Characteristics: 1) The dimension of length and breadth is far larger than that of thickness 2) The force along the plate face for suffering is the face force in parallel with plate face, and along the thickness even, the volumetric force is in parallel with plate force and doesnt change along the thickness, and has no external force function on the surface front and back of the flat par Attention: Plane stress problemo, =0,but 8#0, this is contrary to plane strain problem 77 x y Characteristics： 1) The dimension of length and breadth is far larger than that of thickness. 2) The force along the plate face for suffering is the face force in parallel with plate face,and along the thickness even,the volumetric force is in parallel with plate force and doesn’t change along the thickness, and has no external force function on the surface front and back of the flat panel. Attention: Plane stress problem   z  0 z =0,but ,this is contrary to plane strain problem