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Works addressing the effects of longitudinal magnetic fields in arc welding are still scarce in the literature, and most of them have a theoretical approach. With that in mind, the present work aims to investigate, through an experimental approach, the effects of applying an external longitudinal magnetic field on the physical aspects of the arc and the applicability in TIG welding. For that, tests were carried out using welding currents of 50 A and 100 A and magnetic fields of up to 42 mT. As a result, changes in the stagnation pressure profile and arc constriction were verified. With the results, welding tests were performed in order to verify the effects of such changes in the weld bead morphology and microstructure. Showing that penetration could be reduced and the weld bead could be widened by increasing the external magnetic field intensity, yielding a more refined microstructure in the molten zone. Furthermore, the applied magnetic field direction was observed to have an effect on the unilateral displacement of the weld bead.

Although widely used in GTAW, GMAW and SMAW processes, the weaving technique in the SAW process still goes nearly unexplored in the literature. In this context, given the scarcity of studies and the perceived potential regarding its employment in cladding, groove filling and tempering pass, the present work aimed to investigate the effects of its application in the SAW process with high amplitudes on the morphological aspects of the obtained weld beads. For this purpose, bead-on-plate welding tests with weaving amplitudes of up to 40 mm at different welding energies were performed. As a result, weld beads up to 45 mm width, free of discontinuities and with constant penetration profiles were obtained. However, need was found for a minimum material input of 0.90 g/cm2, regardless of the weaving amplitude, in addition to a minimum welding energy to avoid lack of deposition on the weld beads. Furthermore, when considering the ratio between the molten area and the welding energy, progressively higher values were obtained with the increase in the weaving amplitude, which translates into higher melting efficiency indices of the process.

Fragmentation of transient negative ions of tryptophan molecules formed through electron transfer in collisions with potassium atoms is presented for the first time in the laboratory collision energy range of 20 up to 100 eV. In the unimolecular decomposition process, the dominating side-chain fragmentation channel is assigned to the dehydrogenated indoline anion, in contrast to dissociative electron attachment of free low-energy electrons to tryptophan. The role of the collision complex formed by the potassium cation and tryptophan negative ion in the electron transfer process is significant for the mechanisms that operate at lower collision energies. At those collision times, on the order of a few tens of fs, the collision complex may not only influence the lifetime of the anion but also stabilize specific transition states and thus alter the fragmentation patterns considerably. DFT calculations, at the BHandHLYP/6-311++G(3df,2pd) level of theory, are used to explore potential reaction pathways and the evolvement of the charge distribution along those.

Two welding process parameters (the amplitude and frequency of the pulsed current) were varied in order to investigate their influence on the microstructure of the weld region and the mechanical properties of the joints. This investigation and the subsequent discussion were made based on the results of metallographies, tensile tests, and Vickers microhardness tests. The introduction of pulsed current at ultra-high frequencies resulted in a significant reduction in the size of the heat-affected zone (HAZ) for both materials: up to 54% for carbon steel and up to 73% for stainless steel. An increase in the grain size in the carbon steel HAZ was also noted. There are indications that the pulsed current at ultra-high frequencies has accelerated the atomic diffusion process of alloying elements from the fusion zone (FZ) to the carbon steel HAZ. Martensitic grains were observed in the FZ and the microhardness test verified this finding, once the microhardness values measured were around 400 HV0.3. The tensile strength was around 450 MPa and the rupture occurred on the carbon steel side, for all samples.

In view of the divergent information found in the literature, it would appear that the effects of a longitudinal wire oscillation in the TIG process on the morphological characteristics of the weld beads are still not well understood. Considering that, the present study investigates the influence of the welding operational conditions on the morphological characteristics of weld beads produced with longitudinal wire oscillation in the TIG process. Therefore, the effects of the wire’s oscillation amplitude and frequency under three different conditions were evaluated. The results showed that the operational conditions significantly influence the effects arising from the longitudinal wire oscillation on the weld beads’ reinforcement, width, dilution and, above all, penetration, the latter with a 28% reduction in the operational condition of Intermittent Transfer and an 80% increase in the operational conditions of Uninterrupted Bridge and Buried Wire.

New regional (two-dimensional) seismic reflection data, published Deep-Sea Drilling Project Ocean Drilling Program reports, and unpublished shallow-offshore well information characterize the Mesozoic-Cenozoic evolution of the western Iberian continental slope north of 38°45′N. Two distinct sectors bounded by first-order transfer faults exist between the Galicia Bank and the Nazaré fault. The northernmost sector 1 is filled by Triassic-Aptian (prebreakup) sequences, reaching more than 3.5 s two-way traveltime (TWTT) in thickness in distinct half grabens. Salt pillows, salt ridges, minibasins, and salt-detached overburden faults were generated during the Mesozoic and reactivated in the Cenozoic. Sector 2 shows Triassic-Jurassic units more than 2.0 s TWTT thick, underlying east-tilting half grabens of Early Cretaceous age. Salt structures in this sector evolved into mature salt diapirs. Postbreakup units are up to 2.0 s TWTT thick in both sectors. The evolution of the study area replicates evolutionary settings that have previously been proposed for nonvolcanic passive margins. However, some distinct features are noted: (1) widespread Triassic-Berriasian units deposited over rotated tilt blocks represent the early rifting stage; (2) Early Cretaceous subbasins showing rift-climax units, most likely formed during the advanced rifting stage, are spatially constrained to an approximately 100-km (62-mi)-wide region stretched along the continental slope; and (3) listric blocks and their associated low-angle (deep) detachment faults, formed on the distal margin during the advanced rifting and transition to sea-floor spreading stages, show no developed rift-climax units above them. From the early rifting stage onward, Mesozoic faults and halokinetic structures induced local differences in the thickness and character of seismic facies. Cenozoic (Alpine) tectonism promoted the reactivation of older Mesozoic structures. [ABSTRACT FROM AUTHOR]