This method is used to determine the dynamic mechanical properties of polymer melts. A polymer melts is exposed to a harmonic shear deformation, in a plate-plate rheometer, and the material response detected in the form of a harmonic shear stress.
This gives the storage modulus G’ as well as the loss modulus G’’ and the loss factor tan δ.
The actual measurement, known as the complex viscosity, can then be calculated on the basis of the storage and loss modulus.

An oscillatory shear in the small amplitude range performs the function of a sampling probe during the measurement, ensuring a significantly more precise measurement than with tests that rely on stationary shear flow (capillary rheometer, MFR). This method can be used to quantify such variables as shear viscosity, the linear viscoelastic range or the thermal stability of melts.