A Combined Experimental/Computational Analysis of the Butt-Friction-Stir-Welded AA2139-T8 Joints

Combined experimental and computational investigations are carried out of the mechanical properties of materials residing in different weld zones of friction stir-welded (FSW) joints of thick plates of AA2139-T8. The experimental portion of the work comprised (a) identification of the weld zones within the FSW joints, through the use of optical-microscopy characterization of a transverse section; (b) validation of the weld zones identified in (a) via the generation of a micro-hardness field over the same transverse section; (c) extracting and subsequently testing miniature tensile specimens from different weld zones; and (d) extracting and testing a larger-size tensile specimen spanning transversely the FSW weld. The computational portion of the work comprised (i) validation of the mechanical properties, as determined experimentally using the miniature tensile specimens, of the material residing within different zones of the FSW joint; and (ii) clarification of the benefits yielded by the knowledge of the local material properties within the FSW joint. These benefits arise from the fact that (a) joint mechanical properties are generally inferior to those of the base metal; (b) the width of the weld in thick metallic-armor is often comparable to the armor thickness, and therefore may represent a significant portion of the armor exposed-surface area; and (c) modeling of the weld-material structural response under loading requires the availability of high-fidelity/validated material constitutive models, and the development of such models requires knowledge of the local weld-material mechanical properties.