13th International Conference on Fracture June 16–21, 2013, Beijing, China 3. For performing a life test on an actual turbine attachment under HLCCF loading, there are two key techniques including a high and low cycle nointerference loading method and a blade clamp for a full scale turbine blade. 1.Upper jointer for LCF loading 2.Upper load-transmission pin 3.Drawplate 4.Hold-down bolt 1 5.Blade clamp 6.Left load-transmission plate 7.Heating coil 8.Rolling bearing 1 9.Load-bearing bar 10.Right load-transmission plate 11.Part of actual turbine disc 12.Rolling bearing 2 13.Actual turbine blade 14.Hold-down bolt 2 15.HCF loading transmission plate 16.Vibration point 17.Lower jointer for LCF loading 18.Lower load-transmission pin 19.Electromagnetic vibrator Figure 3. A sketch of the HLCCF loading method The HLCCF loading method places the LCF load exerting point from load-transmission pin (see (2) in Figure 3) to the back of the mortise through the drawplate (see (3) in Figure 3), then transmitting the loading using a load-bearing bar (see (9) in Figure 3) and a pair of load-transmitting plates (see (6), (10) in Figure 3) to the bearing ear welded to the blade clamp (see (5) in Figure 3). Meanwhile, there is a pair of rolling bearing (see (12) in Figure 3) between the loading-transmission plates and the bearing ear so as to reduce the friction of vibration transmission. Thus the high cycle vibrating center point moves backward and lengthens the arm of the high cycle vibration. Another pair of rolling bearings (see (8) in Figure 3) is placed between the drawplate and the load-bearing bar to further reduce the friction of vibration transmission. Therefore, the vibrating force can be transmitted to the mortise teeth with no loss. A clamp to apply LCF loading on the full scale turbine blade (see (13) in Figure 3) to simulate the stress distribution of the fir-tree attachment is designed. The most distinctive characteristic of the clamp is that the load from the hydraulic-servo through the friction force between the clamp and the blade, which causes no damage to the blade. Two interior sides of the blade clamp are CNC(Computerized Numerical Control)-machined into complicated surface shapes just as contrary to the concave surface and convex surface of the turbine blade. The LCF loading is transferred to the turbine blade by means of friction force cause by the normal pressure of four hold-down bolts (see (4) in Figure 3). The full scale turbine blade is attached to a part of actual turbine disc (see (11) in Figure 3) cut from a full size disc. -3-
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