The deflection field of the element is expressed with a polynomial of area coordinates which is corresponding to a polynomial of 4th order in Cartesian coordinates ?(x,y)?.

• 单元的挠度场以面积坐标多项式表示，对应于直角坐标x，y的完全三次式和部分四次式，因而单元是完备的广义协调的板单元。