Unformatted text preview: ailure mode to another. Mechanical Design Factors of Safety
Design factor of safety, Fd
Actual factor of safety, Fa
The “actual factor of safety”, Fa is usually unknown to the
designer, unless a component is tested to destruction or a
Fa of a component = “the load (stress) that causes failure”
“the applied load (stress)”
Fd is the designer’s estimate of what
the factor of safety should be. Mechanical Design Some typical design factors of safety, Fd
Structural components: 2.0
Fd for buildings is relatively low because the loads are well understood and
many structural elements offer redundancy. Pressure vessels: 3.5 to 4.0
Australian Standard AS 1210-1997 Pressure vessels Automobiles: ~3.0
Aircraft and spacecraft: ~1.4 to 3.0
Ductile, metallic materials use lower values.
Brittle materials use higher values.
The field of aerospace engineering uses generally lower design factor of
safety because the costs associated with structural weight are high. A low
design factor of safety in aerospace parts and materials corresponds to...
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