Ultrasonic transducer for generating and detecting ultrasonic waves in a metal test object
Patent Information
- Application Number
- CN202580020161.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-03-14
- Filing Date
- 2025-03-12
- Publication Date
- 2026-10-09
Smart Images
Figure CN122893052A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to an ultrasonic transducer for generating ultrasonic waves in a metal inspection object, comprising: at least one magnet; four sets of printed wire segments, each including at least one linear printed wire segment extending above the magnetic pole of the magnet in a bottom view, wherein the sets of printed wire segments are distinguished from each other by the direction of current flow during operation, and the printed wire segments extend above the magnetic pole at an angle to the longitudinal direction of the magnetic pole in a bottom view; and a control unit for energizing the printed wire segments. Furthermore, this invention relates to an ultrasonic transducer for detecting ultrasonic waves in a metal inspection object, comprising: at least one magnet; four sets of printed wire segments, each including at least one linear printed wire segment extending above the magnetic pole of the magnet in a bottom view, wherein the sets of printed wire segments are distinguished from each other by the direction of current flow during operation, and the printed wire segments extend above the magnetic pole at an angle to the longitudinal direction of the magnetic pole in a bottom view; and a control unit for receiving signals induced in the printed wire segments. Background Technology
[0002] In the publication "A new chevron electromagnetic acustic transducer design for generating shear horizontal guided wave" (Ultrasoncis, Vol. 135, December 2023) by Gautham et al., an ultrasonic transducer device, namely the EMAT device, is introduced, which can be used with a strip permanent magnet array and a Chevron-shaped meandering coil for guided SH waves (horizontally polarized shear waves). Here, the trace wavelength is not defined by periodically alternating magnetic poles, but by a conductor obliquely positioned above the magnetic stripe in the Chevron-shaped coil. The oblique conductor can induce a Lorentz force in the test object, which has longitudinal and transverse components that partially cancel each other out, resulting in the aforementioned shear wave in the far field.
[0003] In particular, metal objects consisting of pipes or planar structures (such as the bottom of a tank or a semi-finished product in the form of a sheet) are used as metal inspection objects.
[0004] In the past, various methods have been described in the literature and / or implemented for technical applications to determine the remaining wall thickness in hard-to-access locations. However, they all have certain physical limitations that restrict practical applications and the capabilities used for probing and dimensional determination.
[0005] In ultrasound methods used for this application, there is a distinction between methods that use guided waves and methods that use angled body waves.
[0006] The "gold standard" for reliably and quantitatively estimating the remaining wall thickness is ultrasonic time-of-flight measurement with perpendicular incidence in a dense grid. However, this method is very time-consuming and can only be applied when there is adequate accessibility.
[0007] Guided waves have the advantage of propagating with low attenuation over long distances. This means that flat test specimens (such as pipe walls or tank bottoms) can be inspected relatively quickly and completely without having to scan fine meshes point by point. Furthermore, hard-to-access areas can also be inspected. In addition to the classic pulse-echo method, the frequency-thickness correlation (dispersion) of guided wave modes can be utilized to identify corrosion or erosion thinning in structures with guided waves in a more sophisticated manner. Specifically, at least three types of features can be considered during inspection: Transmission and reflection amplitudes; Phase velocity and group velocity variations (phase shift and time delay); The cutoff phenomenon of guided waves.
[0008] All these features can be used as single-mode, in multi-mode schemes, or in combination. On the one hand, by selectively exciting multiple modes sequentially in a sequential testing procedure and analyzing and evaluating the reflection and transmission components of the same mode at inhomogeneities in the acoustic path, the sensitivity and ability to quantify defects can be significantly improved. On the other hand, it is also possible to selectively analyze the signals of mode transitions at defects (in transmission and reflection).
[0009] It has been confirmed that higher-order modes are applicable to surface corrosion in thin plates, and the same mode shows different sensitivities for corrosion identification at different phase velocities.
[0010] SH waves are strongly influenced by factors such as surface condition, coating type and thickness, and defect morphology. On the other hand, Lamb waves are additionally affected by liquid loads on one or both surfaces due to leakage waves. Summary of the Invention
[0011] The purpose of this invention is to make ultrasonic transducers, especially EMAT transducers used for inspecting metal objects, more flexible in their configuration.
[0012] This objective is achieved by the subject matter of claim 1 and claim 2. Furthermore, this objective is achieved by the method of claims 13 and 14 and by the subject matter of claim 15. Advantageous embodiments of the invention can be derived from the dependent claims invoking these claims and from the following description.
[0013] According to the present invention, every two sets of printed conductor segments constitute first and second meandering coils, which can be controlled by a control unit of an ultrasonic transducer, wherein the control unit is configured to: control the coils in phase or out of phase to generate Rayleigh waves or Lamb waves, and control the coils out of phase or in phase to generate guided SH waves.
[0014] Furthermore, this objective is achieved according to the invention by the aforementioned ultrasonic transducer for detecting ultrasonic waves, characterized in that each set of two printed conductor segments respectively constitutes a first and a second serpentine coil, wherein a control unit is configured to: add or subtract signals to detect Rayleigh waves or Lamb waves, and subtract or add signals to detect guided SH waves. The control unit thus receives signals. The control unit can be configured in multiple parts such that, for example, the signal is received in a first part of the control unit and, if necessary, processed later in a second part of the control unit (e.g., in an EDV unit separate from the first part of the control unit).
[0015] Two such ultrasonic transducers according to the invention can be used as a transducer pair for inspecting metal objects, particularly pipes or plates, wherein transducers are provided for generating and detecting ultrasonic waves. However, with a corresponding control unit, it can also be a single ultrasonic transducer, which is circuitically configured to energize a printed conductor segment and subsequently to detect and receive signals induced in the printed conductor segment. The ultrasonic transducers of the same transducer pair can be used alternately and mutually to generate and detect ultrasonic waves.
[0016] Accordingly, the inspection equipment according to the invention for inspecting pipes and / or other inspection objects (which can be considered as flat bodies for generating ultrasonic waves) can have one or more such transducers.
[0017] In the context of this invention, a meandering coil is understood as a coil in which the straight printed conductor segments, which are related to generating Lorentz force in the test object, extend parallel to each other or in a direction parallel to each other, and wherein the directly parallel printed conductor segments of the same coil (the printed conductor segments extending above one or more magnetic poles in a bottom view of the magnetic poles) are provided with opposite current directions. When using multiple magnetic poles, in particular, the straight printed conductor segments with the same current direction that are close to each other generally extend across the multiple magnetic poles. Therefore, multiple straight printed conductor segments with the same current flow direction can be arranged to each other such that the corresponding coil is longer, also covering the multiple magnetic poles of the parallel magnets, with the same current direction.
[0018] Here, the magnets are aligned such that, during operation, the magnetic field lines can be assumed to be perpendicular to the printed conductor segment and extend in the direction of the object being inspected.
[0019] In particular, the printed conductor section has multiple parallel extensions of the printed conductor of the corresponding coil, that is, the corresponding coil can have multiple windings with corresponding meandering shapes.
[0020] The bottom view of a magnetic pole is a view taken from the direction of the metal object to be inspected towards the corresponding magnetic pole. The printed conductors of the coil are positioned between the magnetic pole and the surface of the object being inspected during operation. In this view, they extend or stretch above the magnetic pole.
[0021] The control unit is equipped with conventional electronic mechanisms for manipulating the coil and is capable of applying alternating current, particularly at operating frequencies f, between 100 kHz and 2 MHz. Specifically, the control unit is configured to allow the use of different frequencies, enabling adjustment based on the wall thickness of the object under inspection.
[0022] The longitudinal direction of a magnetic pole relates to its bottom view and corresponds in the bottom view to the direction in which the length of the pole is measured, particularly where the length is greater than the width transverse to its observation width. When multiple magnetic poles of the same polarity (e.g., bar magnets with angular or circular cross-sections) are arranged in a row, the direction in which the lengths of the same magnetic poles directly arranged in the row are measured is taken as the longitudinal direction, again in the bottom view. When multiple magnetic poles of opposite polarities are arranged in a row and are side-by-side with each other in the bottom view, the longitudinal direction extends parallel to the boundary between the individual side-by-side magnets in the bottom view.
[0023] Relative to a straight line extending parallel to the longitudinal direction of the magnetic poles in a bottom view, if the printed conductor sections of two coils (which are at the same height relative to the straight line and located on the same magnetic pole) have current directions pointing in different directions in their projection onto the straight line during operation, Rayleigh waves or Lamb waves are generated by the ultrasonic transducer according to the invention via in-phase or out-of-phase manipulation. Then, in the far field of the test object, the transverse components of the Lorentz force are added, such that the longitudinal components of the Lorentz force are retained along the longitudinal direction of the magnetic poles.
[0024] In the coil setup (where, if energization is obtained in different directions in the projection onto the straight line when the coil is operated in reverse phase), the forces induced in the far field (i.e. in the object under test) are added together, such that Rayleigh waves or Lamb waves are then generated accordingly when operated in reverse phase (especially offset by 180°).
[0025] The situation is reversed when a guided SH wave is generated. Here, the projection of the current direction onto a straight line extending in the longitudinal direction parallel to the magnetic pole applies: if printed conductor sections of two coils of the same height and passing through the same magnetic pole are energized in the same direction, an SH wave is generated, depending on whether the control is set to in-phase or out-of-phase.
[0026] The same applies to the detection of Rayleigh or Lamb waves. If the induced currents in the printed conductor sections of the two coils are at the same height on the aforementioned straight line and their projections above the same magnetic poles point in different directions, resulting in in-phase signals, then these signals are added together to detect Rayleigh or Lamb waves, or subtracted in the case of out-of-phase signals. This depends on the coil configuration and the resulting extension of the printed conductor sections.
[0027] If the induced currents in the two printed conductor segments of the two coils point in the same direction when projected and produce out-of-phase signals, then the signals must be subtracted in order to detect the SH wave. However, if in-phase signals are generated in the opposite configuration, then the signals must be added in order to detect the SH wave.
[0028] Therefore, it is feasible to use the same setup to generate Rayleigh waves and Lamb waves, which enables the quasi-instantaneous generation and detection of different wave types at the same location of the object to be inspected at the frequency to be used, and can save further inspection runs or further measurement setups.
[0029] Therefore, according to the invention, two meandering coils are combined and used above the magnetic poles of at least one magnet in a bottom view. In a further embodiment of the invention, the ultrasonic transducer according to the invention is improved such that there are at least two magnets arranged side by side, preferably in strip and / or rod shapes, the magnetic poles of which have alternating polarities in a transverse direction extending transversely to the longitudinal direction of the magnetic poles in a bottom view, wherein one or more printed conductor segments of an assembly of printed conductor segments abut each other extend above at least two adjacent magnetic poles in a bottom view. Thus, the two meandering coils can be used via a magnet array, particularly constructed as an array of permanent magnets, so that, on the one hand, the desired wave can be generated well, and on the other hand, a sufficiently clean signal with a good signal-to-noise ratio can be generated for detection.
[0030] It should be understood that the device according to the invention can also be equipped with a housing or enclosure, as well as any fixing mechanism for the coil and magnet. For example, the coil can be covered with an anti-slip layer, such as a ceramic layer, on the side pointing towards the object being inspected, which is part of the housing of the ultrasonic transducer. The control unit can have a separate housing. The mechanisms can be selected by those skilled in the art according to the setup and are known to them.
[0031] The first and second coils are arranged on the same side of at least one magnet or array of magnets, such that the energy introduced into the coils can be directed in the direction of the object to be inspected. Therefore, this is the side pointing towards the wall during operation.
[0032] The local Lorentz force acting in the test object when two meandering coils are manipulated in phase or out of phase, similar to the conditions described above and below regarding the projection of the current direction during operation, generates particle displacement in the longitudinal direction (particularly in the longitudinal direction of the magnetic poles) in superposition. This ionic displacement is used to excite Rayleigh waves or Lamb waves. The local transverse force components of the Lorentz force induced in the test object are antiparallel aligned and thus cancel each other out. The longitudinal components point in the same direction and thus strengthen, which produces the formation of longitudinal waves. Conversely, when one of the two current directions is exchanged due to out-of-phase manipulation, guided SH waves can be generated.
[0033] To more precisely define the force induced in the object under test and to receive a signal with an improved signal-to-noise ratio, according to an improved form of the invention, in a bottom view, the arrangement of the printed conductors, with a turning portion between parallel printed conductor segments of the same coil, extends outside at least one magnetic pole or on the edge of at least one magnet. Therefore, the printed conductor segments are removed from the region of maximum magnetic linear density and can be neglected when considering the induction used to generate and detect ultrasonic waves.
[0034] In particular, the ultrasonic transducer according to the invention is designed such that the printed conductor segments of two coils are associated with each other in pairs, especially wherein the corresponding pairs of printed conductor segments intersect or cross in a bottom view. Thus, in a bottom view, a very good configuration of the wave to be sensed or the signal to receive the wave can be achieved via one or more preferably strip-shaped magnets, particularly via a magnet array comprising at least four, six or eight permanent magnets.
[0035] By pairing printed conductor segments of two coils located above the same magnetic pole and intersecting, a basic unit can be formed in a bottom view, in which the force action favorable for generation and detection in the object being inspected can be clearly defined and structured.
[0036] The printed conductor segments extend at angles between 20° and 70° with respect to the longitudinal direction, more preferably at angles between 30° and 60°, and even more preferably at angles of 45° with respect to the longitudinal direction, thereby generating ideal Lorentz forces for the corresponding, and particularly for, both wave types. This again relates to the bottom view. Only the degrees matter, regardless of whether the angle is measured in a mathematically positive or negative direction. In particular, the printed conductor segments of the two coils are arranged at 90° angles to each other, thereby generating symmetrical forces for the longitudinal and transverse waves. The printed conductor segments of the two coils are aligned mirror-symmetrically with respect to a straight line parallel to or located on the longitudinal axis.
[0037] In order to generate directional waves in the best way, especially at pipes, printed conductor segments are arranged in a surface with a certain curvature, which is set to adapt to the surface of the object being inspected.
[0038] According to an improved form of the invention (which is particularly advantageous for board material inspection), the printed conductor segments of the same coil are located in a plane in the intersection area of the two coils without regard to the turning portion, wherein the plane is aligned perpendicular to the surface normal of the object being inspected during operation.
[0039] If the magnet has a length of three to six trace wavelengths in a bottom view, the ultrasonic transducer arrangement according to the invention is particularly good for pipe and plate inspection. Trace wavelength ʎ S It is the spatial period length of the guided ultrasonic mode excited in the board, and corresponds to the distance between two parallel printed conductor segments of the corresponding coil with the same current direction, but relative to the longitudinal direction.
[0040] For the purposes of this invention, it is preferable to arrange a plurality of bar magnets having alternating polarities side by side, wherein this is preferably an even number. The magnets have a width of one to six trace wavelengths in a bottom view, wherein bar magnets with a width less than the length of the magnet (relative to the bottom view) are preferred.
[0041] The initial objective is also achieved through a method for generating ultrasound, in which the aforementioned or described ultrasonic transducer is provided with a meandering coil, which is manipulated in phase or out of phase via a control unit of the ultrasonic transducer to generate Rayleigh or Lamb waves, and manipulated out of phase or in phase to generate guided SH waves. Similarly, applicable to the method for detecting ultrasound according to the invention is that the signal from the meandering coil of one of the aforementioned or described ultrasonic transducers is added or subtracted in the control unit of the ultrasonic transducer to detect Rayleigh or Lamb waves, and subtracted or added to detect guided SH waves. The control unit can be configured as a single part or multiple parts as described above. In particular, the components of the control unit can be a first part of a control unit in the form of an electronic mechanism for storing signals, and a second part of a control unit, the second part receiving data recorded by the first part separately from the first part and the second part processing the signals according to the invention. The control unit is therefore a single-part or multiple-part data recording and evaluation device.
[0042] Finally, the objective stated at the beginning is achieved by means of inspection equipment configured for inspecting pipes or for testing sheet metal, and said inspection equipment having one or more transducers as described above or below. This also has corresponding advantages.
[0043] For the phase relationship of the signal induced in the coil, please refer to the above and below. Attached Figure Description
[0044] Other advantages and details of the invention will become apparent from the following description of the accompanying drawings. Indicatively:
[0045] Figure 1a This diagram illustrates the schematic of the inspection device according to the invention in a pipeline.
[0046] Figure 1b An ultrasonic transducer according to the present invention is shown.
[0047] Figure 1c The first meandering coil is shown.
[0048] Figure 1d The second meandering coil is shown.
[0049] Figure 2 Showing according to Figure 1b A bottom view of the magnet array in direction U.
[0050] Figure 3 Showing according to Figure 1b The object is in a bottom view and contains the portion that generates forces during operation.
[0051] Figure 4 Showing according to Figure 1bThe part of the object that generates force during operation.
[0052] Figure 5 Showing according to Figure 1b A bottom view of the magnet array.
[0053] Figure 6 This shows how to control two coils in phase according to Figure 1b A bottom view of a magnet array with meandering coils.
[0054] Figure 7 The basis for inverting the operation of two coils is shown. Figure 5 The object,
[0055] Figure 8 The dispersion diagram of a guided SH wave in a 2mm steel plate is shown.
[0056] Figure 9 The dispersion plot of a Lamb wave in a 2mm steel plate is shown.
[0057] Figure 10 This illustrates signal reception and evaluation using an object according to the invention on an incident Lamb wave.
[0058] Figure 11 The diagram illustrates signal reception and evaluation when the object according to the invention is subjected to an incident guided SH wave.
[0059] Figures 12 to 15 A bottom view of a portion of another object according to the invention is shown.
[0060] The various technical features of the embodiments described below can also be combined with the features of the embodiments described above, one of the independent claims, and any other claims relating to the object of the invention. Elements that are at least partially functionally identical are given the same reference numerals, as long as it is meaningful. Detailed Implementation
[0061] according to Figure 1a The inspection device 2 according to the invention is designed to function as a detection pig for an inspection object 4 of a pipeline. A propulsion mechanism 6 in the form of a cup or disc is arranged at the central body 5 of the detection pig. Through this, the detection pig is passively carried by the fluid along with the medium located in the pipeline. A plurality of ultrasonic transducers 10 according to the invention are arranged circumferentially around the central body via spring-loaded arms 8; these transducers are configured to generate ultrasonic waves in the pipe wall, and only two are shown. Other ultrasonic transducers 12 according to the invention are configured to detect the ultrasonic waves generated in the pipe wall, and are again arranged circumferentially.
[0062] Control unit 14 is used to load the coil present in ultrasonic transducer 10. Furthermore, the same control unit 14 or another control unit can be configured to receive signals induced in the coil of ultrasonic transducer 12 and for their evaluation. Alternatively, control unit 14 can also be configured only for receiving signals and storing them, such that the evaluation itself is performed in another part of the control unit, which may not be physically connected to the portion of the control unit shown.
[0063] The ultrasonic transducers 10 and 12 according to the invention comprise a plurality of magnets in the form of a magnet array 18 in the shape of strips and configured as permanent magnets, the magnets being directly abutted against each other with alternating polarities. Figure 1b During operation, magnet 18 is aligned with its north-south alignment, which is generally perpendicular to the surface of the pipe or the object to be inspected. The longitudinal direction L of the magnetic poles of magnet 18 extends perpendicularly to the north-south alignment A in the longitudinal extension direction of magnet 18.
[0064] On the side of the ultrasonic transducer facing the tube wall, there are two coils 20 and 22 stacked directly on top of each other, the coils being arranged in a meandering or serpentine manner. Figure 1c and 1d Regarding the coils, in-phase operation means respectively regarding Figure 1c and 1d The view shows the current flow from connection point 21 of coil 20 and connection point 23 of coil 22 downwards from above magnet 18 to connection points 25 and 27. The coils are connected to the control unit via these connection points or joints.
[0065] according to Figure 1c The first meandering coil has a printed conductor segment 24, which, during operation and in accordance with... Figure 1b In the bottom view U, the current directions are the same, and the printed conductor segments are each composed of shorter printed conductor segments placed sequentially, and subsequently also indicated by 24. The current direction is typically indicated by a closed arrow on the printed conductor segment ( Figure 3 , 4 (6 and 7). Furthermore, coil 20 includes other printed conductor segments 26 that also extend above the magnetic poles in the bottom view, and which are distinguished from printed conductor segment 24 by opposite current directions during operation. The printed conductor segments 26 can also be subdivided into multiple sequentially placed printed conductor segments 26. Accordingly, printed conductor segments 24 and 26 constitute two sets of printed conductor segments for coil 20. A similar situation applies to printed conductor segments 28 or 30 of coil 22. The turning segments or turning portions 32 of coils 20 and 22 have a value corresponding to half a trace wavelength ʎ. SThe lengths of the printed conductor segments. They are located outside the magnetic poles in the bottom view U and are not considered in terms of any force acting on them. The printed conductor segments 24, 26, 28 and 30 of the corresponding coil 20, 22 extend in parallel or parallel directions to each other.
[0066] Printed conductor segments 24 or 26 and 28 or 30 can be divided into a series of smaller printed conductor segments 24 or 26 and 28 or 30 that are adjacent to each other; however, the smaller printed conductor segments each have the same current direction. The corresponding division is in... Figure 3 and Figure 4 As shown in the diagram. This division of the coil allows for the definition of... Figure 2 The identifiable basic unit 34 is used for subsequent force observation, and the basic unit typically has a length equal to half the trace wavelength in the longitudinal direction. S The length of the basic unit. The basic unit describes the force applied in test object 4.
[0067] During operation, the force shown is obtained in the tube wall within the unit and relative to the corresponding printed conductor segment 24, wherein F L The Lorentz force, F, acts within the pipe wall. L,l It is the longitudinal component of the Lorentz force, and F L,t It is the transverse component of the Lorentz force. Typically, in... Figure 2 In the accompanying diagrams, the magnetic pole without a shaded line is the North Pole, and the dotted magnetic pole is the South Pole.
[0068] Therefore, within the tube wall, due to coil 20, the particles present there are... Figure 3 The force shown in the figure. Figure 4 The force shown is due to the force exerted by coil 22 on particles present in the tube wall. This is the case when controlled in phase via connections 21 and 23. Figure 3 and Figure 4 The forces shown and obtained in test object 4 are superimposed in the corresponding basic unit 34 according to the control of coils 20 and 22, so as to obtain an effect that is beneficial to the generation of ultrasonic waves.
[0069] exist Figure 5 The diagram shows how the printed conductor segments of two coils 20 and 22 cross at a 90° angle in the corresponding basic unit 34 in the bottom view U. Coils 20 and 22 are arranged on the same side of the magnet array and are also arranged close to each other or as close as possible to the same plane to maintain the same magnitude of the force induced in the tube wall. It should be understood that the coils are insulated from each other, and the coil turning portion at the crossing point is not considered for planar configuration.
[0070] In basic unit 34, the printed conductor segments of coils 20 and 22 are associated with each other in pairs. The printed conductor segments are perpendicular to each other and intersect. Therefore, for example, according to... Figure 4 In the upper left basic unit 34, the printed conductor segment 24 is arranged perpendicular to the printed conductor segment 30. In the basic unit 34 located to its right, the printed conductor segment 26 is arranged perpendicular to the printed conductor segment 28. When operating the two meandering coils 20 and 22 in phase, according to Figure 6 The particles present in the tube wall generate a resultant force in the direction of double arrow 36, resulting in a longitudinal wave or Lamb wave running in the propagation direction 38. The same result occurs when one of the two coils is manipulated at its opposite end, with opposite-phase manipulation.
[0071] Based on the above, when the winding coil is operated in reverse phase, a synthetic Lorentz force is obtained in the test object 4 according to the basic unit 34. This synthetic Lorentz force causes the particles in the tube wall to be displaced in a direction transverse to the propagation direction 38 according to the double arrow 40. Therefore, the particle displacement in the tube wall is transverse to the propagation direction of the ultrasonic wave, thereby generating SH waves.
[0072] According to Figures 5 to 7 In the bottom view, a magnet array consisting of four bar magnets 18 arranged side by side can be identified, which has two trace wavelengths. S Width and 3 trace wavelengths S The length. The propagation direction 38 is parallel to the length of the propagation direction. Figure 1b The longitudinal direction L of the magnetic poles in the bottom view U. Except for the intersection, the printed conductor sections of the corresponding coils 20 and 22 are located in a plane.
[0073] The operating frequency f, the thickness d (wall thickness) of the test object 4, and the trace wavelength λ of different plate wave modes. s There exists a mathematical-physical relationship, which is derived from the solution of the wave equation under special boundary conditions of a plate waveguide. The solution is usually represented in the form of a dispersion diagram.
[0074] By means of the ultrasonic transducer according to the present invention, it is possible to generate an ultrasonic transducer in a 2mm steel plate according to the present invention. Figure 8 The guided SH wave is exemplarily shown in the dispersion plot, where the velocity is plotted in mm / µs on the y-axis and the frequency in MHz on the x-axis. Lines 42, 44, and 46 represent the phase velocities of modes AS1, SS1, and AS2. Dashed lines 48, 50, 52, and 54 correspond to the group velocities of modes SS0, AS1, SS1, and AS2. The phase velocity of mode SS0 corresponds to the group velocity of mode SS0.
[0075] exist Figure 9An exemplary dispersion plot for a Lamb wave in a 2mm steel plate is shown, where lines 56, 58, 60, and 62 represent the phase velocities of the A0, S0, A1, and S1 modes, respectively, while dashed lines 64, 66, 68, and 70 mark the group velocities of the corresponding modes in the same order (A0, S0, A1, and S1 modes).
[0076] If a straight line with the slope of the trace wavelength is plotted at zero, the operating frequency f can be read from the graph. The intersection point with the mode curve is then used to derive the operating point from the frequency and phase velocity.
[0077] The following shows the operating points of the lowest four SH and Lamb wave modes in a 2mm steel plate at a 4mm trace wavelength, where f = operating frequency, c p = phase velocity, and c g =Group velocity.
[0078] exist Figure 10 and Figure 11 The image shows the signal obtained by the ultrasonic transducer 12, designed for detecting ultrasonic waves, in the meandering coils 20 and 22. Figure 10 This shows the signal in the Lamb wave case, where the coil is based on... Figure 5 Arrangement. In Figure 10 The upper left figure shows the received signal of the meandering coil 20, and the lower left figure shows the received signal of the coil 22. In the upper right corner, in the case of a Lamb wave, a clearly detectable sum signal is obtained due to in-phase induction of the signal, while the difference signal disappears. The opposite is true in the case of an incident guided SH wave, where an out-of-phase signal is induced in the meandering coil, as in… Figure 11 As shown in the two left figures, the signal then disappears in the addition and is clearly identifiable as a difference signal in the subtraction. Figure 11 (The image on the right).
[0079] Instead of based on Figure 5 The settings of the present invention, in accordance with Figure 12 In a structure with only a single magnet 18 and a single coil, the same effect can already be achieved in certain applications. Here, the ultrasonic transducer consists of only two basic units 34, and also has a correspondingly small size, transverse to its longitudinal direction by only half a trace wavelength and with a length of only one trace wavelength. Instead of a precise right-angle arrangement, the ultrasonic transducer can also be provided with meandering coils, which are not perpendicular to each other in the basic unit, but are angled between 20° and 70° with respect to the longitudinal direction. Figure 13 and Figure 14In the variations, only one coil is shown for better overview. Compared to printed conductors that otherwise extend at a 45° angle to the longitudinal direction L, approximately 90% of the longitudinal force component is obtained with an angle α of approximately 63°, while the lateral force component is 44.7%. Therefore, the longitudinal force component can be increased, which is advantageous for generating the corresponding Lamb wave. When the printed conductors are arranged more steeply at an angle α of only about 26° ( Figure 14 The increased lateral force component is advantageous for generating guided SH waves. However, it is particularly preferred that the printed conductor segments be aligned at a 45° angle to the longitudinal direction L, so that guided Lamb waves and SH waves are generated equally well, regardless of their different amplitudes.
[0080] An array of bar magnets with circular cross-sections (the bar magnets are arranged side by side with alternating polarities in the transverse direction L, but with the same polarity in the longitudinal direction L) is thus obtained, which again consists of an array of bar magnets 18 with the same polarity. Figure 15 This also generates longitudinal and transverse waves, where the basic unit is then transmitted only through... Figure 15 The magnetic poles in the view are formed by the surface of the magnetic poles, and the printed wire segments are located outside the basic unit 34.
Claims
1. An ultrasonic transducer for generating ultrasonic waves in a metal inspection object (4), said ultrasonic transducer having: At least one magnet (18); Four sets of printed conductor segments, each set comprising at least one linear printed conductor segment (24, 26, 28, 30) extending above the magnetic poles of the magnet (18) in a bottom view, wherein the sets of printed conductor segments are distinguished from each other by the direction of current flow during operation, and the printed conductor segments (24, 26, 28, 30) extend above the magnetic poles at an angle to the longitudinal direction (L) of at least one magnetic pole in the bottom view (U); and A control unit is used to energize the printed conductor segments (24, 26, 28, 30); Its features are, Each pair of printed conductor segments constitutes a first meandering coil and a second meandering coil (20, 22), the first meandering coil and the second meandering coil being controllable via the control unit (14) of the ultrasonic transducer, wherein the control unit (14) is configured to: control the coils (20, 22) in phase or out of phase to generate Rayleigh waves or Lamb waves, and control the coils out of phase or in phase to generate guided SH waves.
2. An ultrasonic transducer for detecting ultrasonic waves in a metal inspection object (4), said ultrasonic transducer having: At least one magnet (18); Four sets of printed conductor segments, each set comprising at least one linear printed conductor segment (24, 26, 28, 30) extending above the magnetic poles of the magnet (18) in a bottom view (U), wherein the sets of printed conductor segments are distinguished from each other by the direction of current flow during operation, and the printed conductor segments (24, 26, 28, 30) extend above the magnetic poles at an angle to the longitudinal direction of at least one magnetic pole in the bottom view; and Control unit (14) is configured to receive signals induced in the printed conductor segments (24, 26, 28, 30); Its features are, Each pair of printed conductor segments constitutes a first meandering coil and a second meandering coil (20, 22), wherein the control unit (14) is configured to: add or subtract the signals to detect Rayleigh waves or Lamb waves, and subtract or add the signals to detect guided SH waves.
3. The ultrasonic transducer according to any one of the preceding claims, characterized in that, The assembly includes at least two magnets (18) arranged side by side, preferably in the shape of bars and / or rods, wherein the magnetic poles of the magnets have alternating polarities in the transverse direction extending transversely to the longitudinal direction (L) of the magnetic poles in the bottom view (U), wherein the printed conductor segments (24, 26, 28, 30) of the assembly of printed conductor segments extend above the at least two magnetic poles arranged side by side in the bottom view (U).
4. The ultrasonic transducer according to any one of the preceding claims, characterized in that, The first coil and the second coil (20, 22) are arranged on the same side of the at least one magnet (18).
5. The ultrasonic transducer according to any one of the preceding claims, characterized in that, In the bottom view, the turning portion (32) arranged between the printed conductor segments (24, 26, 28, 30) of the same coil (20, 22) extends outside the at least one magnetic pole or on the edge of the at least one magnet (18).
6. The ultrasonic transducer according to any one of the preceding claims, characterized in that, The printed conductor segments (24, 26, 28, 30) of the two coils (20, 22) are associated with each other in pairs, and in particular, the corresponding pairs of printed conductor segments (24, 26, 28, 30) intersect in the bottom view (U).
7. The ultrasonic transducer according to claim 6, characterized in that, The printed conductor segments (24, 26, 28, 30) form angles between 20° and 70° with the longitudinal direction (L), particularly an angle of 45° with the longitudinal direction (L).
8. The ultrasonic transducer according to claim 6 or 7, characterized in that, The printed conductor segments (24, 26, 38, 30) of the two coils (20, 22) intersect at an angle of 90°.
9. The ultrasonic transducer according to any one of the preceding claims, characterized in that, The printed conductor segments (24, 26, 28, 30) extend in a surface with a certain curvature, which is set to adapt to the surface of the test object (4).
10. The ultrasonic transducer according to claim 9, characterized in that, The printed conductor segments (24, 26, 28, 30) of the same coil (20, 22) are located in a plane.
11. The ultrasonic transducer according to claim 10, characterized in that, The magnet (18) has a length of 3 to 6 trace wavelengths in the bottom view.
12. The ultrasonic transducer according to claim 11, characterized in that, The magnet has a width of 1 to 6 trace wavelengths in the bottom view.
13. A method for generating ultrasonic waves in a metal inspection object by means of an ultrasonic transducer according to any one of the preceding claims, including claim 1, characterized in that, The meandering coil is manipulated in phase or out of phase by the control unit (14) of the ultrasonic transducer to generate Rayleigh waves or Lamb waves, and out of phase or in phase to generate guided SH waves.
14. A method for detecting ultrasonic waves in a metal inspection object by means of an ultrasonic transducer according to any one of the preceding claims, including claim 2, characterized in that, The signals from the meandering coil are added or subtracted in the control unit (14) of the ultrasonic transducer to detect Rayleigh waves or Lamb waves, and subtracted or added to detect guided SH waves.
15. An inspection device for inspecting pipes or for inspecting sheet metal, characterized in that, The device comprises one or more ultrasonic transducers according to any one of claims 1 to 12.