Abstract
In the present paper, the multiaxial fatigue life assessment of notched structural components is performed by employing a strain-based multiaxial fatigue criterion. Such a criterion, depending on the critical plane concept, is extended by implementing the control volume concept reated to the Strain Energy Density (SED) approach: a material point located at a certain distance from the notch tip is assumed to be the verification point where to perform the above assessment. Such a distance, measured along the notch bisector, is a function of both the biaxiality ratio (defined as the ratio between the applied shear stress amplitude and the normal stress amplitude) and the control volume radii under Mode I and Mode III. Once the position of the verification point is determined, the fatigue lifetime is assessed through an equivalent strain amplitude, acting on the critical plane, together with a unique material reference curve (i.e. the Manson-Coffin curve). Some uniaxial and multiaxial fatigue data related to V-notched round bars made of titanium grade 5 alloy (Ti-6Al-4V) are examined to validate the present criterion.
Highlights
INTRODUCTIONI n situation of practical interest, metallic structural components often contain geometrical irregularities (such as notches, fillets and key-seats) because of the design requirements
I n situation of practical interest, metallic structural components often contain geometrical irregularities because of the design requirements
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)
Summary
I n situation of practical interest, metallic structural components often contain geometrical irregularities (such as notches, fillets and key-seats) because of the design requirements. Several multiaxial fatigue criteria available in the literature represent a reformulation of their counterparts for smooth components, by considering the detrimental effect of the stress/strain concentration phenomena on the material fatigue strength. 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]. 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
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