1,721,053 research outputs found
A novel algorithm for a continuous and fast 3D projection of points on triangulated surfaces for CAM/CAD/CAE applications
Full text linkIn the present work, a novel algorithm for the continuous projection of point triangles belonging to a triangle mesh is presented. The algorithm uses the normals defined at the vertices of the triangle to perform the projection. The direction of projection is not chosen a priori but depends on the point to be projected: the proposed algorithm, named Fast Continuous Projection method (FCP) lets the projection direction vary continuously on the mesh. Moreover, the direction is coherent with the original surface that is approximated with the triangle mesh. An optimized version of the algorithm is also presented: this uses pre-evaluated matrices to reduce the calculation time. This algorithm can be effectively used when a large set of points has to be projected on a coarse mesh as, for example, to generate the scanning vectors for laser engraving/milling
Water Soluble CdTe Quantum Dots and their Laser Reverse Patterning in Polyvinyl Alcohol Films
No full textThe CdTe quantum dots of different size are obtained in water and are dispersed within a polyvinyl alcohol polymer. The nanocomposite is then irradiated with different UV laser to test the reverse laser patterning conditions
Correction to: Point Inversion for triparametric NURBS (International Journal on Interactive Design and Manufacturing (IJIDeM, (2020), 10.1007/s12008-020-00719-z)
No full textAuthors would like to correct the error in article title. Word “for” in the title has been inadvertently changed to “ior”. Correct version of article title updated here. The original article has been corrected
Point Inversion for triparametric NURBS
No full textIn this paper a Point Inversion algorithm for NURBS volumes is presented. This algorithm is an extension to 3D of the classic Newton–Raphson iteration, thus implying the calculation of the NURBS volume partial derivatives. Explicit formulas for the derivatives are deduced and reported, in turn requiring the evaluation of the corresponding derivatives of the rational basis functions. Also these derivatives are inferred and shown together with some examples of applications. The method, applicable to any free-form shape NURBS volume is moreover compared with Fast Mapping, a novel approach presented here that, once applied to simple NURBS boxes give performance 20–50 times higher
Numerical analysis of the gas-assisted laser cutting flow from various supersonic nozzles
No full textIn the present paper, the exit jet patterns from four different supersonic nozzles have been numerically simulated using OpenFOAM® Computational Fluid Dynamics (CFD) toolbox. The desired-design operating condition, for each of these nozzles, has been calculated using quasi 1-D gas dynamics theory. Mach number and pressure distributions are presented for each nozzle to illustrate the effect of both the nozzle geometry and the operating conditions on the behaviour of the exit jet. Then, the predicted numerical results have been validated by comparison with the experimental measurements reported in previous literature. As main outcomes, the simulations results are quantitatively in high agreement with the reported experimental observations. The correlations between jet flow stability and divergence angle are discussed and the effect of Mach number and exit diameter on the jet divergence are presented
Experimental investigation on a novel approach for laser surface hardening modelling
Full text linkLaser surface hardening is rapidly growing in industrial applications due to its high flexibility, accuracy, cleanness and energy efficiency. However, the experimental process optimization can be a tricky task due to the number of involved parameters, thus suggesting for alternative approaches such as reliable numerical simulations. Conventional laser hardening models compute the achieved hardness on the basis of microstructure predictions due to carbon diffusion during the process heat thermal cycle. Nevertheless, this approach is very time consuming and not allows to simulate real complex products during laser treatments. To overcome this limitation, a novel simplified approach for laser surface hardening modelling is presented and discussed. The basic assumption consists in neglecting the austenite homogenization due to the short time and the insufficient carbon diffusion during the heating phase of the process. In the present work, this assumption is experimentally verified through nano-hardness measurements on C45 carbon steel samples both laser and oven treated by means of atomic force microscopy (AFM) technique
Solid state synthesis of CdS quantum dots through laser direct writing
No full textThe synthesis of colloidal photo-luminescent semiconductor quantum dots (QDs), belonging to II-VI groups, even from single source precursors is presented. Since three decades their synthesis has been pursued implementing new and easier synthetic conditions that standardize their production. In this work is reported the production of luminescent of CdS QDs in a polymeric film induced by laser processing (www.miledi-h2020.eu/). A film of PMMA doped with two types of precursors (cadmium xanthates) is irradiated with an UV laser source with different energy doses. The structured film will then be observed with confocal fluorescent microscope. The interesting results shows that the two different xanthates display a different behavior under the laser source even if their absorption spectrum is similar. The second interesting result is that the effect of the laser is the production luminescent pattern only for certain fluences and that the same film treated with the temperature did not show any luminescence
Generation and Characterization of Laser Induced Periodic Surface Structures on Plastic Injection Molds
No full textIn injection molding, high pressure is required to fill the mold, due to the high viscosity of thermoplastic polymers, the reduced thickness of the cavity and the low mold temperature. In this work, we investigate the functionalization of mold cavities for Injection Molding by means of Laser-Induced Periodic Surface Structures (LIPSS) generated on the ground surface of AISI 420 stainless steel through a picosecond laser. The LIPSS formation is examined with reference to the process parameters, highlighting how they affect the generated pattern. The improvements of the functionalized mold surface on the Injection Molding process are experimentally characterized and discussed. In particular, the slipping of molten PET was investigated as a function of nano-structuring orientation and injection velocity. The results demonstrate that LIPSS parallel to flow induce strong wall slip of the polymer melt, allowing a maximum reduction of the injection pressure of 10%
Effects of anisotropic and isotropic LIPSS on polymer filling flow and wettability of micro injection molded parts
Full text linkIn micro injection molding, the specific cavity surface texture and roughness directly influence the polymer flow and the heat transfer between polymer melt and mold. In this work, two different types of laser-induced periodic surface structures, linear and hexagonal, were generated, and their impact on the flow length in micro injection molding was evaluated. A complete investigation of the surface treatment effect on the polymer flow was carried out, comparing the performance of an untreated cavity surface with surfaces modified by LIPSS. The phenomenon was examined by localizing the weld lines created by the polymer flowing in two parallel channels having different surface treatments. Several cavity inserts were treated by varying the LIPSS process parameters to generate surfaces with different micro-and nanostructures directions and periodicity. Furthermore, the paper addresses the hydro-phobicity achieved on the micro molded surfaces replicated from mold inserts with different LIPSS-based surface topography. Mold surfaces with linear and hexagonal LIPSS and the respective molded parts were analyzed by optical profilometry and scanning electron microscopy to characterize the cavity surfaces replication and localize the weld lines on the micro injection molded parts
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