Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
  • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
  • G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64F—GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR
  • B64F5/00—Designing, manufacturing, assembling, cleaning, maintaining or repairing aircraft, not otherwise provided for; Handling, transporting, testing or inspecting aircraft components, not otherwise provided for
  • B64F5/60—Testing or inspecting aircraft components or systems

Definitions

• the invention relates to the general field of aeronautics.
• aeronautical part such as parts fitted to aircraft engines such as high pressure or low pressure turbine blades, distributors, etc.
• aeronautical part considered or the material in which the piece is composed. It may be for example a composite material or not.
• non-destructive testing means a set of methods that make it possible to characterize the state of integrity and / or the quality of structures or materials without degrading them.
• Non-destructive testing has a preferred but non-limiting application in the field of aeronautics, and more generally in any field in which the structures whose state or quality are to be characterized are expensive and / or their reliability. operation is critical.
• Non-destructive testing can be advantageously performed on the structure or material considered both during production and during use or maintenance.
• non-destructive testing methods some rely on digital images provided by X-ray or digital tomography systems.
• the advantage of these images is that they provide information directly exploitable on the inside of the structures or materials, and thus make it possible to detect internal defects that may affect these structures or materials, such as for example the presence of inclusions or blowholes.
• the term "part" is generally used to designate the structure or material on which non-destructive testing is envisaged.
• the present invention notably makes it possible to remedy these drawbacks by proposing a non-destructive testing method carried out on an aeronautical part comprising:
• a step of setting up a digital imaging system said digital imaging system being an X-ray or digital tomography system comprising an electromagnetic radiation source and a detector able to detect the electromagnetic rays emitted by the source;
• This non-destructive testing method is remarkable in that it further comprises a prior step of estimating adjustment parameters of the digital imaging system, this estimation step comprising:
• a step of obtaining a digital model characterizing the digital imaging system said digital model comprising a model characterizing the source and a model characterizing the detector;
• the invention also relates to a non-destructive control system of an aeronautical part comprising:
• a digital imaging system being a radiography or digital tomography system comprising a source of electromagnetic rays and a detector able to detect the electromagnetic rays emitted by the source;
• a non-destructive control device for the aeronautical part configured to use at least one digital image of the aeronautical part acquired by the digital imaging system;
• This non-destructive control system is remarkable in that it furthermore comprises a device for estimating so-called optimal values of adjustment parameters of the digital imaging system, the high optimum values of adjustment parameters being intended to be applied to said system.
• digital imaging device before acquiring said at least one digital image of the aeronautical part during an adjustment of the digital imaging system, said estimating device comprising:
• a first obtaining module configured to obtain a digital model characterizing the digital imaging system, this digital model comprising a model characterizing the source and a model characterizing the detector;
• a second obtaining module configured to obtain a digital model characterizing the aeronautical part
• An evaluation module configured to evaluate, for a plurality of distinct values of the adjustment parameters, a contrast-to-noise ratio obtained for the digital imaging system and said piece aeronautical, this evaluation module using the numerical models obtained characterizing the digital imaging system and the aeronautical part;
• An automatic determination module configured to automatically determine optimum values of the adjustment parameters optimizing the contrast-to-noise ratio.
• the source of electromagnetic radiation is, for example, an X-ray source.
• the invention proposes a method and a system for automatically determining the adjustment parameters of a radiographic or tomographic type digital imaging system intended to be used in a non-destructive inspection process of an aeronautical part.
• These parameters comprise, for example conventionally, at least one parameter among:
• a filter thickness applied in the digital imaging system at the source (also referred to as an external filter at the source).
• the method according to the invention is based for this purpose on various numerical models of the digital imaging system and the aeronautical part which allow the automatic determination of optimal adjustment parameters: thanks to the invention, an effective adjustment of these systems while removing any subjectivity that may affect this setting.
• These numerical models may for example be predetermined and stored in databases, in the form of a set of values and / or curves.
• the obtaining of these models then includes access to these databases and the extraction of the relevant modeled physical parameters from these bases to implement the invention.
• the criterion chosen by the invention for optimizing the aforementioned adjustment parameters is the contrast-to-noise ratio which makes it possible to quantify the quality of the images provided by the system.
• digital imaging considered. This ratio is determined, preferably analytically, from the different modelizations made according to the invention: modeling of the digital imaging system, and more particularly of its main components, namely its source of electromagnetic radiation and the detector it uses to detect the electromagnetic rays emitted by the source, and modeling of the aeronautical part on which is carried out the non-destructive control and of which one wishes to acquire images by means of the digital imaging system.
• the approach thus adopted by the invention provides a generic and automatic adjustment solution that can be applied to many conventional digital imaging systems for radiography and tomography.
• the invention advantageously allows to take into account the specificities and uniqueness of this system.
• the setting proposed by the invention takes into account the aeronautical part on which a non-destructive test is carried out. It is therefore adapted to this piece and allows to obtain an optimal image quality for this piece.
• the invention thus provides a quick and efficient solution for automating the parameterization of digital imaging systems used in the context of non-destructive testing.
• the invention does not require any digital image processing in two or three dimensions from the imaging system that is to be tuned is required, which can be cumbersome and complicated and opposes in any state of because of the automatic determination of optimal adjustment parameters of the digital imaging system.
• the accuracy of the solution proposed by the invention makes it easily applicable in an industrial environment to any digital imaging system of radiographic or tomographic type, for any part from the aeronautical industry.
• the invention makes it possible in particular to reduce the use of the source of electromagnetic radiation and to limit the rate of aging of the detector used by the digital imaging system.
• the invention is based on the modeling of the main components of the digital imaging system and the aeronautical part on which it is desired to carry out non-destructive testing. This modeling makes it possible to quantify the impact of these elements on the quality of the digital image provided by the digital imaging system.
• the model characterizing the source and the model characterizing the detector provide energy responses respectively of the source and the detector as a function of a wavelength. This advantageously makes it possible to take into consideration the polychromatic nature of the source.
• the model characterizing the source provides emission spectra of the source for different operation voltage values of the source.
• Each emission spectrum provides the intensity of the rays emitted by the source (i.e. the amount of photons generated per unit time or emission) as a function of the wavelength.
• Such modeling advantageously allows to take into account the polychromatic nature of the source as mentioned above. It takes into account the geometry of the source, and can be determined by means of simulations (eg Monte-Carlo type), empirical data and / or analytical expressions.
• the model characterizing the source further provides estimates of at least two half-attenuation layers of the source for different operating voltage values of the source, the method further comprising a step of validation of the model characterizing the source by comparing the estimates said at least two half-attenuation layers of the source to experimental results.
• This validation step makes it possible to ensure that the numerical model used to characterize the source is well representative of the physical reality of the source and therefore that it is well adapted. This ensures that the adjustment parameters extracted by the invention are optimal for the imaging system considered.
• the model characterizing the detector provides a spectral response of the detector to a ray beam emitted by the source.
• Such a response characterizes the way in which the detector weights the energies of the different photons arriving at the source, as a function of the wavelength.
• the model considered for the detector also allows to take into consideration the polychromatic nature of the source.
• the method further comprises a validation step of the model characterizing the detector comprising:
• the invention relies on a numerical and physical modeling of the main components of the digital system but also of the aeronautical part on which it is desired to perform a non-destructive inspection.
• the numerical model characterizing the aeronautical part provides mass attenuation coefficients of a component material for different energy values of a ray beam emitted by the source.
• each part of which it is desired to acquire a digital image by means of the digital imaging system to carry out a non-destructive inspection has its own physical characteristics (partly related to the composition of the material which composes it) which influence the system. digital imaging and its operation. Taking into account the composition of the aeronautical part and more particularly its mass attenuation coefficient for different energy values of the rays emitted by the source makes it possible to adjust the digital imaging system in a lighted and optimal way for the part in question.
• the obtaining of the numerical model characterizing the aeronautical part comprises for example, in a particular embodiment:
• the mass attenuation coefficient of each element of the material can be obtained for example by consulting a National Institute of Standards and Technology (NIST) database.
• This procedure makes it possible to automatically determine the mass attenuation mass coefficient of an aeronautical part for each ray energy considered.
• the criterion used by the invention to extract the optimal adjustment parameters of the digital system is the Contrast-to-Noise Ratio (CNR). According to the invention, this The ratio is evaluated for different values of the parameters that are to be optimized, and then the values of these parameters leading to the optimal CNR are determined from the reports thus evaluated.
• CNR Contrast-to-Noise Ratio
• the contrast-on-noise ratio is evaluated, for said plurality of distinct values of the adjustment parameters, from signals characterized by physical parameters of the digital imaging system, in other words, of the real system. considered.
• the contrast-to-noise ratio can in particular be evaluated for different values of the parameters that are to be optimized, based on signal values seen by the detector of the digital imaging system when determined thicknesses of the aeronautical part are crossed. by the beam of electromagnetic rays emitted by the source, these signal values being obtained analytically (ie by means of an analytical formula) from the numerical models characterizing the digital imaging system and the aeronautical part.
• This analytical evaluation of the contrast-to-noise ratio taking into account the physical parameters of the digital system facilitates the automatic determination of the optimal adjustment parameters of the digital imaging system.
• the invention is indeed easy to implement because it relies on simple numerical calculations which are more scalar: the calculation of the contrast-on-noise ratio requires only the knowledge of the values of the signals seen by the detector. of the digital imaging system when determined thicknesses of the aeronautical part are traversed by the beam of electromagnetic rays emitted by the source (these values reflecting for example a gray level); in addition, for given adjustment parameters of the digital imaging system, these values themselves vary only as a function of a single quantity, namely the considered thickness of the part traversed by the ray beam emitted by source.
• the invention therefore does not require heavy and complicated processing of digital images in two or three dimensions from the imaging system that we seek to adjust.
• the noise-contrast ratio noted CNR obtained for the digital imaging system and said aeronautical part is evaluated for different values of the adjustment parameters according to the expression:
• S det (L), S det L, e) denotes a signal value seen by the detector of the digital imaging system when a thickness L, respectively a thickness L - ⁇ , of the aeronautical part is traversed by the beam of electromagnetic rays (eg X-rays) emitted by the source, ⁇ denoting a thickness of a desired indicator during non-destructive testing in the aeronautical part, said signal values being defined by:
• a ⁇ E jt L denotes an attenuation factor experienced by the beam of electromagnetic rays emitted by the source whose energy Ej, this attenuation factor dependent on a mass attenuation coefficient of the material composing the aeronautical part and the thickness L;
• Ej, L, E designates an attenuation factor experienced by the beam of electromagnetic rays emitted by the source having energy)), this attenuation factor depending on a mass attenuation coefficient of the component material the aeronautical part, of the thickness L, and the thickness ⁇ of the indicator;
• the calculation proposed by the invention gives an accurate and reliable evaluation of the quality of the images provided by the digital system for the aeronautical part under consideration. This results in the extraction of optimal adjustment parameters for the digital imaging system adapted to the main components of the digital imaging system and to the aeronautical part under non-destructive testing.
• the model proposed by the invention for calculating the contrast-to-noise ratio applies, with an appropriate definition of the thickness ⁇ to different types of indicators sought in the aeronautical part during the destructive inspection.
• indicators we mean structures that are searched in the room and which are representative of the presence of a defect in the part such as for example an extra thickness (eg internal cavity extra thickness in ceramic cores for the elaboration high pressure turbine blades), under-thickness, inclusion, porosity, etc.
• the adjustment parameters determined for the digital imaging system are also adapted to the indicator sought during non-destructive testing in the aeronautical part, and facilitates its detection.
• the thickness ⁇ is chosen to be "negative” so as to translate a variation of negative thickness with respect to the thickness L of the aeronautical part, a sub-thickness -thickness or porosity resulting in a lack of material at the room level.
• the thickness ⁇ is on the contrary chosen "positive” to reflect the presence of a surplus of material.
• the thickness ⁇ reflects the material thickness of the inclusion.
• the attenuation factor A (E j ( L) is defined by:
• a (E j, L) A fint (Ej, L fint) A fext (Ej, Lfext) A mat (Ej, L);
• the attenuation factor A (E j , L, ⁇ ) is defined by:
• a (E j , L, ⁇ ) A fint (Ej, L fint ) A fext (Ej, L fext ) A mat (Ej, L - e) A ind (E f , £) where Annt (Ej, Lfmt) , AfextfEj.
• Liéx A mat (Ej, L) and A mat (Ej, L - e) respectively denote the attenuation undergone by the beam of electromagnetic rays (eg X-rays) whose energy E j due to filtering inherent to the source, the attenuation undergone by the electromagnetic ray beam whose energy E j is due to external filtering at the source, the attenuation undergone by the electromagnetic ray beam having energy E j due to the material composing the aeronautical part and the attenuation undergone by the electromagnetic ray beam having energy E j in the presence of the desired thickness indicator ⁇ .
• electromagnetic rays eg X-rays
• the attenuation factor defined in this embodiment makes it possible to take into consideration in a very complete manner the different attenuations to which the ray beam emitted by the source is subjected when using the digital imaging system.
• These attenuations are modeled here by filtering operations carried out on the beam of rays emitted by the source: filtering inherent to the source (and the material composing the source), filtering external to the source, but also filtering strictly related to the material of the aeronautical part which one wishes to control including the filtering carried out by the elements of the part but also by the indicator which one seeks in the room (this indicator being able to be made up of emptiness for example in the case of a porosity).
• the estimation step comprises the implementation of a plurality of iterations scanning all or part of the plurality of distinct values of the adjustment parameters, and during which the evaluation of the ratio contrast-on-noise is achieved by accessing numerical model values characterizing the source, the detector and the aeronautical part previously stored in databases.
• certain steps of the non-destructive inspection method are determined by computer program instructions.
• the invention also relates to a computer program on an information carrier, this program being capable of being implemented in a device for estimating adjustment parameters of a digital imaging system or more generally in a computer, this program comprising instructions adapted to the implementation of the step of estimating a non-destructive testing method as described above.
• This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other form desirable shape.
• the invention also relates to a computer-readable information medium, comprising instructions of a computer program as mentioned above.
• the information carrier may be any entity or device capable of storing the program.
• the medium may comprise storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording medium, for example a floppy disk or a disk. hard.
• the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means.
• the program according to the invention can be downloaded in particular on an Internet type network.
• the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.
• FIG. 1 represents, in its environment, a non-destructive control system according to the invention comprising a digital imaging system, a non-destructive inspection device and a device for estimating adjustment parameters of the imaging system. digital;
• FIG. 2 represents, in schematic form, the hardware architecture of the adjustment parameter estimation device of FIG. 1;
• FIG. 3 represents, in the form of a flow chart, the main steps of a non-destructive testing method according to the invention, in a particular embodiment in which it is implemented by the non-destructive control system of the figure 1 ;
• FIGS. 4A, 4B and 4C respectively illustrate the main steps implemented by the adjustment parameter estimation device of FIG. 1 to obtain a digital model of the source and a digital model of the detector of the digital imaging system. of Figure 1, and a digital model of an aeronautical part on which operates the non-destructive control system of Figure 1; and
• FIG. 5 represents, in the form of a flow chart, the main steps implemented during the step of estimating the optimal adjustment parameters implemented in the non-destructive inspection method illustrated in FIG. 3. Detailed description of the invention
• FIG. 1 represents, in its environment, a non-destructive testing system 1 according to the invention, in a particular embodiment.
• the system 1 makes it possible to carry out non-destructive testing of aeronautical parts such as, for example, a fan blade 2 of a turbine.
• aeronautical parts such as, for example, a fan blade 2 of a turbine.
• no limitation is attached to the nature of the part on which non-destructive testing is applied. It may be more generally any type of parts, preferably aeronautical, such as for example a part equipping an aircraft engine, rocket, etc.
• the non-destructive control system 1 comprises:
• a digital imaging system 3 able to acquire and supply one or more digital images IM of the aeronautical part 2;
• a non-destructive testing device 4 for the aeronautical part 2 configured to use the digital IM image (s) of the aeronautical part acquired and supplied by the digital imaging system 3 and form an integrity diagnosis DIAG of part 2.
• This diagnosis concerns in particular one or more IND indicators or parameters searched in the part. No limitation is attached to the nature of these indicators; these may be, for example indicators representative of thickness in the room, of under-thickness, or the presence of porosities or inclusions, etc.
• Such a non-destructive testing device is known per se and is not described in more detail here.
• the digital imaging system 3 is here a radiography or digital tomography system. It comprises, in a known manner, a source 3A of electromagnetic rays (for example a source emitting beams of X-rays) and a detector 3B able to detect the electromagnetic rays emitted by the source 3A.
• a source 3A of electromagnetic rays for example a source emitting beams of X-rays
• a detector 3B able to detect the electromagnetic rays emitted by the source 3A.
• the source 3A applies here the principle of the bombardment of electrons on a metal target in an X-ray tube: the electrons are extracted from a metallic filament (the cathode) and then accelerated by a large electrical voltage applied to the source 3A (voltage operating in the sense of the invention) in a vacuum tube.
• This electron beam emitted by the source 3A is focused so as to bombard a metal target (the anode), for example tungsten. Interactions between electrons and matter when they hit the target produce 'X' ray photons. Such operation is known per se and is not described in more detail here.
• the detector 3B of the digital imaging system 3 operates indirectly: a scintillator absorbs the X-ray photons produced by the source 3A, and by fluorescence mechanisms, emits visible light.
• the visible photons emitted are directed on a photodiode array, each element of the photodiode array being associated with a pixel.
• the visible photons are converted into electrical charge at the level of the photodiode array and then into an electrical signal by a photomultiplier.
• the electrical signal conveys gray levels associated with each pixel of the detector and reflecting the absorption of photons at the pixel considered. Such operation is known per se and is not described in more detail here.
• a filter thickness applied in the digital imaging system to the source 3A (also referred to as an external filter at the source).
• the non-destructive control system 1 advantageously comprises a device 5 for automatically estimating the aforementioned adjustment parameters.
• This estimation device 5 is able to estimate optimal values of these parameters. to be applied to the digital imaging system 3 during an adjustment thereof made before the acquisition of the digital images IM of the aeronautical part 2.
• the estimating device 5 has the hardware architecture of a computer as diagrammatically shown in FIG. 2.
• a processor 6 comprises, in particular a processor 6, a random access memory 7, a read only memory 8, a nonvolatile flash memory 9 as well as input / output means 10 enabling an operator of the digital imaging system 3 to interact with the device 5 estimation.
• input / output means 10 comprise, for example, a screen, a keyboard, a man-machine interface enabling the operator of the system 3 in particular to enter data in the estimation device 5 and to obtain the adjustment parameters.
• optimal digital imaging system 3 determined by it in accordance with the invention.
• the read-only memory 8 of the estimation device 5 constitutes a recording medium in accordance with the invention, readable by the processor 6 and on which a computer program according to the invention is recorded.
• the PROG computer program defines functional and software modules herein, configured to implement an estimate of the optimal setting parameters of the digital imaging system 3 according to the invention. These functional modules rely on and / or control the hardware elements 6-10 of the estimation device 5 mentioned above. They include in particular here, as illustrated in FIG.
• a first obtaining module 5A configured to obtain a numerical model MOD3 characterizing the digital imaging system 3, this numerical model comprising a MOD3A model characterizing the source 3A and a MOD3B model characterizing the detector 3B.
• the first obtaining module 5A is configured here to extract these MOD3A and MOD3B digital models from the DB3A and DB3B databases of the estimation device, in which they were previously stored after their determination.
• database is meant in the broad sense any set of data for storing information;
• a second obtaining module 5B configured to obtain a numerical model MOD2 characterizing the aeronautical part 2; the second obtaining module 5B is configured here to extract the digital model MOD2 from a database DB2 of the estimating device in which it was previously stored after its determination;
• a evaluation module 5C configured to evaluate, for a plurality of distinct values of the adjustment parameters, a contrast-to-noise ratio obtained for the digital imaging system 3 and the aeronautical part 2, this evaluation module 5C using the numerical models MOD3 (including the models MOD3A and MOD3B) and MOD2 obtained by the modules 5A and 5B and respectively characterizing the digital imaging system 3 and the aeronautical part 2; and
• An automatic determination module 5D configured to automatically determine optimum values of the adjustment parameters optimizing the contrast-to-noise ratio.
• FIG. 3 illustrates these steps as they are implemented by the non-destructive testing system 1 of FIG. 1.
• step D10 a preliminary adjustment of various parameters of the digital imaging system 3 is performed (step D10).
• these parameters include, as indicated above:
• step D10-i optimal values of these parameters are automatically estimated by the estimation device (step D10-i);
• the optimal values thus estimated are applied to the digital imaging system 3 to parameterize it.
• step D10-2 This setting of the digital imaging system 3 can be performed for example manually by an operator of the system 3 by means of the optimum values provided by the estimating device.
• one or more IM digital images of the aeronautical part 2 are acquired by the digital imaging system 3 and adjusted (step D20), and provided to the non-destructive testing device 4.
• Non-destructive testing of the aeronautical part 2 is then performed via the non-destructive testing device 4 from the digital images IM (step D30).
• a step can be carried out in various ways, in a manner known per se, and is not described in detail here.
• the images thus obtained allow non-destructive access to the part to be controlled. For example, they can be compared by known image processing methods to images acquired by the same method for a sound part in the search for anomaly (s) in the part to be controlled.
• the estimate made in step D10-1 of the optimal adjustment parameters of the digital imaging system 3 for its use on the aeronautical part 2 is based on various numerical models physically characterizing the system 3. digital imaging, and in particular its main components namely the source 3A and the detector 3B, and the aeronautical part 2.
• These numerical models are obtained by the modules 5A and 5B respectively of the estimation device 5. They can be pre-calculated or obtained on the fly when estimating optimal tuning parameters. However, in the embodiment described here, these numerical models are precalculated and stored in databases (DB3A, DB3B and DB2) of the estimation device 5 for future use. This advantageously makes it possible to accelerate the search for optimum adjustment parameters when it is desired to use the digital imaging system 3.
• FIG. 4A represents the main steps implemented to obtain the OD3A model characterizing the source 3A of the digital imaging system 3. It is noted that these steps can be implemented by the module 5A of the estimation device 5 or via any another module external to the estimation device 5 and able to store the model MOD3A obtained in the database DB3A.
• the model MOD3A here provides emission spectra of the source 3A for different operating voltage values of the source denoted i, v 2 , w where N denotes an integer greater than 1.
• the voltages V Lt V 2 , ..., V N range from 0 to 450 kV, in steps of lkV.
• the MOD3A model further provides emission spectra of the source 3A for N operating voltage values of the source and for M values of the tilt angle with respect to horizontal of the anode of the source 3A, M denoting an integer greater than 1. It is noted that the angle of inclination of the anode of the source influences the emission angle of the source 3A; which has an importance on the quality of the spectrum (Heel effect).
• emission spectrum is meant the intensity (ie the number of photons emitted per unit of time or emission) beams of rays emitted by the source 3A as a function of the wavelength of these rays.
• the wavelength is uniquely related to the energy of the beams of rays considered. In other words, at a wavelength indexed by an integer j and denoted by ⁇ , there corresponds a single energy of beams E s .
• the emission spectra corresponding to the N operating voltage values and the M tilt angle values obtained using the SpekCalc software are stored in the DB3A database (step E50).
• the module 5A provides the database DB3A (or equivalent query with):
• the module 5A thus obtains the emission spectrum of the source 3A for the operating voltage et and the angle ⁇ ,, noted in the following description ⁇ ⁇ ⁇ .
• database D3A also includes estimates of at least two half-attenuation layers of source 3A for two distinct materials, namely copper (Cu) and aluminum (Al). for each operating voltage v t and for each inclination angle, These estimates were provided by the SpekCalc software during step E20.
• the D3A database includes:
• the module 5A here accesses these estimates at the same time as the emission spectrum of the source 3A for the operating voltage V t and the angle at t .
• a validation of the numerical model MOD3A, ie emission spectra stored in the database D3A is envisaged.
• This validation can be implemented for example by the module 5A or by another module external to the estimation device 5, by accessing the emission spectra stored in the database D3A and the estimates of the associated half-attenuation layers. .
• the module responsible for this validation will generally be designated by validation module.
• This validation aims here to ensure that the spectra generated for the source 3A are well representative of the physical reality of the source 3A. This contributes to allow the estimation device 5 to obtain, thanks to the invention, optimal values of the adjustment parameters.
• the validation module compares here, for at least one selection of spectra comprising at least two spectra generated during the step E20 for two different operating voltages of the source 3 A, the estimates of the half layers.
• HVLICu, HVL1AI, HVL2Cu and HVL2AI attenuators provided in step E20 for these voltages with experimental results.
• the experimental values of the half-attenuation layers HVLICu, HVL1AI, HVL2Cu and HVL2AI can be generated beforehand, by means of layers of copper and aluminum of different thicknesses and a dosimeter, then stored in the DB3A database to be compared with the values of the half-attenuation layers accompanying the spectra in the DB3A database.
• the validation module will also search the DB3A database for the spectrum having HVL1 and HVL2 values that best correspond to the values of HVLA and HVL2 found experimentally.
• the MOD3B model characterizes how the detector 3B weights the different energies of photons arriving from the source. It should be noted that this spectral response depends to a large extent on the ability of the scintillator of the detector 3B to absorb the different photon energies. Therefore, in the embodiment described here, to obtain the MOD3B model, the so-called response curves showing the amount of energy absorbed in the detector scintillator are simulated beforehand with the aid of appropriate simulation software. 3B as a function of the energy of the incident photons (step F10), as a function of the thickness and type of the scintillator of the detector 3B.
• the dose of the beam absorbed by the scintillator depends directly on its thickness. Several thicknesses are evaluated. Thus, at the end of the simulations, several response curves corresponding to several thicknesses of the scintillators (step F20) are obtained. This then allows the module 5A to choose the one that best represents the detector 3B.
• CsI cesium iodide
• GdOS Gadolinium Oxygen Sulfide
• the simulations carried out in step F10 are performed with the GateDoseSpecUvmActor ⁇ mp] module emertized in the GATE / Geant 4 platform (Giant 4 Application for Tomography Emission), which makes it possible to calculate the detector response. 3B with each energy.
• the GATE / Geant platform 4 implements Monte Carlo simulations for modeling X-ray tomography and radiography.
• the spectral responses obtained for the detector 3B are furthermore validated to ensure that it conforms to the physical reality of the detector 3B (step F40).
• This validation can be implemented by the module 5A or by any other validation module, for example external to the estimation device 5.
• any other validation module for example external to the estimation device 5.
• reference will be made generally to a module of confirmation.
• the average energy and the maximum energy of the photons in a spectrum are characteristics which depend on the operating voltage of the source, and a variation of this latter is manifested in the average gray level noted GL seen by the detector ;
• the average gray level variation GL as a function of the average energy of the photon beams emitted by the source depends on the spectral response of the detector.
• step F20 To validate the spectral response obtained in step F20, the inventors therefore propose to rely on the method proposed by P.V.
• I N
• the operating voltages V X, V 2, ..., V ⁇ coincide with the operating voltages VV 2, ..., V N previously considered to obtain the MOD3A module.
• the measurements can be performed directly by the verification module, or alternatively be obtained by them from a database in which such measurements previously made have been stored.
• the verification module compares the values of CL m and Gi eo, norm for example p
• the verification module performs these operations for all scintillator thicknesses for which a spectral response is stored in the D3B base, and selects the spectral response that best matches the measured gray level values.
• the invention is also based on a third numerical model MOD2 characterizing the aeronautical part.
• This model is stored in the database DB2 so as to be used by the second obtaining module 5B.
• FIG. 4C the main steps implemented to obtain this MOD2 model. These steps are implemented here by the module 5B but they can be implemented by any other module, for example external to the estimation device 5.
• the second obtaining module 5B first obtains the chemical composition of the material composing the aeronautical part 2 (step G10).
• chemical composition is meant the different chemical elements composing the material as well as their mass proportions in the material.
• This chemical composition can be supplied for example to the second module 5B by the operator of the digital imaging system 3 or by any other person via the input / output means 10 of the estimation device 5, or read by the module 5B in a previously informed file.
• step G20 comprises consulting a NIST database, comprising, for each chemical element of the periodic table of elements (also known as the Mendeleev table), the coefficient of mass attenuation of this element.
• M is an integer greater than or equal to 1 denoting the number of chemical elements composing the material of the part 2
• w m is the proportion mass of the chemical element indexed by m in the material of the part 2
• ⁇ ⁇ , ⁇ ) is the mass attenuation coefficient of the chemical element indexed by m for the energy £ ⁇ .
• FIG. 5 represents the main steps implemented by the estimation device 5 during the step D10-1 of automatic estimation of the optimal adjustment parameters of the digital imaging system 3.
• the optimal adjustment parameters of the digital imaging system 3 are automatically estimated by the estimation device 5 by optimizing the contrast-to-noise ratio of the digital images IM of the aeronautical part 2 acquired by the system 3. digital imaging. This optimization is carried out on a plurality of distinct values of the various adjustment parameters, the ranges on which the values of the adjustment parameters are previously configured at the level of the estimation device 5 (for example via the input / output means 10 ).
• each setting parameter can take a plurality of distinct values, in the embodiment described here, to optimize the contrast-to-noise ratio
• the estimation device 5 implements a plurality of iterations scanning all or part of this plurality. of values (see step H 10 of implementation of a new iteration and step H60 end of the iterative process).
• This plurality of iterations is implemented via the prediction of several loops (four loops here), nested in each other and respectively scanning each different values of a separate adjustment parameter, ie a loop scanning the values of the voltage of operation, a loop scanning the current values, a loop scanning the exposure time values and a loop scanning the values of the external filter thickness.
• the estimation device 5 accesses via its obtaining modules 5A and 5B to the numerical models MOD3A, OD3B and MOD2 stored respectively in the databases DB3A, DB3B and DB2.
• modules 5A and 5B extract here DB3A, DB3B and DB2 databases the values of these models corresponding to the operating voltage value of the source 3A (step H20), to the value of the angle d tilt of the anode of the source 3A and the thickness and type of the scintillator of the detector 3B.
• CNR (iter) where SaetiVi, L), respectively S det (y it L, E), designates the signal value seen by the detector 3B of the digital imaging system 3 when a thickness L, respectively a thickness L - ⁇ , the aeronautical part 2 is crossed by the beam of rays emitted by the source 3A.
• This signal value reflects, as mentioned above, a gray level seen by the detector 3B.
• the invention is based on a simple scalar calculation of the contrast-to-noise ratio CNR.
• the thickness ⁇ is predetermined and corresponds to the thickness of an indicator sought during the non-destructive testing in the aeronautical part 2. It is noted that in the embodiment described here, this thickness is a real number which, depending on the The desired indicator may be sometimes positive or negative, as described above. Such an indicator is, for example, an oversize, a sub-thickness, a porosity or an inclusion.
• the thickness ⁇ is supplied in advance to the estimation device 5, for example by the operator of the digital imaging system 3 or that of the non-destructive inspection device 4.
• the signals considered in the calculation of the contrast-on-noise ratio are characterized by the physical parameters of the digital imaging system 3, in other words, of the real system.
• the signal values seen by the detector are obtained here analytically by the evaluation module 5C via the following analytic terms:
• the Q (Ej, Vi) denotes the intensity of the photons present in an energy beam E emitted by source 3A (corresponding to a wavelength ⁇ ) to the operating voltage v t;
• a (Ej.L) and A e (Ej, L, s) denote attenuation factors experienced by the beam of energy rays ( e ) emitted by the source 3A;
• i denotes the value of the current applied to the source 3A corresponding to the current iteration iter
• t denotes the exposure time of the part aeronautical 2 corresponding to the current iteration iter.
• the evaluation module 5C evaluates the attenuation factor A (£ J ( z)) as follows:
• the evaluation module 5C further evaluates the attenuation factor A (E j , L, ⁇ ) as follows:
• a (E j , L, ⁇ ) A fint (Ej, L fint ⁇ A fext (E jt L fext ) A mat (Ej, L - e) A ind (Ej, ⁇ ) in which A ini E ⁇ , e ) designates the attenuation undergone by the beam of energy rays (e) emitted by the source 3A due to the desired thickness indicator ⁇ .
• Each of the abovementioned attenuations is modeled here by a filtering operated by a distinct material (elementary or multi-element), namely the material constituting the filter inherent in the source 3A, the material constituting the external filter at source 3A, the material of the aeronautical part 2 and the material corresponding to the desired indicator (this material may be vacuum, for example in the case of porosity).
• a distinct material elementary or multi-element
• the 5C evaluation module uses Beer Lambert's law, defined by:
• I denotes an index taking the values fint.fext. mat or ind depending on the attenuation considered;
• I denotes the density of the material associated with the attenuation considered
• the 5D determination module 5D of the estimation device 5 compares the ratio CNR (/ fe / ) with a CNROPT threshold (test step H40), initialized to 0 during a preliminary H00 initialization step implemented before starting the iterations.
• the CNROPT threshold is updated with the value of the CNR ratio (/ te /) (step H50).
• the current iteration is also stored in an iteropt indicator
• the CNROPT threshold is kept unchanged.
• the determination module 5D checks whether all the iterations have been implemented (test step H60).
• the determination module 5D determines that the optimum values of the adjustment parameters of the digital imaging system 3 correspond to the values of the adjustment parameters tested during the iteropt iteration (step H70 ).
• the invention thus provides an automatic process for automatically determining the optimal parameters of a digital imaging system such as a radiographic or tomographic system for acquiring images of an aeronautical part. It should be noted that although described with reference to an aeronautical part, the invention applies to other parts that can be subject to non-destructive testing.

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