Energy Methods for Fracture and Fatigue Assessment

The present Ph.D. thesis is the collection of three years of research activity in the fatigue field. The aim of the thesis was to apply Energy based methods to the assessment of the fatigue properties of materials. The Risitano Thermographic Method and the novel Static Thermographic Method were extensively applied to a wide set of materials in order to validate them as rapid test procedures able to derive, in short amount of time and with few specimens, the fatigue properties of materials monitoring the energetic release. Finite element simulations were carried out to applying the Strain Energy Density method as a local approach to predict the fatigue failure of notched mechanical components. The Thermographic Method-s were applied to structural steel from an in-service component, plain and notched medium carbon steel specimens, high strength concrete under compressive loads, high density polyethylene for pressure pipe applications, 3D printed polyamide-12 specimens and short glass fiber reinforced composite PA66GF35. The Strain Energy Density approach was applied to welded components, in particular cruciform welded joints, to compare the fatigue information provided by this method with the ones provided by the international welding standards. The experimental activities were performed at the Laboratory of Mechanics of the University of Messina. Part of the research period was spent by the author at the University of Padova, under the supervision of Prof. Giovanni Meneghetti, and at the Norwegian University of Science and Technology (NTNU), under the supervision of Prof. Filippo Berto, to study local approaches techniques. Several research perspectives have been opened by this thesis, that the author would to pursue in the future.