Fig. 4.

Simulation results of biaxial tensile—stress relaxation tests of collagen gel at different initial stress levels. Solid lines represent the simulation results. Experiment results were shown in symbols for comparison. Material parameters in the hyperelastic model are C₁₀ = 20 kPa, k₁ = 30 MPa, k₂ = 1150, γ = 45 deg and κ = 0.333; material parameters in the viscous model are listed in Table 1.