Key result
A linear material model underestimates peak wall stress in abdominal aortic aneurysms by 35% compared to non-linear models and is not reliable for computations.
In finite element analysis of abdominal aortic aneurysms, stiffer nonlinear material models can reduce computational time by up to 30% without compromising peak wall stress predictions, whereas linear models significantly underestimate stress and should be avoided.
Linear models should be avoided for AAA wall stress computations; leaves open validation of nonlinear models against clinical rupture risk.
• Parametric study of 16 patient-specific abdominal aortic aneurysms performed. • Sensitivity of wall stress to material model in finite element analysis investigated. • The nonlinear material models are mutually replaceable in terms of wall stresses. • Stiffer nonlinear models can save up to 30% of computational time. • Linear material model underestimates peak wall stress by 35% and should not be used. Biomechanics-based assessment of Abdominal Aortic Aneurysm (AAA) rupture risk has gained considerable scientific and clinical momentum. However, computation of peak wall stress (PWS) using state-of-the-art finite element models is time demanding. This study investigates which features of the constitutive description of AAA wall are decisive for achieving acceptable stress predictions in it. Influence of five different isotropic constitutive descriptions of AAA wall is tested; models reflect realistic non-linear, artificially stiff non-linear, or artificially stiff pseudo-linear constitutive descriptions of AAA wall. Influence of the AAA wall model is tested on idealized ( n = 4 ) and patient-specific ( n = 16 ) AAA geometries. Wall stress computations consider a (hypothetical) load-free configuration and include residual stresses homogenizing the stresses across the wall. Wall stress differences amongst the different descriptions were statistically analyzed. When the qualitatively similar non-linear response of the AAA wall with low initial stiffness and subsequent strain stiffening was taken into consideration, wall stress (and PWS) predictions did not change significantly. Keeping this non-linear feature when using an artificially stiff wall can save up to 30% of the computational time, without significant change in PWS. In contrast, a stiff pseudo-linear elastic model may underestimate the PWS and is not reliable for AAA wall stress computations.
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Man et al. (2018) studied Abdominal Aortic Aneurysm (n=20). Non-linear material models vs. Linear material model was evaluated on Peak wall stress. A linear material model underestimates peak wall stress in abdominal aortic aneurysms by 35% compared to non-linear models and is not reliable for computations.
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