Search results for "welding"
showing 10 items of 317 documents
Welding abilities of UFG metals
2018
Ultrafine Grained (UFG) metals are characterized by an average grain size of <1 μm and mostly high angle grain boundaries. These materials exhibit exceptional improvements in strength, superplastic behaviour and in some cases enhanced biocompatibility. UFG metals barstock can be fabricated effectively by means of Severe Plastic Deformation (SPD) methods. However, the obtained welded joints with similar properties to the base of UFG material are crucial for the production of finished engineering components. Conventional welding methods based on local melting of the joined edges cannot be used due to the UFG microstructure degradation caused by the heat occurrence in the heat affected zone…
A continuum based fem model for friction stir welding—model development
2006
Although friction stir welding (FSW) has been successfully used to join materials that are difficult-to-weld or unweldeable by fusion welding methods, it is still in its early development stage and, therefore, a scientific knowledge based predictive model is of significant help for thorough understanding of FSW process. In this paper, a continuum based FEM model for friction stir welding process is proposed, that is 3D Lagrangian implicit, coupled, rigid-viscoplastic. This model is calibrated by comparing with experimental results of force and temperature distribution, then is used to investigate the distribution of temperature and strain in heat affect zone and the weld nugget. The model c…
Design of the friction stir welding tool using the continuum based FEM model
2006
In friction stir welding (FSW), the welding tool geometry plays a fundamental role in obtaining desirable microstructures in the weld and the heat-affected zones, and consequently improving strength and fatigue resistance of the joint. In this paper, a FSW process with varying pin geometries (cylindrical and conical) and advancing speeds is numerically modeled, and a thermo-mechanically coupled, rigid-viscoplastic, fully 3D FEM analysis able to predict the process variables as well as the material flow pattern and the grain size in the welded joints is performed. The obtained results allow finding optimal tool geometry and advancing speed for improving nugget integrity of aluminum alloys.
Gas protection optimization during Nd:YAG laser welding
2004
International audience; Many laser processes, such as welding or surface treatments are associated with an undesired phenomenon, which is oxidation. The solution commonly employed to solve this problem approaches the shielding gas and/or the shielding gas device. What we propose in this paper is a methodology with the goal to optimize the protection gas device design as well as the gas flow in the case of laser welding and surface treatments. The pressure created by the gas flow on the sample surface is recorded and analysed together with the operating parameters influence in order to reach the objectives. The nozzle system designed and presented below assures the protection against materia…
Friction Stir Knead Welding of steel aluminium butt joints
2008
To develop steel aluminium-tailored hybrids in a butt joint for sheets in a thickness of about 1 mm conventional Friction Stir Welding is not feasible due to a high distortion of the welded specimen. Contrary to Friction Stir Welding the tool used for Friction Stir Knead Welding has no pin wherefore higher welding speeds can be realised. Due to the fact that this is a newer process, applied for patent in 2005, the cut contours of the edges and their variations have to be optimised by numerical analysis to transfer a maximum of load in order to improve the formability. The examined materials in this paper are steel DC04, as well as the aluminium alloys AA5182 and AA6016 in sheet thicknesses …
On the linear friction welding process of aluminum alloys: Experimental insights through process monitoring
2013
Abstract Linear friction welding is a solid-state joining process for non-axisymmetric components in which joining of materials is obtained through the relative motion of two components under pressure. In the process the heat source is given by the frictional forces work decaying into heat determining a local softening of the material and eventually bonding conditions. A dedicated fixture was equipped with sensors for the in-process acquisition of variables regarding kinematics, dynamics and temperature levels. The results of an experimental campaign aimed to weld AA6082-T6 aluminum alloy parts are presented and a process window is identified for the used alloy.
An analysis of through-thickness residual stresses in aluminium FSW butt joints
2006
Abstract In 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…
Defect detection in additively manufactured titanium prosthesis by flying laser scanning thermography
2018
Abstract Metal additive manufacturing is nowadays a well-established technology for cutting edge applications in the automotive, aerospace, defense and medical sectors. Since additive metal deposition is basically a welding method, which creates parts by successively adding layers of material, there is a chance for defects like pores, cracks, inclusions and lack of fusion to develop. As a matter of fact, interlayer and intralayer defects are often observed in additive manufactured components. However, if one considers the typical end applications along with the high costs involved in metal additive manufactured components, a “zero defect” target is close to mandatory for this technology. Pl…
Experimental design method to the weld bead geometry optimization for hybrid laser-MAG welding in a narrow chamfer configuration
2017
International audience; The work presented in this paper relates to the optimization of operating parameters of the welding by the experimental design approach. The welding process used is the hybrid laser-MAG welding, which consists in combining a laser beam with an MAG torch, to increase the productivity and reliability of the chamfer filling operation in several passes over the entire height of the chamfer. Each pass, providing 2 mm deposited metal and must provide sufficient lateral penetration of about 0.2 mm. The experimental design method has been used in order to estimate the operating parameters effects and their interactions on the lateral penetration on one hand, and to provide a…
In-process heat treatments to improve FS-welded butt joints
2008
Friction-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 t…