Factor of safety

Factor of safety, also known as Safety Factor, is a multiplier applied to the calculated maximum force to which a component will be subjected. Typically, for components whose failure could result in substantial financial loss, or serious injury or death, a safety factor of at least four (4) is used. Non-critical components generally have a safety factor of two (2). Safety factors are needed to account for imperfections in materials, flaws in assembly, material degradation, and unexpected stresses.

Example

In construction engineering the tensional stress σ is defined as σ = F / A where F is the force acting on the element and A is the cross sectional area. From laboratory testing it is known what the actual failure tensile stress σ_max of materials is. To find the minimum safe cross section of an element, the force acting on the element is multiplied with the safety factor γ, (its magnitude depending on building codes and regulations). The minimum cross section is then found using A_min = F x γ / σ_max

See also

• structural engineering
• strength of materials