as reported in the SAE standards, Heat treater’s guide to metals ASM international, and material data sheets supplied by the materials manufacturers. A significant difference is reported in both hardness and microstructure of the laser deposited samples compared to those of the wrought form.
Authors: Ai Xin Feng, Yong Kang Zhang, H.K. Xie, Lan Cai
Abstract: The interfacial adhesion between thin film and substrate is often the predominant factor and chief target in determining the performance and reliability of thin film/substrate system. A new technique of laser scratch testing technique has been presented by the authors of the article to characterize the interfacial adhesion between film and substrate, which synthesizes the advantages of traditional scratching technique and laser measure technique. The failure procedure is studied detailedly in the article. On different failure step of the film/substrate system, there are different characteristic s of stress and strain, as well as the characteristic of thermal lensing effect, which can be used as the distinguishing rule of the bonding state of the film/substrate system.
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