Chapters authored
Evaluation of the Shielding Gas Influence on the Weldability of Ferritic Stainless Steel
Part of the book: Arc Welding
Gas Tungsten Arc Welding with Synchronized Magnetic Oscillation
The search for improvements in mechanized/automated welding techniques has been intense due to skilled labour shortage. In this line, the combination of operational modes (polarity and/or metal transfer mode) within a process has gained attention, since it expands the adjustability of the arc energy. By combining this feature with arc motion, the arc energy delivered to the workpiece can be optimally distributed. Therefore, this work exploits the synchronization between arc magnetic oscillation and gas tungsten arc welding (GTAW) process to control weld bead formation. A system was devised to control the magnetic oscillation and a welding power source synchronously. Characterization of the synchronized magnetic oscillation was carried out based on high-speed filming and electrical data. The welding process was then synchronized with the magnetic oscillation varying the level of welding current according to the arc time-position, being the effect on weld bead width considered for analysis. Welding without oscillation and with unsynchronized magnetic oscillation were taken as references. The synchronized magnetic oscillation made possible to achieve larger weld bead width on the side with higher current level and longer lateral stop time and vice versa. This technique might be beneficial to applications where extreme weld bead control is required.
Part of the book: Joining Technologies
Fiber-Metal Laminate Panels Reinforced with Metal Pins
Fiber-metal laminates (FMLs) are key to modern composite structures and metal-composite coupling is crucial to improve their effectiveness. Cold-metal transfer (CMT) PIN welding, in correlated efforts, has been successfully explored as a metal-composite hybrid joining approach. This work proposes a novel development on FMLs, which consists of introducing metal pins welded by CMT PIN for anchoring their metal and composite layers together. Thus, miniaturized FML panels with different pin deposition spacing and patterns are evaluated with emphasis in drop-weight testing followed by buckling and by means of Iosipescu shear test as complement. They are also subjected to cosmetic and preliminary modal analyses. Besides not adding significant weight, the pins does not make the panels more brittle and their distribution does not imply significant effect in the capacity that the panels have to dissipate impact. The panels with pins exhibit a less catastrophic trend, indicating damage tolerance improvement as significantly higher loads at longer axial displacements in buckling test after impact are achieved. The anchoring effect of the pins is confirmed throughout the shear test results. The pins also significantly increase the damping factor of the panels and the changes in their metal surfaces by the CMT PIN process are considered as irrelevant.
Part of the book: Optimum Composite Structures