NON-DESTRUCTIVE INSPECTION METHOD FOR POLYCRYSTALLINE PARTS

Abstract

A non-destructive testing method (100) for a polycrystalline part is implemented by a non-destructive testing device comprising electronic circuitry adapted to implement the method. The method comprises at least the following steps: (Step 1) measuring an ultrasonic reflection matrix of the part associated with a multi-element probe containing N piezoelectric transducers; (Step 2) projecting the ultrasonic reflection matrix onto a focused basis; (Step 3) constructing a longitudinal wave velocity map; (Step 4) constructing a transverse wave velocity map; (Step 5) determining local elastic constants of the part; (Step 6) detecting a defect or a particular area in the part by analyzing the local elastic constants of the part determined in Step 5. Figure to be published with the abbreviation: Fig. 1

Description

Title of the invention: NON-DESTRUCTIVE INSPECTION METHOD FOR POLYCRYSTALLINE PARTS technical field

[0001] The invention relates to the field of non-destructive testing of parts made of polycrystalline material. STATE OF PRIOR ART

[0002] A number of critical parts used in aircraft engines are made of polycrystalline metal alloys, such as titanium alloys or nickel-based superalloys. These parts can be forged from cylinders called "billets." They may also be pre-machined or machined.

[0003] To ensure the integrity of these parts before assembly in the reactor and to verify that they do not present any defects such as cracks, porosity, or inclusions, these parts can be inspected non-destructively using ultrasound to detect any indications of defects. These inspections are carried out on the billets and on the parts formed after forging, using one or more piezoelectric transducers. It is known to use a single-element piezoelectric probe or a multi-element (ring or linear) probe.

[0004] Existing ultrasonic techniques are based on the principle of echolocation, that is, the analysis of echoes reflected by obstacles to the propagation of the acoustic wave (walls, changes in medium, defects, etc.) to the piezoelectric transducer. In particular, ultrasound imaging methods such as Total Focusing Method (TFM), Plane Wave Imaging (PWI), or migration in the fk domain make it possible to obtain a map of the medium's reflectivity; they thus provide qualitative information on the structure.

[0005] However, these methods do not allow for the extraction of quantitative properties from the inspected medium, such as its local mechanical properties. Obtaining this information would be beneficial for the non-destructive characterization of polycrystalline material parts, for example, by identifying areas with abnormal mechanical properties generated by the manufacturing processes or corresponding to a defect that locally alters the mechanical properties of the part.

[0006] We thus know, for example, the documents KR19990052679, JP3597182 and EP279531.

[0007] These three documents describe methods for measuring the overall elastic parameters (Young's modulus and / or Poisson's ratio) of a sample or a room, but do not allow these quantities to be measured locally within the volume of the room, nor to identify an area with abnormal properties.

[0008] In this context, it is therefore necessary to provide a non-destructive testing method for a part made of polycrystalline material that allows for the local measurement of the elastic constants of the material within the volume of the part. Description of the invention

[0009] To this end, according to a first aspect, a non-destructive testing method for a part made of polycrystalline material is proposed. The method is implemented by a non-destructive testing device comprising electronic circuitry adapted to implement the method. The method comprises at least the following steps: - (Step 1) measure an ultrasonic reflection matrix of the part associated with a multi-element probe containing N piezoelectric transducers; - (Step 2) project the ultrasonic reflection matrix into a focused basis; - (Step 3) construct a map of the speed of longitudinal waves; - (Step 4) construct a map of the velocity of transverse waves; - (Step 5) determine local elastic constants of the part; - (Step 6) detect a defect or a particular area in the part by analyzing the local elastic constants of the part determined in step 5.

[0010] Thus, the method according to the invention very cleverly uses longitudinal and transverse waves to locally determine the elastic constants of the material, in its volume, which makes it possible to characterize the material and to detect any defects (i.e. an area with abnormal properties).

[0011] According to a particular arrangement, the step (step 4) of constructing a transverse wave velocity map comprises separating the reflection matrix into four sub-matrices: a first sub-matrix composed of emitters from a sub-matrix of the probe located to the left of the focal point, a second sub-matrix of receivers from a sub-matrix of the probe located to the left of the focal point, a third sub-matrix composed of emitters from a sub-matrix of the probe located to the left of the focal point, and a fourth sub-matrix of receivers from a sub-matrix of the probe located to the left of the focal point.

[0012] According to a particular arrangement, in step (Step 4) of constructing a transverse wave velocity map, the total reflection matrix is ​​expressed as follows: lRxx| = ] Rddl + + |Rdçr| + |Rgd| , with a reflection matrix composed of emitters and receivers from a portion of the probe located to the right of the focal point (denoted R dd), a matrix of reflection composed of emitters and receivers from a part of the probe located to the left of the focal point (R gg) and a reflection matrix composed of emitters and receivers from a different part (right or left) of the probe relative to the focal point (R gd and R dg).

[0013] According to a particular arrangement, in step (Step 4) of constructing a transverse wave velocity map, the total reflection matrix is ​​expressed using three or fewer of the four sub-matrices.

[0014] According to a particular arrangement, the step (Step 4) of constructing a transverse wave velocity map includes weighting the total reflection matrix by a function depending on the angle between a transducer and the focal point.

[0015] According to a particular arrangement, the total reflection matrix is ​​filtered using a function expressed as ||(0)| = |sin(20) × 0a| with the filter function and 0 the angle between the normal to the probe and the axis along the line joining the center of the probe and the focal point; or as h(0) = 0) × (0)) with h the filter function, 0 the angle between the normal to the probe and the axis carried by the line joining the center of the probe and the focal point, 0 ) the directivity of an element of the grating for transverse waves and 0 ) the directivity of an element of the grating for longitudinal waves.

[0016] According to a particular arrangement, the step (Step 5) of determining the local elastic constants of the part is carried out by considering that the material has a constant density.

[0017] According to another aspect, a non-destructive testing device is also proposed for a part made of polycrystalline material, comprising electronic circuitry for implementing a method for detecting a defect in a part made of polycrystalline material, comprising at least the following steps: - (Step 1) measure an ultrasonic reflection matrix of the part associated with a multi-element probe containing N piezoelectric transducers; - (Step 2) project the ultrasonic reflection matrix into a focused basis; - (Step 3) construct a map of the speed of longitudinal waves; - (Step 4) construct a map of the velocity of transverse waves; - (Step 5) determine local elastic constants of the part; - (Step 6) detect a defect or a particular area in the part by analyzing the local elastic constants of the part determined in step 5.

[0018] According to another aspect, a computer program product is also proposed, comprising program code instructions for executing the process according to the invention.

[0019] According to another aspect, a non-transient storage medium is also proposed on which is stored a computer program comprising program code instructions to execute the process according to the invention, when said instructions are read from said non-transient storage medium and executed by a processor. Brief description of the drawings

[0020] The features of the invention mentioned above, as well as others, will become clearer upon reading the following description of at least one exemplary embodiment, said description being made in relation to the accompanying drawings, among which:

[0021] [Fig-1] schematically illustrates the sequence of a detection process;

[0022] [Fig.2] illustrates a focal spot measurement (RPSF) as a function of the integrated velocity in a polycrystalline material;

[0023] [Fig.3] illustrates a focused basis reflection matrix measurement for the transverse wave without any additional step performed compared to the processing of the longitudinal wave;

[0024] [Fig.4] schematically illustrates a defined angle for a filter;

[0025] [Fig.5] schematically illustrates a superimposed applied filter with amplitudes simulated;

[0026] [Fig.6] schematically illustrates the directivity of an element for longitudinal ground and transverse wave;

[0027] [Fig.7] illustrates experimental maps of longitudinal wave velocity and transverse wave velocity in a polycrystalline material;

[0028] [Fig.8] illustrates experimental maps of Young's modulus, shear modulus and Poisson's ratio in a polycrystalline material;

[0029] [Fig.9] schematically illustrates a computer system adapted to implement the process.

[0030] DETAILED DESCRIPTION OF IMPROVEMENTS

[0031] Detection method

[0032] With reference to [Fig. 1], according to a first aspect, a method 100 for non-destructive testing of parts made of polycrystalline material is proposed. As will be described below, the method 100 is implemented by a detection device comprising electronic circuitry 200 adapted to implement the method 100. The method 100 comprises at least the following steps: - (Step 1) measure an ultrasonic reflection matrix of the part associated with a multi-element probe containing N piezoelectric transducers;

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[0038] - (Step 2) project the ultrasonic reflection matrix into a focused basis; - (Step 3) construct a map of the speed of longitudinal waves; - (Step 4) construct a map of the velocity of transverse waves; - (Step 5) determine local elastic constants of the part; - (Step 6) detect a defect or a particular area in the part by analyzing the local elastic constants of the part determined in step 5. Step 1 - Measure an ultrasonic reflection matrix As previously stated, process 100 includes an initial step 1 of signal generation with a multi-element probe. According to a particular arrangement, process 100 uses a multi-element probe containing N piezoelectric transducers to generate a wave in the polycrystalline material. It is specified that N is a positive integer strictly greater than zero. The reflection matrix can be measured by acquiring NxN ultrasonic signals, where N is a positive integer. These ultrasonic signals are the impulse responses between each transducer and are denoted as y(t)', with t being the echo time. To do this, the position of each transducer is denoted as f(n) when a transducer is used as a transmitter and as ^out when a transducer is used as a receiver. This notation allows us to define a reflection matrix for the material under study (Full Matrix Capture, abbreviated FMC). The reflection matrix is ​​thus given by the matrix Ru(t) = [R(u - U(t)]]. Alternatively, the reflection matrix can be measured in a plane wave basis. Step 2 - Project the reflection matrix into a focused basis According to a specific arrangement, a change of basis allows the reflection matrix to be projected onto a focused basis using a set of points {xin,z} and {xout,z} to search for local elastic constants of the inspected material. It should be noted that since the RUu matrix is ​​in the form of an FMC matrix, to study the medium locally, it may be necessary to focus the waves within the medium and thus transform the RUu(t) matrix into an Rxx(Z) matrix = [R(Xout, Z)]. The focused basis reflection matrix can be seen as an extension of the classical (or confocal) ultrasonic image where a focal point can be separated at the emission and reception points (xin^xout). This can be achieved, for example, by using different focusing times at the emission and reception points.

[0039] By using a frequency-domain approach to image construction, it is possible to express the focused basis reflection matrix from the reflection matrix. In particular, by defining: [° 04 °] R(u in> u out , f)=TF(R(u in , u ouP t))

[0041] where TF represents the discrete Fourier transform with respect to the time dimension of the reflection matrix and f is the frequency. It is then possible to define the reflection matrix in the focused basis as: Xout' -ut^ (xm' ^iii' ^out' (^out' ^out'

[0043] In this equation, represents the x-coordinate of the emitting focal points, xout represents the x-coordinate of the receiving focal points, z represents the focal depth, and G is a Green's matrix containing Green's functions describing the propagation between the transducers and the focal points for a given ultrasonic wave velocity Gq. The symbol * represents the conjugate matrix.

[0044] According to the embodiment presented here, the reflection matrix is ​​defined with a two-dimensional Green's function:

[0045] i 1 / f \ w G(x p (Uj, z, f) = -k^x r ujj + z 2 ), with k = ^~.

[0046] Step 3 - Construct a map of the velocity of longitudinal waves

[0047] The expression for Rxx(z) = [^(x^Xout, z)] implicitly depends on the velocity of the ultrasonic wave defined to achieve the focusing Gq. In simple scattering, the focused reflection matrix appears as a matrix whose energy is essentially concentrated on the main diagonal (it is logical to "probe" the maximum energy in reception at the point where the focusing was achieved in transmission). The energy spread around the diagonal depends on the difference between the model of the sound velocity Gq and the actual velocity distribution in the medium.

[0048] Thus, to estimate the speed of the longitudinal wave, the energy spreading outside the diagonal of R¥Y (z) can be quantified by expressing the reflection matrix in a de-scanned basis, i.e., as a function of the distance between the points xin and xout; A x =Xout - Xm. Furthermore, the coefficients of the reflection matrix must be expressed as a function of the echo time t, rather than as a function of the depth Z — Cot / 2 of the plane, which depends on the velocity model:

[0049] R( {x m , t}, { AX, c0} ) = R(x ül , x out , z, c0)

[0050] This change of variable allows us to follow the evolution of the point spread function (PSF) for each speckle grain (i.e., speckle or shimmer) defined by its spatio-temporal coordinate ■{ X]n, t}. Generally measured by imaging a point object and observing the size of its image, here it is measured by reflection and corresponds to the dependence of the backscattered energy on A x:

[0051] FPSF( A

[0052] where the symbol (---) denotes an average over the subscript coordinate. This function then provides an estimate of the width of the focal spot; in the absence of aberrations, this is given by diffraction theory: θx = Xz / D, with X the wavelength, z the distance between the emitter and the object, and D the size of the probe aperture. Experimentally, the presence of aberrations (inhomogeneous medium, imprecise knowledge of the ultrasonic wave velocity, multiple scattering, etc.) widens the RPSF. Its effective width A corresponds to the width of the diagonal of the focused basis reflection matrix measured around a position θin for a given velocity and echo time t.

[0053] Thus, the measurement of A as a function of the ultrasonic Fonde velocity hypothesis Cq in the calculation of the focused basis reflection matrix provides information on the actual velocity of the wave in the medium: a minimization of A is directly correlated to a decrease in aberrations, therefore a minimization of the difference between the wave velocity hypothesis and its actual velocity in the medium.

[0054] In the context of studying the microstructure of metallic alloys, many configurations do not present a strong reflector for directly measuring the PSF. Thus, it is estimated using speckle, that is, the superposition of all the signals backscattered by the microstructure. Since the intensity of speckle is inherently spatially fluctuating and locally zero, it is necessary to spatially average the measured PSFs to smooth out the speckle fluctuations and obtain a correct estimate of A; this spatial average can be consistent or inconsistent. A typical size for the averaging area to obtain noise-free measurements can be approximately six wavelengths in both the x and z dimensions.

[0055] In the case, for example, of a nickel-based superalloy Inconel 600, focusing is more accurate when the velocity used for calculating the reflection matrix is ​​the actual velocity of the longitudinal waves (5850 m / s) than if the velocity used in the algorithm is overestimated. In this way, the velocity that minimizes the width and maximizes the intensity of the focal spot will be considered to be the average velocity between the multi-element probe and the focal point, called the integrated velocity. A RPSF measured in a sample of Inconel 600 is shown [Fig. 2].

[0056] From integrated velocity measurements taken on a grid of points, it is possible to construct a map of the integrated velocities between the probe and all the focal points. This map is obtained by estimating the optimal velocity of the longitudinal wave around a given point. By then moving the averaging zone, it is possible to construct a map of the velocities integrated in the inspected area of ​​the material.

[0057] Several methods are possible for calculating a local longitudinal wave velocity map from an integrated longitudinal Fonde velocity map. For example, one can consider the Fonde slowness s, defined as the inverse of the wave velocity (5 = 1 / τ). The integrated slowness sint is given by the average of the local slowness Sjoc along the wave path. Neglecting oblique paths and refraction effects, the integrated slowness between the probe and each point is related to the local slowness by the following relation:

[0058] sint(x zt) = ifgdz sloc(x, z)

[0059] with zt = t / (2s) J' depth of the isochronous volume at the considered echo time t. The preceding equation can be rewritten in matrix form by discretizing the values ​​of the integrated and local slownesses at a set of depths

[0061] By then inverting this equation, the local slownesses are given by:

[0062] zl) Slo& ' süÀX' zl) ^int{.X' z2^ / 1 0 0 ... 0| -12 0 ... 0 z^ ^loÂX' Zn) * = A-1x z2^ * Siiit(X' ZN^ withA-1= 0 -2 3 ... 0 . 0 0 0 ... Ni

[0063] This calculation is very sensitive to noise, which inevitably pollutes the integrated speed map. In practice, a Gaussian filter is therefore applied to the integrated speed map to eliminate this noise before performing the calculation shown in the equation above.

[0064] By applying this calculation to all columns (lateral positions x) of the longitudinal Fonde velocity map, it is thus possible to reconstruct a complete map of the local longitudinal Fonde velocity.

[0065] Step 4 - Construct a map of the velocity of transverse waves

[0066] Determining the velocity of transverse ultrasonic waves presents a problem due to the presence of secondary lobes in the focal spot when attempting to coherently sum the signals from the different transducers. These secondary lobes are related to the angular spectrum of the transverse waves generated by the ultrasonic probe. This spectrum exhibits a dipolar shape with a cancellation of the field along the z-axis, while the maximum amplitude of the longitudinal waves is found opposite the transducer. For transverse waves, the maximum is typically located around 40° from the transducer axis.

[0067] This directivity profile is manifested by a low-intensity diagonal for the reflection matrix in the focused basis obtained from the transverse wave velocity, as shown in Fig. 3. A second problem is the presence of residual signals associated with the longitudinal wave. It is necessary to reduce their contribution to preserve the majority of the transverse wave signal. These two specific properties of the matrix in the focused basis associated with the transverse wave necessitate an adaptation of the algorithm described previously for longitudinal waves. Additional processing must therefore be performed on the focused basis matrix _R(uin, Uout, f) to obtain a usable transverse wave velocity map.

[0068] To this end, a filter is applied to give less weight to longitudinal waves and more weight to transverse waves. To do this, the Green's matrix is ​​weighted by a value depending on the angle θ between the normal to the probe and the axis along the line joining the center of the probe and the focal point. The angle θ is shown schematically in [Fig. 4].

[0069] This filter function h(0) can be the simulated amplitude of the transverse wave propagating in the material of interest or its approximation by an analytical function. The chosen function can be of the form: [00'0] h(0) = |Sjn(20)x0“|.

[0071] where a is the parameter optimized to approximate the simulation. For example, for a simulation in the case of a TA6V titanium alloy and a transducer with a width of 0.4 mm and a center frequency of 3.5 MHz, (1=0.21). This function h can also be normalized. The curve resulting from the simulation and the deduced analytical function are shown in Fig. 5. Alternatively, the choice of the function h can be made with respect to the theoretical directivity of the elements composing the transducer array.

[0072] The calculation of the directivity for longitudinal and transverse waves is performed for a transducer of infinite length (a valid assumption because its width is large compared to the wavelength), of a given width a and for a known material. It is based on the calculation of three terms. The first is the radiation from a source line emitting a signal s(t) for a given frequency f:

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[0083] 'LSl(9, f) = TF(s(t)) with : - w = 2nf the angular frequency with f the frequency of the emitted signal; - TF(s(t)) fia Fourier transform of the signal emitted at frequency f; - VL!T the respective speed of the longitudinal and transverse waves; - Z UT = P vLlT the impedance of the medium respectively for the waves longitudinal and transverse. The second term allows us to take into account the scalar opening of width a relative to the source line: 'scal L (0, f ) = 2a sinc(k L a siu{0)) < ,scal T (9, f)=2a sinc(k T a siiiiô)) with kf / j-= v77~ 'c number of waves respectively of longitudinal and transverse waves. The third term is the Miller-Pursey factor, which takes into account the fact that the generation takes place on the surface of the sample: MPLi.e) = 2ki k'$2sm(d)2 2 2 / 2 ^-2sin^} +2sii^0jxsin^26jx^k^-sii^0] / \ { \ Jl-kisindl MPd 0 = 4cod 0-------••••;.....y..............---1.....................- ' ' ' / ka(l-2sùi(0) )+2sm(9^^^ with Zr = Zl. v T Finally, the directivities of a network element for longitudinal and transverse waves are given, for a frequency f, by: [D l ( 0 ) = I l S l (0, f) x scal L (e, f) x MP L (e) I [D t ( 0 ) = ILS^Û, f) x scalp, f) x MP^ These guidelines are then standardized.

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[0095] An example in the case of the TA6V titanium alloy for an element of width 0.42 mm and for a Gaussian pulse s(t) with a center frequency of 3.5 MHz is shown in [Fig.6]: Finally, the second filter proposed to favor the signal coming from transverse waves and limit that coming from longitudinal waves is h(0)=DT(0)x(l-DL(0)} Taking into account the chosen h function, the modified Green's function applied to focus the reflection matrix is ​​as follows: J __ \x r Ujj +z 2 )h(9), with k = ^et 0 = tan I. . By applying this filter during the calculation of the matrix, the signal of the longitudinal waves is reduced relative to the signal of the transverse waves, which allows an improvement in the signal-to-noise ratio of the matrix and in practice results in a less significant off-diagonal signal relative to the signal on the diagonal. The second step consists of eliminating interference due to the coherent summation of the signal from the side lobes. For this, the reflection matrix can be seen as composed of four terms that can be summed: a reflection matrix composed of emitters and receivers from a part of the probe located to the right of the focal point (denoted R dd), a reflection matrix composed of emitters and receivers from a part of the probe located to the left of the focal point (R gg) and a reflection matrix composed of emitters and receivers from a different part (right or left) of the probe with respect to the focal point (R gd and R dg). To perform the calculation of these four contributions, the matrix G' is separated into two "left" and "right" contributions, (?' and / 5') whose coefficients are calculated as follows: . f G^Xj, Uj, z, f) if Uj< l 0 smon, G'(Xj, Uj, z, f) if Uj> Xj G d (x i ,u i ,z,f) = J \ J J / J v 1 'l 0 otherwise The partial reflection matrices are calculated from and: dd ^iii' XOut? 'Out d (Xjiy Uûl'z,f)R( ^iii' ^out' ) ^ouP -^) J ^out' 2, f)j?(lljn, Uou^ (^out' Uoup Z, f) [ ] Rg^X.^, Xq^, zj — (¾^ Uny Z, f)R(Ujn, u0Ut, f^G^ (xou^ Uout, Z, f) J -^dg^in, X^, zj — uL^d(\ii' ^m' ^out' ^)^ÿ(^out' ^ouV -^)

[0099] An interference-free reflection matrix between transverse waves propagating to the right (towards x>0) and to the left (towards x<0) can then be obtained by the inconsistent summation of the four submatrices defined above:

[0100] 1^1=1^+^+1^+^

[0101] According to a particular arrangement, the total reflection matrix can be expressed using three or fewer of the four submatrices. In particular, the information of R can be predominantly contained in the matrices Rdg and Rgd when the interaction of the wave with the medium is mainly specular (reflectors of a size comparable to or greater than the wavelength) or predominantly contained in the matrices Rdd and Rffff when the scatterers in the medium are smaller than the wavelength. In an intermediate case, all four matrices contain information of interest.

[0102] Next, it is possible to construct a transverse velocity map in the same way as for longitudinal velocities but using the matrix R instead of RrY. Figure 7 shows experimental maps of longitudinal and transverse wave velocities measured in a sample of Inconel 600.

[0103] Step 5 - Determine local elastic constants of the part

[0104] Once the maps of the velocities of transverse and longitudinal waves Once these parameters are met, it becomes possible to estimate the local elastic constants of the material.

[0105] According to a particular arrangement, step 5 of determining the local elastic constants of the part is carried out by considering that the material has a constant density p.

[0106] Furthermore, according to a particular arrangement, step 5 is also carried out assuming that the material is isotropic, the components of the tensor of elastic constants Cqu can be calculated from the speed of the longitudinal wave cb the speed of the transverse wave ct and p.

[0107] In particular:

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[0118] Lamé coefficients can also be calculated: R=c 12 1 / 7 = C44 Finally, Young's modulus E, shear modulus G, and Poisson's ratio v can be calculated using the following relationships: 1 p = „3À+2p x+p "G = ji" XW) Figure 8 presents experimental maps of Young's modulus, shear modulus and Poisson's ratio of an Inconel 600 sample obtained from longitudinal Fonde velocity maps and transverse wave maps (Fig. 7). Poisson's ratio, on the other hand, can be calculated without any assumptions about density, given that: x _ p(qW) _ 1 1 2fX+p) 2p((c2-2c2)+c2) 2 ' Step 6 - Detect a zone of different elastic constant in the part According to a particular arrangement, process 100 may then include a step 6 of detecting a defect or a particular zone in the part by analyzing the local elastic constants of the part determined in step 5. As an example, step 6 may allow the detection of a macrozone or the presence of a hard-alpha or an inclusion in the part. A particular zone can describe a region in which one or more elastic constants (Young's modulus, shear modulus and / or Poisson's ratio) exhibit a deviation from the expected value, given for example by a reference specification or business knowledge, or from an adjacent zone considered as a reference zone.

[0119] Thus, the method according to the invention makes it possible to extract quantitative properties from the inspected medium, such as its local elastic constants. Obtaining the local elastic constants allows for the non-destructive characterization of the polycrystalline material part, by identifying areas with abnormal mechanical properties generated by the manufacturing processes or corresponding to a defect that locally alters the mechanical properties of the part.

[0120] In a particularly advantageous way, if a defect is detected in the part, the part can then be repaired or changed using a third-party device.

[0121] Computer program product

[0122] According to another aspect, a computer program product is proposed comprising program code instructions for executing the detection process.

[0123] Storage medium

[0124] According to another aspect, a non-transient storage medium is proposed on which is stored a computer program comprising program code instructions to execute the detection process 100, when said instructions are read from said non-transient storage medium and executed by a processor.

[0125] Monitoring device

[0126] According to another aspect, a detection device is proposed comprising an ultrasonic probe and electronic circuitry (computer system 200) adapted to implement a process 100.

[0127] As schematically shown in [Fig.4], the computer system 200 may include, connected by a communication bus 210: a processor 201; a random access memory 202; a read-only memory 203, for example of type ROM (Read Only Memory) or EEPROM (Electrically-Erasable Programmable Read Only Memory); a storage unit 204, such as a hard disk drive (HDD) or a storage media reader, such as an SD card reader (Secure Digital); and an input / output interface manager 205.

[0128] The processor 201 is capable of executing instructions loaded into RAM 202 from ROM 203, external memory, a storage medium (such as an SD card), or a communication network. When the computer system 200 is powered on, the processor 201 is capable of reading instructions from RAM 202 and executing them. These instructions form a computer program enabling the processor 201 to implement process 100.

[0129] All or part of the method 100 can thus be implemented in software form by executing a set of instructions by a programmable machine, for example a DSP (Digital Signal Processor) or a microcontroller, or be implemented in hardware form by a dedicated machine or component, for example an FPGA (Field Programmable Gate Array) or ASIC (Application-Specific Integrated Circuit). Generally speaking, the computer system 200 includes electronic circuitry adapted and configured to implement, in software and / or hardware form, the process related to the computer system 200 in question.

[0130] Alternatives - Other embodiments

[0131] As stated previously, typically the ultrasonic probe used is a linear multi-element probe.

[0132] According to a particular arrangement, the ultrasonic probe used can be a matrix (two-dimensional) probe, thus allowing the wave to be focused in three dimensions and obtaining a three-dimensional map of the transverse ultrasonic wave velocity and local elastic constants in a single measurement.

[0133] The Green's function used in the calculation of the focused basis reflection matrix is ​​then: 101341 G(r,u,f) = -2 », with k = <.

Claims

Demands

1. A method (100) for non-destructive testing of a part made of polycrystalline material, the method being implemented by a non-destructive testing device comprising electronic circuitry adapted to implement the method, the method being characterized in that it comprises at least the following steps: - (Step 1) measuring an ultrasonic reflection matrix of the part associated with a multi-element probe containing N piezoelectric transducers; - (Step 2) projecting the ultrasonic reflection matrix into a focused basis; - (Step 3) constructing a longitudinal wave velocity map; - (Step 4) constructing a transverse wave velocity map; - (Step 5) determining local elastic constants of the part; - (Step 6) detecting a defect or a particular area in the part by analyzing the local elastic constants of the part determined in Step 5.

2. A method (100) according to the preceding claim, wherein the step (step 4) of constructing a transverse wave velocity map comprises separating the reflection matrix into four sub-matrices: a first sub-matrix composed of emitters from a sub-matrix of the probe located to the left of the focal point, a second sub-matrix of receivers from a sub-matrix of the probe located to the left of the focal point, a third sub-matrix composed of emitters from a sub-matrix of the probe located to the left of the focal point, and a fourth sub-matrix of receivers from a sub-matrix of the probe located to the left of the focal point.

3. A method (100) according to claim 2, wherein in step (Step 4) of constructing a transverse wave velocity map, the total reflection matrix is ​​expressed as: lR-xxl = l^-ddl + l-Rgr / l "1" + , with a reflection matrix composed of emitters and receivers from a part of the probe located to the right of the focal point (denoted R dd), a reflection matrix composed of emitters and receivers from a part of the probe located to the left of the focal point (R gg) and a reflection matrix composed of emitters and receivers from a different part (right or left) of the probe with respect to the focal point (R gd and R dg).

4. Method (100) according to any one of claims 2 or 3 wherein in step (Step 4) of constructing a transverse wave velocity map, the total reflection matrix is ​​expressed using three or fewer of the four sub-matrices.

5. A method (100) according to any one of the preceding claims, wherein the step (Step 4) of constructing a transverse wave velocity map comprises weighting the total reflection matrix by a function depending on the angle between a transducer and the focal point.

6. Method (100) according to claim 5, wherein the total reflection matrix is ​​filtered using a function expressed as |sin(20) X 0^1 with the filter function and 0 the angle between the normal to the probe and the axis carried by the line joining the center of the probe and the focal point; or as h (0) = DT (0) X (1-DL (0)) with h the filter function, 0 the angle between the normal to the probe and the axis carried by the line joining the center of the probe and the focal point, DT(6) the directivity of an element of the grating for transverse waves and Dl(0) the directivity of an element of the grating for longitudinal waves.

7. A method (100) according to any one of the preceding claims, wherein the step (Step 5) of determining the local elastic constants of the part is carried out by considering that the material has a constant density.

8. A non-destructive testing device for a part made of polycrystalline material, characterized in that it comprises electronic circuitry (200) for implementing a method (100) for detecting a defect in a part made of polycrystalline material, which comprises at least the following steps: - (Step 1) Measure an ultrasonic reflection matrix of the part associated with a multi-element probe containing N piezoelectric transducers; - (Step 2) Project the ultrasonic reflection matrix onto a focused basis; - (Step 3) Construct a longitudinal wave velocity map; - (Step 4) Construct a transverse wave velocity map; - (Step 5) Determine local elastic constants of the part; - (Step 6) Detect a defect or a particular area in the part by analyzing the local elastic constants of the part determined in step 5.

9. Product computer program comprising program code instructions to execute the process (100) according to any one of claims 1 to 7, when the instructions are executed by a processor.

10. Non-transient storage medium on which is stored a computer program comprising program code instructions to execute the method (100) according to any one of claims 1 to 7, when said instructions are read from said non-transient storage medium and executed by a processor.

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