Design of Polymer Extrusion Dies Using Finite Element Analysis

A computational fluid dynamics (CFD) model has been developed to compute the pressure, temperature, velocity, viscosity and viscous dissipation in the high-density polyethylene (HDPE) extrusion process. The numerical approach agrees fairly well with the experimental data recorded during the extrusion process of the material. The extrusion spider die was designed to produce high-density polyethylene pipes of 32 mm inner nominal diameter and 2.4 mm thickness. In order to investigate if the spider legs are able to perform under the pressure occurred using the maximum flow rate provided by the single screw extruder of this study, a stress analysis was conducted on a single spider leg. This fluid-structure interaction (FSI) problem was solved using the COMSOL Multiphysics software. Finally, the results obtained from the FE analysis were applied in the design and fabrication of the spider die, selecting IMPAX (tool steel) as fabrication material

Laser Scribing of Thin Films Relevant for the Second Generation, Large Scale Monolithic Photovoltaic Solar Cells

Date du colloque : 09/2013International audienc

Sol Gel grown compound ZnO Thin Films for photovoltaic applications

Date du colloque : 09/2014International audienc

Friction and Material Modelling in Finite Element Simulation of Orthogonal Cutting

In the present paper the influence of the friction and material modelling on the results of the Finite Element simulations of machining is investigated. An orthogonal cutting model is proposed, which incorporates Coulomb’s friction law. The validity of this model is tested against similar experimental and numerical results from the relevant literature and the influence of the friction coefficient is investigated. Then, a second model, with a friction model based on Zorev’s stick-slip theory, is prepared and compared to the first one. Furthermore, simulations with Johnson-Cook material model for both kinds of friction modelling are presented and compared to the other models. The results of the different kinds of models although exhibit small discrepancies between models’ results such us cutting forces, affect temperatures and chip morphology

Friction in Orthogonal Cutting Finite Elements Models with Large Negative Rake Angle

In this paper, orthogonal cutting finite elements models are built for the investigation of the impact of large negative rake angles on the friction coefficient in the tool-chip interface in machining. The simulation results give an insight on the mechanism of chip formation in processes with large negative active rake angle, such as machining with chamfered tools, grinding and micromachining. For the present analysis, cutting conditions resembling the qualitative and quantitative characteristics of the aforementioned processes were selected. More specifically, tool rake angles varying from -10o to -55o and Coulomb friction with constant friction coefficient were considered. The results indicate that friction coefficient is greatly affected by the negative tool rake angle, exhibiting values well above 1 for the high extreme of the examined rake angle spectrum

Single and multi-objective optimization of FDM-based additive manufacturing using metaheuristic algorithms

The evaluation of additively manufactured components is often conducted by means of experiments assessing product quality, build time, dimensional accuracy and tolerances, production cost and tribological properties of parts. As it occurs to any other manufacturing process, the performance of additive manufacturing is strongly affected by its corresponding process parameters. This work examines the performance of different swarm-based evolutionary algorithms when it comes to single and multiobjective optimization problems related to additive manufacturing with emphasis to fused deposition modelling processes. Five problems adopted by the recent literature have been questioned regarding their number of independent variables and their predetermined optimization objectives. Two of these problems are of single objective, whilst three are of multi-objective optimization nature. The results obtained by the several independent executions of algorithms are compared by means of analogous indicators depending on the problem, i.e. convergence speed for single-objective problem, and quality of Pareto non-dominated solutions in the case of multi-objective optimization problems. The algorithms tested for single objective optimization, are the dragonfly algorithm (DA); the ant-lion algorithm (ALO); the grey-wolf algorithm (GWO); the moth-flame algorithm (MFO) and the wale optimization algorithm (WOA). For the multi-objective optimization problems, the multi-objective grey-wolf (MOGWO), the multi-objective ant-lion (MOALO), the multi-verse algorithm (MOMVO), the multi-objective dragonfly (MODA) the Pareto envelope-based selection algorithm (PESA-II) and the strength Pareto evolutionary algorithm (SPEA-II) have been tested. Even though all algorithms have been proven capable of providing optimal solutions to cope with volatile scenarios, the “No-Free Lunch” theorem has been validated supporting that algorithms do not perform the same when applied to different optimization problems. © 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the FAIM 2021

Modeling and optimization of flexural properties of FDM-processed PET-G specimens using RSM and GWO algorithm

As in every manufacturing process, fused deposition modeling (FDM) is strongly related to its operational parameters. 3D-printed components are anisotropic and brittle and this imposes the need to investigate the effect of FDM-related parameters to improve functionality and strength. In this paper the flexural strength of polyethylene terephthalate glycol (PET-G) is studied by testing different levels for five important process-related parameters; the height of each layer, density of infill, angle of deposited material, printing speed and printing temperature. A response surface experiment with 27 runs was conducted to obtain results for flexural strength (MPa) and proceed with the examination of the effect of each parameter on the response using statistical analysis. The experiments were performed according to ASTM D790 standard. Experimental observations dealing with fructure mechanics and failure modes were recorded and analysed. Based on the analysis of variance (ANOVA) a full quadratic regression equation was generated and verified for its efficiency. Finally the model was implemented as an objective function for a modern population-based algorithm known as grey wolf algorithm (GWO). It was shown that the algorithm can suggest good combination for parameter settings to maintain good flexural strength with a gain close to 15% compared to the highest value obtained by the series of experiments conducted. © 202

On the application of grey Taguchi method for benchmarking the dimensional accuracy of the PLA fused filament fabrication process

The dimensional accuracy of a simple benchmark specimen fabricated with fused filament fabrication (FFF) route is discussed in the present study. FFF is a low-cost 3D-printing process that builds complicated parts by extruding molten plastic. Experimental method was designed according to Taguchi robust design based on an orthogonal array with nine experiments (L9 orthogonal array). The printing material was the polylactic acid (PLA). First, Grey–Taguchi method was used for the identification of the optimal printing parameter levels which result in the best dimensional accuracy for the PLA FFF parts. The printing parameters selected included number of shells, printing temperature, infill rate and printing pattern; they were selected in accordance with relevant studies already published. Then, in the second phase, nine specimens were fabricated using the same optimal printing parameter values determined in the first phase. The tolerance of these specimens was characterized according to international tolerance grades (IT grades). Data analysis showed that nozzle temperature is the dominant parameter. Additionally, the parts printed using the optimized process parameter levels possess good dimensional accuracy, which is compatible with the IT grades specification. © 2020, Springer Nature Switzerland AG

A comparative investigation of Taguchi and full factorial design for machinability prediction in turning of a titanium alloy

This study investigates the machinability performance during dry longitudinal turning of Ti-6Al-4V-ELI titanium alloy using Taguchi Experimental Design (TED) and full factorial design (FFD). Main cutting force (Fc) and mean surface roughness (Ra) are selected as the output machinability parameters. Spindle speed (n), feed rate (s) and depth of cut (a) are the independent input cutting variables, each one having three different levels. A complete combination array of 27 (33) experiments was realized and the machinability performance is recorded. Then, the “full 27-array” is divided in three sub-arrays, each one having the “orthogonality property-OP” according to Taguchi L9 array. The performance of each sub-array is analyzed using both stem-and-leaf and box plots, as well as analysis of means (ANOM) and analysis of variance (ANOVA) and is compared with the FFD one. Data analysis (DA) during present study indicates that Taguchi design is appropriate for analyzing machinability issues of “difficult-to-cut” materials. © 2019 Elsevier Lt