Units, Orientation, and Visualization
Using Units
Enter loads in any unit, independently of the base SI unit system in the model, because COMSOL automatically converts any unit to the base SI unit system. To use the feature for automatic unit conversion, enter the unit in square brackets, for example, 100[lbf/in^2].
Predefined and Custom Coordinate Systems
In this module, different predefined coordinate systems are available when materials or boundary conditions are specified. There is always the global coordinate system. Depending on the dimensionality of the part being worked with, there can also be predefined coordinate systems such as and the local tangent and normal coordinate system for boundaries.
Custom coordinate systems are also available and are useful, for example, to specify a load in any direction without splitting it into components. From the Definitions toolbar, select a Coordinate System () from the menu.
Some coordinate systems can have solution dependent axis directions. If you use such a system for defining a load, the directions of the load follow the moving coordinate axis directions if the Include geometric nonlinearity check box is selected under the Study settings section of the current study step.
Visualization
If you have switched on the physics symbols (see Displaying Physics Symbols in the Graphics Window — An Example in the COMSOL Multiphysics Reference Manual), then an applied load is indicated by a symbol together with a coordinate system indicator displaying the definition directions for the load. The actual direction or magnitude of the load you enter is not, however, reflected by the symbol. As a load in COMSOL Multiphysics can be a function of parameters, variables, the solution, or results from other physics interfaces, it is not possible to display it with only the information available in the individual load feature.
Once you have turned on the physics symbols for a certain physics interface, you can fine-tune the display. Every feature which has associated physics symbols will now have a check box Show physics symbols, by which you can control the display of the symbols for that specific feature.
You can always display the loads actually used after the analysis, since they are available among the result quantities. Sometimes, especially if you have entered complicated load expressions in a large model, it is important to inspect the load distribution before you run the analysis. You can then do like this:
1
On the Study toolbar, click Get Initial Value. This operation is fast when compared to actually solving the problem.
2
From the Results toolbar, add a 3D Plot Group or 2D Plot Group.
3
Add a suitable plot type to the plot group, for example an Arrow Surface plot.
4
Select a result from the Load group in the results for the physics interface.
In the COMSOL Multiphysics Reference Manual:
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Physics Symbols
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Using Units
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Coordinate Systems
For an example showing how to examine the load distribution, see Bracket — Static Analysis: Application Library path Structural_Mechanics_Module/Tutorials/bracket_static. This is also the first example used in the Introduction to the Structural Mechanics Module.