Modern laser welding technology leads to differences in the geometrical and mechanical properties of welded joints when compared to conventionally welded joints. The fatigue resistance of laser-welded joints is important.
Joints that are laser welded produced mechanical properties within the joint that vary strongly, affecting both strains and notch stresses. The stress-strain curve of the parent material provides the basis for a structural analysis and gives the loading for the weld notch. The local analysis uses the stress-strain curve of the heat-affected zone.
The mechanical properties of the material in the weld notch have a strong influence on fatigue resistance. The main reason for the differences between laser-based joints and more traditional-welded joints was the dissimilar grain size in the heat-affected zone. The grain size of laser-welded joints is typically about seven times smaller than that of a traditionally welded joint. Other parameters causing differences include the hardness of the weld materials, as well as the weld size which affects joint stiffness.
One study conducted small scale forming limit tests and modified stretch draw tests on laser-welded high strength steels in order to compare the strength of laser-welded tailored blanks to that of unwelded specimens. The study found that the forming limit curve can be estimated using the forming limit curve of the weaker or thinner parent material.