ヘルツの接触応力
R ∗ = ( 1 R 1 + 1 R 2 ) − 1 , {\displaystyle R^{*}=\left({\frac {1}{R_{1}}}+{\frac {1}{R_{2}}}\right)^{-1},}
E ∗ = ( 1 − ν 1 2 E 1 + 1 − ν 2 2 E 2 ) − 1 . {\displaystyle E^{*}=\left({\frac {1-\nu _{1}^{2}}{E_{1}}}+{\frac {1-\nu _{2}^{2}}{E_{2}}}\right)^{-1}.}
また、最大接触圧力pmaxは、以下で表される:
p m a x = 3 2 π ( 4 3 E ∗ R ∗ ) 2 3 P 1 3 . {\displaystyle p_{\mathrm {max} }={\frac {3}{2\pi }}\left({\frac {4}{3}}{\frac {E^{*}}{R^{*}}}\right)^{\frac {2}{3}}P^{\frac {1}{3}}.}