Application of digital image correction method to test of mechanical properties for weld materials

Weld material is a kind of non-uniform material with the weld, parent material and the heat affected zone possessing different mechanical properties. It is important that the mechanical features of the diverse zones in a weld material are quantitatively investigated in order to reasonably apply it in engineering. This paper uses digital image correlation (DIC) method to measure the deformation field of a TC4 titanium alloy weld under uniaxial extension loading. The strain fields of different areas are obtained under different loads. The parent material zone, weld zone and heat affected zone are each characterized by the strain of its area in a descending order. The strain of the parent material zone is found to be much greater than that of other zones. The local failure strain of the parent material can reach 30%, which means the ductility of the parent material is fine. Then the transformative localization behavior is measured during the loading process. At the peak load, tiny necking of 0.075 mm is formed, while necking reaches 0.271 mm when the specimen fractures. Finally, the error of the test system is also analyzed, from which the reliability of the DIC method is verified.