EP3602029A1 - Method for creating an evaluation table for an ultrasonic inspection and method for ultrasonic inspection - Google Patents

Abstract

The present invention relates to a method for producing an evaluation grid for ultrasonic testing of an object, said method comprising the following steps: - simulating an ultrasound distribution on at least one defect having a predetermined defect size by means of a two-dimensional or three-dimensional computer simulation, the defect size being less than or equal to the ultrasound wavelength and the simulation taking into account a mode conversion of the ultrasounds by the defect; - determine the reflectivity of the fault from the simulation; and - carrying out the evaluation grid by assigning the determined reflectivity to the defect size of the determined defect. In addition, the invention relates to a method for performing ultrasonic testing of an object, wherein an evaluation grid according to the invention is used.

Description

description

Method for creating a rating table for an ultrasonic test and method for ultrasonic testing

The invention relates to a method for generating a rating table for an ultrasonic test of an object, in particular a component. Furthermore, the invention relates to a method for ultrasound testing of an object, in which an inventively created rating table for the assessment ^¬ tion of detected in the ultrasound examination displays, in particular defects, is used.

According to the prior art, the evaluation of small displays in an ultrasound examination by means of a comparison of one of the display underlying defect or defect reflects the ultrasonic amplitude (also referred to as amplitude or echo) with a display of an artificially produced defect. Here, an ad is called small if its size is smaller than that

Sound beam of the ultrasonic sound is. The defects artificially ^¬ Lich produced can be formed as flat bottom holes, side holes or circular discs. By the mentioned comparison, a display or a defect within the object can be assigned a value designated as a substitute defect quantity. Here, the replacement ^¬ correct size indicates how big a comparable reflective man-made defect. Can accordingly from the spare defect size not necessarily be on the actual geometric size or extent of the defect within the object ge ^¬ closed.

An exemplary evaluation of a defect is therefore playing dropwise at ^¬ the following statement: The display Working relationship, the defect is reflected as a circular disk with a diameter of 4 mm. A use of known methods for determining substitute error quantities is possible with sufficient accuracy only up to a minimum defect size, wherein the minimum defect size is essentially determined by the wavelength of the defect

ultrasonic sound is fixed. For smaller De ^¬ fektgrößen, that is, in case of defect sizes that are smaller than the wavelength of the ultrasound used, can most ^¬ te substitute error variables that are based on, for example, holes, used only insufficient.

This is the case because such small diameter bores, in their respective drilling direction, are typically significantly larger than the wavelength of the ultrasound being trapped. As a result, they can not be used as a useful reference, ie as a substitute error variable. In addition, the manufacture and preparation of such small holes is problematic. As a result, the production of defined ultrasound reflectors and thus the provision of substitute defect sizes is only possible for large defect sizes, which, however, are of little relevance in practice.

Furthermore, known substitute error quantities are based on mathematical models. However, the known mathematical models require a scaling of the reflectivity proportional to the reflective surface of the defect. Since the ge ^¬ called proportionality is acceptable only for defect sizes above the wavelength, known mathematical ^¬ specific models are not applicable in case of defects having a defect size smaller than the wavelength.

To resolve smaller defect sizes, higher frequencies could be used. However, this leads to an increased absorption of the ultrasound used (sound attenuation), so that defects are more difficult to detect.

The present invention is based on the object to improve the detection of small defects in an object, in particular in a component, in an ultrasonic test. The object is achieved by a method having the features of independent claim 1 and by a method having the features of independent claim 10. In the dependent claims advantageous refinements and developments of the invention are given.

The inventive method for generating a rating table for an ultrasonic testing of an object, in particular ^¬ a component, comprising at least the following steps:

 Simulating a scattering of ultrasound on at least one defect with a defined defect size by means of a computer-implemented two-dimensional or three-dimensional simulation, wherein the defect size is less than or equal to the wavelength of the ultrasound, and the simulation takes into account a mode transformation of the ultrasound by the defect;

- Determining the reflectivity of the defect from the simulati ^¬ on; and

- Creating the evaluation table by means of an assignment of the determined reflectivity to the specified defect size of the defect. When the defect size is the geometric size of a defect, particularly a defect used in the simulation and out ^¬ stalteten referred perpendicular to the irradiation direction of the ultrasound. A defect in the sense of the present invention is small if its defect size is less than or equal to the wavelength, in particular less than or equal to half the wavelength, of the ultrasound used. In other words, the defect has, in at least one direction, a geometric extension that is less than or equal to the wavelength of the ultrasound used. The simulation can be implemented by means of a computing device, in particular by means of a computer. The further steps of the method according to the invention can also be carried out by means of a computing device.

For objects that have no spatial symmetry, he follows ^¬ a three-dimensional simulation. A two-dimensional simulation can be provided for objects with a spatial symmetry, for example in the case of an object designed as a rotation body. Through the two-dimensional Simulati ^¬ on computation time can be saved. The two-dimensional and three-dimensional simulation can furthermore include a time sequence of the scattering process. According to the present invention, the reflectivity of the defect having a defect size below the wavelength of the ultrasound is determined by the simulation. In this case, the simulation includes a numerical calculation of the scattering of the ultrasound on the defect used. According to the simulation takes into account a mode conversion of the ultra ^¬ sound through its scattering at defect. Thus, the scattering process ge ^¬ called is physically completely as possible represented by the simulation. As a result, the simulation provides at least one time-dependent amplitude of the ultrasound (echo) reflected at the defect, from which the reflectivity can be determined.

The evaluation table according to the invention is created by assigning the determined reflectivity to the defined defect size of the defect. In other words, the ermit ^¬ telten reflectivity is assigned a replacement defect size. Since ^¬ can advantageously by a defect size evaluation of basically arbitrarily small ads or defects gen successes.

If an ultrasound examination of an object results in a ^specific experimental reflectivity of a defect in the object detected, this experimentally detected reflectivity can be compared with the determined or calculated reflectivity within the evaluation table according to the invention. The reflectivity determined according to the invention, a defect size or a replacement defect size ^¬ orders delivered so by the said comparison, the experimentally recorded reflectivity and thus the real defect a replacement defect size is assignable. As a result, small defects can be assigned a sufficiently accurate substitute defect size.

This is therefore the case, first, because the simulation of it ^¬ inventive method takes into account the mode conversions of ultrasound at the defect. In other words, due to the scattering of the ultrasound at the defect, a change in the polarization of the defect typically occurs

sonicated, which takes into account the simulation. For example, scattered at the defect lon- dinalwellen can (ultrasound longitudinally polarized) in Trans- versalwellen (ultrasound transversely polarized) are converted and vice versa ^¬.

The inventive method for ultrasonic testing of an object comprises at least the following steps:

- Sounding ultrasound on at least one Volumenele ^¬ ment of the object;

- detecting at least one due to at least one Defek ^¬ tes reflected by the ultrasound volume element;

 Determining the reflectivity by means of the amount of a time-dependent amplitude of the reflected ultrasound for the volume element; and

- Determining a specific reflectivity associated defect size of the defect by means of an according to the present invention ^¬ or one of their configurations created rating table.

There are the above-mentioned inventive method for creating the evaluation table similar and equivalent advantages of the inventive method for ultrasonic testing of an object.

In the method according to the invention for ultrasonic testing, it is particularly preferred if an SAFT evaluation (synthetic aperture-focus technique, abbreviated SAFT) is used in determining the reflectivity. In other words, determining the reflectivity based on a SAFT From ^¬ evaluation (English: Synthetic Aperture Focusing Technique; off cut SAFT).

This is enhanced by defect sizes advantageously the accuracy and Be ^¬ evaluation. According to an advantageous embodiment of the invention, as the simulation was based on a finite difference simulation, in particular a elastodynamic finite integration method ^¬ (English: Elastodynamic Finite Integration

Technique, abbreviated EFIT).

The simulation method called is particularly advantageous to simulate a physically complete as possible scattering of ultra ^¬ sound on a small defect or to calculate. Further grid-based simulation methods can be provided alternatively or additionally, for example a finite element method (abbreviated to FEM).

In a further advantageous embodiment of the invention, the Auldsche reciprocity theorem is used to determine the reflectivity.

For example, the propagation of the ultrasound (sound propagation) for its way to the defect and its reflection at the defect is simulated by means of an EFIT simulation, and furthermore the propagation of the ultrasound for its

Way to the spatial position of the defect calculated without a reflection at the defect. If the ultrasound field is known on a surface enclosing the defect, then by means of the Auldschen reciprocity theorem reflected amplitude or the reflectivity of ultrasound - no was ^¬ nen way back to simulate - are determined. As a result, advantageously the computing time of the simulation can be reduced.

According to an advantageous development of the invention, the simulation takes place exclusively in a partial area of the object surrounded by the defect.

Advantageously, it is thus not necessary to simulate the Vo ^¬ lumen of the entire object in three dimensions. As a result, advantageously, the computing time of the simulation can be further reduced without sacrificing accuracy.

In this case, it is particularly preferred if the simulation of the propagation of the ultrasound from an insonification position to the subarea is effected by means of an elastodynamic point source synthesis.

In other words, the propagation of the ultrasound from ^¬ finally simulated in an environment of the defect. The sound propagation from the insonification position (test head) to the simulated subrange is calculated by means of elastodynamic point source synthesis. This allows advantageous ^¬, the computing time of the simulation are further reduced.

More ray-based simulation methods may be vorgese ^¬ hen.

According to an advantageous embodiment of the invention, the reflectivity R means

determined or fitted, where x = Df / λ, and Df is the D size, D a transducer diameter of a probe, λ the wavelength of the ultrasound, Q the fit parameter and s denote the sound path. The symbol i denotes the imagi ^¬ ary unit.

In other words, for a maximum value of the reflected amplitude

where A _Q denotes a reference value of the maximum value. The reflectivity is given by the ratio | ^ / ^ ₀ I such that R = \ A / A _Q \.

Typically, the above formula expression for the reflectivity in relation to a gain V (English: Gain) used in the Ultraschallprü ^¬ tion by means of V = 20 ^■ log ₁₀ (7?) Brought. In other words, the reflectivity is given in units of decibels. Advantageously, this is the result of the simulation, that is to say in particular the reflectivity is described by means of a sliding ^¬ chung or a formula expression and gefittet. This allows an interpolation of the results of the simulation. Furthermore, the evaluation table can advantageously be supplemented by non-simulated data points. In addition, the above formula expression can be efficiently implemented, so that an ultrasonic inspection, a direct query and thus an immediate and quick assessment can be done.

Other equations or formula expressions that are comparable and / or mathematically equivalent, and that reproduce the results of the simulation as accurately as possible can be provided. In particular, a fit of the reflectivity can take place on the basis of these further equations or formula expressions. typical It is not the reflectivity that is applied directly, but the gain, ie the reflectivity given in decibels. This is equivalent to a fit of reflectivity.

For example, the above formula expression for the gain V can be reshaped as follows:

Furthermore, advantageously given approximately ^¬ if resonance effects are neglected, which leads to approximation leads, with the variables and parameters as above de fined are. In particular, x = 4Df / λ. In other words, the reflectivity is approximately by means of determined.

The mentioned approximation is independent of the fit parameter Q, so that within the approximation no fit is required.

The above equations can as a theoretical model of the reflectivity of ultrasound at the defect referred to ^¬.

According to an advantageous development of the invention, the simulation is validated by means of a comparative ultrasound test on at least one defect produced, the defect size of the defect produced being greater than the defect Wavelength of the ultrasound used in the comparative ultrasound measurement.

Advantageously, this results in a calibration and / or validation or verification of the simulation of large defects and thus defects that can still be produced.

In an advantageous development of the invention, the evaluation table is determined as a diagram or formula expression.

This allows basie ^¬ rend on the configured as graph or formula expression evaluation table carried an improved evaluation of a defect.

Further advantages, features and details of the invention follow from the ^¬ described in the following embodiments and from the drawings. Shown schematically:

Figure 1 is a schematic flow diagram of the invention ^shown SEN method for creating a Bewertungsta ^¬ Bark for an ultrasonic examination; and FIG. 2 is a comparison diagram of a simulation with a

 Formula expression.

Similar, equivalent or equivalent elements Kings ^¬ NEN be provided in the figures with the same reference numerals.

1 shows the schematic flow chart of the method according OF INVENTION ^¬ dung for creating an evaluation table. In a first step Sl, a simulation of a

Scattering of ultrasound on at least one defect with a defined defect size by means of a computer-implemented two-dimensional or three-dimensional simulation. Here, the defect size is less than or equal to the wavelength of the ultrasound. Furthermore, a mode conversion of the ultrasound through the defect will be taken into ^¬ through the simulation. In other words, a physically most complete simulation of the scattering of the ultra ^¬ sound occurs at the existing within the simulation defect.

In a second step S2, the reflectivity of the Defek ^¬ tes from the simulation, on a defect corresponding to the maximum value of the amount of zeitab ^¬ dependent amplitude of the reflected ultrasound at the defect, for example determined based. Here, the determination of the reflectivity can be made into special ^¬ on a SAFT analysis of the calculated time-dependent amplitudes (A-scans).

In a third step S3 of the method, the evaluation table is created by means of assigning the ermit ^¬ telten reflectivity at the specified defect size of Defek ^¬ tes. In other words, the reflectivity, determined by means of the simulation is correlated with the ver ^¬ used in the simulation defect size. In general, the ^evaluation table is to be understood as a correlation between the reflectivity and the defect size. In other words, a fixed given reflectivity results in exactly one defect size. The rating table may be tabulated, wherein a column of the table of reflectance and a white ^¬ tere column is associated with the table, the defect size. With ^¬ means of the evaluation table according to the invention created to review and defect identification in the ultrasonic testing of the object can be performed. In particular, using the evaluation table according to the invention, defects having a defect size below the wavelength of the ultrasound used can be detected and evaluated. As a result, be associated with a defect size below the wavelength of the ultrasound used in the ultrasonic examination advantageously an equivalent flaw size Defek ^¬ th. FIG. 2 shows a comparison diagram of a simulation with a theoretical model of the reflectivity of the ultrasound. At the abscissa 100 of the illustrated comparative diagram, the defect size in the unit millimeters (mm) is plotted logarithmically. Here, the defect is exemplified as a circular disk. At the ordinate 101, the gain of the ultrasonic signal is plotted in decibels (dB). In other words, the dependence of the normalized amplitude is | .A / .A ₀ | dop ^¬ pelt-logarithmically plotted ^on the defect size Df.

Here, the amplification corresponds to the detected reflectivity of an ultrasound reflected at the defect. The reflected at the De ^¬ fect ultrasound is recognized as a time-dependent Amplitu ^¬ de.

A dashed line 121 denotes a classical distance-gain-size-rating (abbreviated: AVG-method). In the case of the illustrated double logarithmic plot, this extends essentially linearly. The dashed line thus corresponds to a dependence of the amplitude, which is proportional to the square of the defect size, that is AoaDj.

Furthermore, a dotted-dashed line 112 is Darge ^¬ represents, which is based on a dependence of the amplitude proportional to the third power of the defect size, that is AoaD. Thus, the dotted-dashed line 112 has a greater slope than the dashed line 121. Furthermore, it ^¬ the dot-dashed line 112 also extends linearly. The simulated course of the reflectivity or the gain in dependence of the defect size is given by Since ^¬ tenpunkte 142 a simulation of the defect with the defect size jeweili ^¬ gen. For the sake of clarity is only one of the data points is identified by the reference numeral 142. There is a kink within the mentioned course to recognize. The kink corresponds to a transition of the dependence of the amplitude from A oc D for small defect sizes to AoaDj for large defect sizes. The lines 121, 112 thus correspond in each case to an asymptotic area of the data points 142.

The determined data points 142, which reproduce the course of the amplification V selectively, can be determined by means of (see also the formula expressions mentioned in the description).

where x = Df / λ, and Df is the defect size, D is a transducer diameter of a probe, λ is the wavelength of the ultrasound, Q is the fit parameter, and s

Designate sound path. The symbol i denotes the imaginary unit.

The fit is illustrated by the solid line 124 and shows a very good agreement with the numerically determined by the simulation data points 142nd

By means of the illustrated diagram, an evaluation of an ultrasound examination of an object can take place. Is ^¬ example, for a sensed time-varying amplitude of a Ultra ^¬ sound signal requires a gain of about 83 dB, this corresponds, according to the illustrated diagram of an exemplary defect size of about 1 mm. In other words, can by means of the evaluation table, which can correspond in their graphi ^¬ rule representation of the diagram shown, detected defects having a defect size below the wavelength of the ultrasound used and their size relationship ^¬ as spare defect size can be determined. Although the invention in detail by the preferred embodiments is further illustrated and described, the invention is not limited by the disclosed examples is ^¬ restricts or other variations can be derived therefrom by the skilled artisan without departing from the scope of the invention.

Claims

claims A method for generating an evaluation table for an ultrasound examination of an object, comprising the steps of: simulating a scattering of ultrasound on at least one defect with a defined defect size by means of a computer-implemented two-dimensional or three-dimensional simulation, wherein the defect size is less than or equal to the wavelength of the ultrasound , and the simulation a mode conversion of the ultrasound through the Defect considered; - Determining the reflectivity of the defect from the simulati ^¬ on; and  - Creating the evaluation table by means of an assignment of the determined reflectivity to the specified defect size of Defect. 2. Method according to claim 1, in which a simulation based on finite differences, in particular an elastodynamic finite integration method, is used as the simulation. 3. The method according to claim 1 or 2, wherein the Auldsche reciprocity theorem is used to determine the reflectivity. 4. The method according to any one of the preceding claims, wherein the simulation is carried out exclusively in a part of the object surrounding the defect. 5. The method according to claim 4, wherein the simulation of the propagation of the ultrasound from its insonification position to the subarea by means of an elastodynamic point source synthesis. 6. The method according to any one of the preceding claims, wherein the reflectivity means where x = Df / λ, and Df is the defect size, D is a transducer diameter of a probe, λ is the wavelength of, Q is a fit parameter, and s is the sound path. 7. The method according to any one of the preceding claims, wherein the reflectivity approximately by means of is determined. 8. The method according to any one of the preceding claims, wherein a validation of the simulation is performed by means of a comparison ultrasonic testing on at least one manufactured defect, the defect size of the defect produced is greater than the wavelength of the ultrasound used in the comparative ultrasonic measurement ^¬. 9. The method according to any one of the preceding claims, wherein the evaluation table is determined as a graph or formula expression. 10. A method of ultrasonic testing an object comprising the steps of:  - sonication of ultrasound on at least one volume element of the object; - detecting at least one due to at least one Defek ^¬ tes reflected by the ultrasound volume element;  Determining the reflectivity by means of the amount of a time-dependent amplitude of the reflected ultrasound for the volume element; and - Determining a specific reflectivity associated defect size by means of a according to one of claims 1 to 9, created rating table. 11. The method of claim 10, wherein determining the reflectivity is based on a SAFT evaluation.