For austenitic and dissimilar metal welds, standard pulse-echo phased array probe assemblies will not provide the required inspection capability to achieve the desired results. Effective phased array inspection techniques for such welds are typically based on low-frequency (1.5 to 4 MHz) Dual Matrix Array (DMA) probes. These probes consist of separate transmitter and receiver probes fixed onto an exchangeable wedge assembly (see Figure 1) and are mostly used to generate longitudinal waves for better propagation through coarse-grain austenitic weld material and successive acoustic interfaces. The dual transmit/receive configuration offers better sensitivity and signal-to-noise ratio due to the “convolution” of transmitter and receiver beams and avoids “ghost echoes” caused by internal wedge reflections. In addition, 2D-matrix array technology allows for optimized focusing and optimized steering of the acoustic beam and for simultaneous variation of refracted angle and skew angle, to improve detection capability on mis-oriented flaws. Eddyfi Technologies develops and manufactures both standard and custom DMA probes at its facility in State College (PA).
Figure 1: Dual Matrix Array (DMA) probe assembly
Inspection quality and efficiency are driven not only by probe design but also by the performance of the instrumentation and the software. Enter Cypher, Eddyfi’s rugged and portable Phased Array Ultrasonic Testing (PAUT) platform engineered for high-speed inspections without compromising usability (see Figure 2). With its intuitive interface, embedded software, and onboard data recording, Cypher empowers operators to deploy and scan faster—even in demanding environments.
Figure 2: Cypher, compact phased array UT unit
At its core, Cypher is an ultrafast PAUT device capable of advanced Total Focusing Method (TFM), Time of Flight Diffraction (TOFD), Plane Wave Imaging (PWI), and beyond. Its imaging performance is engineered to detect and characterize the most challenging flaws, backed by signal purity that brings new confidence to every scan. Inspectors can trust the data, even in the most complex geometries and materials. In addition, the embedded signal quality isn’t just good; it’s uncompromising. Combined with massive on-board storage, seamless connectivity and hot-swappable batteries, Cypher is more than a tool: it’s an inspection platform.
Version 1.1 of Cypher OS unlocks the on-board support of PAUT and advanced focusing techniques for 2D-matrix and DMA probes, in addition to other new features. Figure 3 shows an example of the intuitive interface that allows the operator to easily implement all common wiring configurations for 2D-matrix arrays, and the parameters of the DMA wedge assembly. Like 1D-linear array probes, the software also includes visual feedback on the selected wiring configuration and the focal law generation, thus ensuring a fast and reliable setup process.
Figure 3: Cypher OS user-interface for DMA probe configuration
Plane Wave Imaging (PWI) is an advanced firing technique that uses a multi-element aperture for pulsing instead of firing each element individually, like Full Matrix Capture (FMC). Receiving is done individually with each element. The firing sequence typically consists of multiple focal laws, with varying angles. Just like for FMC firing, TFM imaging can be generated from the raw A-scan signals live during inspection. PWI data acquisition has several benefits when compared to FMC data recording. The emitted pulse from the full aperture has more energy and is more directional than a single-element excitation. It provides greater sensitivity and excellent signal-to-noise ratio at higher scanning speed because of a significantly shorter firing sequence.
The first case study is a 304 stainless steel V-bevel weld with a thickness of 1 inch, and we will look at inspection data from a 2.25 MHz DMA probe with a TRL wedge. A 5 mm deep toe-crack is insonified from the opposite surface. Figure 4 shows the scan plan for a multi-mode PWI-TFM inspection in Cypher OS (the position of the flaw has been added). For each of the wave modes, 13 pulses were fired.
Figure 4: Cypher OS scan plan for multi-mode PWI-TFM inspection
Figure 5 shows the data from the PWI-TFM scanning sequence in the region of the crack with 4 wave modes simultaneously. On the left side, we have the tandem LL-L and the direct L-L modes, and on the right side the direct T-T and the tandem TT-T modes. All modes clearly detect the crack at the far-surface, the SW modes as well as the LW modes, because the inspection was performed through base material. Accurate length and through-wall sizing can be performed using the direct L-L mode. With a scanning resolution of 1 mm, a scan speed of more than 60 mm/s can be achieved for this multi-mode examination, with an Amplitude Fidelity better than 0.3 dB for all TFM frames.
Figure 5: Cypher PC, examination data from multi-mode PWI-TFM inspection
Cypher is also capable of running FMC-TFM and FMC-PCI simultaneously. Figure 6 shows the images from an FMC scanning sequence in the same region with 4 direct wave modes simultaneously: on the left side, we have L-L modes with PCI and TFM, and on the right the T-T modes. With complete FMC firing sequences for 4 modes, a scan speed of roughly 25 mm/s can be achieved.
Figure 6: Cypher PC, examination data from multi-mode FMC-TFM and FMC-PCI inspection
The second case study in this paper is a specimen with a CRA dissimilar metal weld in 8-inch NPS carbon steel pipe with ID SS cladding. The wall thickness is about 1.2 inches. The weld contains machined circular notches at the OD and the ID. Figure 7 shows examination data in Cypher PC, obtained with a 4 MHz DMA probe. Standard PAUT was performed, using a sectorial sweep with longitudinal waves from 30 to 89 degrees and focusing on the weld center line. It can be observed that both the OD and the ID notches are clearly detected. For the ID notch on the weld center line, both the corner and the tip echoes are very well visible, which allows for accurate through-wall sizing. For this type of weld, it is adequate to use a higher frequency because most of the sound path goes through fine-grain carbon steel.
Figure 7: Cypher PC, examination data from CRA weld with 4 MHz DMA probe
In summary, advanced focusing techniques and innovative firing sequences such as PWI are redefining what’s possible in the inspection of austenitic welds—delivering faster, sharper, and more reliable results. By combining the right phased array probes with the powerful capabilities of Cypher 1.1, operators can achieve unmatched efficiency and precision in their inspections. Ready to elevate your weld inspection performance? Contact Eddyfi Technologies to learn how our experts and cutting-edge solutions can help you overcome your toughest inspection challenges.