Investigating the Influence of Initial Ramp on the Viscoelastic Parameters for Cardiac Muscle Representative Material

In this paper, mechanical parameters of a gel-type material as representative of cardiac muscle are identified by regarding and disregarding the effect of the initial ramp. It is commonly accepted that biological tissues exhibit viscoelastic behavior due to their time-dependency. Since the dead heart tissue properties are changed throughout the tests, all experiments performed on a gel-type material as representative of the cardiac muscle. A particular test setup is developed to capture the experimental data based on the stress relaxation test method where its outputs are time histories of the force and strain. All stress relaxation tests with different loading speeds are carried out. Time-dependent standard linear solid model is used to modeling the specimen. By using experimental data through related equations of stress relaxation, mechanical parameters of the standard linear solid model for the specimen are identified by implementing an appropriate identification procedure. For investigating the influence of the initial ramp on the accuracy of predicted parameters, the identification process is performed by regarding and disregarding the initial ramp of the loading. Results demonstrate that consideration of the initial ramp of strain significantly influences the specimen’s mechanical parameters and increases the identification precision.

Keywords:

Cardiac muscle , Stress relaxation test , Standard linear solid model , Initial ramp , Viscoelastic material