1,721,032 research outputs found
Comparison of AA 2024 T3 friction stir welded and riveted overlap joints with the addition of a pressurization test
No full textThe aim of this work is to investigate the Friction Stir Welding (FSW) process applicability to a typical aeronautical joint: the union of the stiffeners to sheets constituting the fuselage. To do this analysis FSW parameters of flat overlapped sheets were first identified by monitoring the temperature reached using thermography. 1.3 mm thick AA 2024 T3 overlapped sheets were welded with success and the thermal effect due to the use of different welding parameters was compared with the results of mechanical tests and microstructural investigations. FSW joint mechanical properties were compared with those detected by performing tensile tests of joints made by riveting, showing absolutely comparable values.
FSW identified parameters were used to make overlap joints between flat panels and stiffeners, so as to realize a typical structure of the aeronautical sector and to compare, by pressurization tests, the resistance of such panels with similar riveted.
The innovative character of this research is represented by cyclic pressurization tests, conducted as indicated by the FAR (Federal Aviation Regulation) rules on a scale model.
Thus it was possible to verify that the fatigue strength of welded panels is such as to overcome the acceptability limits fixed in the aeronautical field
Laser surface texturing of polypropylene to increase adhesive bonding
No full textIn this paper, the main parameters of laser surface texturing of polymeric substrates have been studied. The final aim of the texturing is to increase the performance of bonded joints of grey-pigmented polypropylene substrates. The experimental investigation was carried out starting from the identification of the most effective treatment parameters, in order to achieve a good texture without compromising the characteristics of the bulk material. For each of these parameters, three values were individuated and 27 sets of samples were realised. The surface treatment was analysed and related to the mechanical characteristics of the bonded joints performing lap-shear tests. A statistical analysis in order to find the most influential parameter completed the work
Hybrid FSWeld-bonded joint fatigue behaviour
No full textAluminium alloys, widely used in aeronautics, are increasingly involved in the automotive industry due to the good relationship between mechanical strength and specific weight. The lightening of the structures is the first objective, which allows the decreasing in the weight in motion. The use of aluminium alloys has also seen the introduction of the Friction Stir Welding (FSW) technique for the production of structural overlapping joints. FSW allows us to weld overlap joints free from defects, but with the presence of a structural notch further aggravated by the presence of a "hook" defect near the edge of the weld. Furthermore, FSW presents a weld penetration area connected to the tool geometry and penetration. The experimental activity will be focused on the combination of two different joining techniques, which can synergistically improve the final joint resistance. In particular, the welding and bonding process most commonly known as weld-bonding is defined as a hybrid process, as it combines two different junction processes. In this paper we analyse FSWelded AA6082 aluminium alloy overlapped joint with the aim of quantitatively evaluating the improvement provided by the presence of an epoxy adhesive between the plates. After optimising the weld-bonding process, the mechanical behaviour of welded joints will be analysed by static and dynamic tests. The presence of the adhesive should limit the negative effect of the structural notch inevitable in a FSW overlapped joint
Ti 6Al-4V FSW weldability: mechanical characterization and fatigue life analysis
No full textFriction stir welding (FSW) is an innovative solid-state process, patented in 1991 by The
Welding Institute, which avoids solidification problems associated with conventional fusion
welding, providing joints having excellent mechanical and metallurgical properties.
Due to its many advantages, FSW is successfully applied to weld various aluminium, magnesium
and copper alloys. In recent years, FSW of high melting temperature materials such as steels and
titanium alloys has become a key research topic. However, the high softening temperature of high
melting temperature materials result in extreme stress of the pin tool during FSW, which adds to the
difficulty in creating defect-free joints, especially for titanium alloys.
This work is a preliminary investigation of FSW application on titanium alloy Ti–6Al–4V. The
research focused on optimization of tool material and geometry, as well as process parameters.
Complete microstructural and microhardness evaluations were conducted in addition to surface
examinations. In order to evaluate the service behaviour of the joints realized with the optimized
parameters, an in-depth investigation was also conducted on the fatigue properties of FSW joints
Cold Plasma Pretreatment of Carbon Fibre Composite Substrates to Improve Adhesive Bonding Performance
Full text linkThe purpose of the paper is to investigate the effects of low pressure plasma treatment on wettability of carbon fibre reinforced polymer samples and on shear properties of adhesive bonded joints based on these substrates. In particular, two plasma process parameters, exposure time and power input, were optimized, performing contact angle evaluation on lap-shear tests. The plasma treatment was also compared with a conventional mechanical abrasion and untreated and only degreased specimens. The experimental results show that choosing the optimal parameters is possible to improve the wettability of composite substrates and reduce the contact angle
Saldatura Laser di componenti in Inconel 718 per usi aeronautici
No full textLe leghe di nichel rappresentano un gruppo di materiali molto particolare, caratterizzato da elevate qualità meccaniche e di resistenza alla corrosione. La capacità di mantenere inalterate tali caratteristiche, anche a temperature estremamente elevate, rende questi materiali idonei all’utilizzo nelle applicazioni più estreme. La saldatura delle leghe di nichel viene genericamente realizzata mediante processi ad arco elettrico. Tuttavia, per minimizzare le alterazioni subite dal materiale, sta prendendo sempre più campo l’applicazione di tecniche più avanzate, come quella basata sull’uso di sorgenti laser. Nel presente lavoro, viene affrontato il problema della realizzazione, mediante tecnologia laser, di giunti a sovrapposizione tra lamiere di diverso spessore di una lega Ni-Cr-Fe denominata Inconel 718, caratterizzata da eccellente resistenza alla corrosione e da elevate caratteristiche meccaniche
- …
