35.5.2 Assigning thicknesses and offsets

Like all shell faces in Abaqus/CAE, midsurface model faces require a defined thickness. After you have created the shell geometry for the midsurface model, the Assign Thickness and Offset tool provides a method to accurately capture the thickness of the solid model that you are replacing. You can also use this tool to edit thicknesses assigned automatically by Abaqus/CAE. For example, you can edit the thickness of faces that were created using the face offset process (for more information, see Offset faces, Section 69.7.7). Abaqus/CAE automatically derives the shell thickness for offset faces from the parameters used in the offset operation.

There are two ways to assign a thickness to shell faces in Abaqus/CAE. You can apply a shell thickness definition by using the section properties in the Property module, or you can assign thicknesses by selecting faces and editing their thicknesses with the Assign Thickness and Offset tool in the Part module. During the section assignment process you select which method Abaqus/CAE uses to assign thickness to a particular set of geometric faces. (For more information on section assignments, see Assigning a section, Section 12.15.1.)

Note:  Thickness data assigned in the Part module—either automatically or using the Assign Thickness and Offset tool—appear as From geometry in the thickness section of the Edit Section Assignment dialog box in the Property module. You cannot use thickness data assigned in the Part module to calculate the offset in an Abaqus/Explicit analysis.

Defining the thickness in the Part module allows you to define where the midsurface of the solid lies with respect to the shell faces of the midsurface model. The default thickness definition places the midsurface in the center of the thickness. However, you can select surfaces to define a top and bottom thickness, effectively creating an offset between the midsurface and the middle of the shell thickness. Selecting top and bottom faces allows you to easily define different thicknesses at each node and define a different shell offset for each element. This freedom is useful when you use a midsurface model to approximate thin solid models with varying thickness. Using top and bottom faces also allows Abaqus/CAE to automatically update thickness data if you edit the model geometry.

Assigning thickness to shell faces:

  1. From the main menu bar, select ToolsMidsurfaceAssign Thickness and Offset.

    Tip:  You can also assign thicknesses and offsets using the tool, located with the midsurface tools in the Part module toolbox.

    Shell faces are colored yellow if they are not currently associated with a thickness.

  2. If the part contains multiple shell faces, select the faces to which you want to assign thicknesses and offsets (for more information, see Chapter 6, Selecting objects within the viewport”).

  3. When you have finished making selections from the viewport, click mouse button 2 to commit your selections.

    Abaqus/CAE opens the Assign Thickness and Offset dialog box.

  4. If necessary, click the Edit button next to Faces to assign thickness to change the selections you made in the previous steps.

  5. Use one of the following methods to assign a thickness to the selected faces:

    Enter or Measure the thickness

    Enter a value for thickness, or click to measure a distance in the viewport and enter it as the thickness.

    Compute thickness from opposite faces

    Toggle on this option, and click Select to select the top and/or bottom faces from the viewport.

    Abaqus/CAE highlights the faces in the viewport and calculates the thickness.

    If you select only top or only bottom faces, Abaqus/CAE applies the same thickness to both sides of the target shell faces. If you select both top and bottom faces, Abaqus/CAE calculates the thickness and an offset value so that the selected shell faces are not centered within the thickness.

  6. Click OK to apply the thickness and offset (if used) to the target faces and to close the dialog box.

You can view the thickness of faces in the model by toggling on Render shell thickness in the Abaqus/CAE display options. For more information, see Visualizing shell thicknesses, Section 35.5.3, and Controlling shell thickness display, Section 76.8.


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