Inflation Tests of Vena Saphena Mangna for Different Loading Rates

The aim of the study was to verify whether constitutive model parameters obtained from quasistatic inflation-extension test could be used for in-vivo computational simulation of venous graft used as bypass at arterial conditionns. Inflation tests of human vena saphena magna at three loading rates were performed: a quasistatic (slow), moderate, and fast, which was similar to human heart rate. The experimental data were fitted by hyperelastic nonlinear anisotropic constitutive model (Holzapfel-Gasser-Ogden) in order to obtain material parameters. It was found that parameters differ significantly with respect to loading rate. Especially the parameter related to large strain stiffening (k2) increased with loading rate. The results suggest that constitutive parameters are strongly influenced by experimental conditions which we interpret as viscoelasticity of the vein grafts.