| Models predicting strain as a function of time are fit to data obtained from creep recovery experiments on viscoelastic materials. Here we discuss standard non-inertial and instrument-induced inertial creep experiments. We first summarize and illustrate key signatures, which differentiate the models and highlight properties of creep data. The basic signatures distinguishing a solid versus fluid response, respectively, are: a sudden versus gradual rise when a stress impulse is applied; a sudden versus gradual decline when a constant stress is suddenly removed; and recovery to zero strain versus a finite steady state after the applied stress is removed. For completeness, we discuss development of the models, solution methods, and parameter influence on behavior. Finally, software created by Dr. Ke Xu to estimate the model parameters that best fit the experimental data is adapted to illustrate the influence of experimental noise in parameter recovery. |
