MENTAL MODEL · M5657

Poisson's Ratio

TechnicalHigh supportEngineering

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Version 1.0.0 · Updated 2026-07-30

CORE DEFINITION

The degree to which a material contracts laterally when stretched. Most materials become thinner when elongated (positive Poisson's ratio). But some special materials (auxetic materials) become wider when stretched (negative Poisson's ratio).

SCAFFOLDING EFFECT

psychology

Reduce cognitive load

Counterintuitive expansion. Ordinary people (positive Poisson's ratio) tend to narrow their perspective and become conservative under pressure (tension); but those with 'negative Poisson's ratio' traits (antifragile individuals) use pressure as an opportunity to broaden their perspective, increase connections, and become more expansive.

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The ratio of transverse strain to axial strain when a material is axially stretched (ν). Most materials have ν > 0 (elongation leads to thinning); negative Poisson's ratio (auxetic) materials expand laterally when stretched, due to special microstructures that expand transversely under tension. It reflects the coupled response of a material to tension in different directions.

MINIMUM ACTION

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Practice this model in one real situation:

Use Poisson's ratio in material selection/design to predict deformation coupling (e.g., seals, cushions require low or negative Poisson's ratio)
by analogy, for individuals: under pressure, do you 'contract and become conservative' (positive) or 'expand antifragilely' (negative)? You can design yourself accordingly.

Check to track your progress (stored locally)

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Source support: Explicit

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zh.wikipedia.orghttps://zh.wikipedia.org/wiki/%E6%B3%8A%E6%9D%BE%E6%AF%94ZH · Explicit
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