Several classes of metal alloys used in industrial engineering exhibit an anisotropic behaviour. Anisotropy can derive from the microstructure, or can be induced by the technological process and possible post-treatments through which the raw material or the final part is obtained. For a safe and efficient use of these materials, a thorough experimental characterization of their structural behaviour is mandatory. The results of experiments could be then used to calibrate numerical models to be applied within Finite Element codes for design or validation purposes.
Anisotropy is commonly quantified by means of numerous axial tests on specimens machined along different directions. This approach is resource consuming and sometimes leads to inaccurate results.
In the research, different contactless optical techniques will be used to retrieve additional local information on material samples, during uniaxial and multi-axial tests executed on a biaxial testing machine. Alongside the acquisition of the usual global quantities coming from load and displacement transducers, the specimens shape and surface strain field will be reconstructed, acquiring digital images during runs and post processing them using digital image correlation (DIC) and other methods. From the analysis of the shape and strain variations during tests, it will be then possible to identify the proper directional yielding, plastic behaviour and final fracture limits of the investigated materials. To prove the effectiveness of the approach, common yield and plasticity criteria will be calibrated based on the results of uniaxial tests, and subsequently validated under different loading conditions taking advantage of multi-axial tests.
It will be proved that the additional data from optical measurements can greatly reduce the number of tests needed for a conventional characterization of material anisotropic behavior, improving at the same time the calibration accuracy of numerical models.
