研究目的
Demonstrating the use of a multichannel fiber laser sensor system for detecting and locating the source of acoustic emission in a thin aluminum panel during accelerated fatigue testing.
研究成果
The fiber laser sensor system matches the performance of an industry standard piezo-electric AE sensor in terms of signal-to-noise ratio and signal time of arrival. The system is shown to be an ideal candidate for wide area, long term AE detection for structural health monitoring applications.
研究不足
The MTS machine used for the experiment exhibited high levels of hydraulic noise and other mechanical vibrations, generating a high background noise level measured by the sensors, which forced the trigger levels to be set high. This could limit the detection of weaker AE signals.
1：Experimental Design and Method Selection:
The study involves the use of a serially multiplexed array of four fiber laser sensors and four piezo-electric sensors for detecting acoustic emission from a crack in an aluminum panel. A novel algorithm based on the cumulative distribution transform method with hyperbolic positioning is used for estimating the time difference of arrival of signals at each sensor.
2：Sample Selection and Data Sources:
The test coupon is a 6.4 mm thick aluminum plate with dimensions 20 × 61 cm2, including a pre-milled channel to control the location of initial cracking.
3：4 mm thick aluminum plate with dimensions 20 × 61 cm2, including a pre-milled channel to control the location of initial cracking.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment includes a fiber laser sensor array, piezo-electric sensors (Mistras S9225), a hydraulic uni-axial load test frame material testing system (MTS), and a National Instruments Flex-RIO multichannel digitizer.
4：Experimental Procedures and Operational Workflow:
The coupon is fatigued in a hydraulic uni-axial load test frame, with AE signals recorded from a crack initiated in the center of the panel. The location of the crack is determined using the time difference of arrival of signals at each sensor.
5：Data Analysis Methods:
The cumulative distribution transform method is used for estimating the time difference of arrival, and hyperbolic positioning is used for determining the crack location.
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