Differential Data
For multi-stage models, data can be viewed in differential format by setting a non-zero Reference Stage in the Stage Settings option. Some important points to remember when viewing differential data are described below.
Sigma 1 and Sigma 3
The DIFFERENTIAL in-plane principal stresses (Sigma 1 and Sigma 3) are obtained by subtracting the stress tensors and calculating the differential principal stress tensor at each node. DIFFERENTIAL Sigma 1 and Sigma 3 are NOT obtained by simply subtracting the stress magnitudes, since this would not account for changes in principal stress orientation at different stages.
Displacement
DIFFERENTIAL Horizontal and Vertical Displacement are obtained by subtraction of Visible Stage – Reference Stage values. DIFFERENTIAL Total Displacement is obtained by subtracting the total displacement vectors.
Other Data
All other DIFFERENTIAL data (e.g. Strength Factor, Sigma Z, Strain, User Data), is obtained by subtracting the Visible Stage – Reference Stage values.
Display Options
All applicable Display Options will indicate DIFFERENTIAL results, as follows:
- Stress Trajectories will indicate the orientation of the DIFFERENTIAL Sigma 1 and Sigma 3 principal stresses at each node.
- Deformation Vectors will indicate the differential displacement vectors.
Show Yield
The reference stage affects the display of yielded elements as follows:
- Finite elements that yielded AFTER the Reference Stage are displayed in red. Elements that yielded IN or before the Reference Stage are displayed in dark red.
- Yielded bolt elements are displayed in different colours, according to whether they have failed before or after the reference stage, and also whether the bolt element has failed in shear, tension or both. See the Legend for the colour scheme.
- Yielded liner and joint data is NOT displayed in differential format. The reference stage setting does not affect the display of yielded liner or joint elements.
See the Show Yield topic for more information.