## 4 Discussion  
In the biomechanical analysis, the AAA ruptures when the PWS exceeds the aortic strength; evidently, the PWS is a major predictor of AAA rupture. In this study, the correlation between AAA geometry and PWS was analyzed using a computational analysis approach. To accomplish this, the study was conducted in two phases: the calculation of a material constant for simulating the NAA and AAA behaviors, and the scenario simulation based on the AAA geometry. In the calculation of the material constant phase, first, the biaxial tensile test results of the NAA and AAA tissues were investigated to establish the tensile stress and stretch. In addition, the simulation techniques were verified, and the material constants were calculated by comparing the simulation results with those of the Holzapfel model and the experiments. The sample on the circumferentially oriented strip tended to have a higher tensile stress value than the sample on the axially oriented strip, because the arterial tissue was composed of three layers with different fiber orientations according to the layer. Moreover, the AAA tissue tended to have a higher tensile stress value than the NAA tissue; these results were similar to those of [PERSON] et al. and [PERSON] et al. (2018, 2018). In the scenario simulation phase, the AAA geometry (aneurysm diameter, height, neck angle, and iliac angle) was measured using the AAA patient-based three-dimensional model, which was reconstructed in a modeling program, thus creating the scenario simulations. Further, the model was classified into AAA and NAA tissues according to the diameter, and different material constants were set to simulate the behavioral characteristics of the aorta. The correlation between the PWS and AAA geometries was evaluated by the scenario simulation. The increase in aneurysm diameter was found to increase the PWS; this trend was also suggested by other studies ([PERSON] et al., 2018, 2018; [PERSON] et al., 2018; [PERSON] et al., 2018; [PERSON] et al., 2018). When the aneurysm diameter was small, the stress variation was small even when the height was changed; however, when the diameter was large, the stress increased when the height was changed. This was because when the aneurysm diameter was small and the height was large, the curvature became considerably smoother, resulting in a moderate variation in wall stress. In contrast, when both aneurysm diameter and height were large, the wall stress increased even more because the model's curved surface rapidly changed. However, the neck angle and iliac angle did not show any distinct patterns even when the values were changed. In addition, the magnitude of the PWS was observed in the order of intima, adventitia, and media. The intima had the largest stress because it was the thinnest and received the load directly from the inside. The stress in the outermost adventitia was higher than that in the media because the latter was thicker than the former. Other studies suggested that although the material constants of each layer differed, the intima experienced the greatest stress ([PERSON] et al., 2018). Figure 9: Maximum principal stress distributions in the adventitia, media, and intima layers of the representative model. There were certain limitations in this study. First, the geometric parameters of the AAA were not sufficiently considered. Previous studies have shown that when asymmetry is introduced into the AAA model, the PWS increases by 48% [3]. In addition, when the axial extent, circumferential extent, and tortuosity in the XZ plane and YZ plane increased, the PWS increased; however, as the thickness increased, the PWS decreased [7]. Forty-seven indicators were selected for the geometry of the AAA and statistically analyzed. It was confirmed that seven indicators had significant effects on the PWS and were appropriate for discriminating AAA [8]. The application of these various factors to this study resulted in different PWS values. Second, some AAA patients had hypertension but were considered to be under normotensive conditions.