Based on the theory of generalized conforming element, two triangular membrane elements with rotational degree of freedom are developed by introducing internal parameters into its displacement field.

The other one is the triangular unit stress analyse ,a simple and convenient method t.

By using the method of limited unit , we build up the stiffness matrix of triangular unit of the light gauge sheet of variable thickness and produce the mathematic model for the computation of the stress and displacement at the center of the triangular unit.

The error estimation of quadratic Lagrange s interpolation and its interpolating function in triangular element;

A simple and effective triangular element with rotating degree of freedom;

A high-precision triangular element with rotational D. O. F.;

Methods Evaluate the conductivity of the nodes using the conductivity of the adjacent triangle elements.

Adopting the triangle elements to fill the design region,the difficulty to divide irregular design domain by rectangular elements is overcome.