Papers by Keyword: Laser

Abstract: In this article, we probe the atmosphere disturbance such as Attenuation, Scattering, turbulence and thermal blooming on the laser beam propagated it. For investigating, we designed software which gives the vertically propagation characteristics of a general-type beam in atmosphere, based on the Huygens–Fresnel principle. When the required source and medium parameters are entered, the simulator yields the average intensity profile along the propagation axis in a video format. The results show that the peak value of the average intensity can be astonishingly affected by atmospheric turbulence, thermal blooming effect (for typical high power lasers) and the laser beam diameter.

Abstract: Laser allows short-time surface engraving of the patterns of desired variety, size, and intensity on a wide range of textile surfaces with precision and without much damaging the texture of the materials. The laser application in textile material has been applied possible to make denim fabric looked faded and worn out without the use chemical process. In this study, laser was applied on the denim fabric in order to evaluate its effect on fabric shade. The laser power density increased in response to the increase in the level of pixel time and resolution. Under the effect of high laser power density, a paler surface appearance was noted in the denim fabrics and the K/S_sum values indicated that the amount of dye on denim fabric was decreased significantly.

Abstract: Forging temperature is usually around 1000°C in free forging scene. Manual measurement leads to large measurement errors. Adopting the non-contact 3D scanning technology, make the laser beam sweep across the forging surface to get three-dimensional coordinates of the points on the forging surface in space. Neighboring scan points separate by less than 0.25mm. The measurement error is less than 6mm. The coordinate^,s data are sent to the LabVIEW procedure. The procedure analyzes the coordinates to calculate the size of the large-size forging to realize automatic measurement of the forgings. The procedure can also reconstruct the image of the large-size forging. These make us detect the real-time changes of the forging far from the free forging scene.

Abstract: In this work we present an optical laser based method for characterization of periodical microstructure. It allows indirect evaluation of geometrical and optical parameters of periodical microstructures. Proposed method is applicable for optimization and control of technological processes in the cases when traditional measurement techniques are not suitable. The main experimental results are compared with the computer simulations where the standard programs PCGrate-SX6.0 and and GSolver V4.20b were employed. Error of estimation of geometrical parameters of periodical microstructures by comparing theoretical and experimental values of diffraction efficiencies of periodical microstructures is less than 5%.

Abstract: High strength low alloy (HSLA) steel, namely HSLA-65, has shown promise as a replacement for more common high strength shipbuilding steels. However, conventional high heat input welding processes can cause significant distortion, often requiring expensive post-weld reworking. Butt welds in HSLA-65 steel were fabricated using a hybrid fibre laser-gas metal arc welding (GMAW) procedure to investigate the efficacy of distortion mitigation via low heat input joining. Heat input from the laser and arc sources were roughly equal at ~5.2 kW each, and plates were welded in either the laser-leading or arc-leading configuration. In either case, butt welds in ~9 mm thick plates could be made in a single pass at a total heat input of ~0.4 kJ/mm. Welding induced distortion was minimal. Analysis of the microstructure and microhardness of the welds is provided, along with some preliminary results of mechanical and impact testing.

Abstract: Derived from laser cladding, the Direct Metal Deposition (DMD) laser process, is based upon a laser beam – projected powder interaction, and allows manufacturing complex 3D shapes much faster than conventional processes. However, the surface finish remains critical, and DMD parts usually necessitate post-machining steps. In this context, the focus of our work was: (1) to understand the physical mechanisms responsible for deleterious surface finishes, (2) to propose different experimental solutions for improving surface finish. Our experimental approach is based upon: (1) adequate modifications of the DMD conditions (gas shielding, laser conditions, coaxial or off-axis nozzles), (2) a characterization of laser-powder-melt-pool interactions using fast camera analysis, (3) a precise check of surface aspects using 3D profilometry, SEM, (4) preliminary thermo-convective simulations to understand melt-pool hydrodynamics. Most of the experimental tests were carried out on a Ti6Al4V titanium alloy, widely investigated already. Results confirm that surface degradation depends on two aspects: the sticking of non-melted or partially melted particles on the free surfaces, and the formation of menisci with more or less pronounced curvature radii. Among other aspects, a reduction of layer thickness and an increase of melt-pool volumes to favor re-melting processes are shown to have a beneficial effect on roughness parameters.

Abstract: Great interest of the laser beam welding in industry is a new theoretical task, making planning the welding procedure specification and the quality control of welded joints easier. Estimating and calculating the dimensions of a weld pool and temperature distribution near weld mainly concern heat source modelling. In the presented work calculations of welding pool shape and thermal field for cylindrical-powered-normally model of heat source have been presented. Parameters of the model of heat source and weld pool geometry were determined using analytical-numerical calculations. The results of numerical calculations were compared with the experimental data for butt joint made by CO₂ laser beam. Comparable results have been observed. Practical recommendations for assumptions of model parameters - the flux density energy distribution of the heat source in case of calculations of the thermal field in the vicinity of a weld pool are given.

Abstract: In order to confirm laser jamming effect on CCD detectors, experiment study on laser jamming CCD detectors was accomplished on axis and off axis. Pixel saturation threshold and saturation power density threshold were measured. Jamming image on axis was processed with computer. The relation curve was described between laser incident energy and CCD saturation area ratio. Jamming image off axis was also processed with computer. The relation curve was described between laser incident angle and CCD saturation area ratio. The experiment result shows that laser jamming CCD imaging guidance weapons is feasible.

Abstract: This paper, innovative approaches are based on laser scanning and image analysis, presents an efficient composite technique for object profile extraction with real-time image processing. High throughput is obtained by algorithmic prefiltering to restrict the image area, while high accuracy is achieved by neural recontruction of the profile.

Abstract: Aiming at laser weapon damage to anti-ship missile, laser damage to IR guidance anti-ship missile detectors was researched. First, model on laser weapon damage to IR guidance anti-ship missile detectors was set up. Then 1.06μm and 10.6μm laser atmospheric transmittance on the sea was calculated. Finally, 10.6μm laser was given as an example, the necessary laser energy which can damage effectively the IR guidance anti-ship missile detectors was calculated. Some valuable data and conclusions were gained. It is concluded that laser weapon damage to IR guidance anti-ship missile is feasible at present.