Factor of Safety 

FOSFactor of Safety is the ratio of the maximum load that a structural or mechanical component can tolerate and the actual working load that will be applied. The FOS can be calculated from these two loads or it may be specified by a code or standard. Components that are designed in accordance with a particular design code, such as the American Society of Mechanical Engineers (ASME) standards, have to meet a minimum FOS value specified by the code. It is important to understand how the FOS has been derived and its applicability. Factors that affect the FOS include the material properties, the manner of loading, the possible misuse of the component and the environment.

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