Issue 43

F. Berto et alii, Frattura ed Integrità Strutturale, 43 (2018) 1-32; DOI: 10.3221/IGF-ESIS.43.01 20 the advantages and drawbacks of the method when homogenous and non-homogenous materials are considered (see Tab. 1). If the extension of the SED approach at micro- nano-scale will be given near future, an easy and fast tool to design against fatigue will be provided for micro-devices such as MEMS, resulting in a significant technological impact and providing an easy and fast tool to conduct static and fatigue assessment at micro- and nano-scale. K IC R c Plane Strain R c Plane Stress (MPa×m 0.5 ) (μm) (μm) Spec. 1 0.83 0.48 0.56 Spec. 2 1.09 0.82 0.97 Spec. 3 1.08 0.81 0.95 Spec. 4 1.35 1.26 1.49 Average 1.09 0.84 0.99 Table 1: Fracture toughness K IC , and evaluated control radii R c for plane strain and plain stress condition. The applications to micro-systems can take advantage of the application of the SED approach. In fact the miniaturization of electronic and mechanical devices due to the increase of integration and energy saving has pushed the size of components approaching smaller dimension: micro-electro-mechanical systems (MEMS) including small sensors for propulsion and power are good examples. The small dimensions of micro/nanomaterials impose a tremendous challenge for the experimental study of their mechanical properties that prevent a fast development of theoretical and numerical tools for the design of those components. The following main conclusions have been drawn in [137]:  Under very small scales (such as nano- micro- scale), the homogeneity of the bodies return to be present in some cases, giving promising good perspectives on the applicability of SED at those scales;  Single crystal silicon, thanks to its brittle behavior until failure at room temperature and to its large widespread use, is particularly appropriate to conduct preliminary analyses;  Employing the mechanical properties experimentally evaluated, a control volume equal to 0.84 μm and 0.99 μm has been theoretically evaluated under plane stress and plane strain condition, respectively, for a single crystal Si;  A value of critical strain energy density W c =15.38 MJ/m 3 for static assessment has been provided for a single crystal Si;  The lack in the literature regarding the experimental study of the mechanical properties of such components prevent a fast development of theoretical and numerical tools;  The control radius and critical energy provided are the first step to consider further extension of the method to micro and nano scales although difficulties arise when dealing with experimental characterization;  The obtained critical radius should be also applied to other micro materials, verified that the hypothesis of homogeneity is satisfied;  In case of materials inhomogeneity, adoption of multiscaling scheme can be considered Further analyses should be devoted in the investigation of the static and fatigue assessment of notched component made of Si at micro scale, in order to verify that, also at small scales, the Strain Energy Density averaged over a control volume can summarize in a single narrow scatter band all the data, regardless of the notch geometry. Fatigue behavior of additive manufacturing materials In the ambit of continuous digitalization of manufacturing processes, modern short product life cycles and the ever- growing need for high performance, low weight products with minimal production needs, we face stringent requirements on both time and sophistication of modern structural design and property prediction. For digital production and advanced components of the future, conventional design methods, structural evaluation routines and production techniques fail to fulfil necessary requirements for structural complexity leading to increased performance. The autonomous production in the ambit of the 4 th industrial revolution paired with the need for parts that challenge today’s production constraints necessitate the use of enabling technologies such as additive manufacturing (AM). These technologies allow the direct conversion of digital designs into physical products within one production step and completely autonomous avoiding