In the second stage, there are three important characteristics that
should be set to obtain realistic fatigue verificationresults:
- weld type or fat class (notch grade) – which determines the
quality of the weld;
- material – which determines the grade of steel that the
structure is made of; and
- element group – which determines the intensity of
load and usage of the verified structure.
Weld type is crucial because fatigue problems are most
likely to occur on welds. Therefore, in the S-N curve
fatigue analysis method it is necessary to establish a
classification based on a weld type to assign a curve.
The general curve of the stress level against endurance
is shown below.
The first challenge is determining which elements of your
FEA model are welds. The SDC Verifier Weld finder tool
solves this problem by introducing automatic one-click
weld recognition. It automatically finds all welds in the
FEA model based on thickness change, material/property
change, joint angle and user-defined rules or exceptions.
After recognition is complete, the classification must
be determined for all welds in the model. SDC Verifier’s
selector helps you create components for all welds, weld
intersections, weld tips, etc. Moreover, since the Weld finder
reorients the stresses and forces in the welding directions, different
classifications can be made along the weld, perpendicular to the
weld, and for shear.
Material type is often sourced from Ansys Mechanical or can be
easily set in SDC Verifier (there is an automatic reminder if some
of the material properties are not set).
S-N curve graph
Example of SDC Verifier’s weld recognition
Weld classification example