An Experimental Study On Mechanical Properties Of Porcine Thoracic Aorta

Studies on animal arteries are very convenient and useful to obtain the structures and mechanical properties of arteries, and input materials parameters for numerical modeling of arteries related subjects, for instance, reasonable materials properties must be provided while fluidic conditions in the stent-implanted stenosised arterial models are analyzed. Therefore, they are often used as substitutes of human arteries in experiments.In this paper, we have systematically studied procine aortas in the following aspects:uniaxial tensile anisotropic behavior, shear behavior, relaxation anisotropic behavior, opening angle experiment and characterization of the arterial structure in different stress levels.The results of uniaxial tensile tests indicated that the aorta was highly anisotropic. The mechanical properties in the axial direction were the lowest, whereas the circumferential direction reached the greatest. Moreover, different loading rates greatly influenced the Young’s modulus and the ultimate stress but the degree of anisotropy weakly.The load-displacement curves in the picture-frame shear experiments displayed the consistent exponential relationships between samples stemming from different positions of the arteries, and the samples from the proximal end were greater than those from the distal end.Five-parameter discrete Maxwell model was employed to fit the experimental results in the relaxation tests, and the normalized relation functions were obtained for different samples with different orientations. Combing the normalized relation functions with stress-strain curves, the ultimate relaxation function reflecting the viscoelasticity of blood vessels were expressed.In the opening-angle tests, the lengths of the inner- and outer-walls of the arteries in the unloaded and zero-stress states were compared, and it showed that from the unloaded state to the zero-stress state, the length of the inner wall increased while outer wall shrank. And more, open angle gradually decreased from the proximal end to the distal ends.Finally, through two kinds of staining methods, we also observed the different orientations of elastic fibers and collagen fibers under the different stress levels, and it is a pity that the observation was not convincing.In summary, this paper comprehensively explored the mechanical properties of procine aorta through several sets of experiments. The results can be employed as a reference to input material properties in the finite element models of arteries related topics, and be useful in understanding the biomechanical properties of arteries.