Factor of Safety Wizard

The Factor of Safety Wizard allows you to assess the safety of your design based on a failure criterion.

After your run a static study, you can calculate the factor of safety of your model.

To access the Factor of Safety Wizard, do one of the following:
  • After you run a static study, right-click Results and click Define Factor of Safety Plot.
  • Click the down arrow on Results Advisor (Simulation CommandManager) and click New Plot > Factor of Safety .

Step 1 of 3

  All Selects all bodies to plot the factor of safety.
  Selected bodies Select a single or multiple bodies from the menu to plot the factor of safety.
Criterion Select one of the following failure criterion:

Maximum von Mises stress

Maximum shear stress (Tresca)

Mohr-Coulomb stress

Maximum Normal stress

Automatic

 

Composite Options (Available for models with composite shells only)

Tsai-Hill Criterion

Tsai-Wu Criterion

Maximum Stress Criterion

When you select Automatic, the software selects the most appropriate failure criterion across all element types. The software applies the following conditions:
  • The default Failure Criterion assigned in the Material dialog box for each material.
  • If you have not assigned a default failure criterion in the Material dialog box, the software assigns the Mohr-Coulomb stress criterion.
  • If you selected Max von Mises or Max shear (Tresca) criterion for a beam material, the software uses the yield strength as allowable stress.
  • If you selected Max normal or Mohr-Coulomb criterion for a beam material, the software uses the tensile strength as the allowable stress.
  • For composite shells, the Tsai-Hill failure criterion is applied when Automatic is selected.
  • Failure indices for the composite shells failure criteria (Tsai-Hill, Tsai-Wu, and Maximum Stress) are calculated from nodal stresses.
  • For beams, the factor of safety is calculated from: Upper bound axial and bending stress / Yield Strength.
  • For assemblies, the factor of safety is calculated from the unaveraged values of stress components. Clear option Average results across boundary for parts in the Stress Plot PropertyManager to view the maximum values of the selected stress components that are included in the FOS calculations.
  What does this mean Displays the mathematical relation that described the selected failure criterion.

Advanced Options

  Display symmetric results

Available for models with symmetry restraints or cyclic symmetry.

Select to view the FOS values for the whole model. The results are mirrored about the planes of symmetry for models where you analyze half, a quarter, or one-eighth of the actual geometry.

For cyclic symmetry, results are repeated cyclically about the defined axis of revolution.
  Set upper limit for Factor of Safety Select to set the upper limit for the factor of safety plot.

In the FOS legend, enter the value.

Property

  Include title text Enter a custom title for the plot.
  Associate plot with name view orientation Associates a predefined view orientation with the active plot.
Next Goes to the next step.

Step 2 of 3

Units Sets the stress units.
  Set stress limit

to Yield strength

Sets the stress limit to yield strength.

to Ultimate strength

Sets the stress limit to ultimate strength.

to User defined

Sets the stress limit to a user-specified value.

If you selected Mohr-Coulomb stress criterion from the previous step, you must set the tensile and compressive stress limits.
  Multiplication factor Allows you to enter a multiplication factor for calculating the selected stress limit. For example, if you apply a factor of 0.5 to a yield strength stress limit of 2000 psi, Factor of Safety Wizard uses 0.5 x 2000 = 1000 psi for the stress limit.
Beam Results  
  Show combined stress on Beams For beams, the factor of safety is calculated from: (Upper bound axial and bending stress) / Yield Strength.
Shell Results Select the shell face for which you want to perform the Factor of Safety:

Top

Bottom

Minimum

Maximum

Run two checks: one for the top face, and the other for the bottom face.
  Material involved Displays the material names and properties related to the stress limits used by Factor of Safety.
  Composite Options (Available for models with composite shells only.)

Worst-case across all plies

Envelope plot for minimum FOS across all plies (including top and bottom faces of every ply).

Ply number

Allows you to select the ply number for the factor of safety output. This option is not available when Worst-case across all plies is selected. You can select the top or bottom face for the selected ply number.
Prev Returns to the previous step.
Next Goes to the next step.

Step 3 of 3

  Factor of safety distribution Plots the distribution of the factor of safety.
  Areas below factor of safety Plots the regions below the specified factor of safety (displayed in red color). Regions above the specified factor of safety are displayed in blue color.
  Safety result Lists the minimum factor of safety based on the selected criterion.
Prev Returns to the previous step.