Model an initial imperfection

Suppose that you want to model a 500 mm long hollow shaft that is bowed by 1 mm, but is of perfect form otherwise. To do so, mesh the shaft with shell elements as if the bow does not exist and then use the Initial Imperfection command to account for the bow as follows:

1. Mesh the shaft and define the shell properties and materials for the mesh.

2. In the Simulation Navigator, right-click the Fields node→New Field→Formula.

3. In the Formula Field dialog box, in the Domain group, from the Independent lists, select Most Used as the domain type and Z Axis as the domain.

4. From the Dependent lists, select 3-D as the domain type and Length as the domain.

5. From the Type (Spatial Map) list, select Global.In the Expression group, length_1 represents the offset in the X-direction, length_2 represents the offset in the Y-direction, and length_3 represents the offset in the Z-direction.

6. Click length_1, in the box type 1[mm]*sin(pi()*z/500[mm]), and click Accept Edit .Note: The formula assumes that the axis of the shaft is aligned with the +Z-axis, the bow in the shaft lies in the XZ-plane, and one end of the shaft lies at the origin of the global coordinate system.

7. Click length_2, in the box type 0, and click Accept Edit .

8. Click length_3, in the box type 0, and click Accept Edit .

9. In the Initial Imperfection dialog box, in the Model Objects group, select the shell mesh of the shaft or the cylindrical polygon face of the shaft.

10. In the Components group, click Select Existing Field from List .

11. In the Fields dialog box, select the formula field you just created and click OK.

12. In the Initial Imperfection dialog box, click OK.

13. As necessary, create the other loads, constraints, and modeling objects for the model.

14. Solve the model.

How do I

Graph load factor vs. displacement

Learn more

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Modeling initial imperfections

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Model an initial imperfection, Simcenter 3D 2021.1 Series

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