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Round-robin evaluation of various acoustic emission (AE) sensors, systems, and brands were made using four calibration rods. The intent of the evaluation was to determine the suitability of using plastic rods as in situ system calibration check devices. The rods were made of clear acrylic, and were provided with milled flats by which to mount each sensor under test.
Data from five participants in the round robin evaluation shows that among the variables of rod number (4), sensor frequency (2), sensor brand (2), and AE system (5), the largest difference of peak amplitude AE signal was due to sensor frequency, with a coefficient of variation (COV) of 0.26. Differences in sensor resonant frequency are expected to result in large differences in signal characteristics. The remaining variables are ranked by decreasing magnitude of effect: sensor brand (0.11), AE system (0.10), and rod number (0.05). The COV's shown above are based on average signal peak amplitude from at least five lead break events from a 30 in. (76 cm) distance for each sensor-rod combination.
The paper includes data summaries and a discussion of sources which may have led to the observed variations. A conclusion is drawn indicating that the plastic rods are acceptable in situ system check devices. However, serious concern exists due to variations between AE systems and sensor brands. These variations may complicate the use of numerical standards or guidelines for AE test acceptance criteria.
acoustic emission, sensors, calibration
Senior Materials Engineer, Bonneville Power Administration Division of Laboratories, Vancouver, WA