Analysis of phased array transmitters and beamformers.

An adaptive dynamic focusing system used for the ultrasonic nondestructive testing of pipeline girth welds is developed. This system relies on ultrasonic linear phased array transducers connected to a multichannel acquisition system, which provides delay and amplitude laws, allowing one to control the ultrasonic beams dynamically. We introduce a testing method for welds and the system’s structure. Optimization of array transducers has also been pursued based on a mathematical model of the acoustic field for a linear phased array. The experimental results have proved that the phased array transducers system has the same capability to detect as a conventional ultrasonic transducers system, but the components of the system can be simplified greatly, and the testing flexibility and the testing speed can be improved greatly. It provides an excellent basis for further research and development of defect inspection of pipeline girth welds.

The relationship between the bandwidth and sensitivity of ultrasonic transducers (UT) is characterized by a mutually restrictive nature. Consequently, the collaborative enhancement of the acoustic response of the UT is essential for achieving high-quality ultrasound imaging. This study explores the synergistic improvement of the acoustic response in phased array UTs through the implementation of alternating current (AC) poling and the incorporation of an acoustic reflection (AR) layer. Simulation results indicate that the -6 dB bandwidth of the phased array, when utilizing co-optimized structures, exhibits varying degrees of enhancement compared to alternative designs. Furthermore, the increase in echo amplitude associated with the co-optimized structure is significantly greater than the cumulative echo amplitude derived from individual optimization structures, suggesting a substantial acoustic coupling enhancement effect between the two design frameworks. Empirical test results confirm that phased arrays featuring the co-optimized structure achieve a larger -6 dB bandwidth, with improvements reaching up to 89.3% compared to direct current (DC) poling phased arrays. Additionally, the relative sensitivity of the co-optimized phased arrays is 8.39 dB greater than that of the DC poling phased arrays, surpassing the sensitivity observed in the superposition of the single optimized structures, thereby validating the theoretical predictions established in prior simulations. Thus, the coupling optimization effect of the two design structures effectively mitigates performance degradation associated with individual design approaches, enhances the acoustic properties, and ultimately contributes to the advancement of ultrasonic imaging quality.

Previous work has led to the design, simulation, and development of a linear phased array transducer. The intention of the array is to be used as a non-destructive ultrasonic device to monitor and evaluate the health of a given specimen. The phased array has been manufactured and tested for the detection and characterization of defects on a target. The array was fabricated with a four-row stepped design with four wires to transfer data and one wire for grounding. The stepped design allows for the interrogation of a larger region using time delays and beam sweeping without the use of additional electrical channels. The array was designed to be utilized in a water immersion environment with about one inch between the array and the target specimen. An OmniScan MX system was used to operate the phased array and perform real-time linear and sectorial scans on a set of rectangular plates. S-scans allow for beam sweeping over an angle range as well as adjustments for time delays and a true-depth display. The array was operated with sixteen active elements and an angle range of 0 to 30 degrees. The phased array was tested with a variety of targets and was used to investigate and characterize different types of defects such as cracking, warping, and corrosion. The ability of the phased array to distinguish between defect types as well as resolve defect size was evaluated.

Development of a 20-MHz wide-bandwidth PMN-PT single crystal phased-array ultrasound transducer

The purpose of the present investigation was to develop a method for the three-dimensional reconstruction of the surface of the tongue using serial ultrasonic images gathered during the production of the sustained fricative /s/. Using a phased linear array ultrasonic monitoring system, transducer position, subject position, and ultrasonic scan data were recorded simultaneously on composite video for off-line analysis. Reconstruction of a series of ultrasound images was completed using a microcomputer programmed to transform the ultrasonic image contours into three-dimensional space. Additional transformations converting the three-dimensional tongue contours into two dimensions for screen plotting were also developed. Results are discussed in light of previously reported models of the tongue surface.

Ultrasonic phased array transducers can be used to extend traditional time-of-flight diffraction (TOFD) crack sizing, resulting in more quantitative information about the crack being obtained. Traditional TOFD yields a single length parameter, while the equivalent flaw time-of-flight diffraction crack sizing method (EFTOFD) described here uses data from multiple look-angles to fit an equivalent degenerate ellipsoid to the crack. The size and orientation of the equivalent flaw can be used to estimate the actual crack size.

Phased array approach to generate guided waves and extract phase velocities using the V(z) method.

In order to detect the longitudinal cracks on the outside surface of a hollow components, a novel pattern of ultrasonic phased array transducers is designed. The shape of the transducer surface is rectangular and is distributed on the outside surface of a column, with the longer side parallel to the central axis of the column. Meanwhile the transducers are rotated with a certain angle about the longer side of the transducer surface. According to the structure of the transducers, this novel array is named as serrated columnar array. In this paper, a serrated columnar array is placed in the center of the hollow axle. Because of the rotated angle, the surface of each transducer is oblique relative to the surface of the inner surface of the hollow component, the transducers are expected to generate transverse waves in the inspection component. A delayed law calculation method, based on Snell' law, for focus beam forming through the curved interface is described. Two transient acoustic finite element models, one with crack and the other without crack, are established by using the COMSOL software to verify the performance of this array design, one with crack and the other one without crack. With the designed focus delayed laws, transverse waves can be generated and focused at the crack position. By applying the focus laws to the reception channels, and sum up the echo signals, the signal retrieved from the model with a longitudinal crack is stronger than that from the model without cracks. The results show that this special array pattern is potential to serve as an ultrasonic non-destructive tool to detect the longitudinal cracks on the outside surface of hollow components.

Damage localization in aluminum plate with compact rectangular phased piezoelectric transducer array

Monitoring of an ascending air bubble in a viscous fluid/fiber matrix medium using a phased array transducer

We present the Terragraph Sounder platform, developed to promote and enable research in mmWave propagation, systems, and networks, and is actively employed in research studies in over 13 institutions. Recent advancements to the platform include a suite of tools for performing interference measurements and developing interference mitigation techniques through phased-array-based beamforming. The tool provides 6-bits of phase control for 36 individual antenna elements (azimuth plane), allowing users to synthesize custom beam patterns. Researchers can deploy multiple 802.11ad links and quantify the cross-leakage interference as a function of TX/RX beam configurations, measure degradation in SINR due to interference, study co-existence between mmWave links in the same frequency, and assess signal quality as a function of beam pattern design. Four software packages were developed that can run on the same hardware, enabling a wide array of research activities, ranging from RF propagation and modeling, phased array beamforming, protocol optimization, and mesh network routing research.

A series of ultrasonic elements arranged in a phased array transducer can provide the capability to activate each element separately but in a programmed sequence. This will help the acoustic signal to be generated at desired focusing distances and anticipated angles for specific materials and structures. In case of composite material inspection, this characteristic of the phased array method can improve the undesirable effects of the high attenuation and anisotropic structure of composite materials on response signals. In this study different phased array probes and wedges which are commercially available were evaluated for their response signals’ characteristics. First, the capability and resolution of bulk wave generation were studied for each set of probe and wedge, and the response signals were compared to that of the conventional single element ultrasonic transducers for different thicknesses composite plates. Then the resolution of the response signals and their sensitivity to defect size were evaluated and compared to the single element transducers as well. Next, each phased array probe and wedge set was used to generate plate waves in aluminum plates based on plate wave propagation theory, probe and wedge physical properties and the definition of delay law. Results show a general improvement in response signals’ strength and resolution for phased array method in comparison to the single element transducers. Also some plate wave modes could be generated with optimized signal generation parameters in phased array system.

Ultrasonic testing of metal welds has been in use for many years. Scanning methods using both contact and immersion methods are often used at the time of manufacture and also during periodic in-service inspection programs. But because of a variety of component configurations and potential flaw geometries it is often necessary to perform several inspections, each with a different probe configuration to assure adequate defect delegability. It is possible that a properly designed phased array probe can perform several different inspections without changing hardware thereby reducing inspection times. This presentation reviews the design and operation of ultrasonic phased array transducers and the necessary features to achieve the desired performance. Situations in which these probes have already been implemented effectively are also discussed.

The unique features of annular phased array transducers, such as ring-shaped elements and the concentric configuration, cause them to behave differently from commonly used linear array transducers, in terms of sound field distribution and pulse–echo response. Consequently, standard techniques for assessing linear array transducers can introduce significant errors when applied to annular array transducers, especially concerning element-to-element sensitivity variance. This study investigates the consistency of element sensitivity in annular phased array transducers. Through theoretical analysis, a Long-Belt source assumption model was developed based on the Rayleigh integral to characterize the responses of ring-shaped elements in an analytical and explicit form. The model suggests that the response amplitude is linearly correlated with the radial width of the element, which was validated by subsequent numerical simulations. Based on these findings, a modified sensitivity evaluation algorithm for annular array transducers is presented. The response voltage per unit width, rather than the total response voltage, is used to eliminate the influence of varying geometries and sizes across elements. The sensitivity variation of a 32-element annular array transducer was evaluated using the new algorithm. Compared to the uncorrected measurement, the maximum sensitivity variation was reduced significantly from 25 dB to 6 dB, revealing the transducer’s intrinsic consistency despite the different geometric features of each element. Due to its distinct geometry compared to the ring-shaped elements, the central element cannot be corrected or evaluated using this method. These results suggest that the proposed algorithm enables the more accurate evaluation of sensitivity consistency for annular phased array transducers, thereby improving measurement reliability in practical applications.

The data acquisition speed of point scanning microscopy techniques at sub-cellular resolution limits imaging of large samples, as sample stability and focus drift are becoming an issue. Therefore, light sheet fluorescent microscopy (LSFM) has become the method of choice for imaging cleared samples. However, this method still suffers from a trade-off between imaging depth and resolution, due to diffraction of the illuminating beam limiting the achievable field of view. After improvement of the latter with non-diffracting Bessel beams, lattice light sheet microscopy has substantially reduced the illumination point-spread-function (PSF). Here, we propose further improvement by generation of structured light sheets via phased arrays implemented as silicon nitride photonic integrated circuits (PICs). Beam generation with PICs results in much higher power efficiency than beam forming with conventional liquid crystal based spatial phase modulators, as it does not require the use of narrow blocking apertures. Moreover, this approach enables increased control over the generated field profile. Modeling of concrete PIC concepts indicates that sub-cellular resolution with mm scale imaging depths can be concomitantly achieved. Maintaining a small PSF along the axis perpendicular to the direction of light propagation is sacrificed in order to maintain it over increased imaging depth along the beam propagation axis. Rapid lateral scanning of the illumination beam inside the plane of the light sheet is then obtained by scanning of the laser wavelength within the excitation spectrum of the target fluorescent protein, allowing for a wide bidirectional field-of-view with high resolution.