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A B S T R A C TThe process of fatigue failure of materials is generally described by two phases: crack initiation and crack propagation. This study concerns the crack initiation in rubbers submitted to a cyclic loading. A parameter based on the strain energy density (SED) and predicting the onset of primary crack and its probable orientation has been identified for such materials according to the investigations of Mars and Fatemi. More precisely, this criterion has been analytically developed in the cases of simple tension, biaxial tension and simple shear loadings by assuming large strains. The results denote the possibility to predict the orientation plane in which the primary crack would be expected to occur in a material. Then, it was implemented in a finite-elements (FE) program in order to be applied to structures under any kind of the strain states. A good agreement was obtained between FE and analytical results for the usual strain states. Finally, to evaluate lifetime up to crack nucleation, we have achieved a set of experimental fatigue tests using uniaxial tension (UT) and pure shear (PS) test specimens containing a hole in order to localize the crack initiation. The obtained results proved the efficiency of the criterion to describe the fatigue life of rubbers under multiaxial loading.BT = biaxial tensioñC = right Cauchy-Green deformation tensor ET = equibiaxial tensioñẼ = Green-Lagrange strain tensorF = deformation gradient tensor G = shear modulus I = unit tensor I 1 = first strain invariant of the right Cauchy-Green deformation tensor n = stretch biaxiality ratio for infinitesimal strain N i = initiation fatigue life P = damage parameter PS = pure shear PT = planar tension PK 1 = first principal Piloa-Kirchhoff stress (engineering stress) R = normal unit vector in the undeformed configuration defining material plane of interest Correspondence: A. Zine.

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