Computational Modeling of an Aortic Medial Ring: Effect of Residual Stresses On a Mechanical Behavior of the Aortic Ring

The aorta is the largest artery in an animal body and is an important organ in the pulsatile flow regulation from the left ventricle. The mechanical and structural characteristics of the aortic media, which are primarily composed of smooth muscle cell layers (SMLs) and elastic laminae (ELs), have profound effects on the physiology and pathophysiology of the aorta. However, many aspects of the aortic tissue remain unknown due to the inherent layered wall structure and the regionally varying residual stresses. This study aimed to computationally represent EL buckling in the aortic medial ring at the unloaded state and reproduce the transmural variation in residual stresses and EL waviness across the vascular wall. A multiobjective optimization technique was applied to a series of simulations with the "unit" structure to obtain an idealized stress distribution throughout the aortic wall thickness. Hence, an appropriate boundary condition given to an initial reference configuration of the aortic ring was successfully identified. As a result, the average "idealized" residual stresses of SML and EL were on the order of 20 and -80 kPa, respectively, while EL waviness was ~1.01 in the unloaded state. Further, it was verified that the ring model with a radial cut will open spontaneously when the inner and outer layers of the medial wall are subjected to relative compressive and tensile residual stresses, respectively, in the unloaded state.