Differential stress

Differential stress is the difference between the greatest and the least compressive stress experienced by an object. For both the geological and civil engineering convention ${\displaystyle \sigma _{1}}$ is the greatest compressive stress and ${\displaystyle \sigma _{3}}$ is the weakest,

${\displaystyle \!\sigma _{D}=\sigma _{1}-\sigma _{3}}$.

In other engineering fields and in physics, ${\displaystyle \sigma _{3}}$ is the greatest compressive stress and ${\displaystyle \sigma _{1}}$ is the weakest, so

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