Adaptive ultrasonic inspection of volumetric defects.

Abstract

Acoustic evaluation of a target may be performed using an array of electroacoustic transducers. For example, a technique for such evaluation may include generating respective acoustic transmit events using different transmit apertures, the apertures being defined by corresponding zones along the array, the zones including a plurality of electroacoustic transducer elements. In response to the respective acoustic transmit events, respective acoustic echo signals are received. Representations of the respective received acoustic echo signals are coherently summed. The coherently summing includes applying a determined nominal element delay coefficient to the respective representations to approximate a virtual probe perpendicular to a nominal shape of a surface of the inspected structure. Pixel or voxel values ​​corresponding to designated spatial locations within the inspected structure are generated using the coherently summed representations.

Description

[Technical Field]

[0001] Priority claims This patent application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 201,485 (Attorney Docket No. 6409.197PRV) to Lepage et al., filed April 30, 2021, and entitled "ADAPTIVE ULTRASONIC INSPECTION FOR VOLUMETRIC FLAWS," which is incorporated herein by reference in its entirety.

[0002] This document relates generally, but not exclusively, to non-destructive evaluation, and more particularly to apparatus and techniques for providing acoustic inspection in an adaptive manner to detect subsurface or internal defects in structures such as bars. [Background technology]

[0003] Various inspection techniques can be used to image or otherwise analyze structures without damaging such structures. For example, one or more of x-ray inspection, eddy current inspection, or acoustic (e.g., ultrasonic) inspection can be used to acquire data for imaging features on or within a test sample. For example, acoustic imaging can be performed using an array of ultrasonic transducer elements, such as to image a region of interest within the test sample. Summary of the Invention

[0004] Acoustic inspection can be used to detect volumetric or near-surface defects in a non-destructive manner. For example, in bar inspection, a set of ultrasonic inspection probes can be positioned at various radial locations around the bar under test. Volumetric scanning can be performed by acquiring B-scan imaging data including a series of stacked E-scan images. Such an approach can present various challenges, such as producing imaging that does not represent defect locations in a manner corresponding to the defects' actual physical locations. Such imaging can also tend to hide or suppress defect identification in the presence of misalignment between the probe assembly and the bar under test. The inventors have recognized, among other things, that adaptive approaches can be used to determine delay compensation values ​​for individual probe elements to compensate for misalignment, and that zonal imaging approaches can be used, including sparse matrix acquisition schemes (referred to herein as zonal dynamic depth focusing) that can provide imaging that is more meaningfully representative of physical defect locations. The various examples described herein can also be used for shear wave imaging, such as for backwall surface or near-surface defect inspection.

[0005] In one example, acoustic evaluation of a target can be performed using an array of electroacoustic transducers. For example, a technique for such evaluation can include generating respective acoustic transmit events using different transmit apertures, the apertures being defined by corresponding zones along the array, the zones including a plurality of electroacoustic transducer elements. In response to each acoustic transmit event, respective acoustic echo signals are received using receiving ones of the electroacoustic transducer elements to form groups of received acoustic echo signals. For example, the groups are indexed by transmit-receive pairs including the respective transmit zones and respective ones of the receive elements. Representations of the respective received acoustic echo signals are coherently summed, the representations corresponding to the respective transmit-receive pairs. The coherently summing includes applying determined nominal element delay coefficients to the respective representations to approximate a virtual probe perpendicular to a nominal shape of the surface of the inspected structure. The respective delay coefficient corrections are applied to compensate for variations from the nominal shape or nominal alignment of the surface of the structure relative to the array of electroacoustic transducers. Pixel or voxel values ​​corresponding to specified spatial locations within the structure being inspected are generated using the coherently summed representation.

[0006] In one example, an ultrasound inspection system for acoustic evaluation of a target uses an array of electroacoustic transducers. An analog front end including transmit / receive circuitry is coupled to the array of electroacoustic transducer elements. A processor circuit is communicatively coupled to the analog front end. A memory circuit includes instructions that, when executed by the processor circuit, cause the system to perform tasks. For example, the instructions may include generating respective acoustic transmit events using different transmit apertures, the apertures being defined by corresponding zones along the array, the zones including multiple electroacoustic transducer elements. In response to each acoustic transmit event, respective acoustic echo signals are received using receiving ones of the electroacoustic transducer elements to form groups of received acoustic echo signals. For example, the groups are indexed by transmit / receive pairs including the respective transmit zones and respective ones of the receive elements. Representations of the respective received acoustic echo signals are coherently summed, each representing a respective transmit / receive pair. The coherently summing includes applying a determined nominal element delay coefficient to each representation to approximate a virtual probe normal to a nominal shape of a surface of the inspected structure. Each delay coefficient correction is applied to compensate for variations from a nominal shape or nominal alignment of the surface of the structure relative to the array of electroacoustic transducers. Pixel or voxel values ​​corresponding to specified spatial locations within the inspected structure are generated using the coherently summed representation.

[0007] In one example, an ultrasound inspection system for acoustically evaluating a target uses an array of electroacoustic transducers. The system includes means for generating respective acoustic transmit events using different transmit apertures. The apertures are defined by corresponding zones along the array. The zones include a plurality of electroacoustic transducer elements. In response to each acoustic transmit event, the system includes means for receiving respective acoustic echo signals using receiving ones of the electroacoustic transducer elements to form groups of received acoustic echo signals. For example, the groups are indexed by transmit-receive pairs including a respective transmit zone and each one of the receive elements. The system includes means for coherently summing representations of the respective received acoustic echo signals. The representations correspond to the respective transmit-receive pairs. The coherent summing includes applying determined nominal element delay coefficients to the respective representations to approximate a virtual probe perpendicular to a nominal shape of the surface of the inspected structure. The respective delay coefficient corrections are applied to compensate for variations from a nominal shape or a nominal alignment of the surface of the structure relative to the array of electroacoustic transducers. The system comprises means for using the coherently summed representation to generate pixel or voxel values ​​corresponding to specified spatial locations within the inspected structure.

[0008] This Summary is intended to provide an overview of the subject matter of this patent application. It is not intended to provide an exclusive or exhaustive description of the invention. The Detailed Description is included to provide further information regarding this patent application. [Brief explanation of the drawings]

[0009] In the drawings, which are not necessarily drawn to scale, like numerals may describe like components in different drawings. Like numerals with different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in this document.

[0010] [Figure 1] An example is shown generally comprising an acoustic inspection system, such as may be used to implement one or more of the techniques shown and described elsewhere herein. [Figure 2A] 1 illustrates an example of a bar inspection system having multiple probes. [Figure 2B] 1 illustrates an example of a phased array beam that may be generated by an ultrasound probe. [Figure 3A] An illustrative example is shown including acquired E-scan images stacked next to each other obtained by scanning a 0.5 millimeter (mm) mid-wall flat bottom hole (MWFBH) defect using a beam similar to that shown in FIG. 2B. [Figure 3B] An illustrative example is shown including acquired E-scan images stacked next to each other, the E-scan images being obtained by scanning a 0.5 mm back wall flat bottom hole (FBH) defect. [Figure 4] FIG. 3B shows an example including another acquisition using the same 0.5 mm MWFBH defect of FIG. 3A, but with a 0.5 mm lateral mechanical offset of the probe assembly relative to the nominal, centrally located probe position, showing weakly resolved details of the defect. [Figure 5] An example is given involving an adaptive bar inspection principle that can use a zonal dynamic depth focusing (zDDF) approach. [Figure 6] 1 shows a diagram of an inspection configuration in which zDDF can be combined with a Coherent Adaptive Focusing (CAF) approach. [Figure 7] 1 shows zDDF results without the CAF-based technique for various probe positions relative to the bar under test. [Figure 8] zDDF results are shown for various probe positions relative to the bar under test, including the use of CAF-based techniques. [Figure 9] 1 shows an aggregation of multiple images acquired using the zDDF approach. [Figure 10] An illustrative example of a sector-based zDDF is shown. [Figure 11] A diagram illustrating the adaptive zDDF approach is presented overall. [Figure 12] 1 illustrates an independent CAF iterative decision process that can be applied across probes. [Figure 13] FIG. 12 shows an example where the techniques used may be useful. [Figure 14A] We show the CAF convergence by iteration on the basic sub-aperture. [Figure 14B] 10 shows the CAF convergence with iterative CAF for the summed subapertures. [Figure 15] As illustrated in FIG. 14B, an exemplary element probe setup for CAF performed using summed sub-apertures is shown. [Figure 16] The SW excitation scheme is shown. [Figure 17] 10 illustrates the use of different beam steering angles to achieve coverage of various surface defect locations radially around the bar under test. [Figure 18] 10 shows simulation results of the effect of bar positioning offset on the reference amplitude corresponding to the defect. [Figure 19] 1 illustrates techniques, such as machine-implemented methods, that may be used to perform adaptive ultrasound testing as described in various examples herein. [Figure 20] 1 illustrates an example block diagram comprising a machine upon which any one or more of the techniques (eg, methodologies) discussed herein may be performed. DETAILED DESCRIPTION OF THE INVENTION

[0011] Acoustic testing, such as ultrasound-based inspection, can include focusing or beamforming techniques to aid in constructing a data plot or image representing a region of interest within a test specimen. The use of an array of ultrasonic transducer elements can include the use of a phased array beamforming approach and can be referred to as phased array ultrasonic testing (PAUT). For example, a delay-and-sum beamforming technique can be used, which involves coherently summing time-domain representations of received acoustic signals from each transducer element or aperture. The techniques herein facilitate one or more of enhanced inspection productivity (e.g., throughput or sensitivity to defects), reduced sensitivity to positioning errors, and more intuitive imaging that presents defects in a manner that is easier for inspection personnel or analysts to understand.

[0012] FIG. 1 generally illustrates an example including an acoustic inspection system 100 that can be used to implement at least a portion of one or more of the techniques shown and described herein. The acoustic inspection system 100 can include a test instrument 140, such as a handheld or portable assembly. The test instrument 140 can be electrically coupled to a probe assembly, such as using a multi-conductor interconnect 130. The probe assembly 150 can include one or more electroacoustic transducers, such as a transducer array 152 including respective transducers 154A-154N. The transducer array can follow a linear or curved contour, or can include an array of elements extending in two axes, such as providing a matrix of transducer elements. The elements need not have a square footprint or be arranged along a linear axis. The size and pitch of the elements can vary depending on the inspection application.

[0013] A modular probe assembly 150 configuration can be used to allow the test instrument 140 to be used with a variety of different probe assemblies 150. Generally, the transducer array 152 includes, for example, piezoelectric transducers that can be acoustically coupled to a target 158 ​​(e.g., a test sample or "object under test") via a coupling medium 156. The coupling medium can include a fluid or gel, or a solid film (e.g., an elastomer or other polymeric material), or a combination of fluid, gel, or solid structure. For example, the coupling medium can include water and / or other fluids.

[0014] The test instrument 140 may include digital and analog circuitry, such as a front-end circuit 122 including one or more transmit signal chains, receive signal chains, or switching circuitry (e.g., transmit / receive switching circuitry). The transmit signal chain may include amplifier and filter circuitry to provide transmit pulses for delivery to the probe assembly 150 via the interconnect 130 for sonication of the target 158, and to image or otherwise detect defects 160 on or within the target 158 ​​structure by receiving scattered or reflected acoustic energy elicited in response to the sonication. While the test structure may be specifically referred to herein as a bar, it should be understood that the test structure may be any type of structure for which internal visualization is desired.

[0015] 1 shows a single probe assembly 150 and a single transducer array 152, other configurations can be used, such as multiple probe assemblies connected to a single test fixture 140, or multiple transducer arrays 152 used with single or multiple probe assemblies 150 for pitch / catch testing. Similarly, test protocols can be performed using coordination among multiple test fixtures 140, for example, in response to an overall test scheme established from a master test fixture 140 or established by another remote system such as computing equipment 108 or a general-purpose computing device such as a laptop 132, tablet, smartphone, or desktop computer. The test scheme can be established in accordance with published standards or regulatory requirements and can be repeated, as illustrative examples, at initial production or for ongoing monitoring.

[0016] The receive signal chain of the front-end circuitry 122 may include one or more filter or amplifier circuits, along with analog-to-digital conversion facilities, to digitize echo signals received using the probe assembly 150. The digitization may be performed coherently to provide multiple channels of digitized data that are aligned or referenced to each other in time or phase. The front-end circuitry may be coupled to and controlled by one or more processor circuits, such as the processor circuit 102 included as part of the test instrument 140. The processor circuit may be coupled to the memory circuit 104, for example, to execute instructions that cause the test instrument 140 to perform one or more of acoustic transmission, acoustic acquisition, processing, or storage of data related to an acoustic test, or otherwise perform the techniques shown and described herein. The test instrument 140 may be communicatively coupled to other portions of the system 100, such as using a wired or wireless communication interface 120.

[0017] For example, performance of one or more techniques as shown and described herein may be achieved on the test instrument 140 or using other processing or storage facilities, such as using the computing equipment 108 or general-purpose computing devices, such as a laptop 132, tablet, smartphone, desktop computer, etc. For example, processing tasks that would be unnecessarily slow if performed on the test instrument 140 or if performed beyond the capabilities of the test instrument 140 may be performed remotely (e.g., on a separate system), e.g., in response to a request from the test instrument 140. Similarly, storage of intermediate data, such as, e.g., A-scan matrices of imaging data or time series data, or other representations of such data may be achieved using remote facilities communicatively coupled to the test instrument 140. The test instrument may include a display 110, such as for presenting configuration information or results, and input devices 112, including one or more of a keyboard, trackball, function keys or softkeys, a mouse interface, a touch screen, a stylus, etc., for receiving operator commands, configuration information, or responses to queries.

[0018] In the examples herein, data is generally acquired using groups of simultaneously fired transducer elements, these groups defining transmit acquisition "zones." An acoustic transmit event occurs when an acoustic pulse is generated using a group of transducers in the corresponding zone. According to some examples, one or more of the elements of the group of transducers that contributed to the pulse event are also used as receive elements. In some cases, other elements in the array receive echo signals (reflected or scattered acoustic energy) elicited in response to the acoustic transmit. An acquisition matrix is ​​initially defined with two axes, the first corresponding to each transmit event and the second corresponding to each receive location. Each element of the matrix contains time-series data (e.g., an elementary "A-scan") corresponding to a particular receive location and corresponding transmit event. In general, groups of elements may be used for transmit during individual transmit events, and groups of elements may be used for receive during receive events, such as to provide a desired transmit or receive aperture or to provide a combined transmit-receive.

[0019] To construct an image of a particular location (e.g., the location of a pixel or voxel in the imaging data), summing contributions from signals received at each transducer element in response to each transmit event generally involves selecting appropriate samples from the corresponding A-scan that correspond to the spatial location of the pixel or voxel (and associated propagation path). The A-scan data may contain real-valued time-series information or analytical forms. Because the propagation path affects the sum for each voxel or pixel, signal filtering or modulation may be performed in response to one or more characteristics of the propagation path, such as by weighting certain terms in the sum using knowledge of the propagation path. As discussed above, variations between the modeled propagation path and the actual path traversed during acquisition can create imaging artifacts.

[0020] Ultrasonic bar inspection for volumetric defects typically relies on electronic scanning (E-SCAN) using multiple physically separated phased array probes focused on the back wall of the bar. When high sensitivity levels are required (e.g., for reliable detection of calibration features such as 0.5 mm flat-bottom holes), commonly available methods can limit inspection throughput.

[0021] 2A illustrates an exemplary bar inspection system having multiple probes 210, according to examples described herein. Each probe 210 has multiple transducer elements. Each probe 210 may be positioned on an independent plane (allowing for independent parallel firing of the probes). According to various examples, the same phased array probe can be programmed to provide one or both longitudinal wave (LW) and shear wave (SW) pulses to inspect a central volume and / or a subsurface volume of a test structure 220. In some cases, the same phased array probe can be programmed to alternate between LW and SW pulses.

[0022] As an example, one approach can be based on testing using a set of 128 element probes. Inspection of volumetric defects (using LW) can generally involve a beam formed with 32 elements per aperture, with aperture steps of 8 elements. Under these conditions, 13 independent beams are generated to inspect each position within the scan axis. Figure 2B shows an example of a phased array beam that can be generated by an ultrasonic probe 230 according to examples described herein.

[0023] Such an approach for bar inspection outputs a B-scan image corresponding to each probe 210 array formed by stacking multiple (e.g., 13) independent E-SCAN beams next to each other. While this provides an image, it generally does not provide a physically meaningful representation of the actual defect location or geometry, and can be difficult to interpret. Such an approach can also prevent combining the various B-scan images from each probe location around the radius of the bar into a single representative image of the interior or subsurface region of the bar under test.

[0024] 3A shows an illustrative example including E-scan images acquired stacked next to each other obtained by scanning a 0.5 millimeter (mm) mid-wall flat-bottom hole (MWFBH) defect using a beam similar to that shown in FIG. 2B. FIG. 3B shows an illustrative example including E-scan images acquired stacked next to each other obtained by scanning a 0.5 mm back-wall flat-bottom hole (FBH) defect. The FBH defect is indicated by arrows 310, 320, and the mid-wall defect appears much wider in the image than the actual hole size because all of the beams pass through the center of the bar.

[0025] The above approaches can present reliability or repeatability challenges because existing approaches generally involve precise mechanical positioning of the inspected product within the system relative to one or more inspection probes, such as requiring accuracies on the order of 0.1 mm for repeatability. Such constraints increase the complexity (and cost) of the associated mechanical bar positioning or support systems. Such constraints can also limit achievable detection capabilities or hinder inspection altogether, since raw product bars are typically not perfectly straight. Figure 4 shows an example involving another acquisition using the same 0.5 mm MWFBH defect of Figure 3A, but with a 0.5 mm lateral mechanical offset of the probe assembly relative to the nominal, centered probe position, showing weakly resolved details of the defect.

[0026] A re-inspection of the same 0.5MWFBH with a lateral mechanical offset of 0.5 mm is shown, which shows very weak detection (e.g., the defect is no longer clearly visible at the top of the E-SCAN image).

[0027] The subject matter described herein enables relatively high productivity through the use of large aperture transmit that can be focused on the center of the test structure. Voxel-based focusing can be used in receive mode for processed imaging using received acoustic echo signals, such as using a coherent summation approach in a manner similar to a Total Focusing Method (TFM) approach, rather than requiring a full matrix capture approach. The technique described herein may be referred to as a zonal dynamic depth focusing (zDDF) approach. Because the large aperture transmit (e.g., "zonal" transmit) sonicates a large portion of the bar with high frequency waves and the receive beamforming approach enables detection of defects, including off-angle defects, at relatively high focusing (e.g., high F-number) power, the zDDF approach shown and described herein can match or exceed the detection performance (in terms of detection capability) of other approaches, such as using only three transmit events for a 128-element probe (e.g., using a 64-element aperture).

[0028] FIG. 5 illustrates an example involving an adaptive bar inspection principle that can use a zonal dynamic depth focusing (zDDF) approach, according to examples described herein. Combining zDDF with coherent adaptive focusing (CAF, sometimes referred to as surface-adaptive ultrasound) is possible by reusing the delays created by the CAF technique to form a virtual probe at a predetermined position relative to the bar. This can be naturally achieved by the CAF technique focusing on an acoustic wavefront parallel to the bar surface. Generally, a bar inspection system (BIS) inspection probe is assumed to be concentric with the bar structure under test (e.g., concentric when the system is well aligned). Establishing a virtual probe allows for systems where the inspection probe may not be concentric with the bar structure under test. Transmit and receive beamforming delays can be applied in combination with the delays established by CAF to create an adaptive zDDF approach.

[0029] Specifically, the virtual probe can be generated by creating CAF delay corrections for the wavefront at 520 so that the wavefront is substantially concentric to the bar. This can represent transducer element delay coefficients that compensate for off-nominal positioning of the bar relative to the transducer array, lack of concentricity, or non-cylindrical deviations of the bar shape, or a combination thereof. The wavefront is generated by generating respective acoustic transmit events using different transmit apertures. According to various configurations described herein, the apertures are defined by corresponding zones along the array of electroacoustic transducers. The wavefront is transmitted at 530 through active apertures (e.g., "zones") using element-level transmit delays to establish the desired focal position and CAF compensation delays. The wavefront propagates at 540 within the bar structure under test. Respective acoustic echo signals are received at 550. The received element-level A-scans are delayed at 560 using the created CAF compensation delays corresponding to each receive element. The nominal zDDF transmit or receive delays (or both) for the substantially centered bar may be pre-calculated at 565. These pre-calculated delays may be summed with the CAF compensation delay at 570 to produce an adaptive zDDF test result at 580.

[0030] FIG. 6 shows a diagram of an inspection configuration in which zDDF can be combined with a coherent adaptive focusing (CAF) approach, according to examples described herein. A probe 602 has multiple transducer elements 605-1 through 605-N1. Multiple CAF delays 610-1 through 610-N2 are determined to create a wavefront that is substantially concentric with the bar 635 under test, providing compensation for off-nominal probe 602 positioning or the shape of the non-cylindrical bar 635 (or both). According to various configurations, the count of delay values ​​is the same as the count of transducer elements. In other examples, the count of delay values ​​may differ from the number of transducer elements. The count of delay values ​​may depend on the dimensions of the probe. For example, delay values ​​may be calculated at specified positions along the surface of the probe facing the bar. CAF delays may be applied to one or both of the transmit and receive A-scans, such as on an element-by-element basis. The CAF delays are used to establish transmit and receive focusing within the imaging region 630, establishing a wavefront equivalent to the wavefront 625 generated from the virtual probe position 620. The single wavefront 625 can transmit from the entire aperture, and the aperture need not encompass the entire probe 602. The single wavefront 625 may be substantially concentric with the bar when compensation using the CAF delays is performed. According to various configurations, acquisition may be performed using CAF compensation in which the CAF delays are determined corresponding to a bar front wall 645 profile with a transmit focal position 640 substantially at the center of the bar 635. A defect representation 650 is shown in a sector of the bar being scanned. According to various examples, the focal position is at a location other than the center of the bar. In this case, the same CAF delays may be used to create a virtual probe to which actual delays are added to generate a focal position at the desired location.

[0031] FIG. 7 shows zDDF results without CAF-based techniques for various probe positions relative to the bar under test, according to examples described herein. In this example, the bar structure has a diameter of approximately 60 mm, and defects 750A, 750B have a MWFBH of approximately 0.5 mm. According to some examples, defect indications in the images are weakened, distorted, and / or completely absent when CAF is not performed and the bar is not centered. This is particularly noticeable when there is lateral misalignment (e.g., in the y direction). Defect 750A in the centered bar is more readily apparent than defect 750B in the laterally misaligned bar. Defect echoes are also weaker in the z direction compared to the centered bar.

[0032] Figure 8 shows an illustrative example of adaptive (e.g., CAF-enhanced) zDDF results under the same conditions as Figure 7, but showing strong detection of 0.5 MWFBH even in the presence of mechanical misalignment (+ / -1 mm y). This example is shown after one CAF iteration. Because zDDF processes based on voxel position in space (e.g., inspection results are created based on position within the resulting bar), true-to-geometry imaging can be produced. In this example, defects 850A and 850B are readily apparent even when the bar is misaligned.

[0033] Figure 9 illustrates the aggregation of multiple images acquired using the zDDF approach. In one example, inspection results 910, 920, 930 can be generated and imaged only in designated relevant regions for the inspection, reducing processing requirements and allowing all (or a specific subset of) probe acquisition results to be overlaid onto just a single image frame showing a representation of the interior region of the bar. Results can be combined by combining up to two or more individual region results, as shown by combined result 940. While this example shows three zDDF results, it should be understood that two or more zDDF results can be combined to create a meaningful image.

[0034] 10 shows an illustrative example of a sector-based zDDF image of inspection results. In this example, a probe 1002 having multiple elements is configured to be used to provide inspection of a sector 1020 of a test structure 1010. In some cases, inspection results may be provided for multiple sectors of the test structure. It should be understood that at least some of the sectors may overlap with other result sectors. In some cases, none of the result sectors are configured to overlap.

[0035] In general, to achieve the desired inspection productivity while gaining the adaptive acoustic benefits provided by adaptive zDDF technology, inspection aperture firing can be combined with the CAF delay determination process. To perform such a combination, common parameters for the actual zDDF inspection and CAF firing are used, such as establishing a wavefront parallel to the bar surface. Figure 11 shows an overall diagram illustrating the adaptive zDDF approach. In this example, the system iteratively cycles through multiple scan positions along the longitudinal axis of the bar under test or other structure under inspection. Each scan position can use multiple apertures to perform the scan. In this example, multiple transmit apertures (e.g., zones) are used at scan position p-1110, multiple apertures are used at scan position p1120, and multiple apertures are used at scan position p+11130. For each scan position and each aperture, a wide aperture imaged at 1122 focused on the structure center is used for CAF delay calculation at 1126 and zDDF imaging at 1124. The CAF delay calculation at 1126 may be used for acquisition or imaging at a subsequent scan position, for example, p+11130.

[0036] In the example of FIG. 12 , an independent CAF iteration decision process can be applied to the entire probe (e.g., using sparse emission and reception if the front end does not support acquisition of the entire probe at once). Elements of the probe may be multiplexed to provide delays for the entire probe. When using multiplexing, delays may then be interpolated for each individual element (including those not included in the original emission). The CAF iteration process in 1205 can create delay coefficients that compensate for off-nominal probe positions relative to the structure under test, which can then be used to perform zDDF imaging for at least one aperture in 1210. Such an approach also enables adaptive shear wave inspection by applying CAF delays to shear wave (SW) PAUT beamforming delays, which can be established in 1220. The technique of FIG. 12 can be nearly as fast as the technique used in FIG. 11 when only one CAF iteration is used and can provide value for bar inspection by adapting to relatively large mechanical misalignments (e.g., reducing the sensitivity of the BIS to mechanical misalignments during inspection).

[0037] Figure 13 shows an example where the technique used in Figure 12 may be useful. In this example, mechanical misalignment of the real probe 1302 and structure 1330 is compensated for by applying a CAF delay 1315 on top of the beamforming delay established for the SW excitation. Such compensation can correct for the misalignment, such as providing shear wave excitation and receiving equivalents for the probe position corresponding to the virtual probe 1305. One or more transmit apertures and / or zones 1320 encompassing multiple elements may be used.

[0038] FIG. 14A shows CAF convergence with iterations on a basic subaperture. A subaperture can contain one or more elements. In this example, the subaperture contains two elements. The 10 iterations shown here do not achieve complete convergence. In contrast, FIG. 14B shows CAF convergence with iterative CAF on summed subapertures. As can be observed, substantial convergence is achieved by the second iteration, likely resulting in a much faster process than that used in FIG. 14A. The examples in FIGS. 14A and 14B use a 10 mm test bar offset in the z-direction by approximately 1 mm.

[0039] FIG. 15 shows an exemplary element probe configuration for CAF performed using summed sub-apertures, as illustrated in FIG. 14B. Specifically, FIG. 15 is an example of how a 64-channel system can be used to connect at least some elements of a 128-element probe using multiplexers. Using this configuration and summing paired elements of the receive, CAF was shown to converge in a single iteration of FIG. 14B. Using a system that can converge in a low (e.g., single) number of iterations significantly reduces the time to results compared to iterative processes that converge only after many iterations.

[0040] 16 shows an ultrasonic beam generated using a SW excitation scheme, according to an example described herein. A probe 1620 is used to test a structure 1610. In this example, the active aperture 1630 of the probe 1620 includes 16 elements with a 40 degree refracted beam angle 1640. The test structure in this example is a 20 mm diameter bar, with the focal point at the back wall of the bar.

[0041] Figure 17 illustrates the use of different active aperture positions to achieve coverage of various surface defect locations radially around the bar under test. The various beams 1705 correspond to changing the position of the active aperture 1630 on the probe. In this example, the defects are longitudinal surface notches approximately 0.1 mm deep and 6.4 mm long at three locations within the bar. The scan positions are -1 mm, -0.5 mm, 0, 0.5 mm, and 1 mm in the y and z directions.

[0042] 18-20 show simulation results of the effect of bar positioning offset on the reference amplitude corresponding to a defect at an exemplary defect location. As can be seen, defect indicator 1805 is readily apparent in standard mode with the bar substantially centered. In this example, the defect indicator is absent and / or much less visible at some of the larger offsets in SW standard mode. For example, for a y-offset of +1 mm in standard mode, defect indicator 1815 is much less visible. In contrast, for a y-offset of +1 mm, defect indicator 1825 in CAF mode is easily observed. In the example of FIG. 18, the defect amplitude dropped by more than 2 dB at y=0.5 mm in CAF mode, but defect 1805 remains visible for all offsets in corrected and CAF modes.

[0043] 19 illustrates a machine-implemented method or technique that may be used to perform adaptive ultrasound testing, according to examples described herein. In block 1902, routine 1900 generates each acoustic transmit event using a different transmit aperture, where the aperture is defined by a corresponding zone along the array, the zone including multiple electroacoustic transducer elements. According to various embodiments, at least three acoustic transmit events are generated using different transmit apertures corresponding to the different zones. At least one of the zones may at least partially overlap. In some cases, all zones are distinct and non-overlapping.

[0044] At block 1904, the routine 1900 responsive to each acoustic transmit event receives each acoustic echo signal using receiving ones of the electroacoustic transducer elements and forms groups of received acoustic echo signals, the groups being indexed by transmit / receive pairs including each respective transmit zone and each one of the receive elements.

[0045] At block 1906, the routine 1900 includes coherently summing representations of each received acoustic echo signal. The representations correspond to each transmit / receive pair. The representations of each received acoustic echo signal may include A-scan representations. The coherently summing includes applying the determined nominal element delay coefficients to each representation to approximate a beam perpendicular to a nominal shape of the surface of the inspected structure. The respective delay coefficient corrections may be determined using an iterative technique. For example, the iterative technique may include determining the respective delay coefficients using respective apertures including two or more electroacoustic transducer elements. According to various embodiments, the respective delay coefficients are determined using a single iteration. The respective delay coefficient corrections are applied to compensate for variations from a nominal shape or nominal alignment of the surface of the structure relative to the array of electroacoustic transducers.

[0046] At block 1908, the routine 1900 generates pixel or voxel values ​​corresponding to specified spatial locations within the inspected structure using the coherently summed representations. According to various examples, generating pixel or voxel values ​​includes generating images of the multiple spatial locations using respective coherent sums, each coherent sum including applying the determined nominal element delay coefficient and applying a respective delay coefficient correction.

[0047] According to various examples described herein, the structure under test is a bar. The image may represent a sector within the volume of the bar. Another acquisition may be performed to form another group of received acoustic echo signals to generate another image of a different sector within the volume of the bar. In some cases, the group is indexed by a transmit / receive pair including a respective transmit zone and one of the receive elements. Performing another acquisition may include repositioning the array or the structure under test to allow the array to insonify a different portion of the surface of the structure under test. Performing another acquisition may include using a second array configured to insonify a different portion of the surface of the structure under test.

[0048] According to various examples described herein, acoustic transmit events are generated to excite shear waves for imaging a surface of a structure under test. Imaging the surface of the structure under test includes coherently summing representations of the respective received acoustic echo signals, applying determined nominal element delay coefficients to each representation to approximate a virtual probe perpendicular to a nominal shape of the surface of the inspected structure, and applying respective delay coefficient corrections to compensate for variations from the nominal shape or nominal alignment of the surface of the structure relative to the array of electroacoustic transducers. Pixel or voxel values ​​corresponding to specified spatial locations within the inspected structure can be generated using the coherently summed representations.

[0049] FIG. 20 shows an example block diagram comprising a machine 2000 on which any one or more of the techniques (e.g., methodologies) discussed herein may be executed. In various embodiments, machine 2000 may operate as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, machine 2000 may operate as a server machine, a client machine, or both in a server-client network environment. In one example, machine 2000 may function as a peer machine in a peer-to-peer (P2P) (or other distributed) network environment. Machine 2000 may be a personal computer (PC), a tablet device, a set-top box (STB), a personal digital assistant (PDA), a mobile phone, a web appliance, a network router, switch, or bridge, or any machine capable of executing instructions (sequentially or otherwise) that specify actions to be taken by that machine. Furthermore, although only a single machine is shown, the term "machine" is intended to include any collection of machines that individually or collectively execute a set (or sets) of instructions to perform any one or more of the methodologies discussed herein, such as cloud computing, software as a service (SaaS), other computer cluster configurations, etc.

[0050] As described herein, examples may include or operate by logic or several components or mechanisms. Electrical circuitry is a collection of circuits implemented in tangible entities including hardware (e.g., simple circuits, gates, logic, etc.). Electrical circuitry membership can be flexible over time and with variations in the underlying hardware. A circuit includes elements that, alone or in combination, can perform a specified operation when operated. In one example, hardware of electrical circuitry may be invariably designed to perform specific operations (e.g., hardwired). In one example, hardware comprising electrical circuitry may include variably connected physical components (e.g., execution units, transistors, simple circuits, etc.) that include computer-readable media that are physically altered (e.g., magnetically, electrically, e.g., via a change in physical state or a transformation of another physical property, etc.) to encode instructions for specific operations. When connecting the physical components, the underlying electrical properties of the hardware components may be altered, e.g., from insulating to conducting, or vice versa. The instructions enable the embedded hardware (e.g., an execution unit or load mechanism) to create elements of the hardware's electrical circuitry through variable connections to perform portions of specific operations during operation. Thus, the computer-readable medium is communicatively coupled to other elements of the electrical circuitry when the device is operating. In one example, any one of the physical components may be used in more than one element of more than one circuit. For example, under operation, an execution unit may be used in a first circuit of a first electrical circuitry at one time and reused by a second circuit in the first electrical circuitry or by a third circuit in the second electrical circuitry at a different time.

[0051] The machine (e.g., computer system) 2000 may include a hardware processor 2002 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory 2004, and a static memory 2006, some or all of which may communicate with each other via an interlink (e.g., a bus) 2030. The machine 2000 may further include a display unit 2010, an alphanumeric input device 2012 (e.g., a keyboard), and a user interface (UI) navigation device 2014 (e.g., a mouse). In one example, the display unit 2010, the input device 2012, and the UI navigation device 2014 may be touchscreen displays. The machine 2200 may further include a storage device (e.g., a drive unit) 2008, a signal generating device 2018 (e.g., a speaker), a network interface device 2020, and one or more sensors 2016, such as a global positioning system (GPS) sensor, a compass, an accelerometer, or other sensor. The machine 2000 may include an output controller 2028, such as a serial (e.g., universal serial bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection, for communicating with or controlling one or more peripheral devices (e.g., a printer, a card reader, etc.).

[0052] The storage device 2008 may include a machine-readable medium 2022 having stored thereon one or more sets of data structures or instructions 2024 (e.g., software) that embody or are utilized by any one or more of the techniques or functions described herein. The instructions 2024 may also reside, completely or at least partially, within the main memory 2004, within the static memory 2006, or within the hardware processor 2002 during execution thereof by the machine 2000. In one example, one or any combination of the hardware processor 2002, the main memory 2004, the static memory 2006, or the storage device 2008 may constitute a machine-readable medium.

[0053] Although the machine-readable medium 2022 is illustrated as a single medium, the term "machine-readable medium" may include a single medium or multiple media (e.g., a centralized or distributed database, and / or associated caches and servers) configured to store one or more instructions 2024.

[0054] The term "machine-readable medium" may include any medium that can store, encode, or retain instructions for execution by machine 2000 and cause machine 2000 to perform any one or more of the techniques of this disclosure, or that can store, encode, or retain data structures used by or associated with such instructions. Non-limiting examples of machine-readable media may include solid-state memory, and optical and magnetic media. Thus, a machine-readable medium is not a transitory, propagating signal. Specific examples of dense machine-readable media may include non-volatile memory such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)) and flash memory devices, magnetic or other phase-change or state-change memory circuits, magnetic disks such as internal hard disks and removable disks, magneto-optical disks, and CD-ROM and DVD-ROM disks.

[0055] The instructions 2024 may further be transmitted or received over a communications network 2026 using a transmission medium via the network interface device 2020, utilizing any one of several transport protocols (e.g., Frame Relay, Internet Protocol (IP), Transmission Control Protocol (TCP), User Datagram Protocol (UDP), Hypertext Transfer Protocol (HTTP), etc.). Exemplary communications networks may include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), a mobile phone network (e.g., a cellular network conforming to one or more standards such as the 4G standard or Long Term Evolution (LTE)), a plain old telephone service (POTS) network, and a wireless data network (e.g., the Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards known as Wi-Fi, the IEEE 802.15.4 family of standards, peer-to-peer (P2P) networks, etc., among others). In one example, the network interface device 2020 may include one or more physical jacks (e.g., Ethernet, coaxial, or telephone jacks) or one or more antennas for connecting to the communications network 2026. In one example, the network interface device 2020 may include multiple antennas for wireless communication using at least one of single-input multiple-output (SIMO), multiple-input multiple-output (MIMO), or multiple-input single-output (MISO) technologies. The term "transmission medium" should be understood to include any intangible medium capable of storing, encoding, or carrying instructions for execution by the machine 2000, including digital or analog communications signals or other intangible media for facilitating the communication of such software.

[0056] Various notes Each of the above non-limiting aspects may stand alone or may be combined in various permutations or combinations with one or more of the other aspects or other subject matter described herein.

[0057] The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are also commonly referred to as "examples." Such examples may include elements in addition to those shown or described. However, the inventors also contemplate examples in which only the elements shown or described are provided. Furthermore, the inventors also contemplate examples that use any combination or permutation of those elements (or one or more aspects thereof) shown or described with respect to a particular example (or one or more aspects thereof), or with respect to any other example (or one or more aspects thereof) shown or described herein.

[0058] In the event of a conflict of usage between this document and any document so incorporated by reference, the usage in this document shall control.

[0059] As used herein, the terms "a" or "an" are used to include one or more, as is common in patent documents, regardless of any other instance or usage of "at least one" or "one or more." As used herein, the term "or" is used to refer to a non-exclusive or, unless otherwise indicated, such that "A or B" includes "A but not B," "B but not A," and "A and B." As used herein, the terms "including" and "in which" are used as the plain-English equivalents of the terms "comprising" and "wherein," respectively. Also, in the claims, the terms "including" and "comprising" are open-ended, i.e., systems, devices, articles, compositions, formulations, or processes that include elements in addition to those listed after such terms in a claim are still considered to be within the scope of that claim. Moreover, in the claims, the terms "first," "second," and "third," etc., are used merely as labels and are not intended to impose numerical requirements on their objects.

[0060] Embodiments of the methods described herein may be implemented at least in part by a machine or computer. Some examples may include a computer-readable or machine-readable medium encoded with instructions operable to configure an electronic device to perform the methods described in the examples. Implementations of such methods may include code, such as microcode, assembly language code, higher-level language code, or the like. Such code may include computer-readable instructions for performing various methods. The code may form part of a computer program product. Furthermore, in embodiments, the code may be tangibly stored on one or more volatile, non-transitory, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media may include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memory (RAM), read-only memory (ROM), and the like.

[0061] The above description is intended to be illustrative, not limiting. For example, the examples described above (or one or more aspects thereof) may be used in combination with each other. Other embodiments may be used, for example, by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment.

Claims

1. 1. A machine-implemented method for acoustic assessment of a target using an array of electroacoustic transducers, the machine-implemented method comprising: generating respective acoustic transmit events using different transmit apertures, the transmit apertures being defined by corresponding zones along the array, the zones including a plurality of electroacoustic transducer elements; receiving, in response to the respective acoustic transmit events, respective acoustic echo signals using receiving ones of the electroacoustic transducer elements to form groups of received acoustic echo signals, the groups being indexed by transmit / receive pairs including respective transmit zones and respective ones of the receive elements; coherently summing each of the received representations of the acoustic echo signals, the representations corresponding to each of the transmit / receive pairs, the coherently summing including applying determined nominal element delay coefficients to each of the representations to approximate a virtual probe normal to a nominal shape of a surface of the structure being inspected, and applying respective delay coefficient corrections to compensate for variations from the nominal shape or nominal alignment of the surface of the structure relative to the array of electroacoustic transducers; using the coherently summed representation to generate pixel or voxel values ​​corresponding to designated spatial locations within the inspected structure; A machine implementation method, including:

2. The machine-implemented method of claim 1 , wherein generating the respective acoustic transmit events comprises generating at least three acoustic transmit events using different transmit apertures corresponding to different zones.

3. The machine-implemented method of claim 2 , wherein the zones overlap.

4. A machine-implemented method according to any preceding claim, comprising determining the respective delay factor corrections using a single iteration.

5. The machine-implemented method of claim 1 , comprising determining a respective delay coefficient using each aperture containing two or more electroacoustic transducer elements.

6. The machine-implemented method of claim 1 , wherein the representation of each received acoustic echo signal comprises an A-scan representation.

7. 7. The machine-implemented method of claim 6, wherein generating pixel or voxel values ​​corresponding to specified spatial locations on or within the inspected structure includes generating images of a plurality of spatial locations using respective coherent sums, the respective coherent sums including applying the determined nominal element delay coefficients and applying the respective delay coefficient corrections.

8. The machine mounting method of claim 7 wherein the structure under test is a bar.

9. The machine-implemented method of claim 8 , wherein the image represents a sector within the volume of the bar.

10. 10. The machine-implemented method of claim 9, further comprising performing another acquisition to form another group of received acoustic echo signals to generate another image of a different sector within the volume of the bar, the group being indexed by a transmit / receive pair including the respective transmit zone and each one of the receive elements.

11. 11. The machine-implemented method of claim 10, wherein performing another acquisition includes repositioning the array or the structure under test to allow the array to insonify a different portion of a surface of the structure under test.

12. 11. The machine-implemented method of claim 10, wherein performing the separate acquisition includes using a second array configured to irradiate a different portion of a surface of the structure under test with high frequency sound waves.

13. generating acoustic transmit events to excite shear waves for imaging a surface of the structure under test; Imaging the surface of the structure under test includes coherently summing representations of each received acoustic echo signal, applying the determined nominal element delay coefficients to each representation to approximate a beam perpendicular to the nominal shape of the surface of the inspected structure, and applying respective delay coefficient corrections to compensate for variations from the nominal shape or the nominal alignment of the surface of the structure relative to the array of electroacoustic transducers; using the coherently summed representation to generate pixel or voxel values ​​corresponding to specified spatial locations on the inspected structure; The machine-implemented method of claim 1 , comprising:

14. 1. An ultrasonic inspection system for acoustic evaluation of a target using an array of electroacoustic transducers, the ultrasonic inspection system comprising: an analog front end including transmit and receive circuitry coupled to the array of electroacoustic transducer elements; a processor circuit communicatively coupled to the analog front end; a memory circuit containing instructions that, when executed by the processor circuit, cause the ultrasound inspection system to perform the method of claim 1; An ultrasonic inspection system comprising:

15. 1. An ultrasonic inspection system for acoustic evaluation of a target using an array of electroacoustic transducers, comprising: means for generating respective acoustic transmit events using different transmit apertures, the transmit apertures being defined by corresponding zones along the array, the zones including a plurality of electroacoustic transducer elements; means for receiving, in response to each of the acoustic transmit events, each acoustic echo signal using a receiving one of the electroacoustic transducer elements to form groups of received acoustic echo signals, the groups being indexed by a transmit / receive pair including a respective transmit zone and each one of the receive elements; means for coherently summing a representation of each of the received acoustic echo signals, said representation corresponding to each of the transmit / receive pairs, said coherently summing including applying determined nominal element delay coefficients to each of the representations to approximate a beam normal to a nominal shape of a surface of the structure being inspected, and applying respective delay coefficient corrections to compensate for variations from the nominal shape or nominal alignment of the surface of the structure relative to the array of electroacoustic transducers; means for generating pixel or voxel values ​​corresponding to designated spatial locations within the inspected structure using the coherently summed representation; An ultrasonic inspection system comprising:

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