Internal and effective stress analysis in stainless steels using the statistical approach method

The statistical approach method was applied to the analysis of the hysteresis loops in low-cycle fatigue of stainless steels with different crystalline structures. This method, based on Masing hypotheses, allows to determine the effective stress, the effective elastic modulus and the ‘probability density function’ of the internal critical stresses. The dependence of these quantities on the applied strain amplitude was investigated in austenitic, ferritic and duplex stainless steels. The ‘probability density function’ in austenitic stainless steel exhibits a single peak. It changes appreciably with strain amplitude. This dependence on the strain amplitude was less important in the ferritic stainless steel. A double peak form was found on the ‘probability density function’ in duplex stainless steel, which is believed to correspond to the plastic deformations of the two phases, γ and α, respectively.