Effect of Different Fitting Functions on Evaluation Results of Ductile Brittle Transition Temperature of Gas Turbine Disk

In order to study the effect of different fitting functions on the evaluation results of ductile brittle transition temperature of gas turbine disk, the charpy impact tests of gas turbine disk were carried out at different temperatures, the linear interpolation, Boltzmann function and hyperbolic tangent function were used to fit the impact absorbed energy and brittle fracture ratio, the special proportion fracture morphology transition temperatures F_{ATT SEPC} and the special absorbed energy transition temperatures E_{TT AV} were calculated, and the calculated results were compared and analyzed. The results show that for steel materials, both the transition temperature of fracture morphology and impact absorbed energy, the fitting results using hyperbolic tangent function and Boltzmann function by setting reasonable boundary value can be almost consistent. However, the physical meaning of hyperbolic tangent function is more clear, and it has more advantages in fitting some asymmetric transformation curves. Linear interpolation fitting can only roughly estimate whether the transformation temperature is qualified or not. When it is close to the required value, it can not be used to determine whether it is qualified or not. It also needs to use Boltzmann function or hyperbolic tangent function for accurate fitting.