Weld Strength page last updated 7 February 2005
The ultimate load carrying capacity of spot welded joints depends on
many factors including the
spot weld nugget diameter, sheet thickness, and base material properties.
Commonly, standard
tensile shear specimens made of flat plates joined with a single spot
weld are used to evaluate the
strength of the joint. However, these specimens are fairly flexible,
and are usually only used in
tensile loading modes to avoid buckling. Actual spot welded structures
tend to behave differently
than these standard specimens, due the constraint of the nearby welds
and structure.
The project with DaimlerChrysler will investigate the following:
-effect of two welds on the strength of the jointThe testing will be done based on a fully developed DOE matrix, and an analytical model will
-the use of C-channel specimens to induce more realistic structural stiffness
-the effects of various nugget sizes, spacings between welds, and edge distances of the spot welds
-the effect of spot welds alone versus spot welds and adhesives
-the effect of sheet thickness,
-and the effect different materials on the joint performance.
Specimens made with C-Channels do not exhibit the large amount of spot
weld nugget rotation
often seen in standard tensile shear tests. Click on the link
below for a video of a strength test
of the joint.
This joint failed at about 7000 lbs of force. A single spot weld,
standard tensile shear specimen
welded under the same nominal conditions failed at about 2500 lbs of
force.
Thanks to:
Tim Connell (AEM Technician)
Joe and Ken (COE Machine Shop)
Steven Zhang (PhD-ESM student)
Steven thesis will be
based on the work he does for this project.
Guoqing Wang (PhD-ESM student)
Guoqing has helped make
some trial welded samples.