2 lecture 4 - Failure Predictors and Safety Factors - slide

Pressure vessels 35 to 40 australian standard as 1210

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Unformatted text preview: ailure mode to another. Mechanical Design Factors of Safety Design factor of safety, Fd versus 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 failure occurs. 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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