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- 2004 (3) (entfernen)
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- Crack initiation (1)
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Eingeladener Vortrag
- nein (2)
Substantial improvement in the fatigue strength of spot welded high-strength steels has been achieved with the help of a mechanical method, i. e. preloading. Fatigue tests of preloaded tensile shear specimens made from the material H280LA have revealed that their S/N-curves, compared to those of non-preloaded specimens, are not only located at elevated positions, but have flatter slope, too. Low cycle fatigue tests of the triple-spot weld tensile shear specimens examined yielded an increase in fatigue strength of around 50 %. Due to preloading, the notch zones in the spot welded area undergo plastic deformation as a result of high notch stresses. After specimen unloading, compressive stresses arise in this area involving a beneficial specimen behaviour under the load imposed in subsequent fatigue testing, thus causing delayed crack initiation in the spot weld area.