STABILITY OF VARIABLY THICK ORTHOTROPIC ANNULAR PLATES

The static and dynamic stability of variably thick orthotropic annular plates subjected to in-plane periodic forces with respect to time is studied. It is assumed that the periodic radial forces with the same p eriod act along both the inner and outer edges of plate. The finite el ement method is used with a sector element based on the Mindlin plate theory. The wave propagation technique of cyclic symmetry is used in t he formulation. The choice of the element enables the analyst to solve the axi-symmetric and asymmetric dynamic stability problem at the sam e time. Variations in the plate thickness in which it increases or dec reases in the radial direction according to the equations h = h(max)(r /r(o))+lambda or h = h(max)(r/r(i))-lambda, respectively are considere d. The instability regions for different boundary conditions are deter mined by Bolotin's method. It is found that the critical buckling load , buckling mode and instability regions are changed by variations in t he polar orthotropic material properties.