Reliability of Digital Image Correlation methods applied to additive manufactured metallic lattice components

Additive manufacturing (AM) technologies went from being used in the early pre-production and prototyping stages to the main production step in many engineering applications, due to the great design freedom introduced, allowing the creation of components provided with shapes and feature otherwise impossible to produce using traditional subtractive technologies. In this class of features great importance have the lattice structures, which are reticular features comprised of multiple beam of different shapes and arrangements. These are used to create components developed to accomplished specialized task, like heat exchanger and bio-compatible meta-material for prosthetic applications, or to reduce weight in already existing solid components. Due to these specialized uses, and to the high costs of both equipment and raw materials, AM is usually used to produce batches of few components or even single pieces. These characteristics of both uniqueness and high costs discourage the application of testing techniques that could destroy or made unserviceable said components. As the name implies, Non-Destructive Testing methods (NDT) allow to implement these examinations without damaging the pieces. Inside this category of methods Digital Image Correlation (DIC) allow to acquire information of displacement and movement on a wide area of the component, using equipment composed of commonly used tools like digital cameras and workstations. Due to the unique behavior of lattice components under stress the interest was focused on how the DIC can be used to acquire information derived from the experiments, and the accuracy of those information. Using the scientific literature, the accuracy of the application of DIC methods to lattice components has been investigated, along with the preventive measure to adopt in order to obtain the best results possible. We observed a widespread use of the DIC in these applications, from the investigation of the behavior of existing components after optimization, to the small-scale analysis of meta-materials to the influence of the manufacturing parameters to the metallic microstructures. In general, DIC is a widely applied technique, with results comparable to those of the twin destructive tests and used in many cases in conjunction with the latter to confirm the goodness of finite element models. The precautions necessary to obtain the best results will be illustrated, from the preparation of the test environment (cleaning, illumination, vibration control) to the execution of the test (calibration, deformation speed and image acquisition speed) to the subsequent processing of the images. Future development could involve the study of the combination of parameters and algorithm to be used to obtain the best results in specific applications.