Search results for "STEMI"
showing 10 items of 2898 documents
Influence of processing parameters and initial temper on Friction Stir Extrusion of 2050 aluminum alloy
2017
Abstract Friction Stir Extrusion is an innovative production technology that enables direct wire production via consolidation and extrusion of metal chips or solid billets. During the process, a rotating die is plunged into a cylindrical chamber containing the material to be extruded. The stirring action of the tool produces plastic flow in the extrusion chamber, densifying and heating the charge so that finally, fully dense rods are extruded. Experiments have been carried out in order to investigate the influence of process parameters and initial temper of the base material on the process variables and on the extrudates’ mechanical properties.
Single block 3D numerical model for linear friction welding of titanium alloy
2018
A two-stage approach for the simulation of Linear Friction Welding is presented. The proposed model, developed using the commercial simulation package DEFORM, is 3D Lagrangian, thermo-mechanically coupled. The first phase of the process was modelled with two distinct workpieces, while the remaining phases were simulated using a single-block model. The Piwnik–Plata criterion was set up and used to determine the shifting from the dual object to the single-block model. The model, validated against experimental temperature measurements, is able to predict the main field variables distributions with varying process parameters. Titanium alpha and beta phases evolution during the whole process has…
In-process control strategies for friction stir welding of AZ31 sheets with non-uniform thickness
2017
Two different in-process control strategies were developed and compared with the aim to produce AZ31 magnesium alloy joints by friction stir welding on sheet blanks with a non-uniform thickness. To this purpose, sheets with dip or hump zones were welded by either changing the rotational speed or the tool plunging in order to keep constant the value of the vertical force occurring during the welding stage of the process. The influence of the main process parameters on the tool force, the micro- and macromechanical properties, and the joints microstructures in the dip and hump zones were analyzed. The results showed that using the rotational speed change-based approach, the hump zones are sub…
Improving surface integrity of additively manufactured GP1 stainless steel by roller burnishing
2020
Abstract Additive manufacturing can rapidly fabricate the desired components by selectively melting and solidifying feedstock, rather than conventional subtractive machining. However, the difference between the two routes in terms of surface integrity of the final component is relevant. This paper presents a strategy to control the surface characteristics of additively manufactured stainless steel by roller burnishing. In particular, process parameters have been carefully selected to improve the surface integrity of the worked material. The quality of the surface has been analyzed in terms of roughness, hardness, microstructure and residual stresses. The overall product endurance under high…
Magnetic field-assisted single-point incremental forming with a magnet ball tool
2021
Abstract This paper describes magnetic field-assisted single-point incremental forming (M-SPIF) with a Nd-Fe-B magnet ball tool. In M-SPIF, the tool driven by magnetic force plastically deforms a sheet. The polarity of the magnet tool helps to make the magnetic force (i.e., forming force) more controllable. In creating a truncated cone, the direction of the magnetic force gradually points more outward as the process progresses, and material is forced outwards from the cone center, increasing thinning in M-SPIF, while the cone center remains undeformed in traditional SPIF. Moreover, M-SPIF creates less localized plastic strain than traditional SPIF while forming the desired geometry.
Friction Stir Welding of Ti6Al4V complex geometries for aeronautical applications: a feasibility study
2020
Abstract While Friction Stir Welding (FSW) of aluminium alloys can be considered a mature technology, even for complex joint morphologies, as T joints welded “in transparency”, welding of hard material still presents several open issues. In fact, welding of titanium alloys is a challenging process due to the chemical, mechanical and thermal characteristics of such materials which are subjected to atmosphere contamination resulting in joint hydrogen, oxygen and nitrogen embrittlement; additionally, due to the high melting temperature, large distortion and residual stress are found in joints obtained by traditional fusion welding processes as gas metal arc welding, electron beam welding and l…
AZ31 magnesium alloy recycling through friction stir extrusion process
2015
Friction Stir Extrusion is a novel technique for direct recycling of metal scrap. In the process, a dedicated tool produces both the heat and the pressure to compact and extrude the original raw material, i.e., machining chip, as a consolidated component. A proper fixture was used to carry out an experimental campaign on Friction Stir Extrusion of AZ31 magnesium alloy. Variable tool rotation and extrusion ratio were considered. Appearance of defects and fractures was related to either too high or too low power input. The extruded rods were investigated both from the metallurgical and mechanical points of view. Tensile strength up to 80 % of the parent material was found for the best combina…
Linear friction welding of dissimilar AA6082 and AA2011 aluminum alloys: microstructural characterization and design guidelines
2015
This paper presents the results of an experimental and numerical campaign on Linear Friction Welding of dissimilar AA2011-T8 and AA6082-T6 aluminum alloys. Experimental tests were carried out with constant oscillation amplitude and process time. Varying oscillation frequency, interface pressure, specimen geometry and mutual position were used. Grain size measurements, HV tests and EDX analysis were considered to characterize the microstructure of the joints as a function of the input process parameters. A thermal numerical model was utilized to predict the temperature profiles in the joints during the process. The obtained results allowed the identification of four weld categories: sound jo…
Friction stir extrusion to recycle aluminum alloys scraps: Energy efficiency characterization
2019
Abstract Solid state recycling refers to a group of processes allowing direct recycling of metals scraps into semi-finished product. Their main advantage lies in avoiding the molten state of the material which badly affects the environmental performance of the conventional (remelting based) recycling routes. It is expected that such process category would lower the environmental performance of metals recycling. In this paper, the friction stir extrusion process for aluminum alloy AA 2050 wire production is analyzed under the primary energy demand perspective. The process electrical energy demand is quantified with varying process parameters. An empirical modelling approach was applied and a…
Uncovering Technological and Environmental Potentials of Aluminum Alloy Scraps Recycling Through Friction Stir Consolidation
2020
Conventional metal chips recycling processes are energy-intensive with low efficiency and permanent material losses during re-melting. Solid state recycling allows direct recycling of metal scraps into semi-finished products. It is expected that this process category would lower the environmental performance of metals recycling. Friction Stir Consolidation is a new solid-state technique taking advantage of friction heat generation and severe plastic deformation to consolidate chips into billets. In this research, the feasibility of Friction Stir Consolidation as aluminum chips recycling process is analyzed. Specifically, an experimental campaign has been carried out with varying main proces…