... Zεxx=−z∂ 2 Z∂x 2 + 1 2 ∂Z∂x 2 +z 2 2∂ 2 Z∂x 2 2 +∂ 2 Z∂x∂y 2 εxy=−z∂ 2 Z∂x∂y+z 2 2∂ 2 Z∂x∂y∂ 2 Z∂x 2 +∂ 2 Z∂y 2 + 1 2 ∂Z∂x∂Z∂yεyy=−z∂ 2 Z∂y 2 + 1 2 ∂Z∂y 2 +z 2 2∂ 2 Z∂y 2 2 +∂ 2 Z∂x∂y 2 [6.89]In ... finitef (1, 1) = 783 Hz f (1 ,2) out -of- phase = 10 37 Hzf (1 ,2) in-phase = 11 72 Hz f (2, 2) = 14 44 HzFigure 5 .17 . First modes of a plate fixed at the four edges3 12 Structural elements6 .1. Kirchhoff–Love ... m 2 ) 2 ; αn,m= βn,mout -of- phase modes:fn,m=c2Ln 2 +m 2 2−8n 2 m 2 π 2 (n 2 − m 2 ) 2 ; αn,m=−βn,mFigure 5 .17 shows the mode shapes (1, 1) , (1, 2) and (2, 2) of a steel plate(though...