PSI - Issue 68

T. Fekete et al. / Procedia Structural Integrity 68 (2025) 687–693

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T. Fekete et al. / Structural Integrity Procedia 00 (2025) 000–000

Fig. 6. Force – Displacement results

The size of M1 and M2 along the gauge length is slightly different, but the strain field is almost identical. This is a consequence of the fact that the two geometries are symmetric, thus resulting in symmetric strain fields. Consequently, necking occurs at the center of the specimen in both cases. The initial geometry of M3 is imperfect and slightly asymmetric, leading to an asymmetric strain field even in the early stages of plastic deformation. Stress is highest near the cross section where the initial specimen thickness is at its minimum (Figure 2b). Therefore, necking initiates earlier and close to the specimen head. Figure 6 shows the Force–Displacement results representing the global behavior of the M1, M2 and M3 models and the Force–Displacement curve observed during the measurement. It can be clearly seen that the results calculated for M1 and M2 models are of the same nature. For both models, the maximum force occurs at ≈ 5 [mm] displacement. The differences in forces are caused by the fact that the initial cross section of the M2 model is ≈ 2.1 % smaller than that of M1 over the gauge section, and this difference remains present to a good approximation over the entire strain range. The Force–Displacement curve of M3 is almost identical to the Force–Displacement curve of M2 over the displacement range ( 0 , 3.95 ) [mm]. For M3, necking begins at 3.95 [mm]; from this point on, damage of M3 accelerates, and therefore the Force–Displacement curve of M3 bifurcates from that of M2. The measured results are most consistent with those of the M3 model, clearly demonstrating that simulation on an accurate geometric model implementing post-production geometry yields more precise results than calculations on idealized geometric models. To demonstrate the predictive power of the realistic, fine-tuned DT model, Figure 7 shows the results of the experiment and simulation in parallel. The initial state is illustrated on the left, with both the specimen grid and the model grid square. The middle panel depicts the formation of necking near the head of the specimen. The panel on the right depicts severe deformations, including necking, and the specimen nearly reaching its failure limit. The simulation results indicate that, for the small-size specimen under investigation, the precise DT model and the physics-based simulations are an effective means of assessing the impact of geometric imperfections caused by manufacturing.

Fig. 7. Comparison of the specimen and its DT during the test