Interlaboratory comparisons of acoustic emission spectra

Effect of Crack Presence on In-Flight Airframe Noises in a Wing Attachment Component

“…2 shows the helium jet system calibration for this transducer attached to a CF-100 upper forward wing trunnion excited at the location of the crack by the helium jet. This calibration shows a substantial frequency dependence due to the effect of the component and the non-uniform but highly reproducible frequency-dependence of the helium jet (Acquaviva et al, 1980).…”

“…Amplitude and frequency calibration of the electronics was produced in terms of a sine wave inserted at the preamplifier input. Overall system calibration was accomplished using the helium jet (McBride andHutchison, 1976, 1978;Acquaviva et aI, 1980). The sensors used were the D9202A transducers developed by the Dunegan/Endevco Corporation for in-flight acoustic emission use in the Lockheed C-5A study (Bailey, 1976).…”

Neural network detection of fatigue crack growth in riveted joints using acoustic emission

“…The transducers used were supplied with calibration data from the manufacturer, which specifies the sensitivity in decibels (dB) relative to 1 volt per microbar. Moreover, the LOCAN-AT system was periodically calibrated to ensure that it responded accurately suggested a method for removing these variable effects This task was accomplished by applying an approach similar to that proposed by Sachse and Hsu for calibrating AE transducers [27] However, Carlyle produced a reference power spectrum corresponding to a specific sensor placement and source location and divided the spectrum into that caused by a real acoustic emission event This method improved the flexibility of the technology by providing the means for characterizing AE spectra from crack growth in different specimens As mentioned previously, this approach received much attention during the early 1980s when scientists around the world collaborated on efforts to test its versatility By using a helium gas jet to generate reference signals, they compared the average frequency spectra from crack growth in 7039 aluminum using different instrumentation, loading conditions, and specimen geometries The method was found to successfully remove variable effects and allow for true source characterization [12] In order to correct for the effects of sensor placement and specimen geometry in the riveted specimens tested, thirty pencil lead breaks were produced at the crack location…”

Acoustic emission: its techniques and applications

“…This produced a short rise-time output and was satisfactory, provided the same spark source was always used, but was not really adequate as a universal standard. A completely different approach was adopted by McBride [25] and well explored by an international exchange [26]. This used a jet of helium gas issuing from a closely defined nozzle under a predetermined pressure, as shown in Fig.…”