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Prepare thin wall model for analysis

Use commands on the Prepare panel to simplify models that contain thin bodies.

Limits for using the thin parts commands in Stress Analysis
L/D ratio = Length /Thickness, where:

Length = overall length of the body

Thickness = thickness of the body

Consider a thin square plate whose length and width are 100 with a thickness of 1. The L/D ratio of such a plate is 100/1 = 100. We compute the L/D ratio of the input body and compare it with the thin square plate’s L/D ratio.
  • If the L/D ratio is below 100, the body is considered as thick (or solid), and we recommend to analyze it as solid to perform accurate analysis using solid elements.
  • If the L/D ratio of the input body is above 100, then the body is considered as a thin component, and is highlighted as such after you click the Find Thin Bodies command.
  • If the L/D ratio is above 100 and you perform the analysis without converting them to a Shell using either Midsurface or, Offset, a message displays recommending using the Find Thin Bodies command to perform more accurate analysis.
  • If the L/D ratio is above 250, and the body is being analyzed as a thick solid, a warning message displays indicating that results of analysis are very likely to be inaccurate and not precise.
Note: Specific details on how the L/D ratio is computed and compared are not covered here. Autodesk Inventor makes only a suggestion of which body should be considered as a thin. The chosen criteria are not absolute, so they may not be applicable in to some specific circumstances. You can override results of the command.

Prepare thin wall model for analysis

Before analyses of parts and assemblies, simplify models that contain thin bodies to reduce computational resources and increase precision of the simulation.

  1. With a part or assembly file open, on the Environments tab, click Stress Analysis .
  2. Create a simulation.
  3. On the Prepare panel, click Find Thin Bodies . In the browser, solid bodies that meet the thin component criteria highlight. Click OK.

    In the Midsurface dialog box, click OK to generate midsurfaces from selected solid body components.

    Alternatively, click Offset to manually select faces to create thin shell components.

    In the browser, all midsurfaces and offsets are listed under the Shells node.

  4. Add loads and constraints.
    Important: Loads and Constraints applied to solid components become sick when converted to shell elements. We recommend that you apply them after you convert the model.
  5. Solve the simulation, and view the results.

View midsurface or offset thickness

  1. In the browser, right-click a Midsurface or Offset node, and click Show Thickness.
    Note: Context menu option is available only in parametric simulations.
  2. Click Edit Shell in parametric simulations to display the base configuration thickness. Right-click and click Show Thickness.

    An averaged thickness for a particular configuration displays. This averaged thickness is sent to solver for analysis.

For midsurfaces, you can view the body thickness, but you cannot edit it. For offsets, you can edit only the Thickness value, which is twice the Distance value.

Delete instances of midsurface or offset

Delete converts one or multiple parts back from shells to solids. In a multiple selection, you can also view multiple connectors at once to check whether all of the gaps are connected with connectors.

  1. In the browser, right-click the Shells folder, and click Expand All Children.
  2. To delete one item, right-click the Midsurface or Offset node, and click Delete
  3. To delete multiple items, select first middle surface (Midsurface:1), or first Offset (Offset:1).
  4. Hold down Shift, and select the last midsurface, or offset.
  5. Right-click the selection, and click Delete.

Create thin components (shells) from faces

  1. In the Stress Analysis environment, create a simulation.
  2. On the Prepare panel, click Offset .
  3. Click Faces selection icon , and then specify a face from which to create an offset.
  4. To preview the shell before it is created, turn on Enable/Disable Feature Preview .
  5. In the Offset dialog box, specify the thickness. Distance calculates automatically as half of the thickness. You cannot edit Distance.
  6. Click OK.

    Offset inspects the selected bodies, and if they meet the shell feature criteria, creates a shell component from selected faces.

Generate midsurfaces from thin bodies components

We recommend that you use Find Thin Bodies first. If any thin bodies are found, a message box displays. Click OK to open the Midsurface dialog box automatically.

  1. In the Stress Analysis environment, create a simulation.
  2. On Prepare panel, click Midsurface .
  3. Click Solid Bodies selection icon , and then select a solid body from which you want to create a midsurface.
  4. In the Midsurface dialog box, click OK.

    Midsurface inspects selected bodies, and if they meet the shell feature criteria, converts them to shell features defined by midsurface.

Parent topic: About Stress Analysis

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