Papers by Keyword: Laser Beam

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Authors: Ryszard Jabłoński, Roland Nowak
Abstract: The paper presents the method, configuration and calibration of special system for measuring the size of particles. It is designed for real-time measurement of particles in the range up to 10µm, moving with velocity up to 15m/s and under pressure up to 20 bar. The method is based on measuring light scattered by single particle. We focused on studying the output from photomultiplier and finding relationships between pulse shape and particle size, and also the time intervals between pulses.
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Authors: Peng Li, Jian Li, Yong Zhen Zhang, M. Scherge
Abstract: Recent researches have found that surfaces with non-glazed or laser dimpling topography offer improved lubricating efficiency and wear resistance under lubrication conditions over their conventional glazed status. It was carried out in this paper to simulate a pin-on-disk experimental condition and perform hydrodynamic lubrication (HL) calculations for both non-glazed and glazed surfaces under conditions of different sliding velocities and loads with a view of understanding the tribological mechanism and characteristics of non-glazed surfaces. The results showed that the minimum film thickness of non-glazed surfaces, which closed to a typical elasto-hydrodynamic lubrication (EHL) film thickness, was thicker than that of glazed surfaces under the condition of low sliding velocities and small loads. At the same time, a decreased maximum pressure of full-film of non-glazed surfaces demonstrated an even pressure distribution on them.
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Authors: S. Iqbal, Anand Krishna Asundi
Abstract: A Multipoint Diffraction Strain Sensor (MISS) with the novel feature of simultaneous strain measurement at multiple points is characterized. Unlike conventional interferometry based systems, this patented sensor uses principles of diffraction to directly measure strain at large number of points. In this sensor, a high-frequency diffraction grating is illuminated by two symmetric laser beams and the diffracted beams are sampled on a CCD camera via a micro-lens array into an array of dots. The shift of the individual dots is sensed and strains or rigid body tilt are calculated directly. This novel technique is expected to be very valuable in numerous industrial applications.
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Authors: Imed Miraoui, Mouna Zaied, Mohamed Boujelbene
Abstract: Laser cutting is a thermal process which is used contactless to separate materials. In the present study, high-power laser cutting of steel plates is considered and the thermal influence of laser cutting on the cut edges is examined. The microstructure and the microhardness of the cut edge are affected by the input laser cutting parameter: laser beam diameter. The aim of this work is to investigate the effect of the laser beam diameter on the microhardness beneath the cut surface of steel plates obtained by CO2 laser cutting. The cut surface was studied based on microhardness depth profiles beneath the machined surface. The results show that laser cutting has a thermal effect on the surface microstructure and on the microhardness beneath the cut section. Also the microhardness of the hardening zone depends on the laser beam diameter.
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Authors: Kenji Yamaguchi, Itaru Matsumoto, Tsuyoshi Fujita, Yasuo Kondo, Satoshi Sakamoto, Mitsugu Yamaguchi
Abstract: It is well-known that a series of cracks sometimes gets initiated perpendicular to the cutting edges on the rake faces of brittle cutting tools made of materials such as cemented carbide, ceramics, and cermet under high-speed intermittent cutting. The tools used in intermittent cutting processes are exposed to elevated temperatures during cutting and then cool quickly during the noncutting time. Previous studies have suggested that such repeated thermal shocks generate thermal stress in the tool and that the thermal cracks are then propagated by thermal fatigue. Recently, high-speed machining techniques have attracted the attention of researchers. To apply new cutting tool materials to this machining process, it is important to evaluate their thermal shock fatigue resistances. During high-speed intermittent cutting, the frequency of thermal shocks becomes high and the action area of the thermal shocks is limited to the rake face of the tool. Therefore, conventional thermal shock resistance evaluation methods are unsuitable for this case. Consequently, the authors have developed a new experimental evaluation method using a CO2 laser beam. In this study, we irradiated cemented carbide and TiN cermet cutting tools with the CO2 pulse laser beam and gauged the effectiveness of the proposed thermal shock fatigue resistance evaluation method. The results show a correlation between the thermal shock due to the CO2 pulse laser beam and those due to the intermittent cutting experiments.
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Authors: Lin Dong, Ahmed Makradi, Saïd Ahzi, Yves Remond
Abstract: In the selective laser sintering (SLS) manufacturing technique a pre-heated layer of material powder undergoes a laser radiation in a selective way to produce three dimensional metallic or polymeric solid parts. Here, we consider sintering of polymer powder. The phase transformation in this process involves the material heat transfer which is strongly affected by the material sintering phenomena. A transient three dimensional finite element model is developed to simulate the phase transformation during the selective laser sintering process. This model takes into account the heat transfer in the material (powder and solid), the sintering and the transient nature of this process. The numerical simulation of the set of equations, describing the problem, is made possible by means of the commercial finite element software Abaqus. A bi-level structure integration procedure is chosen, in which the density is integrated at the outer level and the heat equation is integrated in the inner level. After successfully computing the integration of the density, a material Jacobian representing the thermal phenomena is computed and supplemented the Abaqus Code via an implicit user subroutine material. Results for temperature and density distribution, using a polycarbonate powder, are presented and discussed.
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Authors: Amer E. Amer, S.A. EL-Ghazaly, Y.S. Shash, S. Weiss
Abstract: Iron-base superalloys are well known materials having excellent high temperature properties .They are used in turbo superchargers and turbine engines required for aerospace and power plants. In this investigation precipitation hardenable X5NiCrTi26-15 was used to study the influence of microstructural changes on the creep behavior at different conditions . Different creep cycles were applied for both base alloy and laser beam welded alloy (6kW CO2 ) namely at 600 , 625 and 650C at applied controlled creep stresses of 400 and 450 MPa . The base material sheet was used in as solution annealed state ( 30 min, 960 C, WQ ).The specimens were hardened in two steps (24h,760 C, FC and 16 h, 705 C,AC ) before being investigated . The microstructural changes due to grain boundary sliding, intergranual fracture perpendicular to the metal flow axis , and the type ,morphology of different secondary carbides were measured and discussed . To examine the changes in microstructure Philips EM 400 TEM with an acceleration voltage of 120KV, and SEM as well as light microscopy were used . It was found that , laser beam welded structure investigated after creep deformation at temperatures lower than 650C and at controlled stress of 400 and 450 MPa , showed a textured weld metal zone with dendrite having lower hardness combined with a higher creep resistance than that for base material .It was found also that creeping at 650C at the same stress values offsets any gain in creep resistance of welded joints as compared with that for the base material at the same conditions.
643
Authors: Ching Yen Ho, Mao Yu Wen, Jui Chang Tsai
Abstract: This paper investigates that polarizations of a laser vary in the process of reflections after a linearly or circularly polarized beam is incident on a paraboloid of revolution-shaped cavity. This analysis is based on the viewpoint of geometry optics because the opening radius is about 100μm, which is ten times the size of the wavelength 10.6μm of an incident CO2 laser beam. Considering the profile of laser beam to be Gaussian distribution, the variation of polarization in the process of reflections is mathematically modeled. The result reveals that the state of polarization for an incoming ray with circular polarization is almost totally transformed into linear polarization perpendicular to the plane of incidence after the ray intervenes multiple reflections. The effects of cavity depth and absorptive index of material on the polarization variation are also discussed. The circularly polarized ray entering the deeper cavity is finally changed into the higher degree of linear polarization. The increase in absorptive index reduces the speed approaching the linear polarization.
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Authors: Beáta Šimeková, Ingrid Kovaříková, Erika Hodúlová
Abstract: The paper is focused on study of cladded layer properties created by laser beam, to abrasive wear resistant. As a basic material was used alloyed tool steel X37CrMoV5, the layers wascreated by laser beam by using a filler materials in the form of wire PZ 6159 and PZ 6168. The aim is research ofcladded layers structures changes, theirmicrohardness changes relative to the basic material and determine the abrasive wear resistance. One of the most important advantages of laser cladding technology is bringing the wire to the exact place of the interaction of a laser beam.
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