Learning Forum

[Jeone]

After I did static analysis in, Ansys the maximum stress is 200 MPa, however nCode FE Display shows 260 MPa. Why are these values different? 

[danielshaw]

There are multiple reasons why the final stresses reported by Ansys nCode Designlife do not precisely match the Mechanical stresses.  The stress reported by DesignLife is the adjusted stress used in the fatigue calculations.  For StressLife fatigue, it is the stress used with the SN curve to predict the number of allowable cycles.

By default, DesignLife calculates fatigue damage only for the surface nodes, and it assumes that a 2D plane stress state exists on the surface.  The FE nodal stresses are converted into a that stress state using local coordinate systems.  Those converted stresses will typically not match the reported 3D FE surface stresses, unless the mesh is very refined.  In addition to the surface stress state, DL will also adjust the FE stresses for factors such as, mean stress correction, surface finish, user specified scale factors, etc.