Factor of Safety Calculator
Calculate the factor of safety by comparing material strength to applied stress or ultimate load to working load.
Factor of Safety
1.67
Factor of Safety vs Material Strength / Ultimate Load
Formula
## Factor of Safety (FoS) The factor of safety expresses how much stronger a system is than it needs to be. ### Formula **FoS = Strength / Applied Load** A FoS of 1.0 means the member is at its exact limit. Values above 1.0 provide a safety margin. Typical minimum factors: buildings 1.5-2.0, bridges 2.0-3.0, aircraft 1.25-1.5, pressure vessels 3.0-4.0.
Exemplo Resolvido
A steel member with 250 MPa yield strength under 150 MPa stress.
- 01FoS = 250 / 150 = 1.67
- 02Utilization = 150 / 250 = 60%
- 03The member has a 67% safety margin above the working load.
Perguntas Frequentes
What is an acceptable factor of safety?
It depends on the application, consequences of failure, and load uncertainty. Buildings typically require 1.5-2.0 on yield, bridges 2.0+, aircraft 1.25-1.5 (because weight is critical), and consumer products 3.0-4.0.
Should I use yield or ultimate strength?
Use yield strength when permanent deformation is the failure criterion (most structural work). Use ultimate strength when fracture is the concern. The required FoS differs for each basis.
What does utilization ratio mean?
Utilization ratio is the inverse of FoS expressed as a percentage. An 80% utilization means the member is loaded to 80% of its capacity, leaving 20% reserve.
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