Cyclic tension-compression testing allows investigating mechanical behaviour after load reversal: during such tests dogbone samples are first loaded in either tension or compression up to a certain amount of plastic strain, after which loading is reversed. Good knowledge of the mechanical behaviour after load reversal is of utmost importance to accurately assess in-use behaviour of components and structures:
Fact is that many metallic materials show a significantly lower yield strength after load reversal. This phenomenon is referred to as the Bauschinger effect, after the German engineer Johann Bauschinger.
OCAS is equiped with two servo-hydraulic tensile benches, each having fatigue rated wedge grips with a capacity of 100 kN and 250 kN respectively to perform cyclic tension-compression tests. Dedicated tools are available to prevent buckling when testing thin gauge material. Strain is recorded by means of a clip-on extensometer.
Results of these cyclic tests also serve to calibrate more advanced constitutive models, and, as such, lead to more accurate Finite Element models.