Enabling bolt forces or displacements in subcases (Simcenter Samcef)

In a Simcenter Samcef nonlinear analysis, forces or displacements in a bolt can be enabled or disabled at the subcase level.

The following example illustrates how you can enable different force values in different subcases for the same Bolt Preload definition. The solution is a Nonlinear Analysis that contains three subcases.

Example workflow in Simcenter 3D

1. With the first subcase active, create a new Bolt Preload with a Force value set to 100 N (1).

2. In the Load Container container, right-click on that bolt preload and clone it.

3. (Optional) Rename that copy (2).

4. Activate the third subcase and drag the new bolt from the Load Container onto that subcase.Now, the first subcase contains the original bolt load (3), and the third subcase contains a modified clone of it (4).The second subcase has no bolt definition (5).

5. Edit the cloned bolt and change the Force value from 100 N to 200 N.

Example output in the Simcenter Samcef input file

Both bolt loads have the same parent. So, one single .BOLT command is issued in the Simcenter Samcef input file:

.BOLT I 1001 ... GROUPE ....  LOAD 100 200

Both bolt load values appear after the LOAD parameter.

In the .SUBCASE command in the input file:

.SUB I 1PRELOAD 1001...I 2...I 3PRELOAD 1001

we can see that:

• The bolt 1001 is referenced for the first time in the first subcase with the PRELOAD parameter: the first load value of 100 N of the bolt definition is activated at that subcase.

• The bolt 1001 is referenced for the second time in the third subcase with the same PRELOAD parameter: the second load value of 200 N of the bolt definition is activated at that subcase.

Grouping bolt definitions

The bolt definitions in different subcases are grouped in a single .BOLT command in the input file if they share all of the following:

• The same Type.

• The same Elements Selection.

• The same properties: Stiffness (KR), Method, and Sensor Position.

But the way the bolts are loaded (Force versus Displacement) may vary from one subcase to another.

For instance, you can create a bolt with a force in the first subcase, clone it to the second subcase, and set a displacement value for that cloned bolt. The input file will contain:

.BOLT I 123 ... LOAD 100 DEPL 0.45....SUBCASEI 1PRELOAD 123I 2PRDISP 123

Note:

The PRELOAD parameter is related to the load values (LOAD) of the bolt, while the PRDISP parameter is related to the displacement values (DEPL) of the bolt.

This reinforces that cloning is the recommended way to create bolts for which you want to vary force and displacement values from one subcase to another.

Subcases with no force or displacement defined for a bolt

When a bolt does not appear in a subcase, the relative displacement of the bolt is fixed in this subcase and the stress in the bolt can vary if external loads or preloads in other bolts are modified.

Limitations

• The same Bolt Preload cannot be defined twice in the same subcase with two different values for the Force (or Displacement) property.

• On the same support, you cannot define two Bolt Preload loads that have different properties (stiffness, method, and so on).

• In a Static linear analysis, you define the Bolt Preload at the solution level. The same force or displacement value is used in all the loadcases.

For more information, see the LOAD and DEPL parameter of the Samcef .BOLT command and the PRELOAD and PRDISP parameters of the Samcef .SUBCASE command.

Look up more details

Bolt Preload dialog box (Simcenter Samcef)

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Enabling bolt forces or displacements in subcases (Simcenter Samcef), Simcenter 3D 2021.1 Series

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