WO2008130344A1 - Examen doppler à impact acoustique, précoce et à distance - Google Patents

Examen doppler à impact acoustique, précoce et à distance Download PDF

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Publication number
WO2008130344A1
WO2008130344A1 PCT/US2007/009479 US2007009479W WO2008130344A1 WO 2008130344 A1 WO2008130344 A1 WO 2008130344A1 US 2007009479 W US2007009479 W US 2007009479W WO 2008130344 A1 WO2008130344 A1 WO 2008130344A1
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WIPO (PCT)
Prior art keywords
processing
measurements
pixel
velocities
anomalies
Prior art date
Application number
PCT/US2007/009479
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English (en)
Inventor
David C. Macenany
Original Assignee
Bae Systems Information And Electronic Systems Integration Inc.
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Filing date
Publication date
Application filed by Bae Systems Information And Electronic Systems Integration Inc. filed Critical Bae Systems Information And Electronic Systems Integration Inc.
Priority to PCT/US2007/009479 priority Critical patent/WO2008130344A1/fr
Publication of WO2008130344A1 publication Critical patent/WO2008130344A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
    • G01H5/00—Measuring propagation velocity of ultrasonic, sonic or infrasonic waves, e.g. of pressure waves

Definitions

  • the presently disclosed embodiments relate to an improvement on current methods of non-destructive structural analysis that use acoustic impact Doppler techniques.
  • Nondestructive inspection techniques have been employed for many years in the field of structural analysis.
  • the theory itself is simple: an object is bombarded by waves (in many cases, sound waves) such that the incident waves do not fundamentally alter the structure of the object.
  • the waves excite various elements of the objects, which are then analyzed.
  • information may be obtained regarding the internal structure of the object, and the object itself may be accurately imaged.
  • a primary utility of this technique is its ability to examine the structural integrity of an object (for example, an airplane wing) without disassembling the object.
  • Defects such as stress fractures, voids, manufacturing defects, and the like all affect the excitation of the object and thus may be imaged during the processing of the received signals. Comparing a known control image with one generated by the nondestructive analysis and evaluating for said stress fractures, voids, or manufacturing defects is a viable method for determining the quality of a given object. While it may be necessary under certain circumstances to expend the time and resources to disassemble the object and examine it piece by piece, accurate nondestructive testing can greatly streamline the process of structural analysis.
  • RAID Remote Acoustic Impact Doppler
  • U.S. Patent No. 5,616,865 Webster
  • the surface response information is collected, . processed, and combined to generate an image of the interior of the object, revealing anomalies in the substructure.
  • a primary requirement for this method is the generation of high-quality imaging by the acoustic bombardment.
  • the production of such a high quality image is strongly dependent upon the precise positioning of the sources and detectors, as well the minimization of external noise. It is in this step that the disadvantages of the conventional techniques become clear.
  • the current RAID method uses a full spectral analysis of the long-term velocity history obtained at each surface location ("pixel"). That is, the readings from each surface location are collected from the full time record of the inspection and analyzed accordingly. This type of detection scheme is a primary disadvantage with the RAID technique.
  • data collected using conventional RAID techniques might involve various artifacts from microphonics or late-time acoustic reflections from rooms in which the measurements were conducted, involving features having little to do with objects of interest.
  • reflections due to acoustic impacts that occur inside the object may add coherently or incoherently and produce results that do not consistently indicate the true nature of the structure.
  • Anisotropics within the object wherein different elements of the object have different structural characteristics, for example, density, material, etc.
  • the presently disclosed embodiments relate to a method that can significantly improve the image quality in remote acoustic impact Doppler inspection.
  • the primary disadvantage of conventional RAID techniques arise from the fact that over sufficient periods of time, in a multidimensional space, energy from multiple sources mix. Because RAID depends upon its very accurate local response to acoustic impacts, any sort of global energetic response can negatively affect the accuracy of the result.
  • the presently disclosed embodiments refer to a method that focuses the analysis of the impacts on the response of the object in the brief span of time following the acoustic impact ("early time”)-
  • the method overcomes the limitations of conventional RAID evaluation by controlling the initial acoustic impact and limiting the length of time each location is subjected to spectral analysis to the early time. In this way, the problem of energy mixing is traversed by limiting the time scale of the analysis.
  • the method comprises the following steps. First, the distance between the acoustic source and each point on the surface of the object must be estimated. This is necessary for the proper interpretation of the excitation of the object.
  • the distance estimation exploits the fact that the extremely early-time response (i.e., in the span immediately following the 75 impact) has an essentially fixed form, excepting amplitude. This form is nearly functionally independent of location on the object, as well as the material composition at a given location.
  • the qualitative form of this response may be estimated in advance and used .
  • an optimization for example, a least squares optimization
  • the optimization may be repeated to arrive at the best estimation for at each location, allowing for good early- time line-up of the signals received from the object.
  • the object is acoustically impacted by a pressure wave, and the surface 85 response of said object is measured.
  • the surface measurements are then processed to accommodate for various anomalies that may negatively impact the quality of the measurements. These anomalies may include such features as background noise, background pressure, and the like. . ⁇
  • the early-time 90 response is subjected to initial processing, including lining up the signals according to time, spatial distribution, and the like.
  • the full early-time response may then be taken as a small, fixed number of cycles or zero-sum section after the starting time estimate for each pixel.
  • the end result is an optimal segment with a definite initial time that spans and defines the early- time response for each pixel. Additionally, the process may be repeated 95 and a number of such segments may be averaged. Each such segment, or average segment, is then used to describe each pixel to be evaluated.
  • the measurement is sufficiently processed, it is analyzed for indications of , structural anomalies in the object, such as voids, unintended heterogeneities, and manufacturing errors.
  • the parsed data is used to estimate the size and location of the 100 discovered anomalies, which are then classified according to type.
  • Figure 1 depicts an embodiment of the preparations required before the object is impacted.
  • Figure 2 depicts an embodiment of the initial processing that may be performed upon each pixel.
  • Figure 3 depicts an embodiment of the follow-up processing that serves to refine and classify the information gathered from each pixel.
  • Figure 1 depicts an embodiment of the initial stages of the method, during which . the necessary preparations and calculations are accomplished.
  • the surface of the object is divided, specifying the points at which the acoustic impacts will be targeted 100. 115 These points are referred to as pixels, and the process is referred to as pixelization.
  • the distance between the source and each pixel is accurately determined.
  • the calculation of an optimal observational span in step 104 for each pixel exploits the fact that the form (but not the amplitude) of the extremely-early-time response to an acoustic impact is functionally independent of location on the object, as well as the material 120 composition of the object at a specific pixel location.
  • an optimal observational span is calculated for each pixel. This is the time immediately following acoustic impact, when the signal from the surface response is least affected by anomalous external information.
  • these optimal observational spans are collected and
  • the acoustic source 200 generates an air-coupled pressure wave with a smoothly varying spectral content that impacts the object.
  • the surface response is measured by a laser velocimeter 202, . which also serves as a "bad shot” detector 204, determining if the pressure wave impacted 130 the target properly. If a "bad shot” is detected, wherein the pressure wave misses the : intended target, the acoustic source 200 is instructed to emit another pressure wave.
  • the shot velocity • signal received by the laser velocimeter is sent through filters to smooth out meaningless anomalies.
  • a punctured smoothing filter is applied, which is a nonlinear 135 processing filter that smoothes out two-dimensional spikes in the data.
  • a simple low-pass filter is applied to filter some of the background noise inherent in the system.
  • Figure 3 depicts the more advanced processing steps performed upon the signal following the determination of shot velocities 300.
  • any background vibrations now 140 present in the object are estimated as velocities 302 analogous to the velocities induced by the acoustic impact. These estimated background velocities are subtracted from the received shot velocities 304.
  • the velocity readings have now been sufficiently processed to allow for the estimation of probable meaningful anomalous velocities, i.e. velocities that refer to some flaw or feature within the object. From this new data set, anomalous shot 145 velocities are estimated in step 306.
  • step 308 the localized background pressures are estimated at each pixel. These results are used in step 310 to normalize the amplitudes of the recorded anomalous shot velocities and to allow for accurate imaging of the interior. Finally, in step 312, this information is collected and shot velocities indicating meaningful anomalies are culled 150 from the data set. The anomalies are divided according to physical location and segmented into pieces for analysis in step 314, resulting in an estimation of the sizes of the defects or flaws that are represented by the determined anomalies. Finally, the characteristics of the interpreted shot velocity anomalies are analyzed in step 316 to classify the anomalies, for example, in terms of the type of flaw or defect determined.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

L'invention concerne un procédé permettant une analyse non destructive. Le procédé comprend la mesure d'une distance entre une source acoustique et chacun des points qui doivent être analysés (pixels) sur la surface d'un objet. Une optimisation est ensuite définie à l'aide des mesures de distance. Ensuite, l'objet au niveau de chaque pixel cible est bombardé acoustiquement, et la réponse de surface au niveau de chaque pixel est enregistrée et mesurée. Facultativement, les mesures de réponse de surface peuvent être traitées pour prendre en compte des informations extérieures. L'optimisation calculée peut ensuite être utilisée pour générer l'alignement précoce des mesures enregistrées, et les informations traitées peuvent être analysées en utilisant l'alignement précoce généré pour représenter l'image de l'objet à structure interne.
PCT/US2007/009479 2007-04-18 2007-04-18 Examen doppler à impact acoustique, précoce et à distance WO2008130344A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US2007/009479 WO2008130344A1 (fr) 2007-04-18 2007-04-18 Examen doppler à impact acoustique, précoce et à distance

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2007/009479 WO2008130344A1 (fr) 2007-04-18 2007-04-18 Examen doppler à impact acoustique, précoce et à distance

Publications (1)

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WO2008130344A1 true WO2008130344A1 (fr) 2008-10-30

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20240053303A1 (en) * 2022-08-12 2024-02-15 Palo Alto Research Center Incorporated Nondestructive methods and systems for detecting and/or characterizing damage

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050244073A1 (en) * 2004-04-28 2005-11-03 Renato Keshet Polynomial approximation based image filter methods, systems, and machine-readable media
US20070026975A1 (en) * 2001-09-12 2007-02-01 Pillar Vision Corporation Trajectory detection and feedback system
US20070060817A1 (en) * 2005-09-15 2007-03-15 Tim Davies Determining attributes using ultrasound

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070026975A1 (en) * 2001-09-12 2007-02-01 Pillar Vision Corporation Trajectory detection and feedback system
US20050244073A1 (en) * 2004-04-28 2005-11-03 Renato Keshet Polynomial approximation based image filter methods, systems, and machine-readable media
US20070060817A1 (en) * 2005-09-15 2007-03-15 Tim Davies Determining attributes using ultrasound

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20240053303A1 (en) * 2022-08-12 2024-02-15 Palo Alto Research Center Incorporated Nondestructive methods and systems for detecting and/or characterizing damage

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