Application of Finite Element Method and Photoelasticity to a Lap Welded Connection

Abstract

The stress distribution in the plates of lap fillet welded connections is known to be non-uniform. In order to examine the stress distribution in the plates of a double-cover- Strap joint with fillet welds, a theoretical model of the joint was analysed using the Finite Element method of analysis. Photo-Elastic model tests were carried out to confirm the assumptions made in the analytical model. An understanding of the Finite Element method of analysis was obtained by applying this method manually to the solution of a single plate under uniform and parabolic tensile loading. A lap weld connection with a very coarse mesh was then examined manually in order to determine the most appropriate method of element and joint numbering. Using a computer programme an analytical model of a side fillet welded connection having equal thickness cover plates and main plate was analysed by the Finite Element method. The effect of varying the relative thickness of the cover and main plate was examined, together with the effect of cutting a hole in the cover plate and welding the cover plate all round. Photo-Elastic models were made for the side fillet welded and the welded all round cover plate cases. The stresses were frozen into the models and after separation of the Joint each plate was analysed in a photo-elastic bench, ‘Graphs and pictorial plots were made to compare the Finite Element and Photo-Elastic results. The pictorial plots clearly show that the stress distribution in the plates for the welded all round case is far superior to the side fillet welded case. Results obtained by varying the relative thickness of cover and main plate indicate that the best joint, is obtained by using a main plate thickness of half the thickness of each cover plate, and welding the cover plates all round. To determine the most efficient joint, further work is required to obtain the best weld length for optimum plate and weld stresses.