Initial Stress and Strain
You can add the Initial Stress and Strain subnode to the Linear Elastic Material, Layered Linear Elastic Material, or Section Stiffness material models in order to specify the stress or strain state in the structure before applying any constraint or load. The values given are not initial values in the mathematical sense but rather a contribution to the constitutive relation
When used with the Layered Linear Elastic Material, the contribution can be applied to arbitrary layers in a multilayered shell when the Composite Materials Module is available.
See also Layered and Nonlayered Shells.
In many cases Initial Stress and Strain and External Stress are interchangeable when prescribing stresses, but you can find some more options in the latter.
Shell Properties
This section is only present when this node is added under Layered Linear Elastic Material node. Select the layers in which initial stress and strain needs to be modeled.
Table 5-9: Layer Selections; Initial Stress and Strain
Selection
Use All Layers
Selection of Individual Layers
Boundary
Same as parent selection when the node is added.
When Use all layers is not selected.
Only a subset of the layers selected in the parent can be selected.
If the initial stress or strain differ between layers, you will need to add several Initial Stress and Strain nodes with different layer selections.
If the same layer is selected in two Initial Stress and Strain nodes being active on the same boundary, the contributions will be added.
For a general description of this section, see Layer and Interface Selections in the documentation for the Composite Materials Module.
Coordinate System Selection
Select a Local coordinate system defining the directions along which the initial stresses and strains are given.
As Subnode to Linear Elastic Material
The Shell local system is selected by default. This means that the orientations are the same as used for the material description.
If you select Projected from coordinate system, you can select any coordinate system present in the model. The Coordinate system list will then contain any coordinate system present in the model. The coordinate system given is projected onto the shell surface as described in Local Coordinate Systems.
As Subnode to Layered Linear Elastic Material or Section Stiffness
You can select any available boundary system.
Initial Stress
Specify the initial stress as the Initial in-plane force, the Initial moment, and the Initial out-of-plane shear force. Enter values or expressions in the applicable fields for the:
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Initial in-plane force N0
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Initial moment M0
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Initial out-of-plane shear force Q0
Initial Strain
Specify the initial strain as the Initial membrane strain, the Initial bending strain, and the Initial transverse shear strain. Enter values or expressions in the applicable fields for the:
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Initial membrane strain γ0
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Initial bending strain χ0
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Initial transverse shear strain ζ0
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For definitions of the generalized strains, see Theory for the Shell and Plate Interfaces.
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For details about initial stresses and strains, see Inelastic Strain Contributions and Initial Stresses and Strains.
Location in User Interface
Context Menus
Shell>Linear Elastic Material>Initial Stress and Strain
Shell>Layered Linear Elastic Material>Initial Stress and Strain
Shell>Section Stiffness>Initial Stress and Strain
Plate>Linear Elastic Material>Initial Stress and Strain
Plate>Section Stiffness>Initial Stress and Strain
Ribbon
Physics tab with Linear Elastic Material, Layered Linear Elastic Material, or Section Stiffness node selected in the model tree:
Attributes>Initial Stress and Strain