thus showing that the expression (6) fulfills the stress-free boundary conditions. This approach is restricted to plates bounded by a convex polygon in order to obtain a physically reasonable solution. Instead of the normal form (5), any other convenient form Ak x + Bky + Ck = 0 of the edge equation may be used. An application of the above to airplane problems occurs in the determination of the in-plane thermal stress distribution in delta and tapered wings. As an example, a stress function for the delta wing shape in Fig. 2 is given below. The edge equations are