Karaciğer nakli esnasında prezervasyon zamanının yumuşak dokuların dinamik malzeme özellikleri üzerindeki etkisi

We investigate the effect of preservation time on the dynamic material properties of bovine liver using a viscoelastic model derived from the impact and ramp and hold experiments. First, we measure the storage and loss moduli of the bovine liver as a function of frequency using an impact hammer. Second, the time-dependent relaxation modulus of the liver is measured via the ramp and hold experiments performed with a separate compression device. Third, a generalized Maxwell solid model that successfully simulates the frequency and time-dependent dynamic response of the liver is developed to estimate the number of Maxwell arms (N) in the model and the viscoelastic material coefficients by minimizing the error between the experimental data and the corresponding values generated by the model. Finally, the changes in the estimated material coefficients are investigated as a function of preservation time for liver samples tested 1, 2, 4, 8, 12, 18, 24, 36 and 48 hrs after harvesting. The results of the experiments performed with three different animals show that the tissue becomes stiffer and more viscous as the preservation time increases. The results also suggest that a linear model is appropriate for investigating the effect of preservation time on the viscoelastic response of bovine liver.