A Material Sound Velocity Measurement Method Based on Envelope Cross-Correlation Algorithm

Abstract

This invention relates to a method for measuring the sound velocity of materials based on an envelope cross-correlation algorithm, belonging to the field of automated detection technology. It addresses the problem of severe waveform distortion interference in existing sound velocity measurements of internally inhomogeneous materials. The method includes the following steps: initialization settings and benchmark acquisition; point-by-point scanning of the current scanning surface of the sample to obtain sample echoes; plotting the sound velocity distribution map of the current scanning surface of the sample; rotating the sample to continue measurement until the detection of three orthogonal surfaces is completed; and obtaining the average sound velocity of the sample. Applying this material sound velocity measurement method can eliminate interference from scattering attenuation and dispersion effects caused by material anisotropy, reduce "period jump" errors caused by carrier phase ambiguity, effectively improve the signal-to-noise ratio of the detection signal, achieve automation and high repeatability of sound velocity measurement, and improve the accuracy of identifying minute sound velocity differences.

Description

Technical Field

[0001] This invention relates to the field of automated detection technology, and in particular to a method for measuring the sound velocity of materials based on an envelope cross-correlation algorithm. Background Technology

[0002] Material sound velocity, as a core parameter characterizing the physical properties of a medium in nondestructive testing (NDT) technology, directly determines the reliability of thickness detection, defect location, and mechanical property evaluation in industrial applications for various composite materials, polycrystalline metals, and novel structural materials. However, due to the inhomogeneous characteristics within these materials, ultrasonic waves propagate through the medium with significant scattering attenuation and dispersion effects, leading to envelope distortion, a slower leading edge, and nonlinear phase drift in the received signal waveform. Currently, traditional sound velocity calculation algorithms (such as the fixed threshold method or the direct cross-correlation method based on the original RF waveform) have significant limitations in processing such distorted signals. They are difficult to adapt to changes in waveform shape and are prone to phase ambiguity or "period jump" errors due to asynchronous changes in the waveform envelope and carrier wave (i.e., separation of group velocity and phase velocity), severely reducing the robustness of the measurement results. Therefore, a signal processing method that can effectively reduce waveform distortion interference and improve the accuracy of sound velocity calculation for internally inhomogeneous materials is needed. Summary of the Invention

[0003] This invention aims to solve the technical problem of severe waveform distortion interference in the measurement of sound velocity of internally non-uniform materials in the prior art, and provides a material sound velocity measurement method based on envelope cross-correlation algorithm.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0005] A method for measuring the sound velocity of materials based on an envelope cross-correlation algorithm, the applicable measurement system of which includes: a signal generator / receiver, a robotic arm and an ultrasonic sensor;

[0006] The ultrasonic sensor includes an ultrasonic transmitting sensor and an ultrasonic receiving sensor respectively disposed on both sides of the sample being tested; the ultrasonic transmitting sensor and the ultrasonic receiving sensor are respectively connected to a signal generator / receiver;

[0007] The signal generator / receiver is used to emit ultrasonic waves through an ultrasonic transmitting sensor and receive ultrasonic waves through an ultrasonic receiving sensor.

[0008] The robotic arm is used to adjust the position of the ultrasonic transmitting sensor and / or the ultrasonic receiving sensor.

[0009] The sample to be tested is placed in water;

[0010] The method for measuring the sound velocity of this material includes the following steps:

[0011] Step 1: Initialization settings and baseline acquisition;

[0012] The temperature of the environment in which the sample is located is detected in real time; the interval between the ultrasonic transmitting sensor and the ultrasonic receiving sensor is set; a pulse excitation waveform is generated by a signal generator / receiver to excite the ultrasonic transmitting sensor to emit the first ultrasonic wave, and the ultrasonic receiving sensor is used to receive the second ultrasonic wave to obtain the no-sample echo as a reference.

[0013] Step 2: Scan the current scanning surface of the sample under test point by point according to the preset three-dimensional orthogonal path, obtain the sample echo, and perform single-point detection and calculation process at each scanning point;

[0014] Step 3: Plot the sound velocity distribution map of the current scanned surface of the sample and calculate the average sound velocity;

[0015] Step 4: Rotate the sample to be tested by 90 degrees, and repeat steps 2 and 3 until the detection of the three orthogonal surfaces is completed;

[0016] Step 5: Obtain the average sound velocity of the sample being tested.

[0017] In the above technical solution, step 2 involves performing a single-point detection and calculation process at each scanning point, specifically as follows:

[0018] Ultrasonic sensor 4 performs Repeated acquisitions were performed, and for each acquisition, a signal processing algorithm was applied to the sample echoes. This involved Hilbert envelope extraction, normalization, and cross-correlation analysis with the non-sample echoes to determine the maximum correlation point and obtain the time-of-flight difference. The speed of sound corresponding to this measurement is calculated using the following formula:

[0019]

[0020] in, The average sound velocity at a single scanning point on the surface of the sample being tested is calculated. For the sample being tested Thickness in three directions, This represents the number of times a single point is repeatedly sampled. For a single scan point The speed of sound calculated from the second scan. The speed of sound in water, For each scan point During the second scan, the time-of-flight difference of the ultrasound waves was obtained using a cross-correlation algorithm between waves with and without sample echoes. , They are natural numbers, , These represent the row and column numbers of the current scan point on the current scan plane, respectively. Number the number of samples.

[0021] In the above technical solution, the preset three-dimensional orthogonal path in step 2 is:

[0022] Scan a certain distance in the scanning direction; then, rotate 90 degrees and scan again. Distance; then, rotate 90 degrees and scan a certain distance again; next, rotate -90 degrees and scan again. Distance; then, rotate -90 degrees; repeat the above scanning process continuously; This is the step size.

[0023] In the above technical solution, step 3 specifically includes:

[0024] After the measurement of all scanning points on the current scanning surface is completed, draw the sound velocity distribution map of the current scanning surface;

[0025] Calculate the average sound velocity on the currently scanned surface using the following formula. :

[0026]

[0027] in, These represent the average sound velocities on the three orthogonal surfaces of the sample being tested. This represents the number of scan points for each row or column of the current surface. , These represent the row and column numbers of the current scan point on the current scan plane, respectively. This represents the number of scan points on a single scanned surface of the sample being tested. It is a positive integer.

[0028] In the above technical solution, step 5 specifically includes:

[0029] Determine whether the material of the sample being tested is anisotropic:

[0030] If so, record the average sound velocity on each surface;

[0031] If not, calculate the overall average sound velocity of the sample using the following formula. :

[0032]

[0033] in, The overall average sound velocity of the sample being tested. , , Respectively represent and , , The average sound velocity on the measuring surface perpendicular to the axis.

[0034] The present invention has the following beneficial effects:

[0035] The material sound velocity measurement method based on the envelope cross-correlation algorithm of this invention can eliminate the interference of scattering attenuation and dispersion effect caused by material anisotropy, reduce the "period jump" error caused by carrier phase ambiguity, effectively improve the signal-to-noise ratio of the detection signal, realize the automation and high repeatability of sound velocity measurement, and improve the accuracy of identifying minute sound velocity differences.

[0036] The material sound velocity measurement method based on the envelope cross-correlation algorithm of the present invention introduces a three-dimensional orthogonal automatic scanning process and a statistical analysis strategy of N repeated acquisitions to improve detection efficiency and data robustness, optimize the acoustic characterization process of materials, and apply the detection system to different objects being tested.

[0037] The material sound velocity measurement method based on the envelope cross-correlation algorithm of the present invention provides a new solution for the existing sound velocity measurement of materials such as carbon fiber composites and textured alloys. Attached Figure Description

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0039] Figure 1 This is a schematic diagram of the control and testing structure of the measurement system applicable to the material sound velocity measurement method based on the envelope cross-correlation algorithm of the present invention.

[0040] Figure 2 This is a sound velocity distribution diagram of the sample being tested.

[0041] Figure 3 The diagram shows the waveform of the excitation signal emitted by the signal generator. In the diagram, (a) is the time-domain waveform of the excitation signal, and (b) is the frequency-domain waveform of the excitation signal.

[0042] Figure 4 The diagram shows the echo detected by the ultrasonic receiving sensor. In the figure, (a) is the time-domain echo after normalization, and the red solid line is the echo diagram measured without a sample; (b) is the echo diagram after Hilbert envelope transformation of the echo in (a).

[0043] Figure 5 This is a schematic diagram of the scanning path of the robotic arm on the current sample surface. In the figure, This is the step size.

[0044] Figure 6The diagram shows a waveform cross-correlation analysis. In the diagram, (a) shows the sliding waveform window in the cross-correlation calculation, and (b) shows a diagram of cross-correlation analysis using the echo within the sliding waveform window and the measured echo of the water without a sample, according to the sliding direction.

[0045] Figure 7 A single sound velocity detection point on the surface of the sample being tested. After the second sampling ( Sound velocity distribution diagram.

[0046] Figure 8 This is a flowchart of the single-point sound velocity detection process for the sample being tested.

[0047] Figure 9 This is a flowchart of the overall sound velocity detection process for the sample being tested.

[0048] The reference numerals in the figure are:

[0049] 1-Host computer; 2-Signal generator / receiver; 3-Robotic arm; 4-Ultrasonic sensor; 5-Sample to be tested; 6-Water tank; 7-Water; 8-Thermometer;

[0050] 41-Ultrasonic transmitting sensor; 42-Ultrasonic receiving sensor;

[0051] 43 - First ultrasound; 44 - Second ultrasound. Detailed Implementation

[0052] The inventive concept of this invention is as follows:

[0053] This invention presents a material sound velocity measurement method based on an envelope cross-correlation algorithm, primarily applied to the time-domain analysis and processing of ultrasonic signals penetrating materials. This enables accurate calculation of material sound velocity, effective characterization of physical properties, and assessment of structural uniformity. The invention aims to eliminate interference from scattering attenuation and dispersion effects caused by the complex internal structure of materials, reduce the "period jump" error caused by carrier phase ambiguity in traditional methods, and significantly improve the resolution and signal-to-noise ratio of distorted signals. The method optimizes the waveform modulation and data processing flow of the ultrasonic signal to reduce inherent system delay errors and suppress spectral sidelobes. Based on this, using the acquired time-domain transmission waveform data as input, and employing signal processing methods based on Hilbert envelope extraction, amplitude normalization, and cross-correlation analysis, highly robust measurement, high-precision calculation, and automated analysis of the sound velocity within materials are achieved.

[0054] The present invention will now be described in detail with reference to the accompanying drawings.

[0055] like Figure 1As shown, the material sound velocity measurement method based on envelope cross-correlation algorithm of the present invention has an applicable measurement system including: host computer 1, signal generator / receiver 2, robotic arm 3 and ultrasonic sensor 4.

[0056] The signal generator / receiver 2 and the robotic arm 3 are respectively connected to the host computer 1; the ultrasonic sensor 4 includes an ultrasonic transmitting sensor 41 and an ultrasonic receiving sensor 42; the ultrasonic transmitting sensor 41 and the ultrasonic receiving sensor 42 are respectively connected to the signal generator / receiver 2; the ultrasonic transmitting sensor 41 is used to emit a first ultrasonic wave 43; the ultrasonic receiving sensor 42 is used to receive a second ultrasonic wave 44; the robotic arm 3 is used to adjust the position of the ultrasonic transmitting sensor 41 and / or the ultrasonic receiving sensor 42.

[0057] The sample 5 to be tested is placed in the water 7 within the water tank 6. An ultrasonic transmitting sensor 41 is positioned on one side of the sample 5 (e.g., ...). Figure 1 The left side of the sample 5 shown in the diagram); the ultrasonic receiving sensor 42 is located on the other side of the sample 5 (as shown in the diagram). Figure 1 (The sample 5 shown is on the right side); a thermometer 8 for monitoring the temperature of water 7 is installed in the water tank 6.

[0058] In this embodiment, the tested sample 5 is in The thickness in three directions is The material of sample 5 is silicon carbide. Figure 8 and Figure 9 As shown, the material sound velocity measurement method based on envelope cross-correlation algorithm of the present invention includes the following steps:

[0059] Step 1: Initialization settings and baseline acquisition;

[0060] The temperature of the water in the tank 6 is monitored in real time using thermometer 8. To ensure a constant sound velocity in water 7. In this embodiment, the temperature in water 7... .

[0061] The distance between the ultrasonic transmitting sensor 41 and the ultrasonic receiving sensor 42 is set. In this embodiment, the distance between the ultrasonic transmitting sensor 41 and the ultrasonic receiving sensor 42 is set to 20cm.

[0062] The host computer 1 configures the signal generator / receiver 2 to generate a pulse excitation waveform (e.g., ...). Figure 3 As shown, that is Figure 3 The excitation signal waveform in (a) excites the ultrasonic transmitting sensor 41 to emit the first ultrasonic wave 43, and the ultrasonic receiving sensor 42 receives the second ultrasonic wave 44. The echo in the water 7 when there is no sample 5 is measured is obtained, and the echo when there is no sample is obtained (e.g., the waveform of the excitation signal in (a) excites the ultrasonic transmitting sensor 41 to emit the first ultrasonic wave 43, and the ultrasonic receiving sensor 42 receives the second ultrasonic wave 44. The echo when there is no sample is obtained is obtained). Figure 4The first echo shown by the red solid line in (a) and (b) is used as a reference. In this embodiment, the pulse excitation waveform is a pulse excitation waveform modulated by a Hanning window, with a center frequency of 5 Hz. (See) Figure 3 In (b), the transmit pulse width is 5 cycles.

[0063] Step 2: Scan the current scanning surface of the sample 5 under test point by point according to the preset three-dimensional orthogonal path, obtain the sample echo, and perform single-point detection and calculation process at each scanning point.

[0064] The sample 5 to be tested is placed in water 7. The host computer 1 controls the robotic arm 3 to carry the ultrasonic transmitting sensor 41 and the ultrasonic receiving sensor 42, following a preset three-dimensional orthogonal path (such as...). Figure 5 As shown), the current surface of the sample 5 is scanned point by point, and the echo when the sample 5 is present is measured to obtain the sample echo (e.g.). Figure 4 The first echo, second echo, third echo, and fourth echo are shown by the black solid lines in (a) and (b). A single-point detection and calculation process is performed at each scan point.

[0065] Figure 5 The specific description of the three-dimensional orthogonal path shown is as follows:

[0066] Scan a certain distance in the scanning direction; then, rotate 90 degrees and scan again. Distance; then, rotate 90 degrees and scan a certain distance (the same distance scanned in the previous scanning direction); next, rotate -90 degrees and scan. Distance; then, rotate -90 degrees; repeat the above scanning process continuously. This is the step size.

[0067] The ultrasonic sensor 4 (ultrasonic transmitting sensor 41 and ultrasonic receiving sensor 42) performs Next (in this embodiment, Repeated acquisition is performed. The host computer 1 calls a signal processing algorithm on each acquired echo (i.e., the first echo), performing Hilbert envelope extraction and normalization (e.g.,...). Figure 6 (a) The black solid line in the middle and the no-sample echo (e.g.) Figure 6 Cross-correlation analysis (shown by the red solid line in (a)) is performed to determine the point of maximum correlation (e.g., ...). Figure 6 (b) (As shown) to obtain the flight time difference , The most relevant point The corresponding time window sliding distance is used to calculate the corresponding sound velocity value for this measurement using formula (1):

[0068] (1)

[0069] in, The average sound velocity at a single scanning point on the surface of the tested sample 5 is calculated. , They are natural numbers; for Figure 2 The sample 5 shown in the figure is in Thickness in three directions, This represents the number of times a single point is repeatedly sampled. For a single scan point The speed of sound calculated from the second scan. The speed of sound in water, For each scan point During the second scan, the time-of-flight difference of the ultrasound waves was obtained using a cross-correlation algorithm between waves with and without sample echoes. , They are all natural numbers. The measured sample 5 used in calculating the speed of sound The thickness in three directions is taken as the side length of the cubic sample 5 under test in the current ultrasonic wave propagation direction. In this embodiment, the current ultrasonic wave propagation direction is along... Axial propagation; the thickness used to calculate the sound velocity of the measured sample is... Figure 2 As shown Thickness of the sample 5 in the axial direction .

[0070] When the direction of ultrasonic wave propagation is along Axial propagation; the thickness used to calculate the sound velocity of the measured sample is... Figure 2 As shown Thickness of the sample 5 in the axial direction When the direction of ultrasonic wave propagation is along Axial propagation; the thickness used to calculate the sound velocity of the measured sample is... Figure 2 As shown Thickness of the sample 5 in the axial direction . Figure 2 middle , , These represent the scanning process at... axis, axis, Scan step size in the axial direction, , , These represent the average sound velocity values ​​at the corresponding scan points located in the 1st row and 1st column, the 1st row and 2nd column, and the 2nd row and 1st column of the current scan plane, respectively.

[0071] The location to be scanned After all data collection and calculations are completed, The results of this measurement are statistically analyzed and averaged to determine the final sound velocity at the scanning point. The robotic arm 3 is then controlled to move the ultrasonic transmitting sensor 41 and the ultrasonic receiving sensor 42 along the scanning path (e.g., ...). Figure 5 (As shown) Move to the next scan point; as Figure 7 As shown, The statistical analysis of the results of this measurement shows an approximate normal distribution.

[0072] Step 3: Plot the sound velocity distribution map of the current scanned surface of the sample 5 and calculate the average sound velocity;

[0073] After completing the measurement of all scanning points on the current surface, draw the sound velocity distribution map of the current scanning surface (e.g., Figure 2 As shown), the average sound velocity of the scanned surface is calculated using formula (2). :

[0074] (2)

[0075] in, These represent the average sound velocities on the three orthogonal surfaces of the cubic test sample 5. This represents the number of scan points for each row or column of the current surface. , These represent the row and column numbers of the current scan point on the current scan plane, respectively. This represents the number of scan points on a single scan surface of the cubic test sample (sample 5). It is a positive integer. In this embodiment, .

[0076] Step 4: Rotate the sample 5 to be tested by 90 degrees, and repeat steps 2 and 3 until the detection of the three orthogonal surfaces is completed;

[0077] If the detection of the three orthogonal surfaces is not completed, the sample 5 to be tested will be rotated 90 degrees so that the next orthogonal surface to be tested is aligned with the sound beam path, and the above point-by-point detection and calculation steps will be repeated.

[0078] Step 5: Obtain the average sound velocity of the sample (5) being tested;

[0079] After all surfaces have been scanned, determine whether the material of the tested sample (5) is anisotropic:

[0080] If so, record the average sound velocity on each surface;

[0081] If not, then use formula (3) to calculate the overall average sound velocity of the tested sample 5. :

[0082] (3)

[0083] in, The overall sound velocity of the tested sample 5. , , Respectively represent and , , The average sound velocity on the measuring surface perpendicular to the axis.

[0084] Finally, save all data and end the process.

[0085] The material sound velocity measurement method based on the envelope cross-correlation algorithm of this invention can eliminate the interference of scattering attenuation and dispersion effect caused by material anisotropy, reduce the "period jump" error caused by carrier phase ambiguity, effectively improve the signal-to-noise ratio of the detection signal, realize the automation and high repeatability of sound velocity measurement, and improve the accuracy of identifying minute sound velocity differences.

[0086] In the above specific embodiments, the test sample involved is a silicon carbide material sample. The method of the present invention is also applicable to the sound velocity measurement of other materials.

[0087] In the above specific embodiments, the method of the present invention involves a serpentine scanning path of a single measurement surface, and the method is also applicable to other scanning paths.

[0088] In the above specific embodiments, the mechanical motion device involved in the test system of the present invention is a robotic arm, and the method is also applicable to other mechanical motion devices that can realize three-degree-of-freedom or multi-degree-of-freedom motion.

[0089] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for measuring the sound velocity of materials based on an envelope cross-correlation algorithm, wherein the applicable measurement system includes: Signal generator / receiver (2), robotic arm (3) and ultrasonic sensor (4); The ultrasonic sensor (4) includes an ultrasonic transmitting sensor (41) and an ultrasonic receiving sensor (42) respectively disposed on both sides of the sample (5) being tested; the ultrasonic transmitting sensor (41) and the ultrasonic receiving sensor (42) are respectively connected to the signal generator / receiver (2); The signal generator / receiver (2) is used to emit ultrasonic waves through the ultrasonic transmitting sensor (41) and receive ultrasonic waves through the ultrasonic receiving sensor (42). The robotic arm (3) is used to adjust the position of the ultrasonic transmitting sensor (41) and / or the ultrasonic receiving sensor (42); The sample (5) to be tested was placed in water (7); The method for measuring the sound velocity of this material is characterized by the following steps: Step 1: Initialization settings and baseline acquisition; The temperature of the environment where the sample (5) is located is detected in real time; the distance between the ultrasonic transmitting sensor (41) and the ultrasonic receiving sensor (42) is set; a pulse excitation waveform is generated by the signal generator / receiver (2) to excite the ultrasonic transmitting sensor (41) to emit the first ultrasonic wave (43), and the ultrasonic receiving sensor (42) is used to receive the second ultrasonic wave (44) to obtain the no-sample echo as a reference. Step 2: Scan the current scanning surface of the sample (5) point by point according to the preset three-dimensional orthogonal path, obtain the sample echo, and perform single-point detection and calculation process at each scanning point; Step 3: Draw the sound velocity distribution map of the current scanning surface of the sample (5) and calculate the average sound velocity; Step 4: Rotate the sample (5) to be tested by 90 degrees, and repeat steps 2 and 3 until the detection of the three orthogonal surfaces is completed; Step 5: Obtain the average sound velocity of the sample (5) being tested; In step 2, a single-point detection and calculation process is performed at each scanning point, specifically as follows: Ultrasonic sensor (4) performs Repeated acquisitions were performed, and for each acquisition, a signal processing algorithm was applied to the sample echoes. This involved Hilbert envelope extraction, normalization, and cross-correlation analysis with the non-sample echoes to determine the maximum correlation point and obtain the time-of-flight difference. The speed of sound corresponding to this measurement is calculated using the following formula: in, The average sound velocity at a single scanning point on the surface of the tested sample (5) is calculated. For the sample to be tested (5) in Thickness in three directions, This represents the number of times a single point is repeatedly sampled. For a single scan point The speed of sound calculated from the first scan. The speed of sound in water, For each scan point During the second scan, the time-of-flight difference of the ultrasound waves was obtained using a cross-correlation algorithm between waves with and without sample echoes. , They are natural numbers, , These represent the row and column numbers of the current scan point on the current scan plane, respectively. Number the number of samples.

2. The material sound velocity measurement method based on envelope cross-correlation algorithm according to claim 1, characterized in that, The preset 3D orthogonal path in step 2 is: Scan a certain distance in the scanning direction; then, rotate 90 degrees and scan again. distance; Then, rotate 90 degrees and scan a certain distance; next, rotate -90 degrees and scan again. Distance; then, rotate -90 degrees; repeat the above scanning process continuously; This is the step size.

3. The material sound velocity measurement method based on envelope cross-correlation algorithm according to claim 1, characterized in that, Step 3 specifically involves: After the measurement of all scanning points on the current scanning surface is completed, draw the sound velocity distribution map of the current scanning surface; Calculate the average sound velocity on the currently scanned surface using the following formula. : in, These are the average sound velocities of the three orthogonal surfaces of the tested sample (5), respectively. This represents the number of scan points for each row or column of the currently scanned surface. , These represent the row and column numbers of the current scan point on the current scan plane, respectively. The number of scan points on a single scan surface of the sample (5) being tested. It is a positive integer.

4. The material sound velocity measurement method based on envelope cross-correlation algorithm according to claim 1, characterized in that, Step 5 specifically involves: Determine whether the material of the tested sample (5) is anisotropic: If so, record the average sound velocity on each surface; If not, the overall average sound velocity of the tested sample (5) is calculated using the following formula. : in, The overall average sound velocity of the sample (5) being tested. , , Respectively represent and , , The average sound velocity on the measuring surface perpendicular to the axis.

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