Sheet - FEM representation

Sheet in T-SIM is represented using a finite elements mesh with thickness and temperature data. Each element has its own thickness and temperature. The sheet representation is created directly in T-SIM using a simple dialog. Once a sheet is created, thickness and / or temperature of every element can by changed. The finite elements grid can be also refined when open in T-SIM Grid view. However, refinements from post-processing are more advanced - see Refinement from post-processing.

Advanced: Sheet file format

The sheet of rectangular shape can be created within T-SIM when using the built-in sheet editor. The result of this editor is a text file which holds the geometrical and topological data of the sheet. The sheet lies on the plane xy (with z = 0), before the inflation.

To create a new sheet representation, click on the icon with the tool tip "New grid (sheet)" on T-SIM shortcut bar:

or click on File / New and select T-SIM Grid (sheet) as the document type and click OK.

x- and y- coordinate of the left upper corner (mm or inch).
This is a point on the sheet with minimum (x, y) coordinates.
x- and y- coordinate of the right lower corner (mm or inch).
This is a point on the sheet with maximum (x, y) coordinates.
thickness of the sheet (mm or inch)
temperature of the sheet (oC or oF)
number of elements (typically 1000 - 5000 elements)
Symmetry (full, half or quarter) of the sheet means that in the case when the mold has two planes of the symmetry, there is no need to solve the whole problem using the full symmetry; one quarter of the entire sheet can be selected, thus reducing the time and memory requirements.

Full - without plane of symmetry
Half - one plane of symmetry ; plane x = const.
Quarter - two planes of symmetry : x = const1, y = const2.

Once all the items are specified, click Create. The sheet representation is automatically created and opened for further modifications:

To edit the temperature profile of an existing sheet, open the sheet in T-SIM Grid view - click on the icon with the tool tip "Open grid (sheet)"

and in Windows File Open dialog, browse for the sheet file. Once the file is selected, click Open. A new window with the picture of the selected sheet appears.

Now, click Grid(sheet) / Edit temperature to change the sheet temperature inside a selected rectangular area. Then move the cursor into a required position and press and hold down the left mouse button. Move the cursor to the second corner of the rectangle and release the mouse button.

Specify the value and click OK to modify the temperature inside the area selected. To cancel the procedure of the modification of temperature, click Cancel.

If the temperature profile is changed, the sheet document is marked as modified. When closing this document, T-SIM displays a warning offering to save the modified sheet under a new name (i.e. Windows File Save as dialog appears).
Before closing T-SIM Grid view, the modified sheet can be saved also using File / Save (or File / Save as) command.

Starting from T-SIM Version 4.5, a temperature matrix can be used to specify sheet temperature profile. For more information, please see Temperature matrix help.

To edit the thickness profile of an existing sheet, open the sheet in T-SIM Grid view - click on the icon with the tool tip "Open grid (sheet)"

and in Windows File Open dialog, browse for the sheet file. Once the file is selected, click Open. A new window with the picture of the selected sheet appears.

Now, click Grid(sheet) / Edit thickness to change the sheet thickness inside a selected rectangular area. Then move the cursor into a required position and press and hold down the left mouse button. Move the cursor to the second corner of the rectangle and release the mouse button.

Specify the value and click OK to modify the thickness inside the area selected. To cancel the procedure of the modification of thickness, click Cancel.

If the thickness profile is changed, the sheet document is marked as modified. When closing this document, T-SIM displays a warning offering to save the modified sheet under a new name (i.e. Windows File Save as dialog appears).
Before closing T-SIM Grid view, the modified sheet can be saved also using File / Save (or File / Save as) command.

To refine an existing sheet, open the sheet in T-SIM Grid view - click on the icon with the tool tip "Open grid (sheet)"

and in Windows File Open dialog, browse for the sheet file. Once the file is selected, click Open. A new window with the picture of the selected sheet appears.

Click Grid(sheet) / Refine to refine the sheet inside a selected rectangular area. Then move the cursor into a required position and press and hold down the left mouse button. Move the cursor to the second corner of the rectangle and release the mouse button. The sheet is automatically refined.

The refinement in T-SIM Grid view is an old-fashioned way how to increase the sheet grid density in selected areas. There is no connection with the deformation of every element during the simulation of the forming process. It is hard to refine the areas of the flat sheet (before forming) where the density of grid is not high enough after forming. For this reason, more sophisticated ways of refinement are implemented in T-SIM - see Refinement from post-processing.

Clamping in T-SIM is understood as a fixation of sheet grid nodes. It means that the clamped nodes cannot move in any direction. Any clamped node can be made free from its constrains and any node can be clamped. Fixed nodes (fixed nodes are not clamped nodes in T-SIM) cannot be made free from their constrains. Also nodes with boundary conditions cannot be made free from their boundary constrains. See also Nodes and their boundary conditions.

To modify clamping on an existing sheet, open the sheet in T-SIM Grid view - click on the icon with the tool tip "Open grid (sheet)"

and in Windows File Open dialog, browse for the sheet file. Once the file is selected, click Open. A new window with the picture of the selected sheet appears.

Click on Grid (sheet) / Clamping. The following commands are accessible in the Clamping sub-menu:

Use the commands 1,2,3 or 4 to add a new clamping inside / outside an area selected.
Use the command 5 to specify the clamping area exactly. Rectangular, circular or elliptic clamping curve can be used. Nodes are fixed outside or inside the clamping curve.
Use the command 6 to remove the sheet clamping within an area selected.

Commands 1-4:
Select required command and click it. Then move the cursor into a required position and press and hold down the left mouse button. Move the cursor to the second corner of the rectangle / ellipse and release the mouse button. The clamping is immediately added inside / outside the area selected or removed inside the area selected (the operation performed depends on the selected command).

For the rectangular type, specify the clamping rectangle dimensions.
For the circular / elliptic type, specify the clamping curve center and the two radii - R1 and R2 (R1 = R2 for circular clamping curve).
Check Clamp inside to clamp nodes (triangle vertexes) inside the clamping curve. Leave Clamp inside unchecked to clamp nodes outside the clamping curve.
Click Add clamping to perform. Remark: This dialog is modeless. It means it is possible to use for example the Shift + RB info to get information about the grid (sheet) node coordinates etc.

Command 6:
Click on this command and click it. Then move the cursor into a required position and press and hold down the left mouse button. Move the cursor to the second corner of the rectangle / ellipse and release the mouse button. The clamping is immediately removed inside the area selected.

To remove boundary condition applied on nodes, open a sheet in T-SIM Grid view - click on the icon with the tool tip "Open grid (sheet)" and in Windows File Open dialog, browse for the sheet file. Once the file is selected, click Open. A new window with the picture of the selected sheet appears.

Click on Grid (sheet) / Boundaries / Remove boundaries. Then move the cursor into a required position and press and hold down the left mouse button. Move the cursor to the second corner of the rectangle and release the mouse button. The boundary conditions are immediately removed inside the area selected. Save the sheet to keep changes.

Remark: At this moment, it is not possible to add boundary condition to nodes (except Clamping and "No pressure" flag).

Any sheet node can have "No pressure" flag. This means that during simulation, pressure will not be applied on those elements where all three nodes have the "no pressure" flag.

To create a new "No pressure" area, click on Grid / No pressure areas / Create within rectangle. Then move the cursor into a required position and press and hold down the left mouse button. Move the cursor to the second corner of the rectangle and release the mouse button. The "no pressure" flag is immediately added inside the area selected.

To remove "No pressure" flag within an area, click on Grid / No pressure areas / Remove within rectangle. Then move the cursor into a required position and press and hold down the left mouse button. Move the cursor to the second corner of the rectangle and release the mouse button. The "no pressure" flag is immediately removed inside the area selected.

T-SIM Grid view is a window enabling to display and perform modifications of sheets (represented by T-SIM Grids). A sheet is displayed in T-SIM Grid view after creation or after opening:

and in Windows File Open dialog, browse for the sheet file. Once the file is selected, click Open. A new window with the picture of the selected sheet appears: