1,721,025 research outputs found
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
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
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
Prediction of liquid nitrogen die cooling effect on the extrusion process parameters by means of FE simulations and experimental validation
No full textThe temperature monitoring during aluminum extrusion is a crucial task performed in order to avoid profile defects, to increase the die life and to optimize the process productivity. Among the different available systems used to control the process temperatures, in the last decade, the die cooling through liquid nitrogen has been installed on several extrusion plants. In order to provide extruders and die makers with a modelling tool able to gain a better understanding of the extrusion and die thermal field, a numerical model of the extrusion that accounts for liquid nitrogen cooling has been developed in the present work. A simplified 1D modelling of the cooling channel was used and validated against an experimental investigation previously specifically carried out to evaluate the cooling efficiency in a multi-hollow industrial profile. Results showed a significant impact of the design aspects of channel on the thermal efficiency of the cooling and an important heat removal when the liquid nitrogen cooling is used. A good experimental-numerical agreement was achieved in terms of temperature map and extrusion load both in cooled and uncooled conditions, thus suggesting the reliability of the developed simulation tool and its potential integration in a flexible procedure to be used for die/cooling system design and process optimization
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
The extrusion process towards Industry 4.0:a multi-objective simulation approach
Full text linkThe extrusion of aluminum alloys is a prcess able to manufacture high tolerances and high mechanical properties profiles. However, the main drawback of the process is that many objective functions need to be satisfied at the same time and many of these are potentially conflicting one each other. Example of conflicting objective functions are thre requirement fro high seam welds quality (in hollow profiles), an extended die lifetime and an high productivity. In order to solve the problem, the authors developed a comprehesive mutli-objective optimization of the extrusion process base on meta-models. The proposed procedure has been validated against two industrial profiles of a different complexity and a thrid case in now under investigation. Preliminary experimental analyses of the third case are presented
Scrap assessment in direct extrusion
No full textThe continuous direct extrusion is an economic and efficient process to manufacture high-quality aluminium profiles. However, because of multiple billets processing, transient defects (coring and charge welds) can be generated affecting portions of the profiles and deteriorating their mechanical properties. In case of structural applications, the reliable prediction of the onset and extend of these portions is therefore mandatory in order to be scrapped by the commercialized length. In this context, the present work has been aimed at examining the dynamic evolution of the coring and charge weld defects in the direct extrusion of an industrial solid profile. Both experimental and numerical activities have been performed and results evaluated in terms of coring and charge welds defect evolution achieving a good agreement for both phenomena. Results have been also compared with the outcomes of the analytical models available in literature. For the charge weld extension, the analytical model returned a poor predictably while a very good match with numerical data was obtained for the coring defect
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
Prediction and validation of grain shape evolution by 3D FEM simulations of a real industrial profile
No full textThe simulation of microstructural evolution during the extrusion of an AA6063 industrial profile with the commercial Qform VX code is presented and discussed. The description of the grain shape evolution model through specifically developed user-routine is initially presented, then the experimental setup is described in details. Predicted numerical results are compared and discussed with respect to experimental data: relevant outputs like load-stroke diagram, profile speed and thermal distribution in the profile well match with the experimental data. The prediction of the final grain size obtained by the code with air quenching conditions is then compared to experimental measurements. A discussion on potentials and limits of the proposed model is finally presented
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