Researcher:
William P. Robbins, Electrical Engineering
Project Description:Acoustic emission sensors detect the
ultrasonic waves launched (often termed acoustic emission or AE
events) when cracks develop and grow in materials, particularly
those under high stress. Often a significant increase in AE event
rate is an indicator of mechanical failure of a part. AE sensors
are commercially available but are relatively large and expensive
and thus it is not practical to consider instrumenting critical
mechanical parts (such as engine and transmission components)
in planes and helicoptors with AE sensors. The goal of this project
was to develop a small and inexpensive AE sensor with an onboard
amplifier capable of driving a relatively long interconnection
cable so that such instrumentation becomes practical. Figure 1
shows the AE sensor developed in this project. The overall size
is approximately a 6 mm square footprint and about 5 mm thick.
The onboard IC chip includes a charge amplifier having a gain
of 10^(11) Volts per coulomb followed by 40 db of voltage gain.
The bandwidth of the amplifiers is 50 kHz to 1 MHz. An on-chip
voltage regulator allows the dc power needed by the onboard amplifiers
to be sent down the interconnection line.
Figure 1. AE sensor with protective cover removed.