PSI - Issue 72

Levente Tatár et al. / Procedia Structural Integrity 72 (2025) 345–353

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Fig. 3. Engineering and true strain-stress curves measured by clip gauges and computed based on photos.

3. Simulation, digital twin Simulation of tensile tests has a quite long history, see Grossbeck and Maziasz (1979), Wilkins et al (1980). Tvergaard and Needleman (1984), Tsukahara and Iung (1998). Digital twin however is a relative old concept, but the term “digital twin” was used for the first time in early 2000 s . A good overview can be read in Sharma et al (2022). Regarding simulation, we follow the nomenclature of Hexagon MARC/Mentat (2025) FE code.  Geometry  Constraints  Material  Loadcase, Job Regarding Geometry , we have 3 possibilities (Fig. 4 ): a) Simplified geometry using 1/8 symmetry b) Precise, but idealized geometry c) Realistic geometry taking into account microscopic irregularities (difference from case b) cannot be presented in global picture)

Fig. 4. Meshes used by different approaches.

Regarding Constrains , constrain type depends on the geometry. For simplified geometry as in Fig. 4a symmetry conditions need to be applied. These symmetry conditions can be applied as fixed displacements (as in the picture) with zero displacement in the x, y and z directions. As an alternative these can be replaced by contact surfaces representing symmetry. Contact is not really needed in the analysis, however it is convenient to use both in the simplified or in the more sophisticated models as axial force as a single value is provided in each increment on a rigid contact body. Without contact, one should sum up individual nodal reaction forces at the nodes with imposed fixed displacements.