Figure 5.

Instability of a straightened homogeneous circular cylindrical sector modelled by the Gent strain-energy function. (a–c) The critical stretch λ_cr for wrinkling versus the radii ratio ρ=R₁/R₂ for different open angles Θ₀, in the cases where the Gent stiffening parameter is (a) J_m=20 (rubber), (b) J_m=2.3 (old aorta) and (c) J_m=0.4 (young aorta). As summarized in table 1, the number of wrinkles k depends on the constitutive parameter J_m, on the angle Θ₀ and ρ. For instance, for J_m=20, Θ₀=π and ρ=0.15, the number of wrinkles is k=4; see (a) and (d). (Online version in colour.)