1,721,360 research outputs found
On the Choice of Tool Material in Friction Stir Welding of Titanium Alloys
No full textFriction Stir Welding (FSW) is a solid state welding process patented in 1991 by TWI; initially adopted to weld aluminum alloys, is now being successfully used also for magnesium alloys, copper and steels. The wide diffusion the process is having is due to the possibility to weld both materials traditionally considered difficult to be welded or "unweldable" by traditional fusion welding processes due to peculiar thermal and chemical material properties, and complex geometries as sandwich structures and straightening panels. Recently, research is focusing on titanium alloys thanks to the high interest that such materials are getting from the industry due to the extremely high strength-weight ratio together with good corrosion resistance properties. At the moment, the main limit to the industrial applicability of FSW to titanium alloys is the tool life, as ultra wear and deformation resistant materials must be used. In this paper a, experimental study of the tool life in FSW of titanium alloys sheets at the varying of the main process parameters is performed. Numerical simulation provided important information for the fixture design and analysis of results. Tungsten and Rhenium alloy W25Re tools are found to be the most reliable among the ones considered
An analysis of through-thickness residual stresses in aluminium FSW butt joints
No full textIn the paper, the results of a wide experimental campaign on friction stir welding (FSW) of aluminum alloys are reported. The attention was focused on the through-thickness residual stresses that occur on aluminum joints, after the welding process. In detail, using the hole-drilling method the residual stresses distribution in the zone close to the tool shoulder border of the joint advancing side, has been investigated; four different aluminum alloys and three different process conditions have been considered. The experimental analysis has shown that unlike traditional welding processes, the residual stresses are negative in the surface of the examined zone, and increase with depth until values of about 100–150 MPa that occur at a depth of about 0.5–1.0 mm. As expected, the maximum value of the residual stresses induced by the FSW process influences the mechanical behavior of the joint significantly, as it has been observed for the AA6082-T6 aluminum alloy by considering its static and fatigue resistance.
Such results corroborate that the hole-drilling method, widely employed in the industrial field due to its simplicity and low cost, can be used for an accurate estimation of the maximum residual stresses that occur in an aluminum butt joint obtained by friction stir welding
Prediction of phase evolutions during friction stir welding of Ti-grade 5 T-joints using finite element modeling
Full text linkFriction Stir Welding (FSW) is a solid-state welding technology pioneered by The Welding Institute (TWI) in 1991. Originally used to weld aluminum alloys, it is now effectively utilized to weld high-resistance materials as well. The ultimate mechanical characteristics of the joints are inextricably linked to the microstructural evolutions that occur during the process in terms of phase change. It is then crucial, in order to carry out an effective process engineering, to predict the final material microstructure determined by the thermal history that occurred during the process itself. In the paper, a 3D Finite Element Method (FEM) model for the FSW of T-joints is proposed, based on a thermo-mechanical staggered analysis, able to predict the phase transition of the Ti6Al4V alloy. The model, which has been fine-tuned using experimental data, can predict the phase volume fraction in the different joint zones. The acquired findings allow assessing the effectiveness of the FSW FEM model as a process design tool
Selective Laser Melting of Ti6Al4V: Effects of Heat Accumulation Phenomena Due to Building Orientation
Full text linkTitanium alloy Ti6Al4V is one of the most utilized alloys in the field of additive manufacturing due to the excellent combination of mechanical properties, density and good corrosion behavior. These characteristics make the use of this material particularly attractive for additively manufacturing components with complex geometry in sectors such as aeronautics and biomedical. Selective Laser Melting (SLM), by which a component is fabricated by selectively melting of stacked layers of powder using a laser beam, is the one of most promising additive manufacturing technologies for Ti6Al4V alloy. Although this technique offers numerous advantages, it has some critical issues related to the high thermal gradients, associated with the process, promoting the formation of a metastable martensitic microstructure resulting in high tensile strength but poor ductility of the produced parts. The formation of microstructural defects such as balling and porosity can occur together with the presence of residual stresses that may significantly affect the mechanical characteristics of the component. Specific process parameters and geometries can determine heat accumulation phenomena that result in a progressive decrease in thermal gradients between layers. These heat accumulation phenomena are influenced by the number of layers deposited, but also by the building orientation that, for a given geometry, determines a variation of the deposited surface for each layer. © 2022 The Author(s). Published by Trans Tech Publications Ltd, Switzerland
In-process heat treatments to improve FS-welded butt joints
No full textFriction-stir welding (FSW) is a relatively new but already well known solid-state welding process whose main advantage with respect to fusion welding processes is the possibility to successfully weld light alloys, traditionally considered difficult to weld or unweldable. Despite the good mechanical performances that can be obtained, there exists the possibility to further improve the joints' effectiveness through post-welding heat treatments that are however time and cost-expensive and, therefore, not best suited for industrial applications. In the present paper, the authors report the results of an experimental campaign, developed on FSW of AA7075-T6 aluminum alloy, aimed to investigate the possibility to enhance the joint performances through in process heat treatments. Welded joints were developed under three different conditions, namely, free air, forced air, and with water flowing on the surface of the joint itself. The influence of the external refrigerants was investigated at the varying of the specific thermal contribution conferred to the joint. Both mechanical and metallurgical investigations were developed on the welded joints highlighting both improvements of mechanical performances of the joints and reductions in the softening of the material when external refrigerants are used. © 2008 Springer-Verlag London Limited
Latest developments in manufacturing processes at NAMRC 45
No full textManufacturing processes are tightly connected to innovation.They have been the key areas that support and influence a nation’scompetitiveness and economy since the eighteenth century. Asthe primary driving force behind economic growth, manufactur-ing processes enable and facilitate innovative products realization,ranging from heavy-duty machinery to hi-tech home electronics.In the past centuries, they have contributed significantly to moderncivilization and created the momentum that drives today’s econ-omy. Despite various achievements in manufacturing processes, weare still facing challenges due to growing complexity in manufac-turing operations, introduction of new manufacturing technologiesto industries, and pressing sustainability considerations
Special Issue of Journal of Manufacturing Processes on Advancing Manufacturing Processes Research at NAMRC 46
Full text linkDuring the refereeing process of papers submitted
to NAMRC 46 this year, nine high-quality papers have
been selected and fast-tracked to a special issue of
Journal of Manufacturing Processes (JMP) entitled
“Advancing Manufacturing Processes Research at
NAMRC 46”. The selection of the fast-track papers
was based on authors’ preferences, quality of the
papers, reviewers’ recommendations, Track Chairs’
picks, pre-selection by the Chair of NAMRI/SME
Scientific Committee, and final approval by the JMP
Editor. The nine papers published in JMP are therefore
excluded from the Proceedings of NAMRC 46 in
Procedia Manufacturing. Nevertheless, these papers
are presented in person at NAMRC 46. Details of the
fast-tracked papers and their hyperlinks to the JMP special issue are provided below for quick reference
and for completion of the NAMRC Proceedings
without duplicatio
On the role of intermetallic and interlayer in the dissimilar material welding of Ti6Al4V and SS 316L by friction stir welding
Full text linkJoining titanium with stainless steel can lighten the structure of numerous industrial applications. However, a vast disparity of thermal, physical, and chemical properties between these alloys leads to defects in conventional arc welding techniques, viz., brittle intermetallic compounds, pores, cracks, etc. Friction stir welding (FSW) is a renowned solid-state joining technology for creating dissimilar material joints producing visco-plastic material flow at the interface. The present investigation compares the intermetallic layer thickness and properties as a function of the thickness of the Cu interlayer sandwiched in lap joints. Macrostructural and microstructural characterizations were carried out to understand the localized microstructural evolution comprising intermetallic, grain refinement, defects, etc. Mechanical properties were also evaluated for prepared lap joints
Special issue of journal of manufacturing systems on new trends in manufacturing systems research
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