Extraction of viscoelastic functions from creep data with ringing

Sometimes the creep ringing phenomena are observed as results of the coupling between the instrumental inertia and the viscoelasticity of the materials. Especially, biopolymer solutions are apt to be the victim of creep ringing because creep test is usually conducted to enlarge the frequency range of dynamic data. To overcome the creep ringing problems, we developed a general method which extracts pure material response functions from creep data with ringing by the use of Laplace transform and nonlinear regression method. The method is not based on spring-dashpot models and gives continuous relaxation time spectrum.