PSI - Issue 47

G. Morettini et al. / Procedia Structural Integrity 47 (2023) 296–309 Author name / Structural Integrity Procedia 00 (2019) 000–000

305

10

4. Numerical Prediction Before proceeding with the application of the ASED method, as previously discussed, it is necessary to evaluate the mechanical characteristics of the equivalent material. Additionally, an assessment of the fracture toughness of this material must also be made. As is well known, in fact, this parameter is influenced by the technology used to produce the test specimens. Therefore, further analysis is required. 4.1. Equivalent material evaluation Fig.8 shows the stress-strain curve of the evaluated Equivalent Elastic Material. This material is capable of storing the same energy of the plastic PLA material, but it has an elastic modulus �� of 2930 and an ultimate tensile strength of ��� , �� � 68 , with the same elongation.

Fig. 8. Stress-strain curve of the evaluated Equivalent Elastic Material compared with the PLA real tensile curve.

4.2. Fracture toughness evaluation At this point, we have all the necessary elements for the application of the ASED method, except for the evaluation of fracture toughness. We know that this parameter may be influenced by the additive manufacturing process. For this reason, it is necessary to evaluate it through a commonly accepted calibration procedure (Seibert at al. (2021)). Following an iterative approach, as illustrated in Fig.9 the experimental data on the maximum average force recorded from the 2nd set of notched specimens ��� 10, �� 2 � are used in a finite element simulation that accurately replicates the experimental test, as shown in Fig.9. In the graph of Fig.9, by varying the radius of the critical volume used to calculate the ASED value, it is possible to identify the value of ( �∗ ) for which the equality � ��� � �∗ �� � is verified. Using the inverse formulation expressed in equation (8), the calibrated value of fracture toughness for the specific application can then be determined. �� �� �� � �∗ � � ��� ���� ������ (11)