Step 6: Specify boundary conditions
The boundary conditions given in the problem specification are summarized in the schematic below. Keep in mind that the edge conditions need to be applied to the plate as well as the stiffeners.
Apply Symmetry along AH
We'll apply this BC in two steps:
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Utility Menu > PlotCtrls > Numbering: Turn off area and node numbering; turn on line numbering.
Select all edges along AH: Utility Menu > Select > Entities
We are going to continually use the Select Entitiesmenu to apply the BC's. So resize and rearrange the windows slightly so that you can access this menu, the ANSYS GUI, and the tutorial simultaneously.
Select Entities menu: Select Lines from the pull-down menu at the top. Select below that. Choose By LocationY coordinates. Under Min,Max, enter 0
. This will select all lines whose centers lie at y=0. Make sure From Full is selected so that we are selecting entities from the full model. Click Apply.
Check which lines have been selected: Select Entities menu >Plot. You should see that the edges along AH have been selected.
Apply symmetry condition to the selected edges: Main Menu > Preprocessor > Loads > Define Loads > Apply > Structural > Displacement > Symmetry B.C. > On Lines > Pick All
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Select the entire model: Click Select All and then Replot in the Select Entities menu. You should see the S symbol along the edges where the symmetry BC has been applied.
Apply Symmetry along AJ
We'll first select all edges along AJ. Go back to Select Entities menu: Leave Lines and By Location in place. Choose X coordinates. Under Min,Max, retain 0
. This will select all lines whose centers lie at x=0. Make sure From Full is selected. Click Apply.
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Select the entire model: Click Select All and then Replot in the Select Entities menu.
Apply Clamped BC along HI
Now that we've gotten the hang of this boundary business, let's mop up Operation BC's in short order.
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Constrain all six nodal degrees of freedom (DOF) for the selected edges:Main Menu > Preprocessor > Loads > Define Loads > Apply > Structural > Displacement > On Lines > Pick All > All DOF > OK
The (cluttered) display will show that all six DOF's have been constrained.
Select Entities menu: Select All and Replot
Apply Clamped BC along JI
Select Entities menu: Leave Lines, and By Location in place. Choose Y coordinates. Under Min,Max, enter L1
. This will select all lines whose centers lie at y=L1. Make sure From Full is selected. Click Apply.
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Select Entities menu: Select All and Replot
Save: Toolbar > SAVE_DB
Apply Pressure on Plate
Utility Menu > PlotCtrls > Numbering: Turn off line numbering.
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Apply a pressure of 0.05 N/mm2 on the plate in the +z direction: Main Menu > Preprocessor > Loads > Define Loads > Apply > Structural > Pressure > On Areas > Pick All
For VALUE, enter 0.05
. Click OK.
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Select Entities menu: Select All, Replot and Cancel. You should now see the entire model. Review that all the BC's have been applied correctly.
Save: Toolbar > SAVE_DB
Create Log File
In parametric studies to be undertaken later, we'll start with the log file containing the commands from the first six steps that we just went through. To save this log file, select
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Under Write Database Log to, enter the filename for the logfile: shell_step6.lgw. At the bottom of this menu, select Write Essential Commands only. Click OK. Review shell_step6.lgw by opening it in a text editor.
Go to Step 7: Solve!
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