MANE-4030: Elements of Mechanical Design: Worksheet #18
4/25/11: Welds
A steel side plate is to be welded to a vertical steel column according to the specifications in the figure
(dimensions in mm). In this problem, you are to determine the required weld size if an E 60 welding
electrode is to be used, and a safety factor of 2.5 guarding against yield is required.
(a) Think about what types of forces the welds see due to the point force and what stresses those forces
will cause (direct shear, torsion, or bending?). W here do you think the critical location is? Is there just
one location or more than one location that should be checked?
(b) Compute the stress due to the direct shear (force over total weld area) in terms of the weld size. This
stress is assumed to be equal over the entire weld.
(c) There should also be a stress due to torsion. From the figure, think about where the welds are located.
Imagine them as two long, thin rectangles, and find the centroid of the combined weld area (you can use the
weld table handout for this). Also compute the unit second polar moment of area (see handout).
(d) Compute the moment (torque) due to the force about that centroid. Using that torque, the unit second
polar moment, and the weld centroid location, compute the shear stress due to torsion at the critical
location(s) in terms of the weld size. Also determine the direction(s) by assuming that the direction is
perpendicular to the line from the centroid to the critical location(s).
(e) Using vector addition, add the shear stresses at the critical location(s) and determine the maximum
shearing stress in terms of the weld size.
(f) Using the safety factor and the value of the weld yield strength from Table 13.13, find the required
weld size.
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