V. Tagliaferri

Laser cutting of fibre-reinforced polyesters

Abstract Composites of aramid, graphite and glass cloth-reinforced polyester have been cut by a laser and the morphology of the cut surfaces examined by scanning electron microscopy. The results are examined using a numerical thermal model and a mechanism for the laser-induced thermal changes observed in the composites is proposed. The thermal properties of the fibres and matrix are the principal factors which affect cutting performance. For the range of experimental parameters used in this study, the quality of the cut surfaces obtained depends on the type of composite being cut.

An Experimental Study of the Drilling of Aramid Composites

Major drilling characteristics of Aramid fiber-reinforced plastics are experimentally investigated. The chip appears highly deformed and tends to smear on the tool. Forces and, mainly torque are more influenced by the tool diameter than by the feed rate and cutting speed. On the contrary, the specific cutting energy strongly depends upon the feed rate due to size effects of the tool tip. The damage in the work, i.e., delamination at entry and exit side, can be controlled by taking into account the relationships between machining parameters and forces and torque. Generally, the tool fails by gross brittle failure at the periphery rather than by generalized land wear.

An experimental study on grinding of silicon carbide reinforced aluminium alloys

This paper presents the results of an experimental research on the grinding of metal matrix composites. The aim of the investigation is to enhance the knowledge about the machinability of some aluminium alloys reinforced with SiC of different shape (powder or whiskers) and content. Investigations on chip morphology, ground surfaces and trend of forces acquired during the grinding process were carried out. The results show that the presence of the reinforcement enhances the machinability in terms of both surface roughness and lower tendency to clog the grinding wheel, when compared to a non-reinforced Al alloy. Particle-reinforced composites exhibit a linear relationship between the roughness of the ground surface and the average hardness of the material. Whisker-reinforced composites show higher roughness values than particulate composites. Data of grinding forces obtained under different machining conditions are reported which permit the evaluation of the specific cutting energy.

Artificial neural networks to optimize the extrusion of an aluminium alloy

Extrusion of aluminium alloys is a complex process which depends on the characteristics of the material and on the process parameters (initial billet temperature, extrusion ratio, friction at the interfaces, die geometry etc.). The temperature profile at the die exit, largely influences microstructure, mechanical properties, and surface quality of an extruded product, consequently it is the most important parameter for controlling the process. In turn the temperature profile depends on other process variables whose right choice is fundamental to avoid surface damage of the extruded product. In the present work, two neural networks were implemented to optimize the aluminium extrusion process determining the temperature profile of an Al 6060 alloy (UNI 9006/1) at the exit of induction heater (ANN1) and at the exit of the die (ANN2). The three-layer neural networks with Levemberg Marquardt algorithm were trained with the experimental data from the industrial process. The temperature profiles, predicted by the neural network, closely agree with experimental values.

Fluidized Bed Assisted Abrasive Jet Machining (FB-AJM): Precision Internal Finishing of Inconel 718 Components

The relatively new technique of fluidized bed assisted abrasive jet machining (FB-AJM) is applied to finishing the inner surfaces of tubular Inconel 718 components. The effects. of abrasive size, jet pressure, and machining cycle were evaluated, and the behavior of abrasive cutting edges acting against the surface during the process to remove material is accounted for. The finished surface was found to be highly dependent on jet pressure because it affects the abrasive contact against the surface as well as the finishing force acting on the abrasive, on the abrasive grain size, which controls the depth of cut, and on machining cycle, which controls the interaction time between the abrasives and the surface being finished. By altering these conditions, this process achieves surface roughness (R-a) as fine as 0.1 mu m and imparts minimal additional residual stress on the surface. This study also reveals the mechanisms that determine the smoothing of the inner surface of Inconel 718 tubes and improve the form accuracy, i.e., the internal roundness of the Inconel 718 tube.

Self-cleaning and self-sanitizing coatings on plastic fabrics: Design, manufacture and performance

Self-cleaning and self-sanitizing coatings are of utmost interest in several manufacturing domains. In particular, fabrics and textile materials are often pre-treated by impregnation or incorporation with antimicrobial pesticides for protection purposes against bacteria and fungi that are pathogenic for man or other animals. In this respect, the present investigation deals with the design and manufacture of self-cleaning and self-sanitizing coatings on plastic fabrics. The functionalization of the coatings was yield by incorporating active inorganic matter alone (i.e., photo-catalytic TiO2 anatase and Ag(+) ions) inside an organic inorganic hybrid binder. The achieved formulations were deposited on coextruded polyvinylchloride-polyester fabrics by air-mix spraying and left to dry at ambient temperature. The performance of the resulting coatings were characterized for their self-cleaning and self-sanitizing ability according to standardized testing procedure and/or applicable international regulations.

Drilling Polymeric Matrix Composites

This chapter presents the basics of drilling of polymeric matrix composites (PMCs). PMCs are becoming widely used in the manufacturing of products where a high mechanical strength must be accompanied by a low weight. However, the machining of PMCs implies coping with problems that are not encountered when machining other materials. Drilling is a particularly critical operation for PMCs laminates because the large concentrated forces generated can lead to widespread damage. This damage causes aesthetic problems but, more importantly, may compromise the mechanical properties of the finished part.

Process-efficiency prediction in high power diode laser forming

The present work is an experimental investigation on the laser forming process of aluminum alloy and stainless-steel thin sheets. A high-power diode laser (HPDL) with a nonsymmetric spot configuration was employed at medium and low scanning rates. The tests were performed at different operating conditions: scanning rate, laser spot orientation, and laser beam power. The experimental results revealed the great influence of the laser spot orientation on the total bending angle and the harmful effect of the surface melting during heating. Spot orientation significantly affects the treated area extension during laser scanning. Employing an analytical thermo-mechanical model, a dimensionless processing map can be presented that allows the prediction of the sheet bending angle depending on the material properties and machining parameters. Dimensional terms of the processing map can be associated to efficiency terms for heat transfer and bending.

Nd-YAG Laser Sculpture of WC Punches for Micro-Sheet Forming

A Q-switched Nd-YAG laser was used to sculpt a WC micro-punch in a sintered preform. A cylindrical punch was obtained with a nominal diameter of 400 μm and 80 μm in height. Laser machined surface was characterized both qualitatively and quantitatively by means of scanning surface topography instrument. A 20 μm thick aluminum sheet was micro-punched using a testing machine as a drive and a gasket material for support. The gasket followed the micro-punched disk during all the shearing process, collapsing under the punching load. This simple forming process was defined to reduce the micro-part distortion and to avoid the fabrication of a micro-die. Finally, optical microscopy showed that the punched part had a flat surface in the centre and some anomalies at the edges where the punch melted zones were reproduced.

Metal foams for structural applications: design and manufacturing

In this paper, the design and manufacture of metal foams, using the powders compact melting method (PCMM), is investigated. Experimental tests were performed to study the influence of several process parameters, that is, compaction pressure, foaming time, temperature and amount of foamable precursor material, on the kinetics of foaming process. As the large number of experimental factors involved in metal foams manufacturing, an experimental approach based upon DOE techniques was employed to reduce the trials need for individuating the best process windows. Hence, in such operative ranges, further experimental tests were carried out to trace the full trends of foaming efficiency according to leading parameters, thereby laying the basis to support manufacturers on how to deal with the operative troubles and process settings.