Camilla Ronchei

In engineering practice, additively manufactured (AM) metal and metal alloy structural components, which often contain geometric discontinuities to fulfil functional requirements, are subjected to cyclic service loads. Among the possible loading configurations, far-field Mode I loading is frequently considered as a nominal reference condition. Within this context, a methodology for the fatigue assessment of notched AM Scalmalloy components subjected to Mode I far-field loading is proposed, combining the Strain Energy Density (SED) approach with a multiaxial critical plane-based fatigue criterion. The fatigue assessment is carried out at a verification point whose position is defined as a function of the characteristic length of the SED control volume for Mode I loading, determined through two alternative procedures, and of the surface roughness of the component. The proposed methodology is validated against experimental fatigue data available in the literature for AM Scalmalloy specimens featuring a circumferential semi-circular notch and subjected to Mode I far-field cyclic loading, which induces a locally multiaxial stress state at the notch root, given that the formulation does not rely on material-specific assumptions and could in principle be extended to other notched AM metal and metal alloy components.

Metallic structural components, placed in contact with other bodies while experiencing vibrations in operating conditions, are susceptible to fretting, which can have a significant impact on their fatigue performance. Although extensive research has been conducted over the past decades to analyze the effects of various fretting influencing factors (including loading conditions, friction coefficient, relative slip amplitude, contact configuration, surface finishing, material properties, and environmental factors), this area of study remains an active field of investigation. In this paper, an experimental campaign reported in the literature, involving Al-4Cu specimens subjected to a partial slip regime cylindrical fretting contact, is examined by means of an analytical methodology developed by the authors. The results obtained through the proposed methodology demonstrate good agreement with the experimental observations in terms of both fatigue life and crack propagation direction. Furthermore, a parametric analysis is carried out to assess the role of different parameters in influencing the fretting fatigue behaviour, providing valuable insights into their effects on crack orientation and component durability.

The present paper is dedicated to the mechanical and fracture characterization of a specific earthen material, that is, the shot‐earth 772. Although such a material has been recently characterized from a microstructural, chemical and physical point of view, the knowledge of its mechanical and fracture properties (essential for extending its use in construction industry) is still lacking. Such characterizations are here performed both experimentally, through laboratory tests, and numerically, through a FE model. The experimental tests (i.e., flexural, compression, and fracture tests) are carried out on shot‐earth specimens according to recommendations available for concrete and a method proposed by the present authors, named Modified Two‐Parameter Model. The numerical analyses are performed by employing a micromechanical model (implemented in a nonlinear 2D FE homemade code), which allows to simulate both flexural and fracture behavior of the shot‐earth examined. Finally, the obtained numerical results are compared with the experimental ones.

In the present paper, a procedure for fatigue strength assessment of metals containing solidification defects is employed to analyze the fatigue behavior of a ductile cast iron (DCI) characterized by a relevant micro‐shrinkage porosity. The procedure implements (i) a statistical method deriving from extreme value theory, (ii) the ‐parameter model, and (iii) the multiaxial critical plane‐based criterion by Carpinteri et al. According to the above statistical method, both the distribution of defects and the return period are determined. More precisely, the return period is computed by also exploiting a relationship here proposed to optimize the accuracy of the procedure in terms of fatigue strength estimation. The great potential of the present procedure is that the defect content analysis (performed by means of a statistical method deriving from extreme value theory) can be easily performed using machine learning techniques.

This work proposes an efficient cohesive finite element modeling approach based on a diffuse interelement interface strategy to reproduce the fracture behavior of quasi‐brittle materials under general loading conditions. The proposed model involves zero‐thickness interface elements, whose strength and toughness properties are spatially randomized, thus avoiding the well‐known nonuniqueness issues that can affect the stability of the associated numerical computations, which potentially lead to physically meaningless predictions of the fracture behavior. The reliability of the proposed refined fracture approach is assessed by performing several numerical simulations of the direct tensile test on various quasi‐brittle specimens. Results show that a proper calibration of the cohesive properties of the diffuse embedded interfaces is fundamental to ensure the desired numerical accuracy and stability properties. Besides, comparisons with experimental and numerical data found in the literature are used to fully validate the proposed approach.