Creo Simulate > Modeling Structure and Thermal Problems > Structure Loads > Pressure Loads > Pressure Loads
Pressure Loads
You can use Home > Pressure in both native and FEM structure mode, to create a pressure load on 3D model surfaces or 2D model curves. For 2D models, you can select a curve that bounds only one surface. You cannot pick datum curves, free-floating curves, or curves shared by more than one surface.
A positive pressure load always acts in opposition to the normal direction of an entity at every location, even if the entity is curved. Creo Simulate sets the normal direction automatically for entities as you create them.
When you click Home > Pressure, the Pressure Load dialog box opens with the following items:
Name—The name of the load. The color swatch adjacent to Name allows you to change the color of the icon, the distribution, and the text displayed for the load.
Member of Set—The name of the load set. You can select an existing load set, or create a new set by clicking New to display the Load Set Definition dialog box.
References—Select geometric entities—edges or curves for 2D models, and individual or intent surfaces for 3D models. You can select the geometric entity before or after opening the Pressure Load dialog box. Your selections appear in the collector in the References area.
If you select a quilt surface, Creo Simulate displays the surface normal using a purple arrow at the time of selection, and gives you the option of flipping the normal direction. If you selected the surface before entering the dialog box, you can reselect the surface and determine its normal direction.
Advanced—Expand the dialog box to define the spatial variation by indicating how you want to vary the load across the geometric entity. You can choose a uniform load—one that remains the same across the selected geometry.
Alternatively, you can vary the load:
As a function of coordinates
Through interpolation
As an external coefficient field (not supported in FEM mode)
To vary the load as an external coefficient field, you need a FEM Neutral Format (FNF) file that specifies a coefficient field. Creo Simulate automatically maps the coefficients from the FNF file to one or more of the model's surfaces that lie within the specified tolerance limit.
Click the icon in the File area to browse to the FNF file that is a file with a .fnf extension. Specify the limits of tolerance in the Auto Map Surfaces area. The default tolerance values are controlled by sim_auto_map_max_angle and options. Click Preselect Surfaces to complete the automatic mapping.
If one or more surfaces are selected before clicking Preselect Surfaces, the Message dialog box allows you to discard the previous selection. In the message displayed, click Yes to discard the initial selection. Only those surfaces that satisfy the maximum tolerance conditions are displayed in the Surfaces selector. Click No to append Creo Simulate's selection to the existing surface set displayed in the Surfaces selector.
At any time, you can select or clear the selection of surfaces manually.
Value—Type a real number, an arithmetic expression, or a parameter name for the magnitude of the pressure load. If you enter a negative magnitude, the pressure direction is coincident with the normal direction. Select appropriate units of pressure from the adjacent drop-down list.
Preview—Adds a series of arrows to your model showing the location and distribution of the pressure load.
In the native mode, you can customize the preview of the external loads. When you apply an external load, clicking Preview opens the Load Preview dialog box.
When you click Preview, Creo Simulate checks the load for errors. If there are no errors, Creo Simulate displays the preview of the load distribution. When you click OK, yellow arrows indicating load distribution appear on the model.
If the model has preselected surfaces for varying the load as an external coefficient field, preview the load to ensure mapping of the imported mesh on the model surfaces meets your requirement.
If errors appear, you are issued a warning. In such a case correct the load definition before proceeding.
The software determines the pressure load direction by the sign that you use to specify the magnitude. Be aware of the following behavior when determining the sign of a pressure load:
Solid Faces—If the pressure value is positive, the load pushes toward the surface because the normal for solids is always outward from the solid face. If the pressure value is negative, the load pulls away from the surface.
Quilts—If the pressure value is positive, the load pulls in the direction opposite of the normal direction that is displayed when you selected the pressure load surface. If the pressure value is negative, it pulls in the same direction as the normal direction.
Note that, if you switch to Creo Parametric and change the surface normal of a quilt to which you have applied a pressure load, the load direction in Creo Simulate changes.
See Guidelines for Pressure Loads for more information. See Example: Pressure Load for an example of pressure load distribution.
See Example: Auto-mapping an Imported Coefficient Mesh for an example of importing pressure load coefficients.
Return to About Structure Loads.