Constitutive model of tendon responses to multiple cyclic demands (II) - Theory and comparison

The hereditary integral form of a quasi-linear viscoelastic. law has been e mployed. Four new concepts have been employed: 1. a reduced relaxation func tion with a non-linear exponential function of time, 2. an inverse method t o determine the scale factor of the elastic response, 3. an instant elastic recovery strain during unloading, and 4. the results of a constitutive mod el for cyclic tests may be a function of the Heavyside class. These concept s have been supported by agreement between measured and predicted responses of soft connective tissue to three types of multiple cyclic tests which in clude rest periods of no extension and alternations between different strai n levels. Such agreement has not been attained in the previous studies. Chu n and Hubbard (2001) is our companion experimental analysis paper.