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13.4: Safety Factors

  • Page ID
    142484

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    14.4 Safety Factors as Ethical Design

    \[ SF = \frac{\text{Allowable value}}{\text{Actual value}} \nonumber \]

    Designing at SF = 1.0 assumes perfect material, perfect modeling, perfect loading, and zero variability. None of those assumptions are physically realistic. A safety factor is an honest acknowledgment that our models and materials are imperfect, and that the people who rely on engineered systems deserve a margin that accounts for what we do not know.

    Reducing a safety factor to save cost is therefore not just a technical decision — it is an ethical one. It transfers the risk of uncertainty onto the public without their knowledge or consent.

    ✓ Mini Case Study 14.1 — Circuit Overload

    A 330 Ω resistor dissipating 0.26 W with a 0.25 W rating. Options: (A) Approve — difference is small. (B) Replace with 0.5 W. (C) Lower voltage. (D) Ignore — usage is short.

    Ethical analysis: The rating is exceeded. Whether the excess is "small" depends on unstated assumptions about temperature, tolerance, and usage duration — precisely the kind of hidden assumptions that belong in a memo's Background section, not in a silent approval decision.

    Professional action: Option B or C. Engineering ethics is often about small decisions made consistently, not dramatic confrontations.

    ✓ Mini Case Study 14.2 — Structural Margin Reduction

    A project is behind schedule. An engineer is asked to reduce SF from 2.0 to 1.2 to cut material cost.

    Ethical analysis: The original SF = 2.0 covered material variability, load estimation uncertainty, model simplification, and fatigue. Reducing to SF = 1.2 eliminates most of that margin without addressing any of the underlying uncertainties. The engineer has no obligation to approve this change — and has an obligation to document the request and the specific uncertainties the original SF covered. If the reduction is escalated over the engineer's objection, that objection should be recorded in writing.


    This page titled 13.4: Safety Factors was last modified on Thu, 24 Sep 2026 17:38:43 GMT and is shared under a CC BY-NC license and was authored, remixed, and/or curated by .

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