Feasibility analysis for monitoring fatigue crack in hydraulic turbine blades using acoustic emission technique |
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Authors: | Xiang-hong Wang Chang-ming Zhu Han-ling Mao and Zhen-feng Huang |
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Affiliation: | (1) School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai, 200030, China;(2) Guangxi Radio and Television University, Nanning, 530004, China;(3) School of Mechanical Engineering, Guangxi University, Nanning, 530004, China |
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Abstract: | In order to investigate the feasibility of monitoring the fatigue cracks in turbine blades using acoustic emission (AE) technique,
the AE characteristics of fatigue crack growth were studied in the laboratory. And the characteristics were compared with
those of background noise received from a real hydraulic turbine unit. It is found that the AE parameters such as the energy
and duration can qualitatively describe the fatigue state of the blades. The correlations of crack propagation rates and acoustic
emission count rates vs stress intensity factor (SIF) range are also obtained. At the same time, for the specimens of 20SiMn
under the given testing conditions, it is noted that the rise time and duration of events emitted from the fatigue process
are lower than those from the background noise; amplitude range is 49–74 dB, which is lower than that of the noise (90–99
dB); frequency range of main energy of crack signals is higher than 60 kHz while that in the noise is lower than 55 kHz. Thus,
it is possible to extract the useful crack signals from the noise through appropriate signal processing methods and to represent
the crack status of blade materials by AE parameters. As a result, it is feasible to monitor the safety of runners using AE
technique.
Foundation item: Project(50465002) supported by the National Natural Science Foundation of China |
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Keywords: | fatigue crack acoustic emission hydraulic turbine blade |
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