Speaker
Description
For decades, the ISO-16630 Hole Expansion Test (HET) has been the industry standard for expressing the edge formability of sheet metals through the Hole Expansion Ratio (HER). However, in recent years, this test has been criticized for its high scatter in results for repeated experiments. This scatter has been suspected to be caused by the operator-reliant post-processing of the test, or variations in the cutting conditions for the different test specimens. A previous study by Barlo et al [1] investigated the boundary conditions of the test by introducing draw beads to the experimental setup as well as use images captured by a 3D DIC system to evaluate the hole expansion ratio, thereby reducing the impact of the operator-reliant post-processing.
This study will build on top of the conclusions of [1] by investigating the hypothesis that the scatter is caused by the stochastic behavior of fracture and move the point of the evaluation from a through-thickness crack to the onset of surface fracture to get a more realistic evaluation suited for industrial use. As the experimental setup used by [1] deployed a 3D DIC system, FEM models can be calibrated against the experimental results, and a fracture limit strain value can be determined from the calibrated models.
References
[1] Barlo, A et al (2022). “A Study of the Boundary Conditions in the ISO-16630 Hole Expansion Test”. IOP Conf. Ser.: Mater. Sci. Eng. 1238 pp. 012031