WO1992008128A1 - Detection de defauts dans le beton - Google Patents

Detection de defauts dans le beton Download PDF

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Publication number
WO1992008128A1
WO1992008128A1 PCT/GB1991/001905 GB9101905W WO9208128A1 WO 1992008128 A1 WO1992008128 A1 WO 1992008128A1 GB 9101905 W GB9101905 W GB 9101905W WO 9208128 A1 WO9208128 A1 WO 9208128A1
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WO
WIPO (PCT)
Prior art keywords
frequency
signals
acoustic
khz
defects
Prior art date
Application number
PCT/GB1991/001905
Other languages
English (en)
Inventor
Patrick Andrew Gaydecki
Frederick Michael Burdekin
Original Assignee
Capcis Limited.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Capcis Limited. filed Critical Capcis Limited.
Publication of WO1992008128A1 publication Critical patent/WO1992008128A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/46—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by spectral analysis, e.g. Fourier analysis or wavelet analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/043—Analysing solids in the interior, e.g. by shear waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/34—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor
    • G01N29/348—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor with frequency characteristics, e.g. single frequency signals, chirp signals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/4454—Signal recognition, e.g. specific values or portions, signal events, signatures
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/023—Solids
    • G01N2291/0232—Glass, ceramics, concrete or stone

Definitions

  • the present invention relates to a method and apparatus for detecting the presence and condition of components or defects embedded in a non-homogeneous body, for example a structural member fabricated from reinforced concrete.
  • Ultra-sonic fault detection has been used for many years to inspect the internal composition of metal components and castings.
  • Transform Technique is used to compute the frequency content of received pulses. This study shows that the frequency spectrum includes dominant frequencies corresponding to for example boundaries of the .plate and planar faults the presence of which within the plates are known. A low frequency peak was noted which corresponded to reflections from the bottom surface of the plate and a higher frequency peak was noted corresponding to reflections from a small diameter disc incorporated in the plate. This technique therefore makes use of wavelengths produced by thickness-mode vibrations of the sample, that is, the depth of the planar defects determines the wavelengths generated.
  • the frequency content of acoustic waves transmitted through a body determine the size of the flaw that can be detected by a monitoring the amplitude of those acoustic signals.
  • a flaw to be detected it must be of the same order of, or larger than, the component wavelengths in the acoustic wave.
  • Higher frequency components have shorter wave lengths and it is only higher frequency components which will be reflected by smaller faults.
  • higher frequency pulses have less penetrating ability as they are attenuated more quickly than low frequency pulses in a non- homogenous material such as concrete.
  • Ultrasonic testing of concrete has generally been restricted to use of transit time measurement at one nominal (low) frequency, to determine pulse velocity, from which physical properties of the concrete itself have been inferred by empirical correlations.
  • a method for detecting the presence ' and condition of components or defects embedded in a non-homogeneous body wherein the body is insonated with an acoustic signal including a predetermined band of frequencies, a receiver transducer is positioned in contact with the body, acoustic signals detected by the transducer are transformed to the frequency domain to produce a frequency spectrum, the detected signals are filtered to produce output signals representing the magnitude of the acoustic signals in each of at least two discrete frequency bands, and the magnitudes of the output signals are compared to derive frequency dependent data relating to defects in the body.
  • the analysis technique of the present invention is entirely different to that described in the above paper by Carino and ' Sansalone.
  • an analysis is made of wavelengths resulting from thickness-mode vibrations, i.e. the frequencies generated are geometry dependent.
  • the transmitter itself generates all frequencies that form part of the analysis, irrespective of sample size or geometry.
  • the body is insonated with acoustic waves in the band from 0 to 400 kHz.
  • This 40Q kHz wide band is then divided into eight bands each 50 kHz in width by filtering to produce eight sets of data which are then inverse transformed. The energies in the eight bands are then compared.
  • comparison depends on the kind of defect which is being sought.
  • comparison can be in the form of cross- multiplication, in which all the energy bands are simply multiplied together, an operation similar in some ways to cross-correlation.
  • This approach is particularly successful in locating moderate to large size voids when increased reflection of all wavelengths is to be expected.
  • smaller faults for example small regions of delamination or complete breakage or separation of reinforcing cables
  • the higher frequency components display changes in energy beyond the limits normally attributable to random variability.
  • Lower frequencies because of their longer wavelengths, remain relatively unaffected by such small faults.
  • a ratio is taken of the high frequency energy in for example the 350-400 kHz band to the low frequency energy in for example the 0 to 50 kHz, using the low frequency energy to check for background variability.
  • filtering in accordance with the present invention enables data to be extracted from signals despite the fact that those signals are dominated by frequency components which do not carry any information of interest.
  • the invention thus makes ultra-sonic techniques applicable to the detection of small faults in concrete in a manner not suggested by the prior art.
  • the use of low frequencies to correct for background variability is not suggested by the prior art.
  • the present invention also provides an apparatus for detecting the presence and condition of components or defects embedded in a non-homogeneous body, comprising means for insonating the body with a wide band acoustic wave, a receiver transducer which is positionable in contact with the body to detect acoustic signals, means for transforming the detected acoustic signals to the frequency domain to produce a frequency spectrum, means for filtering the detected signals to produce output signals representing the magnitude of the acoustic signal in each of at least two discrete frequency bands and means for comparing the magnitudes of the output signals to derive frequency dependent data related to defects in the body.
  • Figure 1 is a schematic illustration of an embodiment of the present invention.
  • FIGS 2 and 3 illustrate typical results obtained using the apparatus illustrated in Figure 1.
  • the system comprises a pair of roller probes, the rollers 1, 2 of which are in use placed in contact with the surface 3 of a concrete body to be investigated.
  • the roller 1 couples signals to the surface 3 and thus acts as a transmitter whereas the roller 2 detects acoustic signals from the surface 3 and acts as a receiver.
  • the rollers are C.N.S rolling probes which are 80 mm in diameter and 40 mm in width with a nominal resonance of 360 kHz. In use, good acoustical couplings to the concrete surface 3 is assured by the soft outer neoprene tyres of the transducers which roll across the surface 3.
  • the surface 3 is also sprayed with water so that a continuous water film is built up between the surface and the probe tyres.
  • the probes are matched symmetrical devices, in that they may act as both transmitters or receivers. Thus the probes are rolled in parallel across a surface to be scanned, the spacing between the rollers in one example being 65 mm as measured from the tyre mid points.
  • the transmitting probe 1 is energized by a Steinkamp pulser unit 4 which generates a 600 volt spike lasting for a few microseconds once every second.
  • a pulse of this nature shocks the transducer into resonance in much the same way that a strike from a clapper excites a bell into ringing at its fundamental frequency.
  • the resulting ultrasonic wave contains the fundamental resonance frequency and in addition many harmonics so that a wide band of frequencies make up the ultrasonic wave which travels through the concrete.
  • the concrete body is thus insonated.
  • the ultrasonic wave is not focused and thus spherical waves are propagated through the body underlying the surface 3, the spherical waves being centred on the point of contact between the transmitting transducer 1 and the surface 3.
  • Acoustic waves are then detected by the probe 2, amplified by an amplifier 5 and applied to a waveform analyzer 6.
  • a synchronization signal is also generated by the unit 4 and applied to the analyzer 6.
  • the synchronization signal instructs the analyzer to record the data then present at its input, that is the signal being picked up by the receiving probe 2.
  • the wave form analyzer 6 may be obtained from the Analogic Corporation, comprising a model 630 analogue to digital converter and a model 610 processing unit.
  • the A to D converter is a twin channel device, featuring independent time bases, a sampling rate ranging from 1.7mHz to 35MHz, a maximum record buffer length of 8192 points, and an in-built anti ⁇ aliasing filter set at 5MHz.
  • Standard sampling resolution is 9 bits (512 levels), with 12 bits in signal compression mode (4096 levels).
  • the device can be triggered in a wide variety of ways, either internally or externally, or clocked for each sample point. Pre- and post-triggering is available as standard.
  • the 6100 processing unit is built around a 16 bit 68000 microprocessor, and has a very comprehensive repertoire of. operations, with more than 50 waveform analysis, manipulation, signal processing and display functions. These include forward and inverse FFTs (typically 400ms for a record length of 512 points), chirp-Z transforms, convolution, correlation and all standard scalar calculations.
  • the analyzer 6 is controlled by a host computer 7 (IBM or compatible) via an IEEE communications interface.
  • a "supervisor" software system instructs the analyzer to perform various signal processing operations on acquired data (described below), and also stores the data onto its hard disc and floppy disc. Using the same program, the data may be read back into the analyzer at a later stage for off-line processing.
  • the supervisor software is a menu based program written in Turbo-Pascal revision 4.0. Its purpose it to provide the user of the system with a simple, powerful and rapid means of control of the analyzer. For instance, many of the operations performed on the data, such as digital filtering of up to 100 records with subsequent energy calculation, would' require a great number of key-presses (not to mention time) if they were executed using the analyzer's front panel controls.
  • the supervisor software By merely providing the supervisor software with the basic information, i.e. which records are to be processed and in what manner, the program instructs the analyzer to automatically sequence through the data, processing and storing the results of the analysis.
  • the roller type transmitting transducer 1 is connected to the 600V output of the pulser/synchronisation unit 4, and the synchronisation output of this device is connected to the trigger input of the A to D converter.
  • the roller type receiver 2 is then connected to one input of the 4-channel amplifier 5, with the gain set to 40dB (X100).
  • the output of the amplifier is in turn fed to one channel input of the A to D converter.
  • the analyzer itself is connected to the host computer by means of a standard IEEE cable. The analyzer, amplifier and computer are then switched on. The supervisor software held in the computer is activated and the program automatically configures the analyzer to the set up normally required for a standard scanning operation.
  • the concrete surface 3 to be scanned is sprayed with water and a transducer bogie supporting the other transducer is positioned at the first scan point.
  • the pulser is then turned on, and a reading is taken every 10 mm.
  • the time records are then stored in the analyzer's memory after each successive reading.
  • the data are transferred to the computer's hard disc by using a file-handling sub ⁇ menu.
  • This sub-menu may instruct the analyzer to - calculate simple scalar measurements on each record and present them as a single trend trace; alternatively it can instruct the analyzer to perform "brick- wall” filtering on the data and then make the above scalar measurements on the filtered data.
  • the supervisor software instructs the analyzer to plot the traces on a Hewlett Packard plotter (not shown).
  • a wide-band signal ranging from near d.c. to several hundred KiloHertz, travels through the concrete.
  • the concrete contains inclusions such as small voids and steel cables, with interface regions between the steel and the concrete.
  • the wide-band signal rapidly loses high frequency energy due to the heterogeneous nature of the medium. Where these frequencies encounter boundary conditions, reflection will occur, the strength being dependent upon the size of the defect in relation to the wavelength.
  • the total signal that arrives at the receiver transducer 2 will include low frequency components of large amplitude and relatively little information content, and high frequency components that do change in strength according to the internal conditions but whose energy may be of the order of a thousand times weaker than the whole signal.
  • the supervisor software instructs the analyzer to convert each ultrasonic record to the frequency domain through the use of its FFT function, and to produce eight new time records of different bandwidths by filtering and inverse transforming the data. These bands are 50 kHz in width, ranging from 0-50 kHz to 350-400 kHz.
  • the analyzer then compares the energies in these bands. The manner in which the bands are compared or combined depends on the kind of defect that is being sought; it can take the form of cross- multiplication, in which all energy bands are simply multiplied together (an operation not dissimilar to cross-correlation), and this has been particularly successful in locating moderate to large sized voids when increased reflectance of all wavelengths is to be expected.
  • Figures 2 and 3 show typical results obtained using the system described above from two regions of a test beam in which paper towels, saturated in salt solution, were wrapped around the reinforcing cables prior to pouring the concrete.
  • the scans were conducted 14 months after casting. Each scan comprised 30 readings, in this case with a scan step of 20 mm. The scans started and finished 300 mm either side of the mid-point of the defects.
  • the vertical axis represents high frequency energy between 350 and 400 kHz, enhanced by normalizing against low frequency variability. The peaks clearly indicate the defective regions.
  • the described system is capable of detecting, through non ⁇ destructive means, many defective conditions inherent to prestressed concrete structures that have hithertofore only been identifiable using invasive or partially destructive methods. It is considered prudent however for the described system to be used in conjunction with other existing systems to obtain the fullest information about the condition of steel components buried in concrete.
  • Tests of the described equipment have shown that the equipment is capable of identifying voids of the order of 30 mm diameter at depth of the order of 100 mm from the surface and major breaks in cables involving a total separation of not less than 30 mm at a depth of approximately 70 mm.
  • the system is also sensitive to regions affected significantly by chloride contamination over similar depths. -Detection of single breaks in a multi-wire cable is however more difficult but this is not surprising given the frequencies used in the described equipment and the relationship between frequency and the size of defects which can be detected. It should be possible however to make the equipment more sensitive to smaller defects by extending the upper limit of the frequency range.
  • the system could be implemented with a plurality of receiving transducers in order to enable tracking and comparison of signals from adjacent regions to be carried out.
  • a central transmitting transducer could be provided with four receiving transducers evenly distributed therearound.
  • the analysis is based mainly on calculations of the energy content of filtered signals.
  • the system is capable of measuring many other scalar quantities relating to the filtered signals, such as amplitude, rates of decay, duty cycle and point-in-time of signal peak.
  • amplitude amplitude
  • rates of decay amplitude
  • duty cycle amplitude
  • point-in-time of signal peak amplitude
  • diagnostic properties relating to the system
  • the accuracy, resolution and diagnostic properties of the system can be enhanced.
  • the spatial accuracy of the system may be . improved.

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  • Physics & Mathematics (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Pathology (AREA)
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  • Engineering & Computer Science (AREA)
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  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

Procédé et appareil permettant de détecter la présence et l'état de composants ou de défauts dans un corps non homogène, dans lesquels ledit corps est d'abord sondé par un signal acoustique à bande de fréquences prédéterminée, par exemple entre 0 et 400 kHz. Un transducteur récepteur est placé en contact avec le corps pour détecter les signaux acoustiques. Les signaux détectés sont transformés en un domaine de fréquences, permettant ainsi de produire un spectre de fréquences. Les signaux sont ensuite filtrés pour produire des signaux de sortie représentant l'intensité des signaux acoustiques dans chacune d'au moins deux bandes de fréquence distinctes. Les intensités des signaux de sortie sont ensuite comparées pour produire une information concernant les défauts du corps sur la base de la fréquence. Grâce aux techniques d'ultrasons utilisées dans l'invention, il est possible de détecter de petits défauts dans des matériaux non homogènes, tels que le béton.
PCT/GB1991/001905 1990-10-30 1991-10-30 Detection de defauts dans le beton WO1992008128A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB909023555A GB9023555D0 (en) 1990-10-30 1990-10-30 Detecting defects in concrete
GB9023555.7 1990-10-30

Publications (1)

Publication Number Publication Date
WO1992008128A1 true WO1992008128A1 (fr) 1992-05-14

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PCT/GB1991/001905 WO1992008128A1 (fr) 1990-10-30 1991-10-30 Detection de defauts dans le beton

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EP (1) EP0555298A1 (fr)
GB (1) GB9023555D0 (fr)
WO (1) WO1992008128A1 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0769143A1 (fr) * 1994-06-07 1997-04-23 Washington Suburban Sanitary Commission Procedes d'examen non destructif de structures de beton precontraint
EP0794430A2 (fr) * 1996-03-07 1997-09-10 E-Systems Inc. Procédé et apparail pour l'évaluation et l'inspection des structures réparées an mayen d'un makrian composite
EP1357381A1 (fr) * 2000-11-02 2003-10-29 Ishikawajima-Harima Heavy Industries Co., Ltd. Procédé et dispositif pour détection de défauts par ultrasons
DE10355297B3 (de) * 2003-11-21 2005-02-17 Hochschule für Technik und Wirtschaft Dresden (FH) Einrichtung und Verfahren zur Erkennung von Defekten in Bewehrungen von Betonbauteilen
GB2475225A (en) * 2009-10-30 2011-05-18 Wayne Rudd A method for monitoring and/or maintaining the condition of a structure such as a pipeline
CN109459494A (zh) * 2018-11-22 2019-03-12 中建四局第六建筑工程有限公司 一种用于钢管内柱高标号山砂混凝土的检测方法及装置
CN115467378A (zh) * 2022-08-16 2022-12-13 江苏鸿基节能新技术股份有限公司 一种移动式地基基础工程智能无线检测设备
CN116893222A (zh) * 2023-08-29 2023-10-17 铁正检测科技有限公司 基于人工智能的铁路隧道混凝土缺陷冲击回声波检测方法

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3008553A1 (de) * 1979-03-12 1980-09-25 Kretztechnik Gmbh Schallkopf fuer untersuchungen mit ultraschall nach dem impuls-echoverfahren und mit diesem schallkopf ausgestattetes ultraschallgeraet

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3008553A1 (de) * 1979-03-12 1980-09-25 Kretztechnik Gmbh Schallkopf fuer untersuchungen mit ultraschall nach dem impuls-echoverfahren und mit diesem schallkopf ausgestattetes ultraschallgeraet

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
IEEE 1988 ULTRASONICS SYMPOSIUM vol. 1, October 1988, CHICAGO, IL, USA pages 915 - 918; XING LI, ET AL.: 'Spectral histogram and its application to flaw detection.' see the whole document *
ULTRASONICS vol. 28, no. 4, July 1990, GUILDFORD SURREY, GB pages 229 - 240; J.D.AUSSEL: 'Split-spectrum processing with finitr impulse response filters of constant frequency-to-bandwidth ratio.' see the whole document *

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0769143A1 (fr) * 1994-06-07 1997-04-23 Washington Suburban Sanitary Commission Procedes d'examen non destructif de structures de beton precontraint
EP0769143A4 (fr) * 1994-06-07 1997-07-09 Washington Suburban Sanitary C Procedes d'examen non destructif de structures de beton precontraint
EP0794430A2 (fr) * 1996-03-07 1997-09-10 E-Systems Inc. Procédé et apparail pour l'évaluation et l'inspection des structures réparées an mayen d'un makrian composite
EP0794430A3 (fr) * 1996-03-07 1999-03-10 E-Systems Inc. Procédé et apparail pour l'évaluation et l'inspection des structures réparées an mayen d'un makrian composite
EP1357381A1 (fr) * 2000-11-02 2003-10-29 Ishikawajima-Harima Heavy Industries Co., Ltd. Procédé et dispositif pour détection de défauts par ultrasons
US6640632B1 (en) 2000-11-02 2003-11-04 Ishikawajima-Harima Heavy Industries Co., Ltd. Ultrasonic flaw detection method and apparatus
DE10355297B3 (de) * 2003-11-21 2005-02-17 Hochschule für Technik und Wirtschaft Dresden (FH) Einrichtung und Verfahren zur Erkennung von Defekten in Bewehrungen von Betonbauteilen
GB2475225A (en) * 2009-10-30 2011-05-18 Wayne Rudd A method for monitoring and/or maintaining the condition of a structure such as a pipeline
CN109459494A (zh) * 2018-11-22 2019-03-12 中建四局第六建筑工程有限公司 一种用于钢管内柱高标号山砂混凝土的检测方法及装置
CN115467378A (zh) * 2022-08-16 2022-12-13 江苏鸿基节能新技术股份有限公司 一种移动式地基基础工程智能无线检测设备
CN115467378B (zh) * 2022-08-16 2024-01-30 江苏鸿基节能新技术股份有限公司 一种移动式地基基础工程智能无线检测设备
CN116893222A (zh) * 2023-08-29 2023-10-17 铁正检测科技有限公司 基于人工智能的铁路隧道混凝土缺陷冲击回声波检测方法
CN116893222B (zh) * 2023-08-29 2024-04-09 铁正检测科技有限公司 基于人工智能的铁路隧道混凝土缺陷冲击回声波检测方法

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Publication number Publication date
GB9023555D0 (en) 1990-12-12
EP0555298A1 (fr) 1993-08-18

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