Tips & Tricks - which weld is the best?
Weld 2: combination groove and external fillet weld
(images sourced from Welding Magazine) - you can read the full article here.
A fillet weld is used to attach a gear to a shaft, which is subject to a high torsional load. When the design is modified for a larger machine, a bigger shaft is used to carry the increased torque.
The engineer initially specifies a 25mm fillet weld to attach the larger gear, but then decides to add a groove weld as a precautionary measure. The weld specification is changed to a 25mm groove weld with a 25mm external fillet weld.
By carrying out a simple Finite Element Analysis (FEA), we found that the Von Mises stresses are almost identical in the two welds. The weld stress in the combination groove weld was only marginally lower than the fillet weld stress. You can view the stress results for both welds by clicking on the picture opposite.
The main point to note here is that the addition of the groove weld increases the production costs of the shaft, and does not significantly increase the load carrying capacity of the weld. Instead it adds time and cost to the manufacturing process, with little (if any) return on added weld strength.
Blodgett even indicates that according to hand calculations, the groove weld actually decreases the load carrying capacity...but we believe our FEA!