| Abstract Scope |
Using the friction stir welding (FSW) technique as an example, this talk addresses two critical issues that are universal in many modern solid-state additive manufacturing techniques. (1) Quantifying the thermomechanical input: We prove the existence and origin of the interface stick-slip behavior of the frictional contact between the tool and workpiece. The mechanistic analysis allows us to correlate processing parameters to the resulting torque and heat generate rate, and the strain-rate and temperature fields. (2) How solid surfaces bond together: We note that the evolution of interfacial cavities (or pores, voids, etc.) under applied thermomechanical loading histories is a reverse process of the high-temperature creep fracture of polycrystalline materials by grain-boundary cavities, as dictated by both a lateral diffusive process and the creep deformation. This viewpoint allows us to derive an approximate but analytical solution for the determination of process window. |