How to Display Results in a Local Coordinate System

When visualizing the results of an analysis, it can be beneficial to display the results in a coordinate system other than the default. The Superview IV Results environment provides the ability to define local coordinate systems and then display results relative to them. The local coordinate system types include rectangular, cylindrical and spherical and the origin can be located anywhere in space.

The visualization of hoop stress is one example of where a local coordinate system may be used. The hoop stress is a stress tensor which acts in a direction tangential to the radius. When displaying a stress tensor relative to a Cartesian coordinate system, the actual hoop stress only occurs in those areas where the stress tensor vector is aligned with the direction of the hoop stress (Figure 1).

Figure 1: This Stress Tensor Y-Y display is based on the global Cartesian coordinate system.  (Areas of hoop stress are circled.)

As an alternative, a cylindrical coordinate system can be used so that the actual hoop stress is shown around the full circumference of the model.

To create a new local coordinate system in the Superview IV Results environment:

• right click on "Coordinate Systems" in the tree view;
• in the pop-up menu that appears, choose "New...";
• select the coordinate system type and define points "A", "B" and "C" in the "Creating Coordinate System Definition" dialog (Figure 2); and
• click on the "OK" button to add the new local coordinate system.

Figure 2: The "Creating Coordinate System Definition" dialog is used to define local coordinate systems.

Note that in the case of a cylindrical vessel, point "A", the origin, and point "B" would both lie on the axis of revolution.

To activate any local coordinate system in the Superview IV Results environment:

• right click on the coordinate system in the tree view; and
• in the pop-up menu that appears, choose "Apply".

The results are now displayed relative to the active local coordinate system (Figure 3).

Figure 3: This Stress Tensor Theta-Theta display of the hoop stress is based on a local cylindrical coordinate system.

Local coordinate systems can also be defined in the FEA Editor environment to aid in the creation of loads and constraints (see How to Define a Local Coordinate System). For more information about local coordinate systems and their application, see the ALGOR User’s Guide.