Application of Small Punch Test for the characterization of welded joints of tubular structures

Welded joints represent one of the most critical spots of tubular structures, with failures in this kind of structures commonly being related to these parts. However, the characterisation of welded joints is a highly complex task, mainly due to their heterogeneity and reduced dimensions. It is practically impossible, in most cases, to encounter samples that allow one to perform conventional laboratory tests to determine the mechanical properties of the different parts of the joint (base material, heat affected zone and weld material). In this paper the use of a miniature test known as «Small Punch Test» is proposed for the characterization of the different regions of a welded joint. From the force-displacement curve recorded in the test, it is possible to obtain all the material inputs required in a structural calculation such as, for example, yield stress or ultimate tensile strength. In order to demonstrate the great value of this test, the Small Punch test has been used in this work to determine the mechanical properties of the weld and base materials of a bicycle frame.