Issue 41

A. Carpinteri et alii, Frattura ed Integrità Strutturale, 41 (2017) 66-70; DOI: 10.3221/IGF-ESIS.41.10 66 Focused on Multiaxial Fatigue Joined application of a multiaxial critical plane criterion and a strain energy density criterion in low-cycle fatigue Andrea Carpinteri, Giovanni Fortese, Camilla Ronchei, Daniela Scorza, Sabrina Vantadori Department of Engineering and Architecture, University of Parma - Parma, Italy Filippo Berto Department of Engineering Design and Materials, NTNU - Trondheim, Norway A BSTRACT . 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. K EYWORDS . Critical plane approach; Control volume; Notched components; Multiaxial low-cycle fatigue; Strain-based criterion. Citation: Carpinteri, A., Berto, F., Fortese, G., Ronchei, C., Scorza, D., Vantadori, S., Joined application of a multiaxial critical plane criterion and a strain energy density criterion in low-cycle fatigue, Frattura ed Integrità Strutturale, 41 (2017) 66-70. Received: 28.02.2017 Accepted: 15.04.2017 Published: 01.07.2017 Copyright: © 2017 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION n situation of practical interest, metallic structural components often contain geometrical irregularities (such as notches, fillets and key-seats) because of the design requirements. The above irregularities result in stress/strain concentration phenomena which have to be properly take into account during the design process in order to avoid catastrophic in-service failures [1]. The presence of stress/strain concentrators gives rise to a multiaxial stress/strain state close to the geometrical irregularities even if the applied loading is uniaxial. Moreover, the complexity of the stress/strain state is further increased by the presence of multiaxial fatigue loadings as those experienced by structural components during in-service operation. I