Luigi Maria Galantucci

Thermo-mechanical simulation of a rolling process with an FEM approach

Abstract The authors propose a model for the study of a hot rolling process, and the approach is based on thermo-mechanical analysis using the Finite-Element Method (FEM). The model can be used to speed up and improve the design and evaluation of the roughing and finishing phases in plate and sheet production. It is able to calculate the temperature distribution in the roll and the plate, the stress and strain fields, throughout a transient analysis done starting from the first phases of the process. The main hypotheses adopted in the formulation are: the elasto-plastic behaviour of the material; and rolling under plane-deformation conditions. The main variables that characterise the rolling process, such as the geometry of the plate and the roll, the loads and the boundary conditions (radius of the rolls, rolling speed, initial and final thickness, initial temperatures of the plate and the roll), have been expressed in a parametric form, this approach giving a good flexibility to the model. During the simulation, an iterative procedure enables the calculation and updating of the load conditions, such as the heat produced by friction on the plate–roll contact arc, and that caused by plastic deformation. The congruence of the results has been evaluated using experimental and theoretical data available in the literature.

Assembly and Disassembly Planning by using Fuzzy Logic & Genetic Algorithms:

The authors propose the implementation of hybrid Fuzzy Logic-Genetic Algorithm (FL-GA) methodology to plan the automatic assembly and disassembly sequence of products. The GA-Fuzzy Logic approach is implemented onto two levels. The first level of hybridization consists of the development of a Fuzzy controller for the parameters of an assembly or disassembly planner based on GAs. This controller acts on mutation probability and crossover rate in order to adapt their values dynamically while the algorithm runs. The second level consists of the identification of the optimal assembly or disassembly sequence by a Fuzzy function, in order to obtain a closer control of the technological knowledge of the assembly/disassembly process. Two case studies were analyzed in order to test the efficiency of the Fuzzy-GA methodologies.

Reverse engineering techniques applied to a human skull, for CAD 3D reconstruction and physical replication by rapid prototyping

The production of a copy of an existing object of complex shape is one of the typical applications of the integration between two modern computer-based technologies, reverse engineering (RE) and rapid prototyping (RP). The method is extremely versatile and can be used in various applicative domains (e.g. replacement of anatomical parts with artificial prostheses, replication of skeletal remains). Two different acquisition techniques of images of a skull, by laser and by CT scan, were compared to ascertain which enabled more accurate reproduction of the original specimen. The skull was chosen due to it being the body part most often used in medico-legal investigations (for personal identification, skull-photo superimposition techniques, forensic art, etc). Comparison between the copy and the original yielded satisfactory results for both techniques. However, CT scanning demonstrated some advantages over the laser technique, as it provided a cleaner point cloud, enabling shorter pre-reproduction processing times, as well as data on the internal parts, which resulted in the reproduction of a more faithful copy.

Evaluation of filling conditions of injection moulding by integrating numerical simulations and experimental tests

Abstract The authors propose an integrated approach to evaluate gating system configurations to optimize the filling conditions of thermoplastic injection moulded parts. Through data integration between the finite element (FE) analysis and the Design of Experiment approach, the filling of parts with complex geometries was studied to optimize injection process parameters and improve the product quality. The numerical simulation of an injection moulding process allows the evaluation of the component manufacturability at the early stage of the development cycle, without fabricating prototypes and minimizing experimental tests. Normally, the FE analysis interests concerns filling, post-filling and cooling phases of the injection process. Using the FE system, a deeper investigation of stress and strain distributions can be performed to predict defect presence in the final product. However, this methodology is sensitive to existing differences between property of the real part and of its model (material, geometry, etc.).

An experimental study on laser drilling and cutting of composite materials for the aerospace industry using excimer and CO2 sources

Abstract This paper reports on the results of research which investigated the potential for application of an excimer laser in the field of composite material drilling and cutting, by comparing this technology with that using CO2 sources. In particular, the scope of the work was to check whether the interaction between excimer lasers and composite materials, whose characteristic feature is the absence of thermal transfer, could yield better results than those obtainable with CO2 sources once heat transfer-induced difficulties had been eliminated. The materials selected for the experiments were multilayer composites having an epoxy resin matrix (65% in volume), with aramid fibre (Kevlar), carbon fibre and glass fibre as reinforcing materials, all of considerable interest for the aerospace industry. Optimal operational parameters were identified in relation to each source with a view to obtaining undersize holes or through cuts exhibiting severed areas of good quality. A comparison between the two types of processing carried out show that rims processed by excimer lasers are of better quality—particularly so with Kevlar—whereas the ablation rate is undoubtedly rather low compared with the CO2 technology.

Automated landmark extraction for orthodontic measurement of faces using the 3-camera photogrammetry methodology.

Objectives: To set up a three-dimensional photogrammetric scanning system for precise landmark measurements, without any physical contact, using a low-cost and noninvasive digital photogrammetric solution, for supporting several necessity in clinical orthodontics and/or surgery diagnosis. Materials and Methods: Thirty coded targets were directly applied onto the subjects face on the soft tissue landmarks, and then, 3 simultaneous photos were acquired using photogrammetry, at room light conditions. For comparison, a dummy head was digitized both with a photogrammetric technique and with the laser scanner Minolta Vivid 910i (Konica Minolta, Tokyo, Japan). Results: The precise measurement of the landmarks is ranged between 0.017 and 0.029 mm. The system automatically measures spatial position of face landmarks, from which distances and angles can be obtained. The facial measurements were compared with those done using laser scanning and manual caliper. The adopted method gives higher precision than the others (0.022-mm mean value on points and 0.038-mm mean value on linear distances on a dummy head), is simple, and can be used easily as a standard routine. Conclusions: The study demonstrated the validity of photogrammetry for accurate digitization of human face landmarks. This research points out the potential of this low-cost photogrammetry approach for medical digitization.

Coded targets and hybrid grids for photogrammetric 3D digitisation of human faces

The three-dimensional (3D) measure of the human body is currently performed using mostly optical technologies. One of the most cost effective non-contact techniques is photogrammetry; its main disadvantage is the lack of automation because the correspondences between the same points in different images must be taken manually. In this paper the authors present a properly designed low-cost photogrammetric system for 3D scanning of human faces. Results are compared projecting onto the faces patterns composed by coded targets and mixed coded-uncoded targets.

Excimer Laser Cutting: Experimental Characterization and 3D Numerical Modelling for Polyester Resins

Abstract Excimer laser has been proposed in these years as a new technology for precision cutting of plastic materials, due to the photo ablative mechanism and to the low thermal damage. Previous experiments, done by the authors, on the cutting of keviar reinforced composites with epoxy matrix, using excimer laser, highlighted very high qualities not attainable with other technologies. In the present work the attention was focused on thermoset polyester resin, because of the extensive use of this material as matrix for plastic composites. The methodology proposed in this work allows to simulate in three dimensions the laser cutting shape and size by means of a photo-ablation approach, that takes also into account the thermal effects. An experimental characterisation of the resin was performed to determine the threshold fluence (energy surface density) and the other material parameters needed to apply a photo-ablation model. The numerical simulations, compared with the experimental cuts, gave results in good accordance in terms of shape and depth of cut.

Design of process parameters for dual phase steel production with strip rolling using the finite-element method

Abstract Dual-phase steel are low-carbon micro-alloyed steels, characterized by a ferritic multiphase structure (bainite and residual austenite) in which martensite is dispersed. The dual-phase structure depends on the chemical composition of the steel, and on thermo-mechanical treatment realized with lower rolling temperatures. The properties derived from this microstructure give high performance to dual-phase steels in cold-forming applications. In this work the authors propose an approach to simulate tandem rolling for understanding the influence of the process parameters on the thermo-mechanical treatment. The approach is based on the finite-element method (FEM); two models have been developed, the first being a coupled thermo-mechanical model, which describes the behavior of the strip during its travel in each stand of the rolling train; whilst the second is a thermal model, which analyzes the strip transfer between two consecutive stands. The approach has been used also to verify how an existing rolling plant can be adapted to obtain dual-phase steels: the characteristics parameters obtained from an experimental tandem rolling process for dual-phase steel production have been used to design a new rolling process on an existing rolling plant, obtaining the desired thermal cycle of the material during the process.

Surface treatment for adhesive-bonded joints by excimer laser

Abstract In this work a treatment for surface preparation to improve mechanical resistance in adhesive bonding of plastic composites reinforced with fibres and metallic material, has been performed using an excimer laser. The following couplings have been selected to reproduce joints commonly used in the aerospace and automotive industry: CFC (carbon fibre composite) with CFC, CFC with Al 2024T3, Al 99% with Al 99%, GFC (glass fibre composite) with zinc-coated sheet in low carbon steel FeP01. The surfaces have been prepared using an excimer laser, adopting several values of laser parameters. The obtained surfaces have been examined by optical and scanning electron microscope: comparative measures of wetting and roughness have been performed to obtain an accurate characterisation and to select the proper finishes suitable to improve the mechanical resistance of the joints. The results obtained show that laser treatment always improves the final resistance of the joint; notable increases, and no significant surface damages have been highlighted. Better results have been obtained with the Al 99% with Al 99% joints which, with a low number of pulses treatment, have shown an increase of mechanical resistance up to the 70%.