Investigation of crack sizing using ultrasonic phased arrays with signal processing techniques

Conventional ultrasonic array technology has limitations associated with detection and sizing of defects, particularly for difficult structures such as the carbon fibre composites and titanium composites used widely for construction of aircraft components.

This paper describes an investigation of data acquisition and signal processing techniques for crack sizing using electronically-scanned ultrasonic linear arrays. The data acquisition technique involves aperture number variance (that is, varying the number of active elements on the array) and the use of full raw data (FRD) capture. FRD capture accumulates the time domain responses from each transmitter-receiver pair manipulated on the array. With FRD capture, the raw data is collected from the array probe and reconstructed to produce a real-time image during the scan. However, the full data set is also stored and so beam steering and focusing become features of post-processing analysis.

Experimental results obtained from an ultrasonic array inspection of difficult materials with and without FRD capture are compared for detection capability and precision of simulated crack sizing. A detailed description of the distributed data acquisition system has been described previously.