Virtual uniaxial tensile testing of calcified aortic aneurysm tissue

Abdominal aortic aneurysm (AAA) is a socially significant cardiovascular disorder. The thickened aortic wall, combined with its propensity for intraluminal thrombus formation and calcification, complicates the study of its tissue mechanical behavior. Moreover, clinical observations reveal substantial interpatient variability in these parameter values and their outcomes, necessitating further research into the mechanics of such vascular tissues. This study proposes a hierarchy of hyperelastic models regarding the level of tissue calcification using a numerical modeling approach. For the simulations of the uniaxial tensile test mechanics of calcified AAA tissue, leveraging experimental data were used. Both calcification patterns and mechanically tested strength properties of the aortic wall were incorporated. The analyzed specimens belong to two substantially distinct classes based on calcification content. Counterintuitively, specimens with higher elastic moduli exhibited lower calcification, likely attributable to the fibrous microstructure of vascular tissue. Hyperelastic material models were derived from tensile testing data obtained for each specimen on the INSTRON 5944 unit. A three-parameter Mooney – Rivlin model proved inapplicable to the least elastic specimen. For the most elastic specimen, a virtual uniaxial tensile test simulated progressive calcification zone expansion. The simplest models (Neo-Hookean and Yeoh) predicted stress reduction with calcification growth from 0.34 to 0.28 MPa and 0.39 to 0.27 MPa, respectively. In contrast, advanced hyperelastic Mooney – Rivlin models exhibited either stability (3-parameter form) or stress escalation (5-parameter form).