Haigh diagram for fatigue crack initiation prediction of natural rubber components

In order to investigate the fatigue lifetime prediction of natural rubber (NR), a criterion which determines the number of cycles to initiation of a short crack is proposed. uniaxial test results are plotted in the Haigh diagram which uses stress amplitude versus mean stress. It shows the influence of both parameters on the fatigue life. A first extension to multiaxial loadings has been studied using two kinds of axisymmetrical notched samples an an axial fatigue machine. A second test program was carried out with torsion fatigue tests. The corresponding 2D and 3D simulations with finite element analyses have been performed. The uniaxial criterion seems to be conservative considering the multiaxial extension. The experimental results in torsion suggest that the largest principal stress may be the main local parameter for multiaxial fatigue life predictions in NR components.