Welded joints--Fatigue

An experimental investigation was performed to determine the stresses at the weld toe for a group of welded Tee specimens of API 2H Grade 42 steel with thicknesses ranging from 12.7 to 101.6 mm and weld profiles conforming to the American Welding Society Code--AWS Basic, Alternate #1 and Alternate #2. The objective was to improve the understanding of the interactive weld profile - plate thickness effect on fatigue behavior. A finite element technique was employed to compute the stress gradient along and perpendicular to the plate surface. A parametric equation of SCF as a function of weld toe radius and included angle was derived based upon the finite element analysis. The results indicate that the thickness effect can be partially reduced by using an improved weld profile which reduces the stress concentration at the weld toe.

The stress concentration which exists at the toe of an AWS class
'c' weld has been investigated by means of the finite element method.
This type of weld is representative of that specified to join tubular
members for offshore structures. Welded fatigue specimens were sectioned
and the weld profile described in terms of 1) the weld toe
radius (R), 2) the reinforcement angle (e) and 3) the filler metal
height QH). A statistical analysis was performed to determine the
correlation between R, e and H from which it was found that they are
independent of each other. By use of the finite element method, trends
were established for the effect each parameter has on the stress concentration
at the weld toe. Analysis of the effect of undercutting
was also perfonned and the results used to offer an explanation why
fatigue cracks propagate to failure in some cases and arrest in others.