Influence of elastic anisotropy on the shapes of ellipsoidal blisters and stress field around the blisters in solid materials

To address the embrittlement challenges posed by gas blisters in anisotropic materials, the stable shape of constant-pressure blisters in anisotropic materials (hexagonal, tetragonal, and rhombohedral) was energetically investigated based on continuum theory (micromechanics), considering the blister as Eshelby’s ellipsoidal inclusion. The non-negligible change in the blister shape was confirmed in terms of the anisotropic factor η ≡ C3333/C1111. Although the spherical shape of the blister is preferable for isotropic and cubic materials (η = 1), the x3 normal penny and capsule shapes were theoretically confirmed to be the most stable ones for η > 1 and η < 1, respectively. The penny and capsule shape blisters generate larger stress fields around themselves than the sphere shape blisters, thus inducing crack formation. The embrittlement due to the gas (typically hydrogen or helium) inside the blister for the anisotropic materials was more significant than isotropic and cubic embrittlement.