Probability of detection (POD) is a basic tool used to comprehensively characterize the damage detection capability of non-destructive testing (NDT) techniques. Recently, the concept of POD has also received great interest in SHM research and applications. In addition to providing an evaluation of the damage detection capability of a SHM system, the POD value at the minimum detectable damage size (i.e., a “critical damage size” ldmg, which may, for example, characterize the diameter of a damage in a composite structure, or in the case of metal structures, the length of a crack damage therein) is also a valuable parameter in transducer network layout design. Therefore, determination of the POD of a SHM system is of great importance.
Many traditional NDT techniques, such as eddy current testing, demonstrate the nature of single point measurement. That is, for each measurement, the sensor measures only the structural condition within a localized or relatively small area. In such cases, POD curves can be generated by creating real damages of different sizes. However, such traditional testing approaches may be impractical for a SHM sensor network if a large structure area is monitored, since it may not be possible or practical to create and measure damages of different sizes at a large number of locations over a large area.
To overcome the above difficulty, a computational POD curve generation method has been proposed by Shawn and Chang (U.S. Prov. Pat. App. Ser. No. 60/912,112) based on simulated damages characterized by varying size radius at distributed locations on a structure. However, such purely computational methods may not be capable of performing detailed analysis based on actual waveform signal structure. A method is therefore developed in the present invention that creates the damage detection POD curve for the entire network of transducers of a SHM system over a large area structure by synthesizing PODs based on actual signal waveforms obtained from actual test data of individual actuator-sensor paths defined by associated actuator-sensor transducer pairs.
USPTO Backgrounds
USPTO Backgrounds