Abstract: In order to determine the thermal conductivities of LY2 Al alloy during welding, an inverse method is conducted by combination of numerical simulation and temperature mea- surements. After the thermal conductivities are linearized in the different temperature regions, initial thermal conductivity values gotten from handbook and extrapolation are substitu-ted into a finite element model (FEM) to simulate the welding temperature field during the whole welding process. On the other hand, the temperature field is measured by several thermal couples and the errors between simulation and exper- iment are computed. The thermal conductivity values are varied, the temperature field is simulated, and the genetic algorithm is adopted to choose the thermal conductivity values, with which the error between the simulation and the experimental results reaches its minimum. These thermal conductivity values show that the different lag with different rate of temperature change. A model is built to analyze the relation among the thermal conductivity, temperature, and the rate of temperature change.

Key words: Inversion, Numerical simulation, Thermal conductivity, Welding, Self-centering fixture, Shaping processing, Space symmetry degree, Symmetry degree detection device, Symmetry error compensation, Deep hole keyway