Measurement of shear stress and viscosity provides information concerning the flow properties of a system, such as its yield value. Most systems are viscoelastic; therefore, defining their flow properties as a function of shear rate is only a partial characterization of their rheological properties.
This raises important questions, such as: How can one separate the flow component from the elastic component of any given mixture? What happens in systems that are mostly elastic, as opposed to systems that are mostly viscous? How does a change in shear stress or strain affect the rheological properties of the system? Dynamic mechanical analysis is the key to answering these questions.