Dynamic control method using ultrasonic imaging

Abstract

The invention relates to a dynamic method for generating representative data of a part (1) to be inspected, said method comprising: - a step of acquiring data on the part (1) to be inspected by a multi-element sensor (2) comprising: - emitting an ultrasonic pulse (E), and - receiving said reflected wave (R) from the part (1) resulting from the ultrasonic pulse (E), the method further comprising a step of generating representative data of the part (1) to be inspected, characterized in that it further comprises, during the data acquisition step, a relative displacement between the sensor (2) and the part (1) to be inspected, and in that it further comprises a step of generating corrected representative data of the part (1) to be inspected by simulating a relative displacement between the sensor (2) and the element (1) to be inspected up to a reference position. Figure to be published: 3

Description

Title of the invention: Method for dynamic control using ultrasonic imaging. Technical field

[0001] The invention relates to the field of non-destructive testing, such as non-destructive conformity testing of metallic products. More particularly, the invention relates to ultrasonic testing for the presence of defects within a tubular metallic product. Technological background

[0002] Metal tubes are widely used in various sectors of the energy industry, such as power generation, oil and gas, and mechanical engineering. Like most metallurgical products, tubes are susceptible to manufacturing defects, such as inclusions of material in the steel, cracks on their internal or external surface, or porosity. Generally, any heterogeneity in the steel matrix is ​​considered an imperfection that can impair the tube's mechanical strength in service.

[0003] The tubes are therefore checked after their manufacture, not only to detect any defects, but also, where appropriate, to determine information useful for assessing the danger of these defects, in particular their size, depth, position, nature or orientation, and the compliance of these tubes with standards.

[0004] In particular, non-destructive testing techniques using ultrasonic waves are employed. Ultrasonic waves are propagated through the tube, and among the waves reflected by the tube, those that cannot be attributed to the tube's geometry are identified. Defects such as inclusions or absences of material constitute variations within the wave propagation medium and, consequently, generate the reflection of some of the ultrasonic wave energy when they are struck by these ultrasonic waves.

[0005] One type of sensor used for control using ultrasonic waves is a multi-element, sequentially controlled type, generally called a "multi-element transducer" or, by the English expression, a "phased array." This type of sensor comprises a plurality of electroacoustic elements, generally in the form of piezoelectric elements. These piezoelectric elements can be distributed on an active face of the sensor surrounding the tube to be controlled or along a principal alignment direction so as to form an "array."

[0006] In the acquisition strategy called FMC (Full Matrix Capture), with a multi-element sensor comprising n elements, each of the n sensor elements is excited once, these n elements being excited successively to generate n successive ultrasonic emissions. A processing circuit records the individual response, hereafter called A-scan, of the n sensor elements for each of the n emissions. For each element, this individual response represents the amplitude of the ultrasonic waves received by that element during a given listening time. It is then possible to obtain a representative image of a section of the tube by combining the n² recorded A-scans using a TFM (Total Focusing Method) algorithm, also known as FTP (Focalisation en Tout Point) in French.

[0007] In order to obtain TFM images over the entire surface of the tube, acquisition from a plurality of successive shots requires a relative movement of the sensor with respect to the tube in a sequential manner. The sensor is held in a fixed position relative to the tube for a complete series of n shots in order to obtain a static TFM image of the tube in that position, then the sensor is moved relative to the tube to perform the next series of n shots in order to obtain the next image of the tube.

[0008] This method provides accurate images of the tube but requires a significant acquisition time. Therefore, there is a need for a process that allows for obtaining an accurate image of a part to be inspected quickly and reliably. Summary

[0009] One idea underlying the invention is to obtain representative data of a part to be inspected, for example TFM images or A-scans of a tube, quickly and reliably. In particular, one idea underlying the invention is to obtain representative data of the part to be inspected during a relative movement between the sensor used to obtain this data and the part to be inspected. More specifically, one idea underlying the invention is to obtain this data during a continuous relative movement between the sensor and the part to be inspected. One idea underlying the invention is to take into account the relative movement between the sensor and the part to be inspected for the generation of reliable and accurate representative data of the element to be inspected.

[0010] According to one embodiment, the invention provides a method for dynamically acquiring data representative of a part to be inspected, said method comprising: - a data acquisition step on the part to be inspected, said data being obtained by a multi-element sensor, said sensor comprising transmitting elements and receiving elements, the transmitting elements being configured to emit a respective ultrasonic pulse towards the part to be inspected so that said ultrasonic pulse propagates through the part to be inspected, the receiving elements being configured to receive waves reflected by the part to be inspected, i.e. partially reflected and / or entering said part and then at least partially reflected and exiting, resulting from the ultrasonic pulse, said acquisition step comprising: - emit an ultrasonic beam from said emitting element, and - to receive, via said receiving elements, ultrasonic waves for a listening period, said received ultrasonic waves comprising a wave reflected by the part to be inspected resulting from the emitted ultrasonic pulse, the process further comprising a step of generating data representative of the part to be inspected as a function of the waves received by the receiving elements, characterized in that it further comprises, during the data acquisition step, a relative displacement between the sensor and the part to be inspected, and in that it further comprises a step of generating corrected data representative of the part to be inspected, said corrected data generation step comprising: - calculate a corrective displacement based on the relative displacement between the sensor and the part to be controlled, a reference position, and a time period relative to a reference instant, the reference position corresponding to a relative position between the sensor and the part to be controlled at the reference instant, said reference instant occurring during the data acquisition step, said corrective displacement corresponding to a relative displacement between the sensor and the part to be controlled up to the reference position from a relative position corresponding to the relative position between the sensor and the part to be controlled at a time during said time period relative to the reference instant, and - apply to the representative data of the part to be controlled a correction based on the calculated corrective displacement so as to generate said corrected data by simulating a relative displacement between the sensor and the part to be controlled from a relative position between the sensor and the part to be controlled at the time of said duration to the reference position.

[0011] Representative data of a part to be inspected refers to information relating to the shape, thickness, media differences, etc., of the part to be inspected. For example, this representative data of the part to be inspected may take the form of a cross-sectional image of the part to be inspected, a matrix containing a plurality of A-scans of the part to be inspected, A-scans of said part to be inspected, or any other form. Furthermore, the time relative to the reference time corresponds to the time difference between the acquisition time of a representative data point and the part to be checked and the reference time, this duration being positive or negative depending on whether said acquisition time is before or after the reference time.

[0012] Thanks to these characteristics, it is possible to obtain representative data of a part to be inspected reliably and quickly. Indeed, thanks to these characteristics, it is possible to obtain this data quickly because the sensor and the part to be inspected are in motion relative to each other. Furthermore, by applying a correction based on the relative displacement between the sensor and the part to be inspected, the reference position, and the time elapsed relative to the reference instant, it is possible to obtain representative data of the part to be inspected in the reference position with a high degree of accuracy despite the relative displacement between the sensor and the part to be inspected during the acquisition of said data.

[0013] According to embodiments, such a dynamic acquisition method may include one or more of the following characteristics.

[0014] According to one embodiment, the relative movement between the sensor and the part to be controlled is continuous. Such continuous movement during data acquisition allows for a good execution speed of the process.

[0015] The part to be inspected can take many forms. In one embodiment, the part to be inspected is a tube. Such a tube can have many cross-sectional shapes, such as circular, square, or other. Similarly, such a tube can have a constant or variable wall thickness.

[0016] According to one embodiment, applying a correction to the representative data of the part to be inspected includes a step of applying a virtual displacement, for example a virtual rotation around an axis of rotation of the part to be inspected, to said representative data of the part to be inspected so as to generate corrected data. A virtual displacement is understood to mean the modification of the representative data of the profile of the part to be inspected to simulate a corrective displacement of the part to be inspected without said part to be inspected physically undergoing such a corrective displacement.

[0017] In one embodiment, the calculation of the corrective displacement involves calculating a respective corrective displacement for one, several, or each of the representative data of the part to be inspected. In one embodiment, the time relative to the reference instant for a respective corrective displacement corresponds to the time relative to the reference instant corresponding to the time difference between the instant corresponding to the relative position between the sensor and the part to be inspected, represented by said representative data of the part to be inspected, and the reference instant. This time is positive or negative depending on whether said instant, represented by the representative data of the part to be inspected, is before or after the reference instant. the reference instant. According to one embodiment, the application of the correction is carried out for one, several or each data representative of the part to be controlled according to the respective corrective displacement associated with said data representative of the part to be controlled.

[0018] According to one embodiment, the data acquisition step comprises - the emission of a plurality of ultrasonic shots, preferably successively in time, and - for each emission stage of said ultrasonic signal, a corresponding stage, during a respective listening time, of reception of the ultrasonic waves by said receiving elements of the sensor, said received ultrasonic waves comprising at least one wave reflected by the part to be inspected resulting from the corresponding emitted ultrasonic pulse and in which the reference instant is an instant of emission of an ultrasonic shot from the plurality of ultrasonic shots and the duration is a multiple of the duration separating two successive ultrasonic shots from the plurality of ultrasonic shots such that the corrective displacement is calculated as a function of the relative displacement between the sensor and the part to be controlled between the emission of two distinct ultrasonic shots.

[0019] Two ultrasonic shots, and preferably all ultrasonic shots, are carried out sequentially, i.e. at distinct emission times, so as to avoid interference between ultrasonic waves emitted from distinct emitting elements.

[0020] The corrective displacement can be calculated for different portions of a relative displacement between the sensor and the part to be inspected. In one embodiment, the corrective displacement is calculated as a function of the relative displacement between the sensor and the part to be inspected between the emission of two distinct ultrasonic pulses, for example, two successive ultrasonic pulses. In other words, in one embodiment, the reference position is the relative position between the sensor and the part to be inspected at a reference instant corresponding to the emission of an ultrasonic pulse.

[0021] Thanks to these characteristics, and in particular thanks to the execution of a plurality of shots from a plurality of emitting elements of the sensor, it is possible to obtain information on the part to be inspected from different orientations of said part. In particular, each ultrasonic shot makes it possible to obtain a set of data relating to the part to be inspected along an identified ultrasonic path, said path starting from the position of the emitting element and generating reflected waves received at the respective positions of the receiving elements that receive said reflected waves.

[0022] In one embodiment, the corrected data generation step includes selecting a reference position. In one embodiment, the position of The reference position corresponds to a relative position between the part to be inspected and the sensor during a selected ultrasonic pulse. In one embodiment, the reference position, and therefore the corresponding reference time, is provided beforehand, for example, by being selected by default or by being stored in the system's memory. In one embodiment, the reference position is the relative position between the sensor and the part to be inspected at the time of the first pulse. In another embodiment, the reference position is the relative position between the sensor and the part to be inspected at the time of the last emitted ultrasonic pulse.

[0023] Thus, it is possible to obtain a clear image of the part to be checked in a defined position, typically the reference position.

[0024] The representative data of the part to be controlled can take many forms.

[0025] In one embodiment, the representative data of the part to be inspected comprises the intensity of the ultrasonic waves reflected by the part to be inspected and received by one, several, or each receiving element of the sensor over time. Representative data of the part to be inspected in this form are hereinafter referred to as A-Scans. In another embodiment, the representative data of the part to be inspected comprises the A-Scans generated from the ultrasonic waves received by one, several, or each of the receiving elements of the sensor following the same ultrasonic signal emitted by a transmitting element of the sensor.

[0026] In one embodiment, the data representing the part to be inspected comprises the A-scans generated from the ultrasonic waves received by one, several, or each of the sensor's receiving elements following a plurality of ultrasonic pulses emitted successively by a corresponding emitting element of the sensor, and preferably from a plurality of respective ultrasonic pulses emitted successively by several distinct emitting elements of the sensor. In another embodiment, the data representing the part to be inspected comprises a matrix containing the A-scans generated from a plurality of successive ultrasonic pulses and the waves reflected by the part to be inspected following said ultrasonic pulses and received by a plurality of receiving elements.

[0027] According to one embodiment, the data representing the part to be inspected comprises a partial image for one, several, or each of the plurality of ultrasonic shots emitted during the acquisition step, the application of a correction to the data representing the part to be inspected comprising a step of modifying the partial image to simulate a displacement of the part to be inspected from the relative position between the sensor and the part to be inspected illustrated therein. partial image up to the reference position in order to generate a corrected partial image.

[0028] According to one embodiment, a partial image is generated based on the waves reflected by the part to be inspected resulting from a single ultrasonic pulse. In another embodiment, each point of a partial image is determined based on the A-scans generated from the waves reflected by the part to be inspected, which are received by the receiving elements following the emission of the same ultrasonic signal.

[0029] According to one embodiment, the method comprises generating a representative image of the part to be inspected based on the corrected data. According to another embodiment, the method further comprises a step of generating a representative image of the part to be inspected by superimposing a plurality of corrected partial images.

[0030] Such partial images and corrected partial images make it possible to obtain a representative image of the part to be inspected and thus information on the part to be inspected in a quick and clear manner, for example on the location, dimensions and other characteristics of a defect present in the part to be inspected.

[0031] According to one embodiment, the data representing the part to be controlled comprises a matrix, each row of the matrix comprising the data representing the part to be controlled generated following a respective ultrasonic shot, each column of the matrix comprising the data representing the part to be controlled generated from a respective receiving element of the sensor, the calculation of the corrective displacement comprising for each ultrasonic shot a calculation of a respective reception offset in number of receiving elements of the sensor, the application of a correction comprising for one, several or each row of the matrix the application for cells of said row of an offset, in number of columns, of the content of said cells of the corresponding reception offset.

[0032] According to one embodiment, the listening time has a start time equal to the time of emission of the ultrasonic shot, said listening time being greater than or equal to a maximum time of flight between the emission of the ultrasonic shot and the reception by a said receiving element of the sensor of a wave reflected by a face of the part to be controlled opposite to the sensor so that the corrective displacement is calculated as a function of the relative displacement between the sensor and the part to be controlled during a propagation time between a time of emission of an ultrasonic shot and a time of reception of the waves reflected by the part to be controlled resulting from said ultrasonic shot by the receiving element(s).According to one embodiment, the final reception time corresponds to the listening time, that is to say, the time from which, following an ultrasonic blast, the receiving element(s) are configured to no longer receive ultrasonic waves, and in particular the ultrasonic waves resulting from said ultrasonic blast. In other words, according to one embodiment, the corrective displacement is calculated as a function of the relative displacement between the sensor and the part to be controlled during the propagation of the same ultrasonic shot from its emission to the reception of the waves reflected by the part to be controlled resulting from this ultrasonic shot by the receiving element(s).

[0033] According to one embodiment, the data representing the part to be controlled includes, for each receiving element, a respective A-Scan representing an intensity of the waves received by said receiver as a function of a listening time of said receiving element.

[0034] According to one embodiment, the calculation of the corrective displacement involves the division, for the respective A-Scans of the receiving elements, into a plurality of time blocks.

[0035] In one embodiment, the calculation of the corrective displacement involves calculating the signal reception time by a receiver element of the plurality of receiver elements as a function of the relative displacement between the sensor and the part to be inspected. In another embodiment, each time block of an A-Scan has a duration equal to the signal reception time of the receiver element for the relative displacement of the sensor with respect to the part to be inspected.

[0036] According to one embodiment, the signal reception time by said receiving element corresponds to the time during which, during the relative movement between the sensor and the part to be controlled, a signal emitted continuously from the part to be controlled is received by said receiving element, a time greater than this reception time resulting in the reception of said continuous signal by an adjacent receiving element.

[0037] According to one embodiment, one, several or each time block has a duration equal to a signal reception duration of the receiver that received the waves reflected by the part to be controlled that made it possible to generate said A-Scan.

[0038] According to one embodiment, the calculation of the corrective displacement includes the calculation of a shift in the number of receiving elements as a function of the relative positions of the receiving elements, the signal reception times of said receiving elements and the time of emission of the ultrasonic signal.

[0039] According to one embodiment, the offset is an integer representing, for a given time block of an original A-Scan, the number of A-Scans by which said time block must be offset along the direction of relative movement between the part to be inspected and the sensor. In other words, the offset represents the number of A-Scans between the original A-Scan and a target A-Scan to which said time block must be allocated for the same time range.

[0040] According to one embodiment, for a given time block of an original A-Scan, the offset is equal to the maximum number of successive receiving elements following, according to a direction of relative movement between the sensor and the part to be controlled and from the receiving element having received the reflected waves of said original A-Scan, that is to say according to a reference position and the direction of rotation of the part, the cumulative sum of the signal reception times of which is less than the time elapsed between the reference instant and the start instant of said time block.

[0041] According to one embodiment, the application of a correction involves, for at least one time block of the original A-Scan, the replacement of a portion of a target A-Scan by said time block, said target A-Scan corresponding to the A-Scan generated from the nth receiving element following the receiver having received the parts of the energy of the reflected waves of the original A-Scan, in the direction of relative movement between the sensor and the part to be controlled, n being the calculated offset, the portion of the target A-Scan having the same start and end time as the time block.

[0042] According to one embodiment, the relative displacement between the sensor and the part to be controlled results from a displacement of the part to be controlled and the holding in fixed position of the sensor during the displacement of the part to be controlled, the displacement of the part to be controlled having an angular component around an axis of rotation, the calculation of a corrective displacement comprising a step of calculating the angular displacement of the part to be controlled during said relative displacement between the sensor and the part to be controlled.

[0043] According to one embodiment, the calculation of a corrective displacement includes a step of calculating the angular displacement of the part to be controlled during said relative displacement between the sensor and the part to be controlled and in which the correction of the data representing the part to be controlled includes the simulation of a rotation of the part to be controlled around its axis of rotation according to an angle corresponding to the angular displacement of the part to be controlled during the acquisition step.

[0044] Thus, by directly correcting the A-Scans, it is possible to obtain a clear and precise image of the part to be inspected, taking into account the relative displacement between the part to be inspected and the sensor, including during the propagation of the same ultrasonic shot within the part to be inspected.

[0045] According to one embodiment, the relative displacement between the sensor and the part to be controlled can be of different kinds.

[0046] In one embodiment, the relative displacement between the sensor and the part to be monitored results from a displacement of the part to be monitored and the sensor remaining in a fixed position during the movement of the part to be monitored. In one embodiment, the displacement of the part to be monitored has an angular component around an axis of rotation, for example, the longitudinal axis of a tube in the case of a tube-shaped part to be inspected. In one embodiment, the displacement of the part to be inspected has a longitudinal component along a longitudinal axis, for example, the longitudinal axis of the tube being inspected. The part to be inspected is, for example, driven in a helical motion relative to the sensor. In another embodiment, the relative displacement between the sensor and the part to be inspected results from the movement of the sensor and the fixed positioning of the part to be inspected.

[0047] In one embodiment, the calculation of a corrective displacement includes a step of calculating the angular displacement of the part to be controlled. In another embodiment, the calculation of the corrective displacement includes a calculation of the relative displacement between the sensor and the part to be controlled along an axis of relative displacement between the sensor and the part to be controlled.

[0048] According to one embodiment, the generation of the representative image of the part to be checked is carried out based on the corrected A-Scans. Brief description of the figures

[0049] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings.

[0050] [Fig-1] The [Fig. 1] is a cross-sectional view of a tube with a defect and of a multi-element sensor configured to generate data representative of the tube;

[0051] [Fig.2] The [Fig.2] is a matrix of representative data of the tube generated at starting from the sensor of [Fig. 1];

[0052] [Fig. 3] [Fig. 3] is a cross-sectional view of the tube of [Fig. 1] during a rotation of said tube. tube at an angle 'a' between two successive ultrasonic shots;

[0053] [Fig.4] [Fig.4] is a representative image of the tube obtained from the matrix of [Fig.2] in the case of a tube displacement at a rotational speed of 0.109 m / s;

[0054] [Fig.5] [Fig.5] is an image analogous to [Fig.4] in the case of a displacement of the tube at a rotational speed of 0.36 m / s;

[0055] [Fig.6] [Fig.6] is an image analogous to [Fig.4] in the case of a displacement of the tube at a rotational speed of 0.8 m / s;

[0056] [Fig.7] Fig.7 is a cross-sectional view of the tube in Fig.1 illustrating different tube defect positions as a function of tube rotation within a circular multi-element sensor surrounding the tube;

[0057] [Fig-8] The [Fig.8] is a simplified representation of a matrix analogous to the matrix of the [Fig.2] obtained by means of the sensor of the [Fig.7] and illustrating the correction made as a function of a rotation of the tube;

[0058] [Fig.9] Fig.9 is a cross-sectional view of the tube in Fig.1 illustrating different positions of the tube defect as a function of the tube rotation during the same ultrasonic shot;

[0059] [Fig. 10] The [Fig. 10] is a representation of different A-Scans obtained by the sensor of the [Fig.9] during the ultrasonic firing;

[0060] [Fig. 11] The [Fig. 11] is a representation of the different corrected A-Scans obtained from the original A-Scans illustrated on the [Fig. 10].

[0061] [Fig. 12] The [Fig. 12] illustrates a raw image and the amplitudes of the pixels in column 150 of this raw image in the absence of correction;

[0062] [Fig. 13] The [Fig. 13] illustrates a corrected image obtained by modifying the data which enabled the generation of the raw image of the [Fig. 12] to take into account the relative displacement between the tube and the sensor as well as the amplitudes of the pixels of column 150 of this corrected image. Description of the implementation methods

[0063] Oil, gas, and other resource extraction requires a large number of pipes. Due to the numerous stresses these pipes are subjected to during both installation and operation, they must comply with standards to prevent any degradation or leakage into the environment.

[0064] Tubular components manufactured for this type of operation must therefore be inspected to ensure they do not have defects that could compromise their usability. To perform this inspection, representative data of the tube are generated using sensors; this data makes it possible to detect the presence and characteristics of any potential defects in the tube. Such defects include, for example, surface cracks or discontinuities in the material inside the tube wall.

[0065] Fig. 1 schematically illustrates a cross-sectional view of a tube 1 and a sensor 2.

[0066] Tube 1 is circular in shape and has a longitudinal axis 3. The tube 1 has a defect 4. The defect 4 is for example a crack in the wall of tube 1, that is to say that this defect 4 is located between an external surface 5 of tube 1 and an internal surface 6 of said tube 1.

[0067] To provide data representative of the tube 1, the sensor 2 comprises a plurality of elements 7. In the embodiment illustrated in [Fig.1], the sensor 2 comprises a housing 8 carrying all the elements 7. These elements 7 are aligned along a longitudinal axis 9 of the sensor 2.

[0068] Each element 7 is capable of emitting an ultrasonic wave E, also called ultrasonic shot E, and, on the other hand, receiving received waves R. As an example, an element 7 can be a piezoelectric strip having a width of 1mm and a length, also called elevation, of 10mm.

[0069] The sensor 2 is positioned at the periphery, for example above, of the tube 1 so that the elements 7 are oriented to emit the ultrasonic wave E in the direction of the tube 1. For example, the sensor 2 is positioned so as to present its longitudinal axis 9 perpendicular to the longitudinal axis 3 of the tube 1. A coupling separates the tube 1 from the surface of the sensor 2 to allow the propagation of the ultrasonic waves E, for example a column of water, gel or any other medium allowing the propagation of the ultrasonic wave.

[0070] When an ultrasonic wave encounters a change in medium during its propagation, part of the ultrasonic wave's energy is transmitted to the new medium and part of the ultrasonic wave's energy is reflected back at the interface between the two media. Thus, part of the energy of the ultrasonic wave E emitted by an element 7 of the sensor 2 is reflected back for each change in propagation medium encountered, so that part of the energy of the ultrasonic wave E is reflected when this ultrasonic wave E reaches, respectively, the external surface 5 of the tube 1, the defect 4, or the internal surface 6 of the tube 1.

[0071] After each emission of an ultrasonic wave E, the signal representing the ultrasonic waves received and / or the absence of ultrasonic waves received by each of the elements 7 is recorded. These recordings are made during a predetermined time range following the emission of an ultrasonic wave E. During this time range, the ultrasonic waves received by the element 7 include the waves resulting from the reflection of the ultrasonic wave on the tube 1.

[0072] The elements 7 thus make it possible to generate, from the set of received waves R, and therefore from the waves reflected following an ultrasonic pulse E, representative A-Scans of the tube 1. Each A-Scan represents the amplitude of the waves received R by an element 7 as a function of time, this amplitude being zero when the element 7 does not receive an ultrasonic wave. These A-Scans therefore make it possible to determine the state of the tube 1 as a function of the position of the ultrasonic wave emitting element E, the reflected wave receiving element, the time of flight of the ultrasonic waves, and the propagation media.

[0073] During the control of the tube 1, ultrasonic shots E are carried out successively with each of the elements 7 of the sensor 2. For each ultrasonic shot E, a plurality of A-scan type data is thus obtained comprising the ultrasonic waves reflected by the tube 1 and received by each of the elements 7 of the sensor 2.

[0074] For a sensor 2 comprising n elements 7, the set of A-Scans generated from successive ultrasonic pulses E and ultrasonic waves received R by the n elements 7 are recorded in a matrix as illustrated in [Fig. 2], where the A-scan corresponding to the emission by element n and the reception by element m is recorded in the cell EnRm. Such a matrix can be obtained in different ways, i.e., according to different A-Scan acquisition strategies. According to one embodiment, the matrix acquisition strategy is of the TFM type, from the English acronym "total focusing method".According to one embodiment, the acquisition method is of the "sparse-TFM" type (meaning that not all cells of the matrix contain A-scan (emission and / or reception with a portion of the elements), PWI (from the English "Plane Wave Imaging"), i.e., that several or all of the elements are used in emission for each ultrasonic shot, with different angles of incidence by means of a delay law allowing to deflect the ultrasonic beam, sparse-PWI, or any other acquisition method consisting of recording A-scans associated with a multitude of ultrasonic trajectories traveled between one or more emitting elements and one or more receiving elements.

[0075] In such a matrix, each row 10 represents the set of A-Scans generated from the n elements 7 of the sensor 2 following the emission of an ultrasonic wave E; emitted by an ith element 7. These A-Scans are therefore representative of the waves received Ri to Rn by the n elements 7 following the emission of the ultrasonic wave E;. Thus, the first row 10 of the matrix illustrated in [Fig. 2] contains a set of data EiRi, EiR2 ... EiRn i, EiRn, corresponding to the A-Scans generated from the waves received Ri, R2.. .Rn i and Rn by the n elements 7 following the emission of the ultrasonic shot Ei by the first element 7. Similarly, the last row 10 of this matrix contains a set of data EnRi, EnR2....EnRn i and EnRn corresponding to the A-Scans generated from the waves received Ri to Rn by the n elements 7 following the emission of the ultrasonic shot En by the nth element 7.

[0076] Furthermore, each column 11 of this matrix contains the set of A-Scans generated from the received waves R by an ith element 7 following the n successive ultrasonic shots Ei to En by the n elements 7. Thus, the first column 11 of the matrix illustrated in [Fig. 2] contains a set of data EiRi, E2Ri...EnRi corresponding to the A-Scans generated from the received waves Ri by the first element 7 following the n ultrasonic shots Ei to En by the n elements 7.

[0077] The matrix (also called the "FMC matrix") illustrated in [Fig. 2] therefore comprises n rows and n columns, each row 10 corresponding to the set of A-Scans generated following the emission of an ultrasonic shot Ei by an ith element 7 of the sensor 2 and each column 11 corresponding to the A-Scans generated from the waves received Rj by a jth element 7 of sensor 2.

[0078] The matrix illustrated in [Fig. 2] contains a set of data representative of tube 1. It is possible to reconstruct from this matrix an image corresponding to a cross-sectional representation of tube 1. In such an image, each pixel is associated with a value representative of the propagation medium of tube 1. For example, such an image contains, for each point in the image, the sum of the values ​​of the different A-scans in the matrix as a function of the theoretical times of flight at that point in the image. In other words, all the A-scans in the matrix are analyzed and compiled to define the acoustic properties of tube 1 at that point in the image.For each A-Scan and for each point in the image, there is an associated theoretical time of flight of the ultrasonic wave which corresponds to the time required for the ultrasonic wave E from the emitting element to reach the targeted image point plus the time required for a wave reflected from said targeted image point to reach the receiving element corresponding to the A-Scan.

[0079] The amplitude of the A-Scan signal at the theoretical time of flight thus determined is representative of the material constituting the tube 1 for the targeted point. If the tube 1 does not have a defect or a change in the nature of the medium at the targeted image point, the emitted ultrasonic wave E is not reflected at said targeted point, so there is no reflected wave and the A-Scan signal from the receiving element 7 has a zero amplitude, or an amplitude equivalent to the background noise, for example, related to the electronic system or other disturbances, at the determined theoretical time of flight. Conversely, if the targeted image point corresponds to a defect or a change in the medium in the tube 1, then the emitted ultrasonic wave E is reflected at said targeted image point, so that the A-Scan signal from the receiving element 7 has a non-zero amplitude at the theoretical time of flight, this non-zero amplitude being representative of the wave reflected at the targeted image point.The image obtained by adding, for each pixel, the amplitude of the different A-scans as a function of the corresponding theoretical times of flight therefore makes it possible to determine the nature of the medium in which the ultrasonic wave E circulated at each point of the image.

[0080] When successive ultrasonic pulses E are emitted without relative movement between sensor 2 and tube 1, analyzing all the A-scans of the matrix as a function of flight times yields a clear and high-quality image of tube 1. However, this relative immobility between sensor 2 and tube 1 during the acquisition of data representing tube 1 necessitates a significant data acquisition time. Indeed, it is necessary to maintain the relative positioning between sensor 2 and tube 1 during the acquisition of all the A-scans of a matrix. that is, from the first ultrasonic shot Ei until the reception of the received waves Rn following the last ultrasonic shot En by the last receiving element 7. This solution is therefore hardly compatible with an industrial process which requires the analysis of long lengths of tube 1 as quickly as possible.

[0081] In order to improve the acquisition speed of representative data from tube 1, tube 1 and sensor 2 are driven in relative displacement during data acquisition. This relative displacement between tube 1 and sensor 2, and therefore between elements 7, is preferably continuous.

[0082] In the description below, representative data of tube 1 is acquired by holding sensor 2, and therefore elements 7, in a fixed position and rotating tube 1 helically around its longitudinal axis 3. Such a relative displacement between tube 1 and elements 7 is equivalent to a translational displacement of elements 7 along the longitudinal axis 3 of tube 1 and a rotational displacement around said longitudinal axis 3 of tube 1. Such a helical displacement of tube 1 is, for example, carried out at a rotational speed around the longitudinal axis 3 of tube 1 on the order of Im / s. However, this relative displacement between tube 1 and sensor 2 could also be obtained by holding tube 1 in a fixed position and rotating sensor 2 around tube 1, or by any other relative movement between sensor 2 and tube 1.

[0083] The relative displacement between the tube 1 and the elements 7 implies a relative displacement of the defect 4 with respect to the elements 7. This relative displacement results in an angular shift in the location of the defect 4 around the longitudinal axis 3 of the tube 1 with respect to the elements 7. Between two successive ultrasonic shots E, the data recorded by the elements 7 within the same matrix therefore exhibit an angular shift corresponding to the relative displacement between the tube 1 and the elements 7.

[0084] Figure 3 illustrates such a displacement of the defect 4 by an angle θ between two successive ultrasonic shots E1 and E1+i. This displacement of the defect 4 is linked to the rotation of the tube 1 in a direction of rotation 24 around the longitudinal axis 3. For the sake of readability and understanding, the same defect 4 is illustrated both in a first position 12 and in a second position 13 on Figure 3, thus illustrating the shift of angle θ in the positioning of the defect 4 between two successive ultrasonic shots E1 and E1+i.

[0085] In view of this [Fig. 3], it is clear that a sharp image of tube 1 cannot be obtained with the method described above. Indeed, due to this displacement of the defect 4 between the two successive ultrasonic shots E1 and E1, the A-scans generated from The amplitudes of these two successive ultrasonic shots E; and E; +i do not represent the same location for the defect 4 in tube 1. For a targeted point in an image of tube 1, the A-scans resulting from the ultrasonic shot E; have an amplitude corresponding to the presence of the defect 4 in a first position 12, while the A-scans resulting from the ultrasonic shot Ei+i have an amplitude corresponding to the presence of the defect 4 in a second position 13, this second position 13 being offset by an angle 0 relative to the first position 12. Consequently, the sum of the amplitudes of the different A-scans for a targeted point in the image is no longer representative of the structure of tube 1 since, for the same targeted point in the image, the amplitudes of the different A-scans in the matrix do not correspond to the same location for the defect 4.The image thus obtained from the matrix is ​​therefore blurry, with defect 4 being indicated imprecisely on the image, appearing as a trail forming an arc instead of a well-defined spot.

[0086] The image blurring effect is all the more pronounced as the rotation speed of the tube 1 around its longitudinal axis 3 increases. Indeed, the faster the tube 1 rotates around its longitudinal axis 3, the greater the angular shift 0 of the defect 4 between two ultrasonic shots E1 and E1+1, and therefore the greater the angular shift in the positioning of the defect 4 between these two successive ultrasonic shots E1 and E1+1.

[0087] Figures 4 to 6 illustrate, by way of example, three images generated within the frame of a tube 1 and a sensor 2 analogous to those above opposite Figures 1 to 3, with helical displacement of the tube 1 at different speeds. These precise images are generated using a 10 MHz sensor 2 comprising 64 elements 7 spaced 0.35 mm center to center.

[0088] Fig. 4 represents a precise image obtained following ultrasonic shots E of the set of elements 7 with a rotation speed of tube 1 of 0.109 m / s.

[0089] Fig. 5 represents a precise image obtained following ultrasonic shots E of the set of elements 7 with a rotation speed of tube 1 of 0.36 m / s.

[0090] Fig. 6 represents a precise image obtained following ultrasonic shots E of the set of elements 7 with a rotation speed of tube 1 of 0.8 m / s.

[0091] With the tube 1 rotated at a reduced speed of 0.109 m / s ([Fig. 4]), the rotation of the tube 2 has no perceptible impact on the image obtained, which shows the defect 4 to be well localized and reliably dimensionable. However, this speed is too low and does not correspond to industrial production rates.

[0092] With a rotation speed of tube 1 of 0.36 m / s, the image obtained makes it possible to detect the presence of the defect 4 without further information about this defect 4. Indeed, The defect 4 is represented on this image of [Fig.5] in such a blurry way that only the information on the presence of a defect 4 can be obtained from this image, without any further details on the characteristics of this defect 4. With a rotation speed of tube 1 of 0.8 m / s as illustrated in [Fig.6], the image obtained is even more blurry and even the detection of the defect 4 may be questionable because its amplitude is all the more diminished as it occupies a large area on the image.

[0093] In order to obtain a sharp image despite the relative movement between tube 1 and sensor 2, the image reconstruction according to the invention advantageously takes into account the relative movement between tube 1 and sensor 2 during data acquisition. To this end, the representative data of tube 1 obtained during the relative movement between tube 1 and sensor 2 are corrected.

[0094] One idea underlying this correction is to acquire representative data of tube 1 during a relative displacement between tube 1 and sensor 2, and then modify this data by simulating a displacement of tube 1 around a reference position. This reference position is a relative position between sensor 2 and tube 1 during the displacement of tube 1. This reference position can be predetermined or arbitrarily selected. This reference position can be any relative position between sensor 2 and tube 1 during the displacement of tube 1, for example, the relative position between tube 1 and sensor 2 at a reference instant corresponding to the instant of emission of the first ultrasonic pulse Ei or the last ultrasonic pulse En.

[0095] Modifying the data by simulating a relative displacement between tube 1 and sensor 2 to the chosen reference position allows for the generation of corrected data that closely correspond to the data that would have been obtained in the absence of relative movement between tube 1 and sensor 2 at said reference position. In other words, the idea is to generate data representative of tube 1 during a relative displacement between tube 1 and sensor 2, and then to modify this data to simulate an acquisition of said data within the framework of a static relative position between tube 1 and sensor 2.

[0096] In the following description, this reference position and the associated reference time correspond to the relative position between tube 1 and sensor 2 at the time of emission of the first ultrasonic shot Eb. Thus, taking into account the displacement of tube 1 amounts to simulating, for each shot, a reversal of said displacement of tube 1 from the position corresponding to the data to be corrected to the position of the first ultrasonic shot Eb.

[0097] In order to simulate a reversal of the relative displacement between the tube 1 and the sensor 2 between two successive ultrasonic shots E1 and E1, each ultrasonic shot E1 is processed individually to generate a respective partial image. This partial image corresponds to a cross-sectional view of tube 1 in the relative position of tube 1 with respect to sensor 2, generated from the data obtained from a single ultrasonic pulse E. A plurality of partial images are therefore generated, each partial image being generated from the data obtained following a respective ultrasonic pulse E. These partial images are generated in a manner analogous to the method described above, but taking into account only the A-scans obtained for a given ultrasonic pulse E (i.e., a single row of the FMC matrix) and not from the A-scans of the entire matrix.

[0098] Such a partial image includes, for each pixel of the partial image, the sum of the amplitudes of the A-Scans generated from a single ultrasonic shot E. Each pixel of the partial image is therefore associated with the sum of the amplitudes of the A-Scans of a single ultrasonic shot E.

[0099] However, since each partial image is formed from only a single ultrasonic pulse E, each partial image represents tube 1 in a specific relative position of tube 1 with respect to sensor 2. In order to combine the different partial images obtained to produce a clear and precise image of tube 1, it is necessary to take into account the angular offset between the successive ultrasonic pulses E. To this end, the partial images generated from the A-scan lines of the matrix are modified by simulating the reversal of motion between tube 1 and sensor 2 from a relative reference position in order to obtain corrected partial images.

[0100] To simulate a reversal of the relative motion between tube 1 and sensor 2, it is necessary to know the relative motion carried out between tube 1 and sensor 2 between two successive ultrasonic shots E; and E; +[.

[0101] In the context of a helical drive of the tube 1 causing a rotational displacement of said tube 1 around its longitudinal axis 3 at a speed of Vrot, with a sensor 2 presenting a number PRF (from the English expression "Push Repetition Frequency") of ultrasonic shots per second, the external surface 5 of the tube 1 moves between two successive ultrasonic shots E; and E; +[ by a distance AL satisfying the equation AL = Vrot / PRF.

[0102] However, between a first ultrasonic shot E; performed by an emitting element i at a time h and a second ultrasonic shot E; +[ performed by an emitting element i + 1 at a time h + b, the defect 4 has moved by an angle A0. This angle A0 corresponds to the rotation of the tube 1 around its longitudinal axis 3 during a time interval At = f + i - f between two successive ultrasonic shots E; and E; +[. The distance AL traveled by the external surface 5 between two successive ultrasonic shots E; and E; +[ corresponds to therefore also to the equation AL = R* A0, in which R is the radius of tube 1 at the external surface 5 and A0 is the angle expressed in radians corresponding to the rotation of tube 1 around its longitudinal axis 3 between two successive ultrasonic shots E; and E; +i.

[0103] It follows from these two equations that A0 = Vrot / (R*PRF).

[0104] With regard to the matrix illustrated in [Fig. 2], this means that between two rows 10 of said matrix, and therefore between two successive ultrasonic shots E1 and E1, the recorded data are shifted by an angle A0 corresponding to the equation A0 = Vrot / (R*PRF). In other words, the partial images generated from two successive rows 10 of the matrix illustrated in [Fig. 2] are geometrically shifted by a rotation of angle A0 around a point which is the center of rotation of the tube 1, theoretically its axis 3.

[0105] As explained above, the partial image obtained from the first ultrasonic shot E1 is arbitrarily selected as the relative reference position. The angular position of tube 1 relative to this angular reference position is then calculated for all subsequent ultrasonic shots E1. In the example given above, the second partial image obtained from the ultrasonic shot E2 exhibits an angular offset of tube 1 of angle A0 around its axis of rotation relative to the reference partial image, while the i-th partial image obtained from the i-th ultrasonic shot exhibits an angular offset of angle (i1)*A0 around its axis of rotation relative to the reference partial image.

[0106] The partial images are then corrected by applying to the position of the tube 1 represented on said partial images a rotation inverse to the calculated angular offset. In the case of a tube 1 rotating through an angle A0 between two successive ultrasonic shots E; and E; +[, this amounts to generating the partial images and then, for each ith partial image thus generated, simulating on said partial image a rotation of the tube 1 around its longitudinal axis 3 by an angle a=(il)* A0 in a direction of rotation opposite to the direction of rotation of the tube 1.

[0107] With respect to the matrix illustrated in [Fig. 2], taking the first partial image as the reference image, the corrected partial image generated from the first row 10 of the matrix is ​​identical to the partial image generated from said first row 10 since, in this case, i=l and the correction to be applied with respect to the reference partial image corresponds to a rotation by an angle a=(ll)* A0=0 around the longitudinal axis 3 of tube 1. The corrected partial image generated from the second row 10 of the matrix corresponds to the application of a rotation of tube 1 by an angle a=(2-l)* A0=A0 around the longitudinal axis 3 of tube 1 in a direction of rotation opposite to the direction of rotation of tube 1 to the partial image generated from said second line 10 of the matrix. In general, the corrected partial image generated from an nth line 10 of the matrix corresponds to the application of a rotation of an angle a=(nl)* A0 around the longitudinal axis 3 of the tube 1 in a direction of rotation opposite to the direction of rotation of the tube 1 to the partial image generated from said nth line 10 of the matrix.

[0108] With such a correction, the corrected partial images are comparable to images that would have been obtained using a sensor 2 fixed relative to the tube 1 from a single respective ultrasonic pulse E. The corrected partial images thus obtained therefore show an identical position of the defect 4 despite the displacement of said defect 4 during data acquisition, this position of the defect 4 corresponding to the reference position. A clear image of the tube 1 can then be generated by superimposing, after rotation, the corrected partial images obtained, that is to say, by adding the representative amplitudes of the tube 1 for each pixel of the combined corrected partial images.

[0109] The image obtained by superimposing after rotation the corrected partial images does not generate a blurring effect and allows a clear and precise image of the tube 1 to be obtained on which it is possible to accurately characterize the shape and size of the detected defects 4.

[0110] The above example is given in the context of a tube 1 as illustrated in [Fig. 3] which is driven in rotation relative to elements 7 aligned along the longitudinal axis 9 perpendicular to the longitudinal axis 3 of the tube 1. However, the correction could be applied analogously with any other shape of part to be controlled as well as for any other type of relative displacement. The idea is to generate data representative of a part to be controlled during a relative displacement between said part and the sensor, and then to modify this data by simulating a relative displacement so that the corrected data are analogous to data that would have been obtained in the absence of relative displacement between the part to be controlled and the sensor.

[0111] By way of example, in the context of a relative movement in the form of a translation along the longitudinal axis 3 of the tube 1, i.e. without rotation of the tube 1, the correction would consist of simulating a relative displacement along said longitudinal axis 3 of the tube 1 up to the reference position, i.e. to generate partial images corrected by translation along the axis 3 of the tube 1 and in a direction of translation bringing to the reference position the partial images obtained from the matrix.

[0112] Alternatively, it is possible to simulate a reversal of the movement of tube 1 without generating partial images. In an alternative embodiment, the correction is performed by directly shifting the A-Scans in the matrix. This embodiment allows obtaining a corrected matrix from which a clear image of the tube section can be obtained directly by the amplitude summation method of the A-Scans described above.

[0113] Figure 7 illustrates the case of a sensor 2 surrounded by n elements. In this example, only tube 1 is driven in rotation around its longitudinal axis 3. This Figure 7 illustrates in particular the reception shift, in number of receiving elements 7, of the received waves R due to the rotation of tube 1. In this Figure 7, an ultrasonic pulse E is emitted at time t0, this ultrasonic wave E enters the tube at time h, a reflected wave R exits tube 1 at time ti+At and is received by the receiving element 7 at time tf.

[0114] When the tube 1 rotates through an angle A0 during a time interval At, the rotation of the tube 1 generates a shift between the emission and reception points of the ultrasonic shot E of a distance AL on the surface of the sensor 2. To facilitate understanding of this phenomenon, the example illustrated in [Fig.7] presents the case of an AL equal to the pitch of the sensor 2, i.e. the distance between the center of two adjacent elements 7, but the invention applies analogously to any other value of AL.

[0115] In the case illustrated in [Fig.7], we obtain the following equations: AL = Rs x A0 (1) A0 = Vo x At (2) Vrot = Vo X Rt (3) where Rs is the internal radius of sensor 2, Vo is the angular rotation speed of tube 1 in rad / s, Vrot is the rotation speed of tube 1 in m / s and Rt is the external radius of tube 1.

[0116] A distance in number of elements Déi between the emission and reception points of the ultrasonic shot E on the sensor 2, during a single ultrasonic shot E, expressed in number of elements 7 of the sensor 2, corresponds to the ratio between AL and the pitch p of the sensor 2, that is to say responding to the following equation: Dél = AL / p(4).

[0117] In view of equations 1 to 3 above, it follows that: Dei = (Rs x Vrot x At) / (px Rt) (5)

[0118] Thus, by selecting as the reference position the initial position of tube 1 at the beginning of the acquisition, typically during the emission of the first ultrasonic pulse Ei, the displacement of tube 1 at the end of the listening period for the received waves R following the first ultrasonic pulse Ei is equal to the rotation carried out during a time interval At illustrated, for example, in [Fig. 7]. Similarly, with respect to this initial position of tube 1, the displacement of tube 1 at the end of the listening period for the received waves following the second pulse The ultrasonic displacement E2 is equal to the rotation performed during a time interval At + 1 / PRF. Generally, relative to this initial position of tube 1 at the beginning of the acquisition, the displacement of tube 1 upon receiving the received waves R resulting from the keme shot is equal to the rotation performed during a time interval At + (kl) / PRF.

[0119] The distance Déi(k) between the emission and reception points on sensor 2, for the keme shot and expressed as the number of elements of sensor 2, therefore corresponds to the equation: Dél(k) = (AL + AL2) / p (6) With: AL2 = Rs x AOPRF (7), and AOPRF = Vo / PRF (8) Where AOPRF is the angle of rotation of tube 1, during a time interval 1 / PRF

[0120] We therefore obtain: Del(k) = [(Rs x Vrot) / (px Rt)] x [At + (k-1) / PRF)] (9)

[0121] Once Déi(k) has been calculated for each of the n ultrasonic shots E of the acquisition, the following approximations can be made: If Déi(k) < 0.5, the shift in number of elements is zero; If 0.5 < Dfl(k) < 1.5, the shift in the number of elements is 1 element; If x+0.5 < Dfl(k) < x+1.5, the shift in the number of elements is x+1 elements.

[0122] The calculation of Déi allows the matrix to be corrected directly by shifting the recorded A-Scans directly within the matrix. Typically, as explained above with regard to [Fig. 2], when the matrix is ​​generated, the E;Rj cell of the matrix contains the A-scan of the waves received following the ultrasonic firing emitted by element i, and whose reflected waves are received by element j. However, the reflected waves resulting from the ultrasonic firing E; which should be received by element j in the absence of relative movement between tube 1 and sensor 2 are, due to the rotation of tube 1 during data acquisition, received by element j+Dfl(i). Thus, the A-scan E;Rj is actually located in the cell E,R(J ; n of the matrix, depending on the direction of rotation of the tube 1 relative to the direction of numbering of the elements 7 of the sensor 2.It is therefore necessary to take this shift Déi into account in order to obtain a corrected matrix. A complete, unblurred image can then be obtained using the method described above by adding the amplitudes of the A-scans of the corrected matrix obtained.

[0123] Figure 8 illustrates an example of a matrix showing the initial positions of the generated A-scans, denoted E;Rj(s), and the corrected positions of said A-scans in the matrix, denoted E;Rj(d). In this example, the calculated offset in the number of elements Déi increases by one element with each new ultrasonic shot E relative to the initial ultrasonic shot Ei.

[0124] In this [Fig. 8], the first ultrasonic shot Eb, or initial shot, does not require any shifting of the A-Scans EiRj(s) in the first row 10. The A-Scans E;Rj(s) in the second row 10 are shifted by one column according to the direction of rotation of tube 1, one column to the left in the illustrated example. Similarly, the A-Scans E;Rj(s) in the third row 10 are shifted two columns to the left in [Fig. 8], and so on. This yields a corrected matrix in which the A-Scans E;Rj(d) associated with the different cells correspond to the A-Scans that would be generated in the absence of relative movement between tube 1 and sensor 2. It is then possible to generate a clear image by adding the amplitudes of the A-Scans E;Rj(d) to the appropriate times of flight of this corrected matrix as explained above.

[0125] When the offset Dfl causes the cell contents to shift outside the matrix, the matrix is ​​advantageously augmented by a corresponding number of elements, the calculation of the net image taking into account elements 7 virtually added to sensor 2, these elements 7 being added in continuity with the elements 7 of sensor 2, i.e., with an identical pitch. In a variant, these A-Scans shifted outside the matrix can be ignored, but the net image is then calculated from a reduced number of A-Scans.

[0126] In order to improve the sharpness of the images obtained, it is also possible to take into account the rotation of the tube 1 around its longitudinal axis 3 during the propagation of each ultrasonic shot E in the tube 1. Indeed, if the rotation speed of the tube 1 is particularly high, it is possible that the defect 4 moves significantly between the moment of emission of an ultrasonic shot E and the moment of reception of the reflected ultrasonic waves resulting from this ultrasonic shot E.

[0127] The description below is given in the context of a high rotational speed causing the displacement of the defect 4 during the propagation of an ultrasonic pulse E, but this displacement could also be related to factors other than the rotational speed. Such factors could, for example, be the height of the water column and / or the thickness of the tube 1, which also affect the time of flight of the ultrasonic wave and consequently the PRF (peak repetition frequency).

[0128] From a certain rotational speed of the tube 1, the rotation of the tube 1 during the propagation of an ultrasonic pulse E is such that the energy emitted by the same ultrasonic pulse E is received by the elements 7 with a spatial delay in reception. Thus, between the instant of emission of the ultrasonic pulse E by an element 7 of the sensor 2 and the instant of reception of a reflected wave R resulting from this ultrasonic pulse E, the tube 1 may have undergone a rotation such that the reflected wave is not received by the element 7 that would have been the targeted receiving element 7 if the tube 1 had remained stationary, but by another element 7.

[0129] Fig. 9 illustrates this phenomenon of delayed reception of reflected waves during the propagation of the same ultrasonic shot E in the tube 1. In this Fig. 9, the sensor 2 is circular and the elements 7 are arranged in a circular fashion around the tube 1.

[0130] On this [Fig.9], an ultrasonic shot En is emitted by the element n. This ultrasonic shot En impacts the external surface 5 of the tube 1 at time ti, the defect 4 then being in a first position 14 with respect to the sensor 2. The ultrasonic shot En then propagates in the tube 1.

[0131] At time ti+dt, dt representing a rotation time of tube 1, tube 1 has undergone a rotation of angle dç. At said time ti+dt, the ultrasonic shot En has reached the defect 4, the defect 4 then having a second position 15, and a reflected wave elô resulting from the reflection of the ultrasonic shot En on this defect 4 travels towards the external surface 5 of tube 1.

[0132] At time ti+k*dt, the reflected wave 16 resulting from the reflection of the shot En on the defect 4 returns to the external surface 5 of tube 1 and exits tube 1. At said time ti+k*dt, tube 1 has rotated about its longitudinal axis 3 by an angle k*d^. During the time k*dt, the external surface 5 of tube 1 has rotated by a distance DL satisfying the equation DL = Vrot*k*dt

[0133] If the propagation time k*dt of the ultrasonic pulse En in tube 1 and / or the rotational speed Vrot of tube 1 are such that DL is negligible compared to the angular distance between the centers of two adjacent elements 7, and preferably compared to the distance separating the centers of two adjacent elements 7 divided by two, then the displacement of tube 1 relative to sensor 2 can be considered negligible during a single ultrasonic pulse E. The rotation of tube 1 is therefore considered insufficient to create a reception shift during a single ultrasonic pulse E.

[0134] If the propagation time k*dt of the ultrasonic pulse En in tube 1 and / or the rotational speed Vrot of tube 1 are such that DL is greater than the distance separating the centers of two adjacent elements 7, some of the reflected waves received by the receiving elements 7 should normally have been received by other elements. Consequently, the reflected waves R received by a receiving element 25 following the ultrasonic pulse E emitted by a transmitting element 26 are not representative of a propagation path identified for the association between said receiving element 25 and transmitting element 26. The A-Scan generated following the reception of the reflected waves by the receiving element 25 is therefore erroneous.

[0135] The EiR data recorded in the matrix, i.e. the A-Scans corresponding to the waves received R by the different elements 7 following each ultrasonic shot E, are themselves are erroneous. It is then the A-Scans E;R; themselves that must be corrected in the matrix in order to obtain a clear image of tube 1.

[0136] In a manner analogous to the correction of partial images or of the matrix explained above, the correction of A-Scans consists of simulating a relative displacement between the tube 1 and the sensor 2 up to the reference position in order to obtain to generate corrected A-Scans corresponding to the A-Scans which would have been obtained in the absence of relative movement between the tube 1 and the sensor 2.

[0137] To explain this shift phenomenon in A-Scans, the case of an ultrasonic shot E; emitted by a th element 7 and of waves received R; following said ultrasonic shot E; received by this same th element 7 is used.

[0138] Provided that the ultrasonic wave propagation medium E; between the sensor 2 and the tube 1 is not moving relative to the sensor 2, the reflected wave resulting from the impact of the shot E; on the external surface 5 of the tube 1, also called the interface echo, is not impacted by the rotation of the tube 1. This interface echo is therefore received normally by the th transducer 7.

[0139] As explained above, between the instant ti of impact of the shot E; on the external surface 5 of the tube 1 and the instant ti+k*dt at which the reflected wave 16 returns to the external surface 5 of the tube 1, said tube 1 has undergone a rotation of an angle k*d^.

[0140] If k*d^ is greater than the angle co formed by the center of tube 1 and the centers of two adjacent elements 7, then a reflected wave resulting from the impact of the shot E; on the defect 4 and emerging in a direction perpendicular to the external surface 5 of tube 1, which would therefore be received by the ith element 7 in the absence of rotation of tube 1, does not emerge opposite the ith element 7. Consequently, this reflected wave is received by a jth element distinct from the ith element 7.

[0141] Thus, if k*d^ is greater than the angle co, the A-Scans are distorted and it is necessary to correct them by taking into account the rotation k*d^ of the tube 1 during the propagation of the ultrasonic shot E; in the tube 1. As explained above and analogously to taking into account the rotation of the tube 1 between two successive ultrasonic shots E; and Ei+i, the idea is to simulate a displacement of the tube 1 to the reference position, typically a reversal of the movement of the tube 1 when the reference position is the position at the time of emission of the shot, in order to obtain corrected A-Scans substantially analogous to the A-Scans that would be obtained in the absence of movement of the tube 1. For this, for each ultrasonic shot E, the A-Scans resulting from the waves received R by the different elements 7 are generated first and then corrected.

[0142] A first step in correcting A-scans consists of calculating a time increment dtp leading to a rotation dlp equal to the distance separating the center of two adjacent elements 7. In the example illustrated in [Fig.9], this amounts to determining the angle co separating the center of two adjacent elements 7 and calculating the time dtp required for tube 1 to perform a rotation equivalent to this angle co.

[0143] In a second step, the A-Scans are divided into blocks 17 of a duration dtp. In figures 10 and 11, each block 17 is associated with a reference E;Rj(tx-ty) meaning that it is the waves received R during a duration tx-ty by a jth element following an ith ultrasonic shot.

[0144] Figure 10 illustrates A-scans 18 resulting from the reception by a plurality of elements 7 of the waves received R following the same ultrasonic pulse E. In this Figure 10, each A-scan 18 shown is generated from the waves received R by an element 7 during a succession of time intervals dtp. In this Figure 10, each of the A-scans 18 is therefore divided into a plurality of time blocks 17, each time block 17 having a duration dtp corresponding to the rotation time of the tube 1 required to traverse the angle co separating the center of two adjacent elements 7.

[0145] As explained above, on an A-Scan 18 illustrated in [Fig. 10], the various time blocks 17 are not all representative of an identified path between the transmitting element 26 and the receiving element 25 that generated said A-Scan at the corresponding time of flight. Indeed, due to the rotation of the tube 1, these blocks 17 are generated from reflected waves received by the receiving element 25 but which should have been received by other elements 7, due to the rotation of the tube 1.

[0146] The correction of an A-Scan therefore consists, for each A-Scan generated from the waves received R by an element 7, of selecting the blocks 17 which should have been received by another element 7 and associating said blocks 17 with the element 7 which should normally have received this block 17. In the context of a rotation of the tube 1, this amounts to shifting the blocks 17 of an original A-Scan generated from the waves received R by an element 7 towards a respective target A-Scan which would normally have received the reflected waves corresponding to said block 17 in the absence of rotation of the tube 1.

[0147] [Fig. 11] illustrates the different corrected A-Scans for the different elements 7 from the original A-Scans shown in [Fig. 10].

[0148] In [Fig. 10], the i-th blocks 17 are generated from the received waves R during the time ranges dti to dti+i. However, at time dti, tube 1 has rotated around its longitudinal axis 3 by an angle i*co. The reflected waves represented in these i-th blocks 17 were therefore received by elements 7 offset by i blocks 17. In other words, the reflected wave received by a k-th element 7 during the time range dti to dti+i would, in the absence of relative movement between sensor 2 and tube 1, have been received by a k-th element 7.

[0149] The correction of the A-Scans 18 by simulating the reverse movement of the tube 1, within a reference position corresponding to the instant of emission of the ultrasonic shot, can therefore be carried out by shifting the i-th blocks 17 of the range dti-dti+i by a number i of A-Scans 18 in the opposite direction of rotation of the tube 1. In other words, to correct the A-Scans 18, the blocks 17 dtpi-dtpi+i of an A-Scan 18 generated by an nth element 7 are shifted towards the corresponding block 17, that is to say the block 17 of the range dtpi-dtpi+i, of the i+n element,

[0150] Thus, in [Fig. 11], the blocks 17 of the A-Scans 18 illustrated in [Fig. 10] are shifted to simulate the reversal of the movement of tube 1. The i-th blocks 17 of each line in [Fig. 10] are therefore shifted by i lines in [Fig. 11] to correct the A-Scans 18 in [Fig. 10]. In [Fig. 11] obtained by this correction, each line therefore presents a corrected A-Scan 18 corresponding to the A-Scan 18 that would have been obtained by the element 7 associated with said line in the absence of relative movement between tube 1 and sensor 2.

[0151] By comparison between [Fig. 10] and [Fig. 11], we observe that the second blocks 17 of each line L of [Fig. 10], corresponding to a time interval d^-dtp2, are shifted by one line in [Fig. 11] to replace the second block 17 of the following line, i.e., line L+1. Similarly, the third blocks 17 of each line L of [Fig. 10], corresponding to a time interval dtp2-dtp3, are shifted by two lines in [Fig. 11] to replace the third block of line L+2. For example, a corrected A-Scan 19 of [Fig. 11] corresponding to the fifth element 7, typically the fifth line of [Fig. 11], successively includes, from time t0 to time dtp4, a first block 20 of the fifth line of [Fig. 11]. 10], a second block 21 of the fourth line of [Fig.10], a third block 22 of the third line of [Fig. 10] and a fourth block 23 of the second line of [Fig. 10].This corrected A-Scan 19 therefore includes blocks 20 to 23 corresponding to the waves received R by the different elements 7 in the context of a rotation of the tube 1 relative to the sensor 2 and which would have been received only by the fifth element 7 if there had been no relative movement between the tube 1 and the sensor 2. .

[0152] In [Fig. 11], the empty cells correspond to blocks 17 presenting a signal of zero amplitude for the A-Scans. These blocks 17 are of little consequence because they represent a signal of empty amplitude and therefore do not alter the resulting image. In any case, when the shift causes the blocks 17 of the original A-Scan to shift out of the target A-Scan, the duration of the target A-Scan is advantageously increased by a number of blocks 17 corresponding analogously to the virtual increase in the size of the matrix described above.

[0153] Furthermore, to facilitate understanding of the correction performed at the A-Scans 18, Figures 9 to 11 illustrate the case of a circular sensor 2 such that each element 7 covers a circular section of identical angle co around the tube 1. Thus, the rotation of the tube 1 causes a shift in the reception of the reflected waves R which is identical for all elements 7, so that the duration dtp of the block cutting of the blocks 17 is identical for all the A-Scans 18. However, the arrangement of the elements 7 can be achieved in many ways. For example, the elements 7 can be aligned along a longitudinal axis as is the case in the embodiment illustrated in Figures 1 and 3. In this case, it is necessary to take into account the curvature of the tube 1 with respect to the position of the different elements 7.For this, the dtp can be calculated by taking into account other parameters such as the exit angle of the reflected waves or the projection of DL onto the axis 9 of alignment of the elements 7. For each element 7, such a calculation leads to obtaining blocks 17 with different durations depending on the relative location of the element 7 with respect to the tube 1. Similarly, it is necessary to take into account this difference in duration of the blocks 17 between the different elements 7 to determine the offset of the blocks 17 between the different elements 7.

[0154] Furthermore, the relative displacement between the tube 1 and the sensor 2 corrected in the example given above by way of illustration is an angular displacement with respect to the longitudinal axis 3 of the tube 1. However, this displacement could be of another nature such as for example a translation along said longitudinal axis 3 or other.

[0155] Figure 12 illustrates a raw image (left part of the figure) and the pixel amplitudes of column 150 of this raw image (right part of the figure). This raw image is generated from the raw data, i.e., before correction according to the invention, acquired during a relative movement between the tube 1 and the sensor 2. This raw image shows defect 4 in tube 1 but has significant blurring which does not allow for precise characterization of defect 4.

[0156] Figure 13 illustrates the corrected image produced according to the method described above, using partial images and the amplitudes of the pixels in column 150 of this corrected image. This corrected image is clear and allows for the precise and reliable characterization of defect 4, despite the fact that the data used to generate this corrected image were obtained during relative movement between tube 1 and sensor 2. The amplitude gain on the defect resulting from the correction is 5.7 dB. Thus, thanks to the invention, it is possible to obtain a clear and precise image of a part to be inspected reliably and quickly, the data used to obtain this corrected image being acquired during relative movement between tube 1 and sensor 2.

[0157] The above description is made in the context of a tube 1, for example metallic, however the element to be controlled could be of a completely different nature in terms of shape and / or materials.

[0158] The above description is given in the context of a sensor comprising elements 7 that are both capable of emitting and receiving ultrasonic waves. However, such a sensor could comprise separate ultrasonic emitting and receiving elements.

[0159] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

[0160] Thus, the examples described above are carried out within the framework of a linear sensor 2; however, the method can be applied within the framework of sensors comprising elements 7 arranged in two dimensions, allowing the reconstruction of a three-dimensional volume in a manner analogous to the reconstruction described above for a two-dimensional image reconstruction. Such a sensor comprises, for example, a plurality of elements 7 arranged in rows and columns.

[0161] The use of the verb "comprise", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim.

[0162] In the claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

1. Demands A method for dynamically acquiring representative data of a metallic part (1) to be inspected, said method comprising: - a data acquisition step on the part (1) to be inspected, said data being obtained by a multi-element sensor (2), said sensor (2) comprising emitting elements and receiving elements, the emitting elements being configured to emit a respective ultrasonic pulse (E) in the direction of the part (1) to be inspected such that said ultrasonic pulse (E) propagates through the part (1) to be inspected, the receiving elements being configured to receive waves reflected (R) by the part (1) to be inspected resulting from the ultrasonic pulse (E), said acquisition step comprising: - emit an ultrasonic beam (E) from said emitting element, and - receiving, via said receiving elements, ultrasonic waves for a listening period, said received ultrasonic waves comprising a wave reflected by the part (1) to be inspected resulting from the emitted ultrasonic pulse (E), the method further comprising a step of generating data representative of the part (1) to be inspected as a function of the waves received by the receiving elements, characterized in that it further comprises, during the data acquisition step, a step of driving one of the parts (1) to be inspected and the sensor (2) in displacement along and / or around an axis so as to generate a relative displacement between the sensor (2) and the part (1) to be inspected, and in that it further comprises a step of generating corrected data representative of the part (1) to be inspected, said corrected data generation step comprising: - calculate a corrective displacement based on the relative displacement between the sensor (2) and the part (1) to be inspected, a reference position, and a time relative to a reference instant, the reference position corresponding to a relative position between the sensor (2) and the part (1) to be inspected at the reference instant, said reference instant occurring during the data acquisition step, said corrective displacement corresponding to a displacement relative between the sensor (2) and the part (1) to be controlled up to the reference position from a relative position corresponding to the relative position between the sensor (2) and the part (1) to be controlled at a time in said time relative to the reference time, and - apply to the representative data of the part (1) to be controlled a correction as a function of the corrective displacement calculated so as to generate said corrected data by simulating a relative displacement between the sensor (2) and the part (1) to be controlled from a relative position between the sensor (2) and the part (1) to be controlled at the time in said time up to the reference position.

2. A dynamic acquisition method according to claim 1, wherein the corrected data generation step includes a reference position selection.

3. A dynamic acquisition method according to claim 1 or 2, wherein the data acquisition step comprises - the emission of a plurality of ultrasonic shots (E), and - for each emission step of said ultrasonic signal, a corresponding step, during a respective listening time, of reception of the ultrasonic waves by said receiving elements of the sensor (2), said received ultrasonic waves comprising at least one wave reflected by the part (1) to be controlled resulting from the corresponding emitted ultrasonic shot and wherein the reference time is an emission time of an ultrasonic shot of the plurality of ultrasonic shots and the duration is a multiple of the duration separating two successive ultrasonic shots of the plurality of ultrasonic shots such that the corrective displacement is calculated as a function of the relative displacement between the sensor (2) and the part (1) to be controlled between the emission of two distinct ultrasonic shots.

4. A dynamic acquisition method according to claim 3, wherein the representative data of the part (1) to be inspected comprises a partial image for the plurality of ultrasonic shots (E) emitted during the acquisition step, the application of a correction to the representative data of the part (1) to be inspected comprising a step of modifying the partial image to simulate a displacement of the part (1) to be inspected from the relative position between the sensor (2) and the part (1) to be inspected illustrated therein. partial image up to the reference position in order to generate a corrected partial image.

5. A dynamic acquisition method according to claim 4, further comprising a step of generating a representative image of the part (1) to be checked by superimposing a plurality of corrected partial images.

6. A dynamic acquisition method according to claim 3, wherein the data representing the part (1) to be checked comprises a matrix, each row of the matrix comprising the data representing the part (1) to be checked generated following a respective ultrasonic shot (E), each column of the matrix comprising the data representing the part (1) to be checked generated from a respective receiving element of the sensor (2), the calculation of the corrective displacement comprising for each ultrasonic shot (E) a calculation of a respective reception offset in number of receiving elements of the sensor (2), the application of a correction comprising for each row of the matrix the application for cells of said row of an offset, in number of columns, of the content of said cells of the corresponding reception offset.

7. A dynamic acquisition method according to any one of claims 1 to 6, wherein the listening time has a start time equal to the time of emission of the ultrasonic shot, said listening time being greater than or equal to a maximum time of flight between the emission of the ultrasonic shot and the reception by a said receiving element of the sensor of a wave reflected by a face of the part (l) to be controlled opposite to the sensor such that the corrective displacement is calculated as a function of the relative displacement between the sensor (2) and the part (1) to be controlled during a propagation time between a time of emission of the ultrasonic shot (E) and a time of reception of the waves reflected by the part (1) to be controlled resulting from said ultrasonic shot (E) by the receiving elements.

8. Dynamic acquisition method according to claim 7, wherein the data representing the part (1) to be controlled comprise, for each receiving element, a respective A-Scan (18) representative of an intensity of the waves received by said receiver as a function of the listening time of said receiving element.

9. A dynamic acquisition method according to claim 8, wherein the calculation of the corrective displacement includes the segmentation, for the respective A-Scans (18) of the receiving elements, in a plurality of temporal blocks (17).

10. Dynamic acquisition method according to claim 9, wherein the calculation of the corrective displacement comprises the calculation of a signal reception time (dtp) by a said receiver element of the plurality of receiver elements as a function of the relative displacement between the sensor (2) and the part (1) to be controlled, and wherein each time block (17) of a said A-Scan (18) has a duration equal to the reception time (dtp) of the receiver element for the relative displacement of the sensor with respect to the part (1) to be controlled.

11. Dynamic acquisition method according to claim 10, wherein the calculation of the corrective displacement includes the calculation of a shift in the number of receiving elements as a function of the relative positions of the receiving elements, the signal reception times (dtp) of said receiving elements and the emission time of the ultrasonic signal (E).

12. Dynamic acquisition method according to claim 11, wherein, for a given time block (17) of an original A-Scan, the offset is equal to the maximum number of subsequent successive receiving elements, along a direction of relative movement between the sensor (2) and the part (1) to be controlled and from the receiving element having received the reflected waves of said original A-Scan, the cumulative sum of whose signal reception times (dtp) is less than the time elapsed between the reference instant and the start instant of said time block (17).

13. Dynamic acquisition method according to claim 12, wherein the application of a correction comprises, for at least one time block (17) of the original A-Scan, the replacement of a portion of a target A-Scan by said time block (17), said target A-Scan corresponding to the A-Scan generated from the nth receiver element following the receiver having received the reflected waves of the original A-Scan, in the direction of relative movement between the sensor (2) and the part (1) to be controlled, n being the calculated offset, the portion of the target A-Scan having the same start and end time as the time block.

14. A dynamic acquisition method according to any one of claims 1 to 13, wherein the relative displacement between the sensor (2) and the part (1) to be controlled results from a displacement of the part (1) to be controlled and the holding in fixed position of the sensor (2) during the displacement of the part (1) to be controlled, the displacement of the part (1) to be controlled having an angular component around an axis of rotation (3), the calculation of a corrective displacement comprising a step of calculating the angular displacement (d0) of the part (1) to be controlled during said relative displacement between the sensor (2) and the part (1) to be controlled.

15. Dynamic acquisition method according to claim 14, wherein the calculation of a corrective displacement includes a step of calculating the angular displacement of the part (1) to be controlled during said relative displacement between the sensor (2) and the part (1) to be controlled and wherein the correction of the data representing the part (1) to be controlled includes the simulation of a rotation of the part (1) to be controlled around its axis of rotation (3) according to an angle of angular displacement of the part (1) to be controlled during the acquisition step up to the reference position.

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