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In many cases External Stress and Initial Stress and Strain are interchangeable when prescribing stresses. In Initial Stress and Strain, the given stress is however always added to the stress tensor, whereas the option to use the stress as only a load contribution exists only in External Stress.
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When Use all layers is not selected.
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For a general description of this section, see Layer and Interface Selections in the documentation for the Composite Materials Module.
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When Stress tensor is selected, you enter the external stress in the form of Second Piola-Kirchhoff stress tensors. The Membrane part of external stress, Bending part of external stress, and Shear part of external stress lists all behave the same way: Depending on the type, they will contain all membrane (bending, shear) stress tensors announced by any physics interface, and also the entry User defined. When User defined is selected, you can enter the data for the membrane (bending, shear) part of the External stress tensor σext,m (σext,b, σext,s) as Isotropic, Diagonal, or Symmetric depending on the properties of the tensor. The tensor components are interpreted in the selected coordinate system. If a stress tensor announced by a physics interface is selected, the coordinate system setting is ignored — the orientation is handled internally.
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When In-plane force is selected, you enter the external stress in the form of section forces. Specify the external stress as values or expressions for the In-plane force Next, the Moment Mext, and the Out-of-plane shear force Qext. Choose a Contribution type — Add to stress tensor or Load contribution only to determine the effect of the contribution.
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Selecting a stress tensor announced by the same physics interface as where the External Stress node is added, will result in an error (‘Circular variable dependency detected’). This operation would imply that the computed stress depends on itself.
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