External Stress
You can add the External Stress subnode to the Linear Elastic Material, Layered Linear Elastic Material, Layered Hyperelastic Material, or Section Stiffness material models 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.
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 present when this node is added under Layered Linear Elastic Material or Layered Hyperelastic Material node.
Select the layers in which external stress is 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.
Coordinate System Selection
Select a Local coordinate system defining the directions along which the components of the input data are given.
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.
Layered Linear Elastic Material, Layered Hyperelastic Material, or Section Stiffness
You can select any available boundary system.
External Stress
Select a Stress inputStress tensor or Section forces. This selection is not available when the parent node is Section Stiffness, in which case only the section force type of input is possible.
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.
Choose a Contribution typeAdd to stress tensor or Load contribution only to determine the effect of the contribution.
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 typeAdd to stress tensor or Load contribution only to determine the effect of the contribution.
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.
Location in User Interface
Context Menus
Ribbon
Physics tab with Linear Elastic Material, Layered Linear Elastic Material, Layered Hyperelastic Material, or Section Stiffness node selected in the model tree: