Fatigue assessment of notched specimens by means of a critical plane-based criterion and energy concepts

Joined application of a multiaxial critical plane criterion and a strain energy density criterion in low-cycle fatigue

“…Such criteria usually reduce the complex multiaxial stress/strain state to an equivalent uniaxial condition: they are stress-based in High-Cycle Fatigue (HCF), whereas they are strain-based in Low-Cycle Fatigue (LCF). According to the above remarks, the present authors have recently proposed a strain-based multiaxial fatigue criterion in order to estimate the fatigue life of severely notched specimens under LCF [5]. Such a criterion is an extension of the critical plane-based multiaxial fatigue criterion proposed by Carpinteri et al for smooth specimens [6,7] to the case of notched ones.…”

“…[5]). The fatigue life assessment is carried out at a verification point (point P ), which is distant r from the notch tip.…”

“…(1) has been obtained through a best-fit procedure by taking into account some values of  related to the experimental data reported in Refs [5,10]. The values of the material parameters related to the Manson-Coffin curves, required for the application of the criterion, are reported in Ref.…”

“…More precisely, the fatigue life assessment is performed by taking into account the strain state at a material point (named verification point) located at a certain distance from the notch tip, depending such a distance on both the biaxiality ratio  (remote shear stress amplitude over remote normal stress amplitude) and the control volume radii under loading conditions of Mode I and Mode III. The goal of the present paper is to discuss the accuracy and reliability of the joined application of the strain-based criterion together with the control volume concept [5] in estimating multiaxial fatigue lifetime of structural components weakened by notches. In particular, the results obtained by employing the criterion proposed in Ref.…”

“…In particular, the results obtained by employing the criterion proposed in Ref. [5] are compared with some experimental data recently published [10], related to circumferentially V-notched round bars made of titanium grade 5 alloy (Ti-6Al-4V) under both uniaxial and multiaxial fatigue loadings.…”