In the general behavioral analyses of plate characteristics, fundamental assumptions of the linear,elastic, and small-deflection theory of bending of plates may be stated as follows:
the material of the plate is elastic, homogeneous, and isotropic,
the plate is initially flat,
the defection, (the normal component of the displacement vector ) of the mid plane issmall, compare with the thickness of the plate. The slope of the deflected surface is verysmall and the square of the slope is a negligible quantity in comparison with unity.
The straight lines, initially normal to the middle plane before bending remain straight andnormal to the middle surface during the deformation