New Approaches to the Friction Stir Welding of Aluminum Alloys

Friction stir welding (FSW) is a technique able to guarantee welding advantages such as the easy control of tool design, rotation speed, and translation speed. This is also a reason for a continuous research activity to optimize the effect of the different welding parameters and tool-metal setups. In this contribution, two innovative welding methodologies are presented and discussed. A first new FSW configuration was defined as double-side friction stir welding (DS-FSW). In the DS-FSW, the welding is performed on both sheet surfaces, that is, the first welding is followed by a second one performed on the opposite sheet surface. In this chapter, the effect of the welding parameters, tool configuration and sheet positioning on the yield, ultimate strength, and ductility of an aluminum plate, its microstructure and its post-welding formability are discussed. A second new FSW configuration consists of a pin rotation around its centerline welding direction by 0.5 and 1.0 mm. This was defined by authors as RT-type configuration and it is characterized by a welding motion of the pin tool obtained by the combination of two different movements occurring simultaneously

Environmental assessment of an automated impregnation process of carbon fiber tows

Abstract The aim of the present study is to assess the environmental loads of an automated impregnation process of carbon fiber tows with a thermoset epoxy resin. A streamlined Life Cycle Assessment (LCA), in the "gate-to-gate" form, has been carried out, following the ISO 14040/44 methodology. This study has been focused on the following environmental impact categories: global warming potential (GWP), cumulative energy demand (CED) and water consumption. A single linear meter of manufactured towpreg has been chosen as functional unit. Simapro v. 8.5 and Ecoinvent v. 3.5 have been used respectively as LCA software and Life Cycle Inventory database

Reverse Engineering and Scanning Electron Microscopy Applied to the Characterization of Tool Wear in Dry Milling Processes

Abstract An innovative method of tool wear assessment, based on the digitization of the cutting tool performed by a piezoelectric 3D scanner and on the analysis of the surfaces of a 3D model generated using the Reverse Engineering technique, has been developed. To this purpose, face milling experiments were carried out under dry cutting condition on AISI 420 B stainless steel using inserts in cemented carbide, with a two-layers coating (TiN and TiAlN). The time dependence of the insert wear was analysed by interrupting milling at predetermined time values. The proposed approach has been validated by comparing the output provided by the reverse engineering method to that measured experimentally by analysing the worn insert images obtained using a stereo microscope. An excellent agreement between the results given by the two different methodologies has been found. The worn tools have also been analysed using the scanning electron microscopy technique in order to understand the wear mechanisms operating during dry milling

Manufacturing of Isogrid Composite Structures by 3D Printing

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3D printing and testing of composite isogrid structures

AbstractThe present work aims at studying the effect of geometric parameters of isogrid structures on their buckling behavior. To this purpose, isogrid structures in polyamide reinforced with short carbon fibers, with different rib widths, rib thicknesses, and cell heights, were additively manufactured using the fused deposition modeling technology; then, they were subjected to compression test until the occurrence of buckling. It was observed that isogrid structures can undergo to different failure modes, local and global buckling, depending on the values of geometrical parameters. Furthermore, the geometrical parameters that lead to the highest strength are different to those providing the highest specific strength. However, the specific strength of the 3D printed composite material is higher than those of 1XXX and 3XXX aluminum alloys. Rib thickness was characterized by the highest effect on both strength and specific strength while the cell height results in the lowest contribution. Finally, optical and scanning electron microscopies were carried out in order to analyze the fractured ribs and to obtain high magnification three-dimensional topography of fractured surfaces after buckling. The effect of moisture content on polyamide reinforced composites and the comparison between 3D printed and traditionally produced isogrid structures will be investigated in future researches

effect of the rolling temperature on hot formability of zam100 magnesium alloy

Abstract Magnesium alloy sheets are usually obtained by complex processing cycles including hot rolling operations. Temperature of the final stage of rolling strongly affects the microstructure and, consequently, the hot formability of the sheets. In this framework, the present work aims at investigating the effect of the rolling temperature on the hot formability of the innovative magnesium alloy ZAM100. To this purpose, two different rolling temperatures were used and hot formability was investigated by tensile tests performed in extended ranges of temperature and strain rate. The flow curves were analyzed in order to obtain constitutive models of hot formability

a new sustainable direct solid state recycling of aa1090 aluminum alloy chips by means of friction stir back extrusion process

Abstract Friction stir extrusion is an innovative process designed to recycle metal chips from various machining operations. In this research, the feasibility of solid-state recycling of pure aluminum AA1090 machining chips using FSE process is investigated. In the early stage, a FE simulation was conducted in order to optimize the die design (spiral scroll of the plunge, hole size and bearing distance) and the process parameters in terms of plunge rotational speed and extrusion rate. The AA1090 aluminum chips were produced by turning off an as-received bar without lubrication. The chips were compacted on a MTS machine up to 150KN of load. The resulting chip-billets had a diameter of 40mm and 30mm high. The chip-based billet was FS Extruded at 1000rpm rotational speed and 0.8mm/s of plunge displacement. The extruded samples were analyzed by optical microscope in order to see the material flow and to characterize the microstructure. Finally, micro-hardness Vickers profiles were carried out, in both longitudinal and transversal direction, in order to investigate the homogeneity of the mechanical properties of the extrudate

sustainability analysis of friction stir welding of aa5754 sheets

Abstract The environmental impact of friction stir welding process vs. welding parameters was evaluated and analysed in detail. To this purpose, butt joints in AA5754 aluminum alloy sheets were obtained at different rotational and welding speeds. All input and output data, in terms of materials, energies and emissions, were collected and analyzed using a life cycle assessment software in order to evaluate the environmental impact index. Sound weld was used as functional unit and all energy and material flows were based on it. The results given by the life cycle assessment analysis has shown that the environmental impact of friction stir welding is strongly affected by rotational and welding speeds. The environmental impact was also related to the mechanical properties of joints, expressed as ultimate tensile strength and ultimate elongation

in process control of rotational speed in friction stir welding of sheet blanks with variable mechanical properties

Abstract In the present work, an adaptive control constraint system was applied in the friction stir welding of AA6082 aluminum alloy with the aim of tailoring the mechanical properties of the sheet blank to the subsequent forming processes. To this purpose, blanks in the solution heat-treated and artificially aged (T6), and in the annealed (O) conditions were welded according to a well defined layout. Such in-process control strategy was based on the variation of the controlled variable (rotational speed of the pin tool) in order to keep the measured one (vertical force) constant during the welding stage of the process. To this end, a preliminary investigation on the effect of the rotational speed, varying from 1000 to 2500 rpm, on the vertical force during FSW was performed. The capability of the proposed approach in friction stir welding sheet blanks with variable mechanical properties along the welding line was proven

flow curve prediction of zam100 magnesium alloy sheets using artificial neural network based models

Abstract A multivariable empirical model, based on an artificial neural network (ANN), was developed to predict flow curves of ZAM100 magnesium alloy sheets as a function of process parameters in hot forming conditions. Tensile tests were performed in a wide range of temperature and strain rate to collect the dataset used in the training and testing stages of the network. The generalization ability of the model was tested using both the leave-one-out cross-validation method and flow curves not belonging to the training set. The excellent fitting between experimental and predicted curves was proven the very good predictive capability of the model