Factor of Safety

To use Factor of Safety:

1. Run a static study.

2. In the Simulation study tree, right-click the Results folder and select Define Factor Of Safety Plot .

-or-

Click the down arrow on Results (Simulation CommandManager) and select New Plot, Factor Of Safety.

The Factor of Safety PropertyManager appears.

3. In Step 1 of 3:

1. Select All, a component or a body in Component.

When you select All, the stress limit of each component is considered. Factor of Safety skips components for which no stress limit is defined. Such components are grayed out in Factor of Safety plots.

2. Select a failure criterion in Criterion :

• Maximum von Mises stress

• Maximum shear stress (Tresca)

• Mohr-Coulomb stress

• Maximum Normal stress

• Tsai-Hill Criterion (Available for composite shells only)

• Tsai-Wu Criterion (Available for composite shells only)

• Max Stress Criterion (Available for composite shells only)

• Automatic. Automatically 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.

The What does this mean area shows the mathematical statement of the criterion.

NOTE:  For composite shells, the Tsai-Hill failure criterion is applied when Automatic is selected.

3. Under Property:

• Select Include title text and type a custom title for the plot.

• Select Associate plot with name view orientation and select a predefined view orientation to associate with the active plot.

4. Click .

4. In Step 2 of 3:

• For the Max shear stress (Tresca), Max von Mises stress, and Max normal stress criteria:

1. Select stress Units.

2. Under Set stress limit to, select one of the following options:

• Yield strength. To set the limit stress to the yield strength of the material.

• Ultimate strength. To set the limit stress to the ultimate strength of the material.

• User defined. Type a value for the limit stress.

3. Under Multiplication factor, enter the factor to multiply the stress limit with. Default value is 1.0.

The Material involved box shows the material of the selected component and the associated yield and ultimate strengths.

The Max stress in the model box shows the maximum stress in the model.

• For the Mohr-Coulomb stress criterion only:

1. Select stress Units.

2. Under Set tensile stress limit, select one of the following options:

• Yield strength. To set the tensile stress limit to the yield strength of the material.

• Ultimate strength. To set the tensile stress limit to the ultimate strength of the material.

• User defined. Type a value for the tensile stress limit.

3. Under Multiplication factor, enter the factor to multiply the stress limit with. Default value is 1.0.

4. Under Set compressive stress limit, select one of the following options:

• Yield strength. To set the compressive stress limit to yield strength of the material.

5. Ultimate strength. To set the compressive stress limit to ultimate strength of the material.

• User defined. Type a value for the compressive stress limit.

5. Under Multiplication factor, enter the factor to multiply the stress limit with. Default value is 1.0.

The Material involved box shows the material of the selected components, and the associated yield and ultimate strengths.

The Max stress in the model box shows the maximum normal stresses (1st and 2nd principal) in the model.

6. Click .

• For Composite Options:

• Select Worst-case across all plies for an envelope plot of factor of safety (lowest value across top and bottom faces of all plies).

-or-

Select Ply numberand select Top or Bottom face for that ply number.

5. In Step 3 of 3, select:

• Factor of safety distribution. To plot the distribution of factor of safety.

• Areas below factor of safety. Enter a value for the factor of safety.

The Safety result box shows the minimum factor of safety based on the selected criterion.

6. Click .

NOTES:

• Areas of the FOS plot with values larger than 100 are shown with the color of the 100 value. If the maximum FOS value is less than 100, then the chart is scaled from the minimum to the maximum FOS value.

• If you select to plot Areas below factor of safety, the software displays regions of the model with factors of safety less than the specified value in red (unsafe regions) and regions with higher factors of safety in blue (safe regions).