PSI - Issue 24

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Lorenzo Bergonzi et al. / Procedia Structural Integrity 24 (2019) 213–224 Lorenzo Bergonzi et al. / Structural Integrity Procedia 00 (2019) 000–000

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different models. Material properties are reported in Table 2 and were attributed to the specimen as well as to the fixture.

(a)

(b)

Figure 2. FE model of MaCh3D mini specimen (a) and ASTM E8 round specimens (b).

Table 2. Material mechanical properties used in FE models. Material Elastic modulus [MPa] Poisson ratio [--] Steel 210000 0.33

Another linear static model has been created, showed in Figure 2 (b) in order to simulate ASTM E8M specimens to compare stress distribution: the same approach used to simulate the round specimen was adopted for the ASTM E8M sheet specimen. Even in this case, symmetry was used in order to reduce calculation times; only specimen trait outside grips was modeled, assuming the absence of any slippage or deformation in the trait clamped into machine grips. Same elements kind was used, as well as imposed displacement and material: in this case RBE2 elements used to apply the load suppressed only $ degree of freedom to avoid constraining radial deformations. 3. Results Final specimen geometry, defined as “S-Size”, is reported in Figure 3 with main dimensions. Maximum stress level on the reduced section, given the maximum exercisable load of 5kN is equal to 1587.30MPa, enough to reach tensile strength for most AM produced materials. Spline fillets were adopted, since stress concentration at the beginning of the parallel section is reduced in comparison to round fillet, as explained in par. 3.1. Following the same procedure of miniaturization, two more geometries were developed, with larger cross sections and main dimensions are reported in Appendix A.

L 0 [mm] W [mm] L c [mm] T [mm]

10.00

2.10

15.00

1.50 3.15 5.65

2 ]

S 0 [mm

k s

Figure 3. Miniaturized MaCh3D S-Size specimen with main dimensions. Considering dimensions constraint reported in Eq. 1 - 4 in Table 3 are indicated the ones relative to the developed specimen, all exceeding the recommended values. In order to be conservative, has been considered equal to 100 m,