Connection of Dissimilar Meshes using CWELD Elements - OS-1050



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In this tutorial, an existing finite element model of a simple cantilever beam will be used to demonstrate how to connect dissimilar meshes using CWELD elements.

image\os0010_1_reszd.gif

Cantilever beam with dissimilar meshes.

The following exercises are included:

·      Setting up the problem in HyperMesh

·      Submitting the job

·      Comparing results with a control example

Setting Up the Problem in HyperMesh

To retrieve the file dissimilar.hm and load the OptiStruct user-profile:

  1. Launch HyperMesh.

  2. Select OptiStruct in the User Profiles dialog and click OK.

User Profiles… can also be accessed from the Preferences pull-down menu on the toolbar.

The OptiStruct user profile includes the OptiStruct template, macro menu, and import reader, and simplifies the menu system by allowing only the functionality of HyperMesh necessary for using OptiStruct to be active.

  1. Click the Files panel toolbar button image\files_panel.gif.

  2. Select the hm file subpanel using the radio buttons on the left-hand side of the panel.

  3. Click retrieve… .

An Open file… browser window pops up.

  1. Select the dissimilar.hm file, located in the HyperWorks installation directory under <install_directory>/tutorials/os/.

  2. Click Open.

The dissimilar.hm database is loaded into the current HyperMesh session, replacing any existing data.

Note the location of dissimilar.hm displays in the file: field.

  1. Click Return to return to the main menu.

To create membrane elements:

The database contains two unconnected components: solid_fine and solid_coarse. These unconnected components are to be connected by CWELD elements using the "grid to element" option. In order to achieve this, membrane elements need to be created on the matching faces of the solid_coarse and solid_fine components.

  1. Click the Collectors toolbar button image\collectors.gif.

  2. Select the create subpanel using the radio buttons on the left-hand side of the panel.

  3. Click the collector type switch and select components from the pop-up menu.

  4. Click name = and enter membrane_coarse.

  5. Click color and pick a color from the palette.

  6. Click card image = and select PSHELL from the pop-up menu.

  7. Click material = and select steel from the list of existing materials.

  8. Click create/edit.

The PSHELL card image pops up.

  1. Check the box next to MID2_opts.

An option list appears beneath MID2_opts.

  1. Click the switch next to USER and choose BLANK from the pop-up menu.

Notice the MID2 field disappears from the card image.

  1. Check the box next to MID3_opts.

An option list appears beneath MID3_opts.

  1. Click the switch next to USER and choose BLANK from the pop-up menu.

Notice the MID3 field disappears from the card-image.

  1. Set the thickness value, T, in the card-image to 1E-6.

  2. Click return to save changes to the card image.

This creates the new component called membrane_coarse.

  1. Click return to return to the main menu.

  2. From the Tool page select the faces panel.

  3. Select the solid_coarse component and click find faces.

  4. Click the Collector Visibility toolbar button image\collector_visibility.gif.

  5. Choose to display only the ^faces component (deselect other components by right-clicking).

  6. Click return to return to the main menu.

  7. From the Tool page, select the organize panel.

  8. Select only the elements that lie on the matching face (see figure).

image\os0010_2_reszd.gif

Elements on matching face.

  1. Click dest = and select membrane_coarse from the list of components.

  2. Click move.

The elements are now part of the membrane_coarse component.

  1. Click return to return to the main menu.

  2. Select the faces panel from the Tool page of the main menu.

  3. Click delete faces.

  4. Select the solid_fine component and click find faces.

Membrane elements are created on the faces of solid_fine component and they appear on the graphic window.

  1. Click return to return to the main menu.

  2. Select the Collectors toolbar button image\collectors.gif.

  3. Select the create subpanel using the radio buttons on the left-hand side of the panel.

  4. Click the collector type switch and select components from the pop-up menu.

  5. Click name = and enter membrane_fine.

  6. Click color and select a color from the palette.

  7. Click the switch next to card image = and select same as from the pop-up menu.

  8. Click same as = and select membrane_coarse from the list of components.

  9. Click create.

This creates the new component called membrane_fine.

  1. Click return to return to the main menu.

  2. Select the organize panel from the Tool page.

  3. Select only the elements that lie on the matching face.

  4. Click dest = and select membrane_fine from the list of components.

  5. Click move.

The elements are now part of the membrane_fine component.

  1. Click return to return to the main menu.

  2. Select the faces panel from the Tool page of the main menu.

  3. Click delete faces.

  4. Click return to return to the main menu.

  5. Click the Collector Visibility toolbar button image\collector_visibility.gif.

  6. Only display the membrane_coarse and membrane_fine components.

  7. Click return.

To create CWELD elements:

A PWELD property must be created for the CWELD elements.

  1. Select the Collectors toolbar button image\collectors.gif.

  2. Select the create subpanel using the radio buttons on the left-hand side of the panel.

  3. Click the collector type switch and select properties from the pop-up menu.

  4. Click name = and enter welds.

  5. Click card image = and select PWELD from the pop-up menu.

  6. Click material = and select steel from the list of materials.

  7. Click create/edit.

  8. Set the weld diameter, D, in the card image to 0.1.

  9. Click return to save the card image.

This creates a new property definition called welds.

  1. Click the collector type switch and select components from the pop-up menu.

  2. Click name = and enter welds.

  3. Click color and select a color from the palette.

  4. Click the switch beside card image = and select no card image from the pop-up menu.

  5. Click create.

This creates the new component called welds.

  1. Click return to return to the main menu.

  2. Select the spotweld panel from the 1D page of the main menu.

  3. Select the using elems subpanel using the radio buttons on the left-hand side of the panel.

  4. Click property = and select welds from the list of properties.

  5. Click search tolerance = and enter 0.1.

  6. Click the switch under element config: and choose rod from the pop-up menu.

  7. Click elems and choose the displayed option.

  8. Click nodes, choose the by collector option, and select the membrane_fine collector (click select).

  9. Click create.

A weld element is created at each node on the fine-mesh matching face.

A number of plot elements are created too, but we have no need for these and so we will delete them.

  1. Click return to return to the main menu.

  2. Select the delete panel from the Tool page.

  3. Choose elems from the entity selection menu.

  4. Click elems, choose the by config option, and select all of the plot elements in the model.

  5. Click delete entity.

  6. Click return to return to the main menu.

Submitting the Job

To launch OptiStruct:

  1. From the Analysis page, select the OptiStruct panel.

  2. Click save as… following the input file: field.

A Save file… browser window pops up.

  1. Select the directory where you would like to write the OptiStruct model file and enter the name for the model, dissimilar.fem, in the File name: field.

The .fem extension is suggested for OptiStruct input decks.

  1. Click Save.

Note the name and location of the dissimilar.fem file now displays in the input file: field.

  1. Set the memory options: toggle to memory default.

  2. Click on the run options: switch and select Analysis.

  3. Set the export options: toggle to all.

  4. Click OptiStruct.

This launches the OptiStruct job. If the job is successful, new results files can be seen in the directory where the OptiStruct model file was written. The dissimilar.out file is a good place to look for error messages that will help to debug the input deck if any errors are present.

The default files written to the directory are:

dissimilar.html

HTML report of the analysis, giving a summary of the problem formulation and the analysis results.

dissimilar.out

OptiStruct output file containing specific information on the file setup, the setup of your optimization problem, estimates for the amount of RAM and disk space required for the run, information for each optimization iteration, and compute time information. Review this file for warnings and errors.

dissimilar.h3d

HyperView binary results file.

dissimilar.stat

Summary of analysis process, providing CPU information for each step during analysis process.

Post-processing and the Comparison of Results with a Control Example

To view deformation results:

  1. Once you see the message Process completed successfully in the command window, click the HyperView button.

HyperView opens and the results are loaded.

A message window appears to inform about the successful loading of the model and result files.

  1. Click Close to close the message window.

  2. Click the Contour toolbar button image\contour.gif.

  3. Select the first pull-down menu below Result type: and select Displacement (v).

  4. Select the second pull-down menu and select Mag.

  5. Under Display options: check the Discrete color box.

  6. Click Apply.

  7. The resulting colors represent the displacement field resulting from the applied loads and boundary conditions.

  8. Click the Page Layout icon, image\pg_layout.gif, on the toolbar.

  9. Choose the second layout in the 1st row of the pop-up window and click Close.

This changes the graphic area in two separate windows. The left window will have the previously loaded model and the right window will be blank. We will load the control example in the right side window to compare the results.

  1. Click the right-hand pane in the display area.

A blue line appears around the window to show that it is selected.

  1. Click the Load Model toolbar button image\files_panel.gif.

  2. Choose the file control.h3d, located in the HyperWorks installation directory under <install_directory>/tutorials/os, as both the model and results file.

  3. Click Apply.

  4. Repeat the steps 1 through 5 to plot the displacement contour.

You can now visually compare the displacement results from the dissimilar mesh model with a uniform mesh model.

To view von Mises stress results in HyperView:

  1. Under Result type: select Element Stresses (2D & 3D)(t) and vonMises.

  2. Select None in the field below Averaging method:.

  3. Click Apply.

  4. Select the right-hand pane in the display area and repeat steps 1 through 3.

You can now visually compare the von Mises stress results from the dissimilar model with a uniform mesh model.

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