Feasibility analysis for monitoring fatigue crack in hydraulic turbine blades using acoustic emission technique  

作　　者：王向红 朱昌明 毛汉领 黄振峰 

机构地区：[1]School of Mechanical Engineering,Shanghai Jiaotong University [2]Guangxi Radio and Television University [3]School of Mechanical Engineering,Guangxi University

出　　处：《Journal of Central South University》2009年第3期444-450,共7页中南大学学报（英文版）

基　　金：Project(50465002) supported by the National Natural Science Foundation of China

摘　　要：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.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.

关 键 词：FATIGUE CRACK acoustic emission hydraulic turbine BLADE 

分 类 号：O346.2[理学—固体力学] TH49[理学—力学]