Showing papers by "Giuseppe Casalino published in 2010"

Investigation on the effects of laser power and scanning speed on polypropylene diode transmission welds.

Abstract: Diode laser transmission welding was well established as a leading technique for industrial applications of joining plastics. The weld soundness of plastics depends on several variables like the non-isothermal crystallization, the germs growth rate, the dimensions of the heat-affected zone induced by recrystallization. Firstly, this paper proves the reliability of a numerical model based on the finite difference method at calculating the soundness variables for diode laser welding of polypropylene thermoplastic polymer. The numerical model was validated by microscopy observation of experimental polypropylene welds. Then a parametric study on the effects of the laser power and welding speed on the weld soundness variables is presented through a number of plots of the main process variables against time. The overall investigation gives a detailed picture of the influence of laser power and welding speed on the weld soundness from a microstructure point of view.

RT 2 : A Real-Time Ray-Tracing method for acoustic distance evaluations among cooperating AUVs

Abstract: The paper deals with the problem of distributed acoustic localization of teams of Autonomous Underwater Vehicles (AUVs) and proposes a novel algorithm, Real-Time Ray-Tracing (RT2), for evaluating the distance between any pair of AUVs in the team. The technique, based on a modified formulation of the non-linear sound-ray propagation laws, allows efficiently handling the distorted and reflected acoustic ray paths, induced by the anisotropy of the underwater medium. Further it can be easily implemented on-board of low-cost AUVs. Indeed it just requires the presence, on each vehicle, of a simple acoustic modem and a pair of look-up tables, a-priori constructed via the assumed knowledge of the depth-dependent sound velocity profile. On such a basis, every AUV can easily on-line compute its distance w.r.t. to any other neighbour team member, through time-of-flight measurements and the exchanges of depth information only. Further, since the proposed RT2 algorithm makes available accurate distance evaluations (despite the distorted acoustic rays), the effective filtering techniques normally used by terrestrial mobile robots for distributed localization are expected to be transferable to the underwater field.

Archimede: Integrated Network-Centric Harbour Protection System

Abstract: Confined/inshore waters may represent the best type of environment for the conduct of clandestine operations, especially from the sea: the features of such an environment weaken the detection and identification processes carried out by the defenders, while allowing the covert execution of illegal activities, as well as a better exploitation of surprise The most significant illegal activities conducted in such an environment include infiltration, drugs/weapons smuggling, sabotage/disruption of infrastructures, up to terrorist acts; these activities are accomplished through the use of a variety of means of transportation, which include cigarette boats and power boats, rigid hull inflatable boats (RHIBs), Ashing vessels, sailing/leisure boats, midgets, swimmers/divers (with open/closed breathing systems), and swimmer delivery vehicles (SDV) Requirements as flexibility, rapid reaction, resilience, fast deployment, high level automation, modularity, plug & play have a key role in modern surveillance architecture definition The paper will describe the guidelines adopted to develop a CIP (Critical Infrastructure Protection) tactical architecture in accordance with the previous requirements The CIP system integrates different types of sensors (eg radar, IR, TV, SONAR, underwater acoustic network) and classes of vehicles (Surface, Underwater, Air Unmanned Vehicles) which cooperate in a multi environmental scenario (above water, under water, sea surface, ground and air) The focus is to develop the following functionalities: fuse, classify, identify and present all the data provided by the sensors and consequently generate warnings on the Command and Control (C2) and interact automatically with the console The integration is performed to guarantee flexibility and modularity by means of tactical gateways developed in order to decouple the C2 system from sensor systems and vehicles In particular, these gateways are designed to translate the subsystem proprietary data in a unique format This allows integrating every kind and numbers of systems tailoring each time the specific gateway without modifying sensors, vehicles or C2 The system shows Network-Centric features and a wide set of growth above capabilities, even vehicles/sensors swarms, due to the gateway implementing a flexible middleware oriented to publisher/subscriber philosophy

Process parameters optimisation of the Direct Laser Metal Deposition technique

Abstract: Direct Laser Metal Deposition (DLMD) is actually one of the most attractive techniques in the group of Material Accretion Manufacturing (MAM) processes. The objective of this work was to study the effect of two DLMD process parameters, hatch spacing and step height, on the quality of built parts, in terms of density and microhardness. The experimental equipment was constituted by a 6 axis CNC laser machine and by a pneumatic system for the distribution of the powder. The powder chosen for the experimentation was the atomized Colmonoy 227-F, a nickel alloy especially designed to manufacturing moulds. Results of experimentation showed that it is possible to produce parts having properties comparable with those obtainable with conventional processes.