External Stress
You can add the External Stress subnode in order to specify an additional stress contribution which is not part of the constitutive relation. The external stress can be added to the total stress tensor, or act only as an extra load contribution.
External stresses can be added to Linear Elastic Material, Layered Linear Elastic Material, Nonlinear Elastic Material, and Hyperelastic Material. For the Layered Linear Elastic Material, the contribution can be applied to arbitrary layers in a multilayered membrane when the Composite Materials Module is available.
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.
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.
When Use all layers is not selected.
If the external stress input type differs between layers, you will need to add several External Stress nodes with different layer selections.
If the same layer is selected in two External Stress 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.
External Stress
Select a Stress inputStress tensor (Material), Stress tensor (Spatial), or In-plane force.
When Stress tensor (Material) is selected, you enter the external stress in the form of a Second Piola-Kirchhoff stress tensor. The External stress tensor list will contain all 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 External stress tensor Sext 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. Choose a Contribution typeAdd to stress tensor, Load contribution only, or Residual stress to determine the effect of the contribution. Stress tensor components which are not in the plane of the membrane will be ignored.
When Stress tensor (Spatial) is selected, you enter the external stress in the form of Cauchy stress tensor. The components are interpreted in the selected coordinate system. Depending on the properties of the tensor, you can enter the data for the External stress tensor σext as Isotropic, Diagonal, or Symmetric. Choose a Contribution typeAdd to stress tensor, Load contribution only, or Residual stress to determine the effect of the contribution. Stress tensor components which are not in the plane of the membrane will be ignored.
When In-plane force is selected, you enter the external stress in the form of section forces. Specify the initial stress as values or expressions for the In-plane force Next, which has components in the plane of the membrane, along the directions given by the selected local coordinate system. Choose a Contribution typeAdd to stress tensor, Load contribution only, or Residual stress to determine the effect of the contribution.
Since all stress tensor representations coincide in a geometrically linear analysis, Stress tensor (Spatial) is needed only in the case of a geometrically nonlinear analysis. The stress tensor is entered using a Cauchy stress tensor representation, and is internally transformed to a Second-Piola stress tensor.
Location in User Interface
Context Menus
Ribbon
Physics tab with Linear Elastic Material, Layered Linear Elastic Material, Nonlinear Elastic Material, or Hyperelastic Material node selected in the model tree: