Comparative Study On The Calibration Of Piezoelectric Acoustic Emission Sensors With Speed Method And Reciprocity Method

Piezoelectric acoustic emission sensor is mainly used in the field of non-destructive testing.Sensitivity of the sensor is a key factor in acoustic emission detection.Calibration of the acoustic emission sensor is a prerequisite for the acoustic emission quantitative detection technique.Speed and reciprocity methods are two common methods,and there is little discussion on the consistency of the two methods in the reported literature.There are some differences in the results of the two methods.The unified acoustic emission measurement standard and traceable calibration method have not been fully established.The lack of consistency is a major obstacle to the convergence of different approaches and different technical standards.It undoubtedly limits the application of acoustic emission quantitative technology in key safety components.The comparison of calibration methods of piezoelectric acoustic emission sensor will promote the application of acoustic emission quantitative technology in safety components such as pressure vessel and aircraft.Speed and reciprocity methods are based on two different physical principles.The consistencywill also help to improve the Lamb problem analysis under the vertical point source and the reciprocity theory of piezoelectric sensor.In this paper,speed and reciprocity methods for piezoelectric acoustic emission sensor calibration were compared.The main work includes the following parts:(1)Optimizations and analyses of calibration systems for piezoelectric acoustic emission sensor.The optimizations of speed method mainly include the automatic calibration system,different selection of excitation transducer for different frequency,and time interception based on the speed signal,that is,the time window shift to remove the reflection signal of transmission process.The analyses of the systems include the influence of windowing and low frequency sensors.(2)Comparative study on calibration of piezoelectric acoustic emission sensors by speed and reciprocity methods.First,the equivalent reciprocity coefficient was obtained by the displacement calculated based on the Lamb problem.The comparison results showed in a consistent trend.The equivalent reciprocity coefficient of the measured value was calculated,because the parameters of the propagation medium are not easily determined.The normal velocity was measured by laser vibrometer,and the pulse force was evaluated by equivalent process.The calculations of real and equivalent reciprocity coefficients prove the consistency between the two methods.And the consistency is verified by the comparative analysis of the experimental results.