Determination of the Viscoelastic Properties of Agar/Agar-Gelatin Gels Based on Finite Element Method Optimization

An FEM algorithm was developed to determine the viscoelastic properties of soft tissues of agar/agar-gelatin gels based on the curve-averaged data from stress relaxation experiment of parallel plate compression and FEM optimization technique. This approach enabled more realistic and pertinent expression of the mechanical behavior of the gels than conventional methods, and allowed simultaneous and logical characterization of all viscoelastic parameters, based on geometry, relating to both Prony series and Maxwell model such as elastic modulus, Poisson's ratio, relative modulus, relaxation time, and dynamic viscosity, etc. Several assumptions were made in the ITEM model such that the soft tissue materials were homogeneous in phase and isotropic, gravity effect was negligible, and the response was transient and controlled by displacement. To demonstrate the validity of the FEM model, the results of FEM optimization were compared with those of conventional method of nonlinear regression for agar/agar-gelatin gels, and also the predicted mechanical behavior of FEM on compressive creep as an interrelation with stress relaxation by the FEM model was compared with the experimental creep of 1% agar gel. The reliability of the FEM optimization method was confirmed by small stress deviation within 4.7% between experimental data and the ITEM simulation using optimized parameters for stress-relaxation evaluation for agar/agar-gelatin gels and by strain deviation within 3.4% for creep prediction of 1% agar gel.