BIAXIAL LOADING IMPACT ON FATIGUE CRACK PROPAGATION IN METALLIC MATERIALS

Multiaxial fatigue testing generates curved cracks that are extremely difficult to characterize using standard
compliance based and potential drop-based methods. Therefore, an automated online system was
developed to monitor the crack tips positions in plate cruciform specimens. The system periodically
evaluates the deformation fields at small areas around the crack tips by performing digital image correlation
(DIC) on images obtained by a moving camera triggered at desired phases of the loading cycle. The
displacement field obtained by DIC is fitted by a simple model that specifies the crack propagation direction
and enables it to iteratively find new crack tip positions. Moreover, the model is capable of computing the
crack opening displacements near the crack tip and thus characterizes the local loading. This approach
enables fully automated multiaxial testing with controlled crack length and crack tip loading. The method
was successfully tested on an AA5754 aluminium alloy sheet..Multiaxial fatigue testing generates curved cracks that are extremely difficult to characterize using standard
compliance based and potential drop-based methods. Therefore, an automated online system was
developed to monitor the crack tips positions in plate cruciform specimens. The system periodically
evaluates the deformation fields at small areas around the crack tips by performing digital
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