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In this work the problem of underwater radiated noise emitted by cavitating propellers is addressed, considering the case of single screw ships. To this aim, a series of experimental results obtained in model and full scale is presented. The analysis of results reported allows to discuss the effect of the surrounding ambient in model scale measurements and the importance of a correct representation of the ship wake. A comparison of model and full scale measurements is also reported.

Laser welding appears to be the most suitable technology for joining metallic foams. Spatially limited energy input, together with high energy density, determine a small molten material volume and a rapid solidification, which prevents the collapse of the cellular structure and the drainage phenomena. It has indeed already been shown that laser welding is a useful technique for joining metal foam panels with conventional or foamable filler. The welding techniques were also widely applied and studied for the Aluminum Foam Sandwich (AFS). Composite materials obtained by filling with metallic foam hollow profiles are nowadays available. Reliable welding processes have to be carried out in order to realize complex lightweight structures. The present paper investigates the butt-joint laser welding of a composite material made of steel tubes filled with aluminum foam core. Two pieces of a metal foam filled steel tube were prepared by chamfering the edge and foamable filler was then inserted between them. The process was divided in two parts. As a first phase of the method, the joining of the tubes was obtained by tuning the laser parameters in order to weld the whole tube thickness without damaging the metal foam. Finally, the laser beam was used in order to obtain both a sort of heat treatment in the tubes material and a temperature gradient inside the aluminum foam core. In this second stage of the laser processing, the beam parameters were tuned in order to achieve the foaming temperature inside the tubes. The hollow steel profiles were filled up with aluminum powder precursors, which were produced by cold uniaxial compaction according to the powder metallurgical route. They were then foamed in a furnace. A Laser machining center with 3 kW CW FAF CO2 laser source and five CNC axes was used. This study is a preliminary step in order to verify the reliability of the method, and further investigations will be necessary with the aim of optimizing the process. The present investigation was limited to laser beam power and process speed. At the present stage the results are very encouraging and a prototype has therefore been constructed.

This study was performed jointly by ENEA (Italian National Agency for New Technologies, Energy and Environment), Bologna and Florence Universities and the firm FINI COMPRESSORI. The functional unit is an axial air compressor manufactured by FINI COMPRESSORI, lubricated, having a 25-litres air tank, provided by 1.8 kW electrical motor. The system boundaries include raw material extraction and the end of life of the compressor. All metallic materials have the recycling as waste scenario. The LCA is obtained by using the SimaPro 3.1 code and the two methods Eco-indicator 95 and Ecopoints. The results show that air tank and stator of electrical motor are the components with greater environmental damage, even if the damage is mainly due to the electrical energy consumed during use.

This study was performed jointly by ENEA (Italian National Agency for New Technologies, Energy and Environment), Bologna and Florence Universities and the firm FINI COMPRESSORI. A comparison is carried out between the environmental damages of two models (MK10 and MK94) of air axial compressors manufactured by FINI COMPRESSORI, with a volume of intaken air of 226 l/min, a power of 1.8 kW and a maximum pressure of 10 bar. The comparison is obtained by using LCA calculated by SimaPro 3.1 code and two methods: Eco-indicator 95 and a new method obtained by adding to the Eco-indicator 95 method other damage categories such as some raw material depletion, solid and energy. For LCA study we have considered the three components crankshaft, crankcase and valve plate for both the models, the air cooling conveyor for the MK94 and the surplus of consumed energy for the MK10. The damage of air compressor can be diminished by reusing crankshaft and crankcase. A design modification of the blades of the ventilator is proposed to avoid the conveyor.

This study was performed jointly by ENEA (Italian National Agency for New Technologies, Energy and Environment), Bologna and Florence Universities and the firm BEGHELLI. The system function to be studied is the lighting of a room where a blackout has occurred. The functional unit is an emergency lamp manufactured by BEGHELLI, provided by a fluorescent tube and an accumulator battery with lead elements. The lamp life lasts 10 years. is obtained by using the SimaPro 3.1 code and two methods: Eco indicator 95 with the normalisation weight ascribed to 10 years and a new method obtained by enclosing into the Eco -indicator 95 method some new damage categories such as some raw material depletion, solid and energy. The results show that the accumulator battery, the structure of the lamp and the electronic board are the components with greater environmental damage and the electrical energy for use produces 31% of total damage calculated by the Eco - indicator method.

When large steel surfaces have to be hardened by means of a laser heat treatment a multi-track scanning strategy must be exploited in order to overcome the relatively small dimension of the beam spot. Multi-track scanning strategies imply a mutual interaction of adjacent passes, which leads to the tempering of the previously hardened material in dependence to the degree of overlapping of the adjacent trajectories. In this paper an original and computationally efficient modeling for large surfaces processing of hardenable steels by means of laser was developed. Experimental tests have been conducted on AISI 1070 carbon steel and the comparisons with the predicted results are showed.

This paper refers to the development of a numerical simulator for Laser Milling process useful for industrial applications able to predict the machining results when different materials are processed, different surface conditions are encountered and spatial and temporal distributions of the pulsed beam are set. The original software presented, developed by the authors, are well suited for simulating laser milling or laser micromachining operations with power density up to 10 14 W/m 2 and pulse duration in the order of nanoseconds. The temperature of the solid phase is evaluated by solving the Fourier equation by using the finite difference method (FDM). The recession velocity of the ablating surface is evaluated according to the Hertz-Knudsen equation assuming that the explosive effects are negligible. The plasma plume is considered in local thermodynamical equilibrium (LTE) and the energy balance permits to evaluate the plume temperature, ion distribution and pressure under the assumption that the gas expansion, from the surface target, produces a sonic front. The plume energy balance is influenced by the energy lost for irradiation from the plume and by the quantity of laser beam energy reflected from the target surface. Numerical simulations have been conducted to quantify this influence on the plasma plume physical state and, consequently, on the ablation process considering a Nd:YAG diode pumped source and three different target materials: Fe-C alloy, copper and aluminum.