High-cycle fatigue (HCF) is one of the main concerns for spot-welded structures,
and finite element (FE)-based simulations have critical importance for the life
assessment and design optimization. The accuracy of spot weld modeling
methodologies has a key role in achieving the development objectives. This
article presents a comparative study for HCF simulations of different spot weld
modeling methodologies and their comparison with the test data. In this regard,
HCF analyses based on Findley’s multi-axial damage model are conducted with a
commercial software. Direct equivalenced spot weld modeling with and without
offset adjustment, rigid spot weld, and rigid beam (single) spot weld methods
are analyzed for overlapped sheet metals under axial cyclic loading. Two
specimens with different thicknesses, spot weld diameters, and number of nuggets
are simulated under six cyclic load cases: 2000-4000 N, 1400-2800 N, 1800-3600
N, 200-8000 N, 100-8300 N, and 200-6800 N. Direct equivalenced spot weld
modeling with offset adjustment and rigid spot weld methods demonstrate high
levels of accuracy with an average deviation of 8.9% from experimental data. It
has been shown that it is imperative that offset adjustments be made for the
direct equivalenced spot welding method since improper offset results in an
artificially increased life estimate that is ten to twenty times greater than
the data collected from the test. A rigid beam spot weld model with only one
rigid connection concentrated at the center of the weld nugget produces
artificial stress increases and, therefore, has a much shorter fatigue life
cycle than the test results.
