本文根据有限子域热量平衡原理导出在有限单元法中求解平面不稳定温度场的三角形单元、矩形单元公式;求解空间不稳定温度场的轴对称三角形单元、四面体单元及六面体单元公式。对时间的导数均采用抛物线差分公式。按文中公式编制了程序,计算了例题。与精确结果比较表明,文中公式具有较好的精度。此法物理概念清楚,易为工程 Based on the principle of finite sub-field heat balance, a triangular cell and a rectangular cell formula for solving the unstable temperature field in the finite element method are derived. The formulas for solving the axisymmetric triangular, tetrahedral and hexahedron elements of the temperature field are given. The derivatives of time are parabolic differential equations. According to the formula in the paper prepared the program, calculated examples. Comparison with the exact results shows that the formula in the paper has better accuracy. This method is clear physical concept, easy for the project