... 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 ... 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 ... ax 2 + by 2 [6.81] 29 8 Structural elementsIn the particular case of a square plate, they are immediately obtained as:in-phase modes:fn,m=c2Ln 2 +m 2 2+8n 2 m 2 π 2 (n 2 − m 2 ) 2 ;...