Initial Stress and Strain
You can add the Initial Stress and Strain subnode to the Linear Elastic Material, 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.
Initial stresses and strains can be included with Linear Elastic Material, Linear Elastic Material, Layered, and Nonlinear Elastic Material. For Linear Elastic Material, Layered, the contribution can be applied to arbitrary layers in a multilayered membrane when the Composite Materials Module is available
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 present only when the Initial Stress and Strain node is used under Linear Elastic Material, Layered.
Select the layer or layers for which this stress or strain contribution is to be added.
Table 7-9: 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.
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For a general description of layer and interface selections, see The Shell Properties and Interface Selection Sections.
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You can describe stress or strain values with a through-thickness variation by explicitly or implicitly using expressions containing the extra dimension coordinate as described in Using the Extra Dimension Coordinates.
Coordinate System Selection
The given initial stresses and strains are interpreted in this system.
For details about how local coordinate systems are used in the Membrane interface, see Local Coordinate Systems.
Initial Stress and Strain
Specify the initial stress as the Initial local in-plane force N0 and the initial strain as the Initial local in-plane strain ε0 (dimensionless). In addition, you can also provide the Initial out-of-plane strain εn0.
If you know the stress, rather than the force per unit length, type in the stress multiplied by the membrane thickness mbrn.d. In a geometrically nonlinear analysis, the stresses should be interpreted as Second Piola–Kirchhoff stresses, and the strains should be interpreted as Green–Lagrange strains.
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For details about initial stresses and strains, see Inelastic Strain Contributions and Initial Stresses and Strains.
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For details about the different strain measures, see Deformation Measures.
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For details about the different stress measures, see Defining Stress.
Prestressed Micromirror: Application Library path MEMS_Module/Actuators/micromirror
Location in User Interface
Context Menus
Membrane>Linear Elastic Material>Initial Stress and Strain
Membrane>Linear Elastic Material, Layered>Initial Stress and Strain
Membrane>Nonlinear Elastic Material>Initial Stress and Strain
Ribbon
Physics tab with Linear Elastic Material, Linear Elastic Material, Layered, or Nonlinear Elastic Material node selected in the model tree:
Attributes>Initial Stress and Strain