Defining pressure penetration

A pressure penetration interaction allows you to simulate the pressure of a fluid penetrating between two surfaces involved in surface-to-surface contact. The fluid pressure is applied normal to the surfaces. The bodies forming the joint can both be deformable, as is the case with threaded connectors; or one can be rigid, as occurs when a soft gasket is used as a seal between stiffer structures.

See Also
Interaction editors
In Other Guides
Fluid Pressure Penetration Loads
About Contact Pairs in Abaqus/Standard

Context:

Pressure penetration interactions can be applied in three-dimensional, planar (two-dimensional), or axisymmetric models. A pressure penetration interaction can be used only in an Abaqus/Standard analysis.

Before defining the pressure penetration interaction, you must create a surface-to-surface contact interaction to specify the main and secondary surfaces for the pressure penetration; see Defining surface-to-surface contact in an Abaqus/Standard analysis. When you create the surface-to-surface contact interaction, any combination of Sliding formulation and Discretization method can be used (for compatibility with pressure penetration).

In the pressure penetration definition you identify the contact surfaces, the regions on the surfaces exposed to the fluid pressure, the magnitude of the fluid pressure, and the critical contact pressure acting on the regions. In a three-dimensional model points, edges, and faces can be selected as the regions exposed to the fluid pressure. In a two-dimensional model only points can be selected. In a two-dimensional model you must identify the penetration points on both the main and secondary surfaces (unless the main surface is an analytical rigid surface).

The fluid can penetrate from either one or multiple regions on the surface. These regions are always subjected to the pressure penetration, regardless of their contact status. Fluid will penetrate into the region between the contacting bodies until a point is reached where the contact pressure is greater than the specified critical value, cutting off further penetration of the fluid.

  1. From the main menu bar, select InteractionCreate.

    Tip: You can also create a pressure penetration interaction using the tool in the Interaction module toolbox.

  2. In the Create Interaction dialog box that appears, do the following:

    • Name the interaction. For more information about naming objects, see Using basic dialog box components.

    • Select the step in which the interaction will be created.

    • Select the Pressure penetration type of interaction.

  3. Click Continue to close the Create Interaction dialog box.
  4. From the Contact interaction list, select the surface-to-surface contact interaction to which the pressure penetration will be applied.

    The main and secondary surfaces of the contact interaction are shown in the dialog box, and the surfaces are highlighted in the viewport.

  5. For a three-dimensional model, do the following in the Penetration Regions table:
    1. Identify the first region on the secondary surface that is exposed to the fluid pressure.

      Double-click the empty cell in the Region on Secondary column, or select the cell and click the button; then use one of the following methods to select the region:

      • Use the mouse to select a face, edge, or point on the model in the viewport. If you are working in a mesh, you can use the mouse to select nodes.

      • Choose an existing set to specify the face, edge, or point. On the right side of the prompt area, click Sets. Select an existing face, edge, or vertex from the Region Selection dialog box that appears, and click Continue.

        Note:

        The default selection method is based on the selection method you most recently employed. To revert to the other method, click Select in Viewport or Sets on the right side of the prompt area.

      It is not necessary to identify the Region on Main for a three-dimensional model. However, doing so may help you resolve any problems that you encounter with the analysis. You can select the Region on Main in exactly the same way as the Region on Secondary.

      Note:

      If the selected contact interaction has an analytical rigid main surface, the Region on Main column appears dimmed, indicating that adding or editing main surface points is unavailable. Any main surface regions that have already been specified will be ignored.

    2. Enter the Critical Contact Pressure below which fluid will start to penetrate. The higher this value, the easier the fluid penetrates. The default is zero, in which case the fluid penetrates only if contact is lost.
    3. Enter the magnitude of the reference Fluid Pressure.

      If the analysis step is a steady-state dynamic (linear perturbation) step, you can specify both the real (in-phase) and imaginary (out-of-phase) parts of the pressure in the Fluid Pressure (Real) and Fluid Pressure (Imaginary) columns of the table.

    4. To add a row to the table and to continue selecting additional penetration regions, click the button. This action takes you directly to the region picking step in the viewport. Repeat as needed to specify all the regions.
    5. To edit a penetration region, select the region in the table, click the button, and reselect the region.
    6. To delete a region, select the row in the table and click the button.
  6. For a planar (two-dimensional) or axisymmetric model, do the following in the Penetration Regions table:
    1. Identify the first pair of points exposed to the fluid pressure.

      Double-click the empty cell in the Region on Main column, or select the cell and click the button; then use one of the following methods to select the point:

      • Use the mouse to select the point on the model in the viewport.

      • Choose an existing set to specify the point. On the right side of the prompt area, click Sets. Select an existing node or vertex from the Region Selection dialog box that appears, and click Continue.

        Note:

        The default selection method is based on the selection method you most recently employed. To revert to the other method, click Select in Viewport or Sets on the right side of the prompt area.

      Repeat the process to select the corresponding penetration point on the secondary surface, using the Region on Secondary column of the table.

      Note:

      If the selected contact interaction has an analytical rigid main surface, the Region on Main column appears dimmed, indicating that adding or editing main surface points is unavailable. Any main surface points that have already been specified will be ignored.

    2. Enter the Critical Contact Pressure below which fluid will start to penetrate. The higher this value, the easier the fluid penetrates. The default is zero, in which case the fluid penetrates only if contact is lost.
    3. Enter the magnitude of the reference Fluid Pressure.

      If the analysis step is a steady-state dynamic (linear perturbation) step, you can specify both the real (in-phase) and imaginary (out-of-phase) parts of the pressure in the Fluid Pressure (Real) and Fluid Pressure (Imaginary) columns of the table.

    4. To add a row to the table and to continue selecting penetration points, click the button. This action takes you directly to the point picking step in the viewport. Repeat as needed to specify all the points.
    5. To edit a penetration point, select the point in the table, click the button, and reselect the point.
    6. To delete a pair of penetration points, select the row in the table and click the button.
  7. In the Penetration time field, enter the time period for the fluid pressure penetration to reach the full current magnitude on newly penetrated surface segments. The default penetration time is 0.001 of the current step time. The penetration time is not available in a linear perturbation analysis.
  8. Optionally, you can define the variation of the fluid pressure during the step by selecting an amplitude curve in the Amplitude list. By default, the reference magnitude is applied immediately at the beginning of the step or ramped up linearly over the step, depending on the amplitude variation assigned to the step. Fluid pressure amplitude curves are not available for some steps.
  9. Click OK to create the interaction and to close the editor.