Viscoelastic Behavior of Porcine Arterial Tissue: Experimental and Numerical Study

Background: The viscoelastic properties of aortic tissue dictate vessel behavior in certain disease states, injury modalities, and during some endovascular procedures. Objective: We characterized the viscoelastic response of porcine abdominal aortic tissue via test and simulation to demonstrate the utility of a viscoelastic anisotropic (VA) constitutive model. Methods: In this study, the measured stress relaxation response for five samples and uniaxial tensile testing for one sample measured with the digital image correlation (DIC) technique were used to identify material parameters for the VA model using an inverse method through finite element analysis (FEA). Results: Based on the stress relaxation test, the values of the stress-like parameter μ, relative stiffness of the fibers k₁, dimensionless parameter k₂, angle of fibers γ, dispersion parameter κ, relaxation times for the ground matrix T_g1 and collagen fibers T_f1 and the dimensionless parameters for the ground matrix β_g1 and collagen fibers β_f1 for 0 degree specimen orientation were 12.1 ± 8.96 kPa, 77.3 ± 46.4 kPa, 0.032 ± 0.043, 30.25 ± 6.81°, 0.19 ± 0.06, 0.028 ± 0.016 s, 92.76 ± 26.51 s, 3.46 ± 3.78, 0.24 ± 0.08 and for 90 degree specimen orientation were 13.7 ± 7.7 kPa, 72.6 ± 35.4 kPa, 2.18 ± 4.12, 55.35 ± 7.12°, 0.22 ± 0.06, 23.51 ± 38.90 s, 81.52 ± 29.16 s, 5.14 ± 8.72, 0.21 ± 0.05, respectively. The validation revealed an overall good agreement from cycles 2 and 3 based on uniaxial tensile tests and surface strains data from DIC measurements with the material parameters from inverse analysis using FEA for the response in cycle 1. Conclusions: The identified material model and numerical simulations provide a comprehensive description of the viscoelastic behavior of the aortic wall tissue and a quantitative understanding of the spatial and directional variability underlying aortic tissue mechanical behavior.