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 Autodesk® Simulation Results environment provides the ability to define local coordinate systems and then display results relative to them. The types of local coordinate systems include rectangular, cylindrical, and spherical. 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 tangential direction (90° from the radial and axial directions). 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. The axis of the ring is the axis of the cylindrical coordinate system – in this case, the global Z-axis.
Local coordinate systems may be defined either within the FEA Editor or Results environments. Regardless of where the coordinate system is defined, it is available for use in either environment.
To create a new local coordinate system in the 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 box (Figure 2).
- Click on the OK button to add the new local coordinate system.
Figure 2: The "Creating Coordinate System Definition" dialog box 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 Results environment:
- Right-click on the coordinate system in the Browser (tree view).
- In the context menu that appears, choose Activate.
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 cylindrical local coordinate system.
As mentioned previously, local coordinate systems can also be defined in the FEA Editor environment. This facilitates the application of loads and constraints in non-global directions (see How to Define a Local Coordinate System). Also, you may view a series of Essential Skills Videos regarding Local Coordinate Systems, as follows:
For additional information about local coordinate systems and their application and usage, see the Autodesk Simulation In-Product Help or Online Wiki Help.