Application of finite element method and photoelasticity to an 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.

Date of Award	1973
Original language	English