Isothermal Blade Forging Experiment Report

3. Experimental Study

3.1. Experimental setup

In order to carry out the isothermal blade forging process to study the dimensional and geometrical errors during the forging process, there is a need to precisely control the deformation rate and the temperature during the forging process; so, a 6 MN hydraulic press was equipped with a servo-hydraulic power-pack and a PLC control system. An electrical furnace, isolated form the press bed by cooling water plates, was used to heat the dies. The dies were fabricated from a nickel-base superalloy to withstand the isothermal-forging stresses. Both of the preform and dies were held enough in the furnace to remove the temperature gradient inside them.

3.2. Experimental tests

To conduct the isothermal

3). The workpiece was considered as rigid-viscoplastic and elastic-plastic during the forming and cooling processes, respectively. The flow curves were determined by isothermal compression test and presented in [26]. The friction factor was determined as a function of temperature and deformation rate by the isothermal ring compression tests [27] and implemented in the model. The simulation parameters were chosen as the experimental ones. To simulate the isothermal forging process, the temperature of the workpiece, dies and environment were set to the selected process temperature at the start of the

Twist and Bow

The initial temperature, deformation rate and non-uniform deformation affect the temperature distribution inside the forged blade at the end of the forging process. The leading and trailing edges undergo more deformation and more adiabatic temperature rise (Fig. 7). Increasing the deformation rate results in a higher adiabatic temperature rise. Moreover, lower initial temperature leads to more flow stress and more adiabatic temperature rise. The temperature distribution coupled with the varying thickness of the airfoil profile results in the non-uniform cooling of the blade and consequently deviation of the airfoil. Because of small thickness in leading and trailing edges, they cool faster than the central portion of the airfoil that increases their strength. The contraction of the central area results in the warpage of the airfoil and twist and/or bow formation.

The resulted response surfaces as a function of temperature and velocity for twist and bow are presented in Fig. 8 and Fig. 9, respectively. The results show that increasing the initial temperature and decreasing the velocity results to more twist; but the velocity effect on the bow formation is not considerable.

5.3. Tilt and