Safety
Use the Safety subnode to set up variables which can be used to check the risk of failure according to various criteria. It can be used in combination with Linear Elastic Material, Layered Linear Elastic Material, and Nonlinear Elastic Material. Four different variables describing the failure risk are defined, as described in Table 7-10.
You can add any number of Safety nodes to a single material model. The contents of this feature do not affect the analysis results as such, so you can add Safety nodes after having performed an analysis, and just do an Update Solution in order to access to the new variables for result evaluation.
Table 7-10: Variables for Safety Factor Evaluation
Variable
Description
Criterion Fulfilled
Criterion violated
Failure index, FI
For a linear criterion, this is the ratio between the computed value and the given limit.
FI<1
FI>1
Damage index, DI
A binary value, indicating whether failure is predicted or not. DI is based on the value of FI.
DI=0
DI=1
Safety factor, SF
For a linear criterion, this is 1/FI.
SF>1
SF<1
Margin of safety, MoS
SF-1
MoS>0
MoS<0
For orthotropic and anisotropic failure criteria, the directions are given by the coordinate system selection in the parent node.
Shell Properties
This section is only present when this node is added under Layered Linear Elastic Material node.
Select the layer or layers for which the safety factor variables are to be defined.
Table 7-11: Layer Selections; Safety
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.
Each Safety subnode defines its own set of variables, so there is no interaction if you add several such nodes with the same selection.
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All other settings for the Safety node are described in the documentation for Safety in the Solid Mechanics interface.
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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 parameters for the allowable 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.
Location in User Interface
Context Menus
Membrane>Linear Elastic Material>Variables>Safety
Shell>Layered Linear Elastic Material>Variables>Safety
Shell>Nonlinear Elastic Material>Variables>Safety
Ribbon
Physics tab with Linear Elastic Material, Layered Linear Elastic Material, or Nonlinear Elastic Material, node selected in the model builder tree:
Attributes>Variables>Safety