PSI - Issue 42

T. Fekete et al. / Procedia Structural Integrity 42 (2022) 1684–1691

1691

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T. Fekete et al.: Extending reliability of FEM simulations… / Structural Integrity Procedia 00 (2019) 000–000

The cushioning was also assessed. For thickness reductions of 2 and 3 [mm], the effect can be observed with the naked eye on Fig. 3. As shown on figures, the cushioning effect depends on flow curve. For the uncorrected flow curve, a smaller cushioning effect is obtained, as can be clearly seen in the right-hand image of Fig. 3., showing the case of the 3 [mm] thickness reduction. Since the effect was not measured, experimental validation is not available by now.

6. Summary, Conclusions

Complex, nonlinear FE simulations are widely used in research and industry to determine the performance of components. Although nonlinear CMS is a promising method for investigating ductile materials, the inherent capabilities of these methods are difficult to utilize. A common problem in applications is that plastic flow curves obtained from measurement results are not reliable enough, especially for large deformations. In the presented work, standard tensile tests were performed on specimens with square cross-sections. A combination of contact strain gauge and optical system was used in the experiments. The evaluation of the image sequences provided the possibility to follow the deformation of the specimen contours as well as of its surfaces. From the contours extracted from images, it was possible to determine the nominal stresses on the minimum cross-section of the specimen. Correction to the flow curve was developed, based on an analytic approach. The corrected flow curve was used in FE simulations on the DT of the specimen. The geometric changes calculated on the surface and selected points of the FE model were compared with the changes measured on the surface and the corresponding selected points of the test specimen. The results achieved so far show that: (1) DT of the measurements is an essential tool for the evaluation of measurements; (2) the Choung-Cho corrected flow curves seem promising for further applications, like the Bridgman corrected flow curves for cylindrical specimens.

Acknowledgements

The research is funded by the Thematic Excellence Programme 2020 (2020-4.1.1.-TKP2020) supported by the Ministry of Innovation and Technology of Hungary. The encouraging support of Dr. Ákos Horváth is acknowledged.

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