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Welds are currently only inspected after all the passes are complete and after allowing sufficient time for any hydrogen cracking to develop, typically over several days. Any defects introduced between passes are therefore unreported until fully buried, greatly complicating rework and also delaying early corrections to the weld process parameters. In-process inspection can provide early intervention but involves many challenges, including operation at high temperatures with significant gradients affecting acoustic velocities and, hence, beam directions. Reflections from the incomplete parts of the weld would also be flagged as lack-of-fusion defects, requiring the region of interest (ROI) to adapt as the weld is built up. The collaborative SIMPLE (SIngle Manufacturing PLatform Environment) project addresses these challenges by incorporating robotic inspection within a robotic tungsten inert gas (TIG) welding cell. This has been accomplished initially with commercial off-the-shelf ultrasonic phased arrays, but is flexible enough to adapt to future developments with solutions suitable for higher temperatures. The welding and inspection robots operate autonomously. The former can introduce deliberate defects to validate the latter, which uses 5 MHz 64-element phased arrays on high-temperature wedges to generate sector scans after each weld pass. The results are presented, confirming that the challenges have been addressed and demonstrating the feasibility of this approach. [ABSTRACT FROM AUTHOR]

Data acquisition using full matrix capture (FMC) and image reconstruction by the total focusing method (TFM) offers many benefits over conventional ultrasonic array beamforming techniques. These include dynamic focus on both transmit and receive for enhanced resolution and the ability to alter the focus and steer angle without re-scanning. However, the technique has remained in the laboratory because of the costs associated with acquiring many channels in parallel and the absence of a real-time reconstruction capability. This paper describes a solution to these constraints. The paper reviews the issues limiting the current implementations and describes how they were overcome by using flexible and scalable PC-based hardware modules. This new architecture already achieves acquisition and processing at 20 Hz and higher, meeting the requirements for interactive scanning and so enabling these techniques to transfer from the laboratory into the field. Results from the first phase of a continuing investigation are presented. New application approaches, where these techniques offer particular benefits over conventional techniques, are discussed. [ABSTRACT FROM AUTHOR]

Advanced non-destructive techniques integrate ultrasonic arrays with array controllers that perform full waveform capture (FWC). FWC is the term used to describe the acquisition of RF waveforms corresponding to specific transmit-receive beams from an array. With FWC, the full waveform is available for post-processing. However, FWC only allows rectification and gating during data acquisition and post-processing. If the correct information is not acquired the first time, inspection cost and time may be compromised. FRD (full raw data) collection works similarly to FWC, acquiring the time-domain responses from the excited phased array transmit-receive combinations. However, the transmit and receive apertures for FRD are much smaller than for FWC – typically one element each – and there are many receive locations for each transmit location. The main advantages of FRD collection are the facility for real-time imaging and to optimise features such as beam steering, aperture shading and focusing during the post-processing stage. Compounding, a technique previously used for biomedical applications, has the potential to be applied as a novel technique in NDT. Incoherent compounding is a signal processing technique that involves recombination of echoes from different propagation paths. Incoherent compounding only considers the amplitude information from received signals. Therefore, the interpretation of received signals is simplified. A favourable application of this technique is crack sizing. Coherent processing, in which the amplitude and phase of received signals are considered, would be beneficial when enhanced resolution is necessary. Both techniques would be applicable to multi-layered structures commonly found within the aerospace industry. Experimentally, using a B-scan, incoherent compounding can be demonstrated by mirroring the direct image onto the reflected image. This paper will discuss incoherent compounding using a linear phased array probe with FRD capture as an innovative post-processing method. Furthermore, the results confirm the sizing and location of a combination of side-drilled holes that mimic defects. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ultrasonic C-scanning is widely used for large-area flaw detection but acquiring the full RF waveform for each surface point – Full Waveform Capture (FWC) – offers many advantages. A system that used phased arrays to achieve this without loss of area coverage rate has been reported(1). FWC allows many signal processing operations, previously only possible at acquisition, to be performed off-line. Multiple or time-consuming algorithms can be performed on the same data set without compromising inspection speed but some, such as steering and focusing, must still be performed at acquisition. Although ultrasonic arrays are now widely accepted in imaging systems, their full capability will only be realised when viewed as distributed data collection devices(2). The modular array hardware of DSL’s ‘FlawInspecta’ can now achieve this at real-time rates, significantly extending the post-processing operations that can be performed. These include steering and focusing adjustments, data-dependent adaptive focusing, and multi-array data collection and processing. A flexible data formatting has been devised to provide an interface for end-users to develop customised algorithms. The paper reports on the distributed data acquisition architecture and the data storage format. Specific post processing operations are covered elsewhere(3) but some typical options will be outlined. [ABSTRACT FROM AUTHOR]