Criteria for fatigue crack nucleation in rubber under multiaxial loading

This article compares the ability of three equivalence criteria to rationalize the effects of multiaxial loading on fatigue crack nucleation life. Criteria considered include maximum principal strain, strain energy density, and cracking energy density. Comparisons are made based on previously reported results in simple tension and equibiaxial tension, on new experimental results obtained under combined axial/shear loading, and on arguments relating to the mechanics of the fatigue process. Instances in which maximum principal strain may be used effectively are noted, as well as limitations of this approach. It is shown that strain energy density is not an effective criterion for rationalizing multiaxial fatigue of rubber. Finally, cracking energy density is shown to provide a robust multiaxial analysis approach for rubber fatigue.