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# Measuring Mechanical System Safety Factor With OnScale Solve

By Marshall Williams 06 December 2021

The Factor of Safety (FoS) or Safety Factor (SF) is a measure of how safe a mechanical system is. For mechanical design (stress-based), it is defined as the ratio: $SF&space;=&space;\frac{Material&space;\&space;Strength}{Maximum&space;\&space;Stress}$The material strength is extracted from the material where the maximum stress value is located. Note, the maximum stress must be determined under maximum loading conditions for a valid SF value.

### How to Calculate the Factor of Safety with OnScale Solve:

Simulation is a great tool to help engineers obtain a better understanding of how their designs will work under real life situations. In some cases, with the right material models, true to life deformations can be simulated for a better understanding of the failure mechanisms.

From an OnScale simulation, the maximum stress can be derived from either the Von Mises or one of the Principal stress outputs.

When the Safety Factor is calculated to be:

• Less than or equal to 1: Maximum stress is superior to the strength of the material, so the design will fail
• Greater than 1: Maximum stress is inferior to the strength of the material, the design is safe

For mechanical engineers to ensure the highest probability that a mechanical structure is safe and will not catastrophically fail, the safety factor will be designed to always be greater than 1. This is due to tolerances inherent in all aspects of a design (materials, dimensions etc.).

To create a design that has a larger safety factor, engineers may employ more durable materials or more complex geometries to strengthen a structure. Although designs with high SF (10+) is desirable, it may not be required for all applications. Engineers must strike the balance between a well engineered design that is cost-effective whilst maintaining the required SF fit for the target application or industry.

### How to Plot the Factor of Safety with Jupyter Notebooks:

With OnScale’s Jupyter notebook functionality, it is possible to calculate Safety Factor very easily and plot those results either as a bar graph or 2D surface plot for multi-parameter sweeps.

Output data arrays are stored in the VTK output files which can be accessed using the Pyvista python library.

For more information on using Jupyter Notebooks, check out our webinar here.

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