ثابت الالتواء: الفرق بين النسختين

<math>J \approx \frac{\pi a^3 b^3}{a^2 + b^2}</math><ref name="Roark7Roark72">Roark's Formulas for stress & Strain, 7th Edition, Warren C. Young & Richard G. Budynas</ref><ref name="Irjens">Continuum Mechanics, Fridtjov Irjens, Springer 2008, p238, ISBN 978-3-540-74297-5</ref>

<math>J \approx a b^3 \left ( \frac{1}{3}-0.21 \frac{b}{a} \left ( 1- \frac{b^4}{12a^4} \right ) \right )</math><ref name="Roark72">Roark's Formulas for stress & Strain, 7th Edition, Warren C. Young & Richard G. Budynas</ref>