We have completed multi-axial testing of metallic foam samples. The objective was to investigate failure limits under tension, torsion, tension combined with torsion and compression combined with torsion.
Although we usually test materials only in tension or compression, and sometimes in shear, they could experience complex loads as part of real structures such as a bridge or a car. Our tests investigate how the principal strains at failure change as a function of the loading type. Usually, we know only tensile failure stress and rarely shear failure stress. Is it enough to predict the failure under complex load? Yes, and we found a trend, the so-called fracture criterion, that can do just that but it is another story, perhaps for a scientific journal.