Acoustic Emission Sensor Calibration for Absolute Source Measurements

Abstract

This paper describes sensor calibration and signal analysis techniques applicable to the method of acoustic emission (AE) and ultrasonic testing. They are particularly useful for obtaining absolute measurements of AE wave amplitude and shape, which can be used to constrain the physics and mechanics of the AE source. We illustrate how to perform calibration tests on a thick plate and how to implement two different mechanical calibration sources: ball impact and glass capillary fracture. In this way, the instrument response function can be estimated from theory, without the need for a reference transducer. We demonstrate the methodology by comparing calibration results for four different piezoelectric acoustic emission sensors: Physical Acoustics (PAC) PAC R15, PAC NANO30, DigitalWave B1025, and the Glaser-type conical sensor. From the results of these tests, sensor aperture effects are quantified and the accuracy of calibration source models is verified. Finally, this paper describes how the effects of the sensor can be modeled using an autoregressive-moving average (ARMA) model, and how this technique can be used to effectively remove sensor-induced distortion so that a displacement time history can be retrieved from recorded signals.

Challenges and Limitations in the Identification of Acoustic Emission Signature of Damage Mechanisms in Composites Materials

“…The determination of the sensitivity requires three transducers alternatively working as transmitters and receivers. The reception wave sensitivity is measured on a steel block [39][40][41] for Rayleigh waves. The results presented in this paper are obtained with a set of µ80 sensors.…”

Absolute Measurement of Elastic Waves Excited by Hertzian Contacts in Boundary Restricted Systems

“…McLaskey's and Glaser's [15] method was used for calibration of the AE transducer. As a calibration system a steel plate (Toolox40) with dimensions of 1 Â 0:5 Â; 0:051 m was used.…”

“…However, absolute measurement would therefore be required so that the relation between the signal and the wave source could be ascertained. Both McLaskey and Glaser [15] and Jacobs and Woolsey [10] have presented methods for absolute calibration of piezoelectric transducers. However, there are no evaluations of the validity of the methods which are independent of the system.…”

Finite Element Modelling of Cracks as Acoustic Emission Sources

“…Here the detection process using piezoelectric sensors can have significant impact on the bandwidth of the detected signals and their relative frequency content. While some analytical approaches consider the sensors transfer function explicitly [16,21], some attempts have also been made to model the response of piezoelectric sensors themselves [22]. We recently proposed a finite element approach to directly include the piezoelectric sensor in a modeling environment to also account for the interplay between the sensor and the material it is attached on [23].…”