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The use of Probability of Detection (POD) for NDT performances demonstration is a key link in products lifecycle management. The POD approach is to apply the given NDT procedure on a series of known flaws to estimate the probability to detect with respect to the flaw size. A POD is relevant if and only if NDT operations are carried out within the range of variability authorized by the procedure. Such experimental campaigns require collection of large enough datasets to cover the range of variability with sufficient occurrences to build a reliable POD statistics, leading to expensive costs to get POD curves. In the last decade research activities have been led in the USA with the MAPOD group and later in Europe with the SISTAE and PICASSO projects based on the idea to use models and simulation tools to feed POD estimations. This paper proposes an example of application of POD using simulation on the inspection procedure of a complex -full 3D- geometry part using phased arrays ultrasonic testing. It illustrates the methodology and the associated tools developed in the CIVA software. The paper finally provides elements of further progress in the domain. [ABSTRACT FROM AUTHOR]

TFM (Total Focusing Method) is an advanced post-processing imaging algorithm of ultrasonic array data that shows great potential in defect detection and characterization. This technique can be performed using several propagation modes (direct or over skip imaging) and several types of waves (longitudinal or transverse) allowing the imaging of extended defects of complex geometry. However, non physical indications can be observed, leading to misinterpretation. These imaging artifacts are due to the coexistence of several contributions involving several mode of propagation and interactions with possible defects and / or the geometry of the part. In several configurations, a simple time of flight criterion is not sufficient for their identification. This paper presents tools based on the forward CIVA UT models which allow to analyze and to filter these artifacts, without any tuning parameters. The performances achieved are compared to those of conventional TFM on simulated and experimental data. [ABSTRACT FROM AUTHOR]

When imaging with ultrasonic phased arrays, what do we actually image? What quantitative information is contained in the image? Ad-hoc delay-and-sum methods such as the synthetic aperture focusing technique (SAFT) and the total focusing method (TFM) fail to answer these questions. We have shown that a new quantitative approach allows the formation of flaw images by explicitly inverting the Thompson-Gray measurement model. To examine the above questions, we have set up a software simulation test bed that considers a 2-D scalar scattering problem of a cylindrical inclusion with the method of separation of variables. It is shown that in SAFT types of imaging the only part of the flaw properly imaged is the front surface specular response of the flaw. Other responses (back surface reflections, creeping waves, etc.) are improperly imaged and form artifacts in the image. In the case of TFM-like imaging the quantity being properly imaged is an angular integration of the front surface reflectivity. The other, improperly imaged responses are also averaged, leading to a reduction in some of the artifacts present. Our results have strong implications for flaw sizing and flaw characterization with delay-and-sum images. [ABSTRACT FROM AUTHOR]

The targets of therapeutic ultrasound are often located behind strongly scattering objects and layered tissue. These inhomogeneities can degrade the intended foci and misdirect acoustic energy causing unwanted hot spots or failure to meet the therapeutic endpoint at the target. We have previously shown the capabilities of dual-mode ultrasound arrays (DMUAs) in imaging strongly scattering objects in the path of the HIFU beam and, consequently, refocusing the beam to optimize the power deposition at the target while minimizing direct exposure to the obstacles. This capability may be a key to successful transthoracic targeting of abdominal tumors. We have experimentally verified the efficacy of this approach in improving the quality of the therapeutic focus and minimizing collateral damage to critical tissue structures in the path of the HIFU beam. In order to study the phenomena associated with transthoracic focusing more thoroughly, we have developed a finite-difference time-domain simulation capable of characterizing the transient propagation of the therapeutic beam through inhomogeneous, attenuating media. This simulation is shown to provide the necessary information for aberration correction of deep seated foci as well as control over the acoustic field at select points. In addition, the FDTD simulation allows for computation of the temperature rise throughout the therapeutic region as governed by the transient bioheat transfer equation. We have validated the predictive abilities of our simulation with hydrophone measurements as well as thermocouple readings from within tissue mimicking phantoms. The experimental validation of the simulation model allows for its use as a key component in treatment planning of thermal therapy using HIFU. Experimental and simulation results demonstrating the role of the advantages of incorporation of the computational model in optimizing the quality of HIFU beams will be presented and discussed. [ABSTRACT FROM AUTHOR]

This paper reports on the experimental examination of the transmission and reflection characteristics of arbitrarily shaped geometric obstructions in problems of plate wave propagation, such as joints, stiffeners, thickness transitions, and bends. The motivation for this work is noise source location in structures, the specific application being the location of air leaks in spacecraft skins, funded by NASA. In this work, it has been demonstrated that leaks can be located at a distance using array-based sensors which determine direction of signal propagation at the sensor location. The limiting factor in practice is the influence of geometric obstructions between the leak and sensor. This work reports a quantitative examination of the transmission properties of various obstructions such as stiffening ribs. Surface motions arising from a distance source are recorded over a local array of spatial positions using a scanned laser vibrometer. Spatial Fourier analysis is then applied to determine the individual contributions of the constituent mode types to the measured signals. Transmission properties of intervening geometric obstructions are determined by comparison to unobstructed signals. Comparisons to theoretical predictions of transmission characteristics will be presented for selected cases. [ABSTRACT FROM AUTHOR]

Guided ultrasonic waves, generated by air escaping through a small hole, have been measured with an 8×8 piezoelectric phased-array detector. Rapid location of air leaks in a spacecraft skin, caused by high-speed collisions with small objects, is essential for astronaut survival. Cross correlation of all 64 elements, one pair at a time, on a diced PZT disc combined with synthetic aperture analysis determines the dominant direction of wave propagation. The leak location is triangulated by combining data from two or more detector. To optimize the frequency band selection for the most robust direction finding, noise-field measurements of a plate with integral stiffeners have been performed using laser Doppler velocimetry. We compare optical and acoustic measurements to analyze the influence of the PZT array detector and its mechanical coupling to the plate. [ABSTRACT FROM AUTHOR]

Most common defects in textile manufacturing processes include weaving errors (such as missing threads), oil spots and material inhomogeneities. In this work, we demonstrate the feasibility of using ferroelectret-based transducers for the inspection of woven material. A linear array of 32 elements was built for this purpose following an easy fabrication procedure recently proposed. Electronic focusing at the textile sample position allowed us to detect weaving errors and oil spots of up to ∼1 mm of width in through transmission mode, at normal incidence and with a good signal-to-noise ratio. [ABSTRACT FROM AUTHOR]

Weak flaws detection and sizing is especially difficult in solids presenting structural noise. A new approach is presented, where a phase coherence operator modifies the beamforming process to achieve a significant reduction of scattering noise. At every range, the output is a function of the aperture data phase diversity. After application of the focusing delays, the grain noise high phase diversity leads to its suppression. The higher phase coherence of flaws allows keeping their indications. [ABSTRACT FROM AUTHOR]

For therapeutic treatment of adipose tissues it is necessary to dynamically focus acoustic energy at depths from 5 to 40 mm under the skin. One of the ways to achieve this goal is to use a spherical radiator having large aperture angle and comprising a multiplicity of radiating elements. Conventional ways of their manufacture (e.g. composite ceramics) are expensive and time consuming. The authors developed a method of building such an array using a single spherical piece of anisotropic piezoceramics, which is more simple and fast. The goal of this work is to evaluate the array performance, which is characterized by the level of cross-talks between different elements, statistics over resonance frequencies and electric impedances of the elements, etc. Manufactured phased array has aperture diameter and curvature radius of 84 and 54 mm, respectively and comprises 160 elements. Average resonance frequency and electric impedance measured over all elements were 1043±42 kHz and 315±28 Ohm, respectively. To assess the level of cross-talking and surface vibration velocity distribution the approach developed by O. Sapozhnikov et al. for quasi-planar sources was used. We validated this approach for the case of strongly focused transducer by examining a single element spherical radiator with the same geometry and a rubber strap, forming a specified figure, bonded to its radiating surface. The reconstructed velocity distribution showed rather low level of inter-element coupling. All these results demonstrated the validity of proposed method for phased array building. [ABSTRACT FROM AUTHOR]

UT Phased arrays are now widely used in various industrial fields thanks to their inherent versatility compared to inspections carried out with standard probes. In addition to the adaptability to various inspection configurations (beam focusing and deflecting through arbitrary interfaces using modeled delay laws), the ever increasing number of channels in industrial acquisition systems and optimized 2D probes (matrix, sectorial patterns) allow designing new applications using the combination of electronic commutation (use of successive groups at transmission and reception scanned over the aperture of the array), multiple shots and multiple receptions (application of dynamic depth focusing laws). This paper presents new tools dedicated to matrix settings in terms of trajectories, multiple delay laws settings which have been recently gathered in the CIVA platform software. Those skills are illustrated with experimental and simulated configurations for complex inspection cases. [ABSTRACT FROM AUTHOR]

Quantitative NDE methods play a key role when it comes to inspect components, which requires high operational safety. UT-SAFT is one of the well-known reconstruction tools, which provides information about the defect size. In this work we studied the use of phased array technique in combination with the SAFT algorithm to inspect power plant components. As a first example we inspected a real-sized mock-up model representing a part of a reactor pressure vessel with a 180 mm-thick ferritic base material followed by a 6 mm-thick austenitic cladding layer. The phased array probe was coupled at the outer ferritic surface. We detected and sized fatigue cracks within the cladding with a depth ranging from 4 mm to 10 mm. Secondly, we investigated a mock-up model resembling a nozzle including a thermo sleeve inlet and a maximum wall thickness of about 37 mm. Artificially inserted notches with a depth of 3 mm could be detected and sized, where the thermo sleeve is welded at the inside of the nozzle. [ABSTRACT FROM AUTHOR]

An array-based leak location sensor has been developed and improved for application onboard spacecraft. Introduction of a diced piezoelectric element has permitted the successful utilization of lower frequency bands to perform the location. With this new device location across five integral stiffeners has been demonstrated, despite the stiffeners' strong frequency-dependent scattering. Spatial Fourier transforms of plate wave signals determine leak location independent of the effects of dispersive multiple mode signal transport. The performance of the diced-element array sensor on a 2×2-m integrally stiffened aluminum plate is demonstrated. [ABSTRACT FROM AUTHOR]

The automotive industry is in the midst of a time of tremendous change. There is an almost perfect storm of changing governmental and market requirements seeking much higher fuel economy, low or no carbon dioxide emissions, and much higher crash and safety performance. Moreover, this occurs in a globe-spanning market that has more low-cost manufacturers than ever before. This confluence of factors leads to new vehicles with many new types of powertrains having unprecedented power densities and highly-engineered body structures with many new materials and joining methods. These are being turned out with shorter lead times, higher quality requirements, and continuous cost pressures. This talk will review the role in NDE in bringing new materials and processes to market, some of the applications in production, and to highlight some of the current NDE needs driven by these forces on the automotive industry. [ABSTRACT FROM AUTHOR]

Dual Mode Ultrasound Arrays (DMUAs) represent a new paradigm in non-invasive image-guided surgery, offering the unique advantage of inherent registration between the imaging and therapeutic coordinate systems. Furthermore, complete synchronization between the imaging and therapy hardware allows real-time monitoring of tissue changes on a millisecond timescale. The sensitivity of diagnostic pulse-echo ultrasound to HIFU-induced tissue changes has been established. Currently, disparate requirements of imaging and therapeutic piezo-elements present an obstacle to DMUA implementation. High performance imaging requires wide bandwidth, yet most therapeutic piezo-elements are based on narrowband ceramic technology due to its high electro-mechanical coupling. In the current study, we describe a 5-step design approach for image-guided HIFU systems. DMUA prototypes will be optimized for therapeutic performance using continuous wave (CW) simulation tools. Once satisfactory performance in the therapeutic operating field (ThxOF) has been achieved, piezo-element bandwidth will be increased until imaging performance meets specifications in the imaging field of view (IxFOV). Therapeutic performance is quantified based on intensity (focusing) gain throughout the ThxOF, while imaging performance is assessed based on axial resolution in the IxFOV. In addition, a new 4-MHz cylindrical array design prototype will be presented. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

An array-based leak location sensor is being developed for spacecraft application which uses spatial Fourier transformation of plate wave signals to robustly determine leak location, independent of the effects of dispersive multiple mode signal transport. The underlying principle of operation is outlined. The performance of a prototype array sensor on structural skin containing integrally machined stiffeners is demonstrated. A significant frequency dependence of transmission efficiency on stiffener geometry is observed, indicating the importance of pass-band optimization. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

This work presents a technique for controlling the width of a receiving aperture on an ultrasonic phased array system by appropriately programming Dynamic Depth Focusing (DDF) control electronics normally intended for control of depth of focus. The technique simulates deactivation of array elements through use of phase cancellation between neighboring array elements. Underlying principles are discussed. An experimental demonstration is provided. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The use of phased-arrays techniques has considerably contributed to extend the domain of applications and the performances of ultrasonic methods on complex configurations. Their adaptability offers a great freedom for conceiving the inspection leading to a wide range of functionalities gathering electronic commutation, applications of different delay laws and so on. This advantage allows to circumvent the difficulties encountered with more classical techniques especially when the inspection is assisted by simulation at the different stages : probe design (optimization of the number and characteristics of the elements), evaluation of the performances in terms of flaw detection (zone coverage) and characterization, driving the array (computation of adapted delay laws) and finally analyzing the results (versatile model-based imaging tools allowing in particular to locate the data in the real space). The CEA is strongly involved in the development of efficient simulation-based tools adapted to these needs. In this communication we present the recent advances done at CEA in this field and show several examples of complex NDT phased arrays applications. On these cases we show the interest and the performances of simulation-helped array design, array-driving and data analysis. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Focused ultrasound continues to be investigated as an exciting technique for several medical therapy applications including tissue ablation. Phased array transducers serve as important devices for delivering the high intensity focused ultrasound to the targeted tissue. These arrays often produce undesired secondary foci called grating lobes that can result in heating of non-targeted healthy tissue. Grating lobes can be eliminated by setting the element-spacing between adjacent elements to λ/2 or less. The aim of this research was to construct and evaluate a 2-D planar phased array with close to λ/2 element-spacing. A 7×7 element array with element-spacing of 0.76mm was constructed using 1,3-piezocomposite material. Acoustic field measurements of the array focused at three different locations were taken to demonstrate its ability to scan the focus in a volume. In addition, a maximum average intensity of 5.5W/cm2 was measured for the unfocused array using radiation force techniques. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

This work determines the optimum geometry for a phased array transducer surface, through a generalization of the concept of the Fermat surface. This generalization leads to a first order nonlinear differential equation for the surface which minimizes the required number of array elements to perform a specified beam formation task. An algorithm for generating solutions is discussed, and examples of optimized transducer designs are presented. A 50 percent reduction in the required number of array elements is observed over commonly used transducer designs. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Phased array ultrasonic inspections are being used on an ever-wider scale in industrial applications. One of the phased array capabilities is a dynamic-depth focusing (DDF) allowing an effective extension of focal zone. The use of DDF may potentially lead to decreased inspection times and costs for manufactures while maintaining a required sensitivity. The DDF is based on a dynamic re-focusing on reception resulting in a relatively uniform apparent acoustic field through a focusing range. A further improvement may be achieved by optimizing an acoustic field excited on transmission. This paper discusses a transmission field optimization aimed at creating a uniform apparent field and shows corresponding experimental results. A simple visualization tool for qualitative optimization of the transmission field is also discussed. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The inspection of critical rotating components of aircraft engines has made important advances over the last decade. The development of Phased Array (PA) inspection capability for billet and forging materials used in the manufacturing of critical engine rotating components has been a priority for Honeywell Aerospace. The demonstration of improved PA inspection system sensitivity over what is currently used at the inspection houses is a critical step in the development of this technology and its introduction to the supply base as a production inspection. As described in Part I (in these proceedings), a new phased array transducer was designed and manufactured for optimal inspection of eight inch diameter Ti-6Al-4V billets. After confirming that the transducer was manufactured in accordance with the design specifications a validation study was conducted to assess the sensitivity improvement of the PAI over the current capability of Multi-zone (MZ) inspection. The results of this study confirm the significant (≈ 6 dB in FBH[sharp/mesh/hash_synonym] sensitivity) improvement of the PAI sensitivity over that of MZI. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Ultrasonic guided wave inspection techniques are well-known for the inability to scan a long range axial distance of a pipe from a single transducer position. A phased array focusing technique was developed to improve the ultrasonic guided wave inspection results by concentrating the energy onto a defect. Focusing can increase the energy impinging onto the defects, reduce false alarm ratio, locate the defects, and enhance the propagation distance of the guided waves. An ultrasonic system with n (n>1) individual excitation channels is required to achieve phased array focusing. When phased array focusing was carried out, time delays and amplitude factors were applied to control the input signals for each excitation channel. Different from the time delays for bulk wave linear array focusing, the time delays and amplitude factors for guided wave array focusing are non-linear functions of the focal distance, the pipe size, excitation conditions, and the active frequency. A challenge of this technique is to focus beyond welds, defects, or other obstructions. The influence of axisymmetric welds is investigated with 3D FEM simulations and an experimental example. The theoretical analysis and experiments shows that although welds usually decrease the penetration energy, a limited number of welds rarely affects the phased array focal location. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]