PSI - Issue 75

Francesco Collini et al. / Procedia Structural Integrity 75 (2025) 375–381 F. Collini et al. / Structural Integrity Procedia 00 (2025) 000–000

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Fig. 1. (a) Schematic representation of the linear elastic stress fields of Mode 1 and 3 and the structural control volume for the averaged SED model; (b) Atzori-Lazzarin-Meneghetti diagram extend to multiaxial loading condition in Collini et al. (2025).

providing the model reported in Figure 1b. In this paper, only the sharp notch behavior was considered, and thus only Eq. (6) is necessary to analyze the data. However, interested readers are referred to Collini et al. (2025) for the complete theoretical background of the present approach.

3. Materials and Methods

Cylindrical specimens weakened by a sharp V-notch with an opening angle 2 α of 90 ◦ were produced by Laser Powder Bed Fusion. The specimens were fabricated in the vertical direction with the geometry shown in Fig. 2(a). The notch tip radius was set to 0 mm in the input STL file geometry to produce an ideal net-shaped sharp notch. Details regarding the manufacturing system and process parameters have been omitted in this paper for confidentiality reasons. All specimens were heat-treated (HT) using a TAVH 4 − sall − metal furnace. The HT procedure involved annealing by ramping up to 950 ◦ C over 214 minutes under high vacuum, holding for 120 minutes, and then cooling with fan-assisted argon gas (3 bar, top-down) to room temperature. The resulting microstructure is shown in Fig. 2(b). Preliminary axial, torsional, and combined axial-torsional fatigue testing was performed using a StepLab multiaxial electrodynamic testing machine, equipped with an axial actuator UD040 (static load capacity: 30 kN, dynamic: ± 38 kN) and a torsional actuator BV200 (static torque capacity: 120 Nm, dynamic: ± 170 Nm), controlled by a Steplab

Fig. 2. (a) Specimen’s geometry; and (b) microstructure of the Ti6Al4V after heat treatment.