Extending reliability of FEM simulations, based on optically assisted tensile tests and digital twins

Abstract

As it is well known, Finite Element simulations are widely used in research and industry to predict the performance of components. Most challenging task of these simulations is predicting the Structural Integrity limits of components and systems. Despite the fact that nonlinear Continuum Mechanics of Solids is a promising approach for ductile materials, the potential predictive capabilities of these methods are difficult to utilize. Generally, in applications, a common problem is that plastic flow curves obtained from the measurement results are often not reliable enough, especially for large deformations. In the present work, standard tensile tests were carried out on specimens with square cross-section. A combination of contact strain gauge and an optical system were used in these experiments. Square grids were printed on the surface of the specimens. Evaluation of the image sequences provided the possibility to follow the specimen contours as well as the deformation of its surfaces. Based on the contours retrieved from the images, it became possible to determine nominal stresses at the minimum cross-section of the specimen. Corrections were applied to the flow curve, using analytical formulae. The corrected flow curve was used in Finite Element simulations on the Digital Twins of the specimen. The geometry changes of the surface and the selected points of the Finite Element model were compared to the measured changes of the surface and the corresponding selected points of the test specimen.