Experimental Characterization of the Strain Concentration Factor in Welded Junctions of Rectangular Tube Beam Using Digital Image Correlation

The most common cause of failure in bus structures is fatigue, and it is generally located at strain concentration zones that appear in the welded junctions of these structures. Therefore, measurement and characterization of these regions becomes crucial in structural analysis and design of bus structures.In bus structural analysis, simplified finite element models (FEM) are generally used, since they enable to examine different variables with low computational cost. Nevertheless, by utilizing these models, it is impossible to reproduce the structure junction geometry in detail, which impedes the calculation of strain in the concentration areas.In the present paper, measure and characterization of the strain concentration factor (SCF) of welded junctions typically present in bus structure has been carried out. For this purpose, 10 ‘T’ welded junctions were tested, disposed in two different configurations. Every junction was subjected to two types of load, and to 10 different load levels for each load type. A DIC equipment was used to obtain the deformations close to the weld bead. Once processed al the measured data, and calculated the SCF, it was characterized as function of load type and level.The results presented in this article make possible to know the actual strain experienced by the tested junctions in simplified FEM models, allowing a more precise structural design without computational cost increase. Additionally, an alternative methodology for the calculation of SCF based on the DIC techniques has been presented.