Novel technique for DIC speckle pattern optimization and generation

The optical method Digital Image Correlation (DIC) ha s been extensively studied due its capability to measure the entire di splacements field over a body surface. This particular propriety makes this metho d an optimal tool to measure heterogeneous displacements and strains. The main points of the thesis are the proposal of a novel technique capable to prepare a fully controlled speckle pattern on metal surfaces and the discussion of the speckle pattern parameter which influences t h DIC final results. The technique proposed for speckle pattern generati on is very easy and fast to make, economic, reliable, flexible and does not req uest specific devices. It can be employed also with small specimens where other t echniques show the main limits. Thanks to the possibility to obtain a fully control led pattern, the technique is used to define which parameters types ( size of the black spots, spacing between them , quality of images etc) are preferable to emp loy during DIC. Additionally, the proposed technique was applied to create the pattern on tensile test specimens in order to analyse the strain full field of welded metal samplings with different materials.