Strain distribution in cruciform specimens subjected to biaxial loading conditions. Part 1: Two-dimensional versus three-dimensional finite element model

The current study discusses the importance of sufficiently detailed finite element models in the understanding of failure mechanisms in biaxially loaded cruciform specimens. It is shown that the development of two-dimensional models can only be reliable outside the region of geometrical discontinuities such as the fillet corners and the milled centre zone. A comparison with experimentally obtained surface strains, by means of the digital image correlation technique, showed a large mismatch in these regions. However, a more detailed three-dimensional approach proved that this mismatch in strain values between the numerical and experimental results could only be due to a miscorrelation in the digital image correlation images. This conclusion revealed the existence of a crack at the transition zone between the milled and un-milled area, which could only be found due to the more detailed approach of the three-dimensional finite element model.