31-10-2012, 02:48 PM
EMBEDDED SYSTEMS
[attachment=37585]
ABSTRACT
The capability of embedded piezoelectric wafer-active sensors (PWAS) to perform in-situ nondestructive evaluation (NDE) is explored in this article, which includes animations of PWAS interactions with Lamb modes.
PWAS can satisfactorily perform Lamb wave transmission and reception, and crack detection in an aircraft panel with the pulse-echo method is illustrated.
PWAS-GENERATED LAMB WAVES
The basic principles of Lamb-wave generation and detection by PWAS probes were first verified in simple laboratory experiments. A 1.6-mm-thick, 2024-aluminum alloy rectangular plate (914 mm × 504 mm × 1.6 mm) was instrumented with 11 7-mm-square, 0.2-mm thick PWAS that were placed on a rectangular grid.
PULSE-ECHO WITH PWAS
Piezoelectric wafer-active sensor was used to demonstrate pulse-echo capabilities. Figure shows that the sensor signal has two distinct zones:
The initial bang, during which the PWAS acts as transmitter, and
The echoes zone, containing wave packs reflected by the plate boundaries and sent back to PWAS. These echoes were processed to evaluate the pulse-echo capabilities of the method
Conclusion
Embedded NDE piezoelectric wafer active s can be structurally embedded as both individual probes and phased arrays. They can be placed even inside closed cavities during fabrication/overhaul (such as wing structures), and then be left in place for the life of the structure. The embedded NDE concept opens new horizons for performing in-situ damage detection and structural health monitoring of a multitude of thin-wall structures such as aircraft, missiles, pressure vessels, etc.
[attachment=37585]
ABSTRACT
The capability of embedded piezoelectric wafer-active sensors (PWAS) to perform in-situ nondestructive evaluation (NDE) is explored in this article, which includes animations of PWAS interactions with Lamb modes.
PWAS can satisfactorily perform Lamb wave transmission and reception, and crack detection in an aircraft panel with the pulse-echo method is illustrated.
PWAS-GENERATED LAMB WAVES
The basic principles of Lamb-wave generation and detection by PWAS probes were first verified in simple laboratory experiments. A 1.6-mm-thick, 2024-aluminum alloy rectangular plate (914 mm × 504 mm × 1.6 mm) was instrumented with 11 7-mm-square, 0.2-mm thick PWAS that were placed on a rectangular grid.
PULSE-ECHO WITH PWAS
Piezoelectric wafer-active sensor was used to demonstrate pulse-echo capabilities. Figure shows that the sensor signal has two distinct zones:
The initial bang, during which the PWAS acts as transmitter, and
The echoes zone, containing wave packs reflected by the plate boundaries and sent back to PWAS. These echoes were processed to evaluate the pulse-echo capabilities of the method
Conclusion
Embedded NDE piezoelectric wafer active s can be structurally embedded as both individual probes and phased arrays. They can be placed even inside closed cavities during fabrication/overhaul (such as wing structures), and then be left in place for the life of the structure. The embedded NDE concept opens new horizons for performing in-situ damage detection and structural health monitoring of a multitude of thin-wall structures such as aircraft, missiles, pressure vessels, etc.