By introducing Lagrange multiplier,the assumed deformation functions,which were expressed in Fourier series,can satisfy the essential but not necessarily the natural boundary conditions when the potential energy of system takes the stationary value.

• 该方法通过引入拉格朗日乘子,使系统总势能取驻值的同时,形函数能满足一系列基本的,但非完备的边界条件;