1,721,203 research outputs found
Saldatura Laser di Leghe di Titanio e Alluminio
No full textLa saldatura del titanio è largamente diffusa nei vari settori dell’industria metalmeccanica e aerospaziale. Negli ultimi anni è aumentata la necessità di saldare il titanio ad altre leghe leggere ferrose e non come l’alluminio. Le maggiori difficoltà nella saldatura eterogenea del titanio sono dovute alla formazione di un ossido superficiale che si può opporre alla fusione o alla saldobrasatura con metalli dissimili.
In questa memoria sono riportati i risultati relativi alla saldatura con laser a fibre del titanio Ti6Al4V con una lega d’alluminio 5754. I due metalli sono saldati mediante un irraggiamento laser della superficie del titanio in prossimità del giunto con l’alluminio. Quest’ultimo fonde a causa dell’onda di calore che si trasmette dalla zona fusa del titanio verso l’alluminio. La caratterizzazione metallurgica e meccanica del giunto dimostra la possibilità di arrivare così a un giunto di qualità accettabile senza particolari preparazioni delle superfici a contatto
Process parameters effects On Al-Mg alloys MIG-Laser CO2 welding
No full textAmong the non-heat treatable aluminium alloys the Aluminium-Magnesium alloys, which are known as 5xxx series, have good strengths that are achieved by magnesium in solid solution. They still have very good weldability and deformability. Therefore, following the trend to substitute automobile parts with light alloys, the AlMg alloys have received raising interest from automotive industry. In this paper 5005 and 5052 Al-Mg alloys welding was investigated. The CO2 laser and MIG arc sources were used simultaneously. The bead geometry was studied versus the welding parameters for 3 mm thick plates. Moreover bead-onplate welds were obtained for 10 mm thickness, which represent a good benchmark for further investigation. In particular the focal position, the scanning speed, and the power were the adjustable parameters of the laser. The MIG gun-to-laser beam distance and the guntilting angle also varied. The former variation in distance permitted to compare coupled and combined working conditions
Statistical modelling and optimization of nanosecond Nd:YAG Q-switched laser scarfing of carbon fiber reinforced polymer
No full textThis paper explores the effects of laser scarfing on a CFRP tape consisting of unidirectional carbon fiber with a layup of [(45/0/-45/90)4] sym with a total laminate dimension of 5.952 mm. The laser system used in the experimental investigations consisted of a nanosecond Nd: YAG laser source with an average maximum power of 20 W in a pulsed mode. The material was a with a total laminate of 5.952 mm. The laser process aims to investigate the surface modification by laser ablation. In more details, the effects of scanning speed (550 - 650 mm/s) and frequency (23 - 27 kHz) for three different scanning strategies on the scarfing depth, specimen dimensions (in x and y direction) and surface conditions were studied by full factorial experimental plan. By scarfing, the fibers were either oxidized, partially stripped, stripped and excessively stripped. After the statistical analysis, the best results in terms of surface conditions were achieved with the x-parallel laser scanning strategy, where the presence of excessively stripped fibers was not noticed. The mixed-hatching (MH) mode was the strategy that produced the worst results for the scarfing depth, which can negatively affect the ablation rate, even if it turns out to be the most stable strategy. The best results in terms of scarfing depth and x-y dimensions were achieved with MH mode, and with a scanning speed of 600 mm/s and a frequency of 27 kHz
Laser-arc combined welding of aa5754 alloy
No full textLaser-arc combined welding of 5754 magnesium aluminium alloy was performed with the CO2 heat source and MIG torch. The effects of welding conditions on penetration depth, geometry, porosity and crack susceptibility were investigated. Concerning porosity suppression and key-hole stability, optimal process parameters were identified. The grain boundary wetting phenomenon was observed in the fused zone
Transfer mode effects on Ti6Al4V wall building in wire laser additive manufacturing
No full textThis paper analyses the metal transfer process dynamics to assess how weld pool, laser source and filler wire interact to establish a stable and smooth deposition. The investigation led to the definition of suitable manufacturing settings and process parameters. Satisfactory geometrical and microstructural properties were achieved for a 15-layer titanium alloy wall. (C) 2021 Society of Manufacturing Engineers (SME). Published by Elsevier Ltd. All rights reserved
Microstructural analysis of aisi 304 bars welded with high speed pulsed discharges
Full text linkIn a way similar to the resistance welding the high speed pulsed welding exploits the power of elevated discharging current through an electrical circuit, which contains the two parts to be welded. During welding edges profile interact with the process parameters to determine both the weld microstructure and mechanical strength.
In this paper, the welding profiles at the opposite surfaces was machined so to have linear contacts instead of a classic single protrusion contact. The effect of this multilinears contact geometry was a weld that was in the midway between the capacitor discharge welding (CDW) and the projection welding (PW).
Pulsed welding experiments were performed using AISI 304 cylindrical bars in butt configuration. The welded microstructures were studied using an optical microscope and image analysis software. The Vickers microhardness tests were performed to a better characterization of the welding microstructures
Multivariate process incapability index for non-normal data: a case study
No full textWhen several quality characteristics have to be considered in process capability analysis, conventional indices are difficultly applicable. Above all when different processes have to be compared in terms of capability, they rarely univocally express which process can be considered the best one. Moreover, conventional process capability indices (PCIs) separately consider quality characteristics regardless of eventual mutual dependencies existing between them. In order to offset these weaknesses, useful tools are the multivariate capability indices. In this study, based on the non-normal Cpp formulation, the multivariate process incapability index for non-normal data, MCpp(q), is proposed. The non-normal Cpp has been constructed using Clements’ method; however, Burr XII distribution has been used in place of the Pearson distributions family for assessing non-normal percentiles. The bootstrap methodology has been used to draw an interval estimate of the index proposed. A case study on the comparison between two different cold extrusion processes has been presented to demonstrate how the proposed index can be applied to real data
Mathematical Modeling of Weld Phenomena, Part 1: Finite-Element Modeling
No full textThe objective of this chapter is to give an essential presentation on the theoretical foundations of the finite-element modeling of weld phenomena. The presented fundamentals of thermal, microstructure, and mechanical analysis embrace models from computational solid mechanics. The modeling of the weld pool fluid calls for computational fluid dynamics. The modeling techniques are validated against a variety of reference solutions for both fusion and solid-state welding
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