Yielding Behaviour of Viscoplastic Materials

Complex fluids exhibiting a yield stress have extremely variable shear properties ranging from elasto-plastic behaviour below the yield stress to viscous behaviour beyond that. The progressive elastic to plastic transition of viscoplastic materials can be explored by a number of rheological techniques including stress sweep, stress ramp, creep and strain recovery. The non-linear behaviour of such materials under different loading conditions can be investigated using a large amplitude oscillatory shear flow (LAOS) combined with Fourier-Transform (FT) harmonic analysis. Results from these rheological measurements provide a characteristic “rheological fingerprint” for complex materials exhibiting yield stress.