Dissimilar friction welding of shape memory alloy and mild steel rebars for structural engineering applications

To improve the resistance of buildings submitted to extreme conditions such as earthquakes or stormy winds, shape memory alloys are combined to mild steel rebars, as they allow accommodating larger deformations thanks to their extended elasticity domain. Up to now, the two different kinds of bars are assembled by means of long and bulky mechanical couplers. A smart alternative solution consists in welding the two bars together. The present work investigates a solid-state rotary friction welding process to this aim. This master thesis draws some relationship between the main friction welding parameters of a typical mild steel rebar with a NiTi shape memory alloy bar, the microstructure of the dissimilar welded joint and the mechanical behavior of this joint. By means of microstructural analysis and mechanical testing, it is shown that optimized friction welding parameters allow achieving a strength similar to that of the parent materials.