Large amplitude oscillatory shear experiments were carried out on a polyurethane melt
using a sliding plate rheometer incorporating a shear stress transducer. Three types of
nonlinear behavior are described: periodic, quasi‐periodic, and chaotic, and common
methods for characterizing these types of behavior are given. Spectral analysis is shown as
the best way to distinguish between each type of behavior. Attractor reconstruction from
chaos theory is introduced as a way to understand the dynamics of a system from only one …