Criteria of multiaxial random fatigue based on stress, strain and energy parameters of damage in the critical plane

Abstract

In this paper generalized criteria of multiaxial random fatigue based on stress, strain and strain energy density parameters in the critical plane have been discussed. The proposed criteria reduce multiaxial state of stress to the equivalent uniaxial tension-compression or alternating bending. Relations between the coefficients occurring in the considered criteria have been derived. Thus, it is possible to take into account fatigue properties of materials under simple loading states during determination of the multiaxial fatigue life. Presented models have successfully correlated fatigue lives of cast iron GGG40 and steel 18G2A specimens under constant amplitude in-phase and out-of-phase loadings including different frequencies.

Fatigue life estimation for 2017A-T4 and 6082-T6 aluminium alloys subjected to bending-torsion with mean stress

“…The new fatigue life estimation model is based on the criterion by Łagoda and Macha [4,7,[30][31][32]. The equivalent stress is a linear combination of normal and shear stresses and takes up the form: r a;eq ¼ Bðs gs;a þ s gs;m Þ þ Kðr g;a þ r g;m Þ; ð1Þ where r g,a -normal stress amplitude to the critical plane: r g;a ¼ r a cos a 2 þ s a sin 2a;…”

The equivalent stress on the critical plane determined by the maximum covariance of normal and shear stresses

“…The stress criteria of multiaxial random fatigue on the critical plane can be written as a sum of normal and shear stresses on that plane with the weight coefficients B and K [1] r eq (t) = Bs gs (t) + K r g (t).…”

“…They are stress, strain or energy criteria [1]. It is possible to select some criteria coming from all these groups which include the critical plane position.…”

Fatigue life estimation for selected materials in multiaxial stress states with mean stress

“…By analysing the stress condition for pure torsion and pure bending at constant--amplitude load conditions, a relationship is formulated which describes important factors for the combination of individual components. The coefficients can be presented as follows (Kluger, 2015;Łagoda and Ogonowski, 2005)…”