PSI - Issue 68

Jaynandan Kumar et al. / Procedia Structural Integrity 68 (2025) 205–211 Jaynandan Kumar, Anshul Faye / Structural Integrity Procedia 00 (2024) 000–000

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primarily focused on isotropic models of tissue behaviour; however, recent studies indicate that the aneurysmatic tissue exhibits anisotropic behaviour (Holzapfel et al., 2000, 2001; Gasser et al., 2006; Di Achille et al., 2011; Kobielarz, 2020). The growth and instability of micro-voids can be critical for the rupture process. Void growth study on the aneurys matic tissue considering its isotropic nature has been conducted by Volokh (2015). However, the isotropic models failed to capture the directional dependence of void growth and may lead to less accurate behaviour of void growth. The anisotropic nature of aneurysmatic tissue can a ff ect the growth and instability of micro-voids in di ff erent ways, which may or may not be critical for rupture phenomena. To precisely predict rupture risk, it is imperative to investi gate void growth within the tissue, considering its anisotropic characteristics. This study addresses this gap by employing numerical simulations using the Gasser-Ogden-Holzapfel (GOH) model to capture the void growth behaviour of complex iliac aneurysmatic tissue. In addition, the e ff ect of fiber distri bution in anisotropic on cavitation has also been studied. The methodology involved in this study has been presented in Section 2, followed by results and discussion in Section 3. Conclusion of the study presented in Section 4.

2. Methodology

2.1. Material Model

The Gasser-Ogden-Holzapfel (GOH) model (Gasser et al., 2006) was used to represent the anisotropic mechanical properties of the iliac arterial tissue. This model accounts for the directional dependence of the tissue’s mechanical response, considering the distributed collagen fibers in the tissue. The strain energy density function of GOH model for the incompressible case is shown in equation (1), (2) and (3).

iso

ani .

(1)

ψ = ψ

+ ψ

µ 2

ψ iso ( I

( I 1 − 3) .

(2)

1 ) =

k 1 2 k 2 i = 4 , 6

ψ ani ( I

2 }− 1] .

1 , I 4 , I 6 ) =

[exp { k 2 [ κ I 1 + (1 − 3 κ ) I i − 1]

(3)

2.2. Material Parameters

Material parameters for the GOH model were obtained by Gasser et al. (2006); calibrated using data from the experiments performed on adventitial strips of nine iliac arteries (Holzapfel et al., 2004). Parameters were calibrated from the mechanical response of the tissue in circumferential and axial directions. Therefore, elastic parameters are shown in Table 1 and structure parameters κ = 0 . 226 and γ = 49 . 98 ◦ represent the behaviour of iliac adventitia. Since the structure parameters need to be identified from the histology of the artery, the e ff ect of structure parameters is studied with the combination of parameters given in Table 1. 2.3. Representative cavity model

Due to symmetrical about x 1 and x 2 directions, a quarter of the geometry with its symmetric boundary conditions has been considered here for the analysis. A hydro-static pressure of amount g is acting radially on the external