13th International Conference on Fracture June 16–21, 2013, Beijing, China An electromagnetic vibrator (see (19) in Figure 3) is used to exert the sinusoidal vibration force through HCF loading-transmission plate (see (15) in Figure 3) to the blade clamp, and last to the fir-tree attachment. Through measuring the vibration amplitude on the vibrating point (see (16) in Figure 3) using a BSZ605 vibrating amplitude measure apparatus, the dynamic stress on the turbine attachment can be well controlled. 2.2. Tests and results 2.2.1. Test conditions HLCCF tests on actual turbine attachment were conducted using a 140KN hydraulic-servo system Ferris Wheel to simulate the centrifugal force of the blade during operation and an electromagnetic vibrator SIMOVERT MM220/3 produced by Siemens company to act the vibration force. Using high frequency induction local heating, the temperature of the experimental turbine attachment can be controlled about 500˚C±5˚C, measured by an electric thermocouple. In this study, a uniform temperature distribution near the turbine attachment was simulated. The load spectrum is shown in Figure 4, with the centrifugal force 100KN, vibration frequency 23.8Hz and vibration amplitude 3.5mm, and duration time 98s at the peak load. Then crack growth tests on five turbine components with pre-cracked size of 0.5×0.5mm in the second teeth (see Figure 5) were conducted under HLCCF loading at elevated temperature. All the tests were not stopped until the turbine components fractured. Figure 4. Load spectrum of HLCCF tests Figure 5. Pre-crack at the second tooth of the turbine disc 2.2.2. Results and discussions -4-
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