Investigations on the material behaviour of weld seams for the use in finite element analyses

The design of complex structural steel connections by finite element analysis is common practice nowadays. However, for welded joints there are no normative regulations for the static finite-element-analysis. To analyse the specific material behaviour in the weld area and derive a geometry and material model for the finite element analysis, tensile tests on specimens with different weld geometries are made at the Technical University of Darmstadt. During the tests an optical measuring method, called Digital Image Correlation, is used. It records the deformations on the surface of the specimen and assigns the recorded analogue test load to the images. By this way, the load-deformation-behaviour in all areas of the weld can be determined. In addition to the tensile tests, microsection examinations are carried out. The applied colour etching makes the microstructure of the weld zones visible so they can be geometrically superimposed with the strain-images of the tensile tests. In welded connections the stress state is very complex. Therefore, numerical investigation must be performed to derive the final strain-stress-curves of the weld area. These curves can then be implemented as a material model for the finite element analysis of welded connections