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Strength Evaluation of Spot Weld in Fatigue Using Double-Cup Specimen
Last modified: 2013-05-06
Abstract
Double-cup (DC) specimen of spot welded joint is newly produced for high
strength steel (HSS) sheets with the steel grade ranging from 590MPa to 980MPa,
and fatigue tests are conducted under three kinds of loading directions (tensile,
shear and combination of both). The fatigue strength is degraded as the load
component in the tensile direction increases. The HSSes show higher fatigue
strength than the mild steel under the shear loading, whereas the fatigue strength
of the tensile-shear (TS) specimen is almost equal regardless of the steel grade.
Finite element analyses reveal that the rotation of the spot weld in the DC
specimen is smaller than that of the TS specimen due to deformation constraint
around the spot weld and the stress state is close to pure shear, which leads to the
fair evaluation of the effects of the steel grade.
strength steel (HSS) sheets with the steel grade ranging from 590MPa to 980MPa,
and fatigue tests are conducted under three kinds of loading directions (tensile,
shear and combination of both). The fatigue strength is degraded as the load
component in the tensile direction increases. The HSSes show higher fatigue
strength than the mild steel under the shear loading, whereas the fatigue strength
of the tensile-shear (TS) specimen is almost equal regardless of the steel grade.
Finite element analyses reveal that the rotation of the spot weld in the DC
specimen is smaller than that of the TS specimen due to deformation constraint
around the spot weld and the stress state is close to pure shear, which leads to the
fair evaluation of the effects of the steel grade.
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