Validation of a large amplitude oscillatory shear protocol Original Research Article

Oscillatory shear rheology plays a valuable role in assessing rheological properties of viscoelastic materials. In the linear viscoelastic region (LVR), the stress response to a strain input comprises only the first harmonic. Beyond the LVR, higher-order harmonics have significant contributions, which are not accounted for in the traditional calculation of viscoelastic moduli. Previous study has developed a mathematical framework that accounted for higher-order harmonics during large amplitude oscillatory shear (LAOS), yielding a physical interpretation to nonlinear data. However, this protocol was not formally validated with model elastic and viscous systems. To that end, a model elastic solid and viscous liquid were tested using LAOS to compare the protocol to standard oscillatory data and the known nonlinear properties of both systems. Good agreement (α = 0.05) was shown between first-order harmonic viscoelastic moduli data for both systems in the linear region. The protocol correctly indicated linear-to-nonlinear transitions of the elastic system, strain-independent linear behavior of the viscous system, and strain-hardening behavior of the elastic system in the nonlinear region. These results indicate the validity of the protocol, which may be applied to food systems to give valuable insights into nonlinear behavior and elucidate structural keys to texture design.