Ultrahigh-resolution multilayer structure interface layering ultrasonic detection method

Abstract

The invention relates to the technical field of multi-layer composite material defect detection, in particular to an ultrahigh-resolution multi-layer structure interface layering ultrasonic detection method which comprises the following steps: constructing a multi-layer structure interface and a grid model thereof, setting each grid point as an acquisition point, acquiring an original echo signal of each acquisition point by configuring an excitation signal, and calculating the multi-layer structure interface layering ultrasonic detection method according to the original echo signal. Determining a reference signal and translation window parameters, applying a mobile translation window to the original echo signal of each acquisition point, calculating a correlation coefficient of the signal in the window and the reference signal to obtain a relationship between the correlation coefficient and a translation distance, and analyzing the correlation coefficient and the translation distance of each acquisition point to obtain a correlation coefficient of the reference signal; and extracting phase feature data of each acquisition point in combination with an analysis result, mapping the phase feature data to a corresponding spatial position of the grid model, and generating a layering defect detection image of the multilayer structure interface. According to the method, high-precision detection of the layering defect of the interface of the multilayer structure is realized by comprehensively utilizing signal processing and space mapping technologies.

Description

Technical Field

[0001] The present invention relates to the technical field of multilayer composite material defect detection, and in particular to an ultra-high resolution multilayer structure interface delamination ultrasonic detection method. Background Art

[0002] The integrity of the interface of a multilayer structure is crucial to the performance of materials, especially in the fields of aerospace, electronic packaging, etc. Ultrasonic testing, as an effective method for detecting interface delamination defects, has been widely used in recent years. At present, due to the small thickness of interface delamination defects (usually less than a few hundred μm), traditional ultrasonic detection devices are often not adopted when detecting delamination defects due to problems such as low axial resolution and echo overlap; at the same time, ultrasonic waves will be affected by diffraction during propagation, and their minimum resolution distance is about half the wavelength. When the defect size is less than half the wavelength, the scattered signals of the back of the defect and the delamination interface are prone to aliasing in the time domain and are difficult to distinguish. Based on this, in order to improve the detection accuracy and reliability, we designed an ultra-high-resolution ultrasonic detection method for interface delamination of multilayer structures. Summary of the invention

[0003] The purpose of the present invention is to provide an ultra-high-resolution ultrasonic detection method for multi-layer structure interface delamination, which significantly improves the detection accuracy of multi-layer structure interface delamination defects by introducing correlation coefficient method and phase feature analysis, and provides a reliable basis for signal acquisition based on the multi-layer structure interface grid model. The correlation coefficient method can effectively extract the similarity characteristics of the signal, while the phase analysis enhances the sensitivity to tiny defects. Combined with spatial mapping technology, the present invention can generate high-resolution defect detection images, providing a powerful tool for interface integrity assessment.

[0004] The present invention is achieved through the following technical solutions: An ultra-high resolution multi-layer structure interface delamination ultrasonic detection method, the method comprising the steps of: Construct a multi-layer structure interface, and perform translation scanning on the multi-layer structure interface based on a scanning unit to build a multi-layer structure interface mesh model; Each grid point in the multi-layer structure interface grid model is used as a collection point, an excitation signal is configured for each grid point, and a specific angle is selected to perform ultrasonic excitation and reception on each grid point, and the original echo signal of each collection point is obtained, and the original echo signal set is aggregated; Perform signal analysis and benchmark determination on the original echo signal set to obtain benchmark signals and translation window parameters; For the original echo signal of each acquisition point, the translation window is moved within the entire time range of the signal, and the correlation coefficient between the signal in the window and the reference signal is calculated to generate the correlation coefficient and corresponding translation distance of each acquisition point; Perform a positive and negative analysis on the correlation coefficient of each acquisition point, and perform a time delay analysis on the translation distance corresponding to the correlation coefficient of each acquisition point. Combine the positive and negative analysis results with the time delay analysis results to extract the phase feature data of each acquisition point. The phase feature data of each acquisition point is mapped to the spatial position corresponding to the multi-layer structure interface grid model, and the multi-layer structure interface delamination defect detection image is output.

[0005] Optionally, the multi-layer structure interface is constructed by using the first fixed material as the upper propagation medium and the second fixed material as the lower propagation medium, and selecting the air layer as the stratification defect according to the upper propagation medium and the lower propagation medium to form the multi-layer structure interface.

[0006] Optionally, the configuration of the excitation signal for each grid point and the selection of a specific angle for ultrasonic excitation and reception at each grid point are specifically as follows: A single sine function based on Hanning window modulation is perpendicular to the upper propagation medium in the multi-layer structure interface. The center frequency and length are set to excite and receive ultrasonic waves at each grid point.

[0007] Optionally, the obtaining of the original echo signal of each acquisition point and aggregating the original echo signal set further includes a preprocessing process, which is specifically: De-noise and filter the original echo signal of each acquisition point; Align the original echo signal of each acquisition point to the same start time, perform energy analysis on the original echo signal of each acquisition point, define the time range according to the energy analysis result, and determine the time window of the effective echo signal: The original echo signal is intercepted based on the time window of the effective echo signal and normalized to obtain the effective echo signal of each acquisition point, which are summarized to form a set of effective echo signals.

[0008] Optionally, the signal analysis and benchmark determination are performed on the original echo signal set, wherein the signal analysis is performed on the original echo signal set, and the specific process is as follows: Perform oscillation time analysis on the valid echo signal set; Determine the echo range of the effective echo signal according to the oscillation time; The translation window length is determined according to the echo range of the effective echo signal, and the translation window length represents the translation window parameter.

[0009] Optionally, a benchmark is determined for the original echo signal set, and the specific process is as follows: Selecting one or more valid echo signals based on a known defect-free area in the valid echo signal set; If multiple valid echo signals are selected, the average value of the multiple valid echo signals is calculated; The selected or resolved valid echo signal is used as the reference signal.

[0010] Optionally, the correlation coefficient between the signal in the calculation window and the reference signal is calculated by the following specific formula:

[0011] Where r is the correlation coefficient, A and B are two groups of signals, μ and σ are the mean and standard deviation, i is a positive integer, and N is the total amount of data.

[0012] Optionally, mapping the phase feature data of each acquisition point to the spatial position corresponding to the multi-layer structure interface grid model also includes applying interpolation algorithm, image enhancement, median filtering and contrast enhancement for processing, and outputting the processed multi-layer structure interface stratification defect detection image.

[0013] The technical solution of the present invention has at least the following advantages and beneficial effects: The present invention is based on the fact that the reason why the current ultrasonic reflection method cannot detect tiny delamination defects is that the delamination defects are very small, and the echo of the delamination defect will overlap with the echo of the lower medium interface in time. It is impossible to judge whether there is a delamination defect based only on the echo amplitude, because the amplitude will be affected by factors such as the coupling effect and the performance of the probe itself. Therefore, the present invention significantly improves the detection accuracy of delamination defects at the interface of multilayer structures by introducing the correlation coefficient method and phase feature analysis, and provides a reliable basis for signal acquisition based on the multilayer structure interface grid model. The correlation coefficient method can effectively extract the similarity characteristics of the signal, while the phase analysis enhances the sensitivity to tiny defects. Combined with spatial mapping technology, the present invention can generate high-resolution defect detection images, providing a powerful tool for interface integrity assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of a process for ultra-high resolution multi-layer structure interface delamination ultrasonic detection method provided by the present invention; Figure 2 (a) a schematic diagram of the sound wave propagation path and (b) a schematic diagram of the reflected echo signals under the two paths provided by the present invention; Figure 3 Schematic diagram of (a) a simulation model, (b) pressure distribution when there is no defect, and (c) pressure distribution when there is a defect provided by the present invention; Figure 4 The two-dimensional acoustic time-domain simulation time-domain waveform provided by the present invention (a) is a schematic diagram of the echo signal under defects of different thicknesses with a width of 0.7 mm and (b) is a schematic diagram of the echo signal under defects of different widths with a thickness of 0.09 mm; Figure 5 A schematic diagram of the principle of an ultra-high resolution multi-layer structure interface delamination ultrasonic detection method provided by the present invention; Figure 6 This is an imaging result diagram of the ultrasonic detection of planar strip defects provided by the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, what is described is only a part of the present invention, not all of it. Generally, the components of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0016] like Figure 1 As shown, the present invention provides one embodiment: an ultra-high resolution multi-layer structure interface delamination ultrasonic detection method, the method comprising the steps of: Construct a multi-layer structure interface, and perform translation scanning on the multi-layer structure interface based on a scanning unit to build a multi-layer structure interface mesh model; Each grid point in the multi-layer structure interface grid model is used as a collection point, an excitation signal is configured for each grid point, and a specific angle is selected to perform ultrasonic excitation and reception on each grid point, and the original echo signal of each collection point is obtained, and the original echo signal set is aggregated; Perform signal analysis and benchmark determination on the original echo signal set to obtain benchmark signals and translation window parameters; For the original echo signal of each acquisition point, the translation window is moved within the entire time range of the signal, and the correlation coefficient between the signal in the window and the reference signal is calculated to generate the correlation coefficient and corresponding translation distance of each acquisition point; Perform a positive and negative analysis on the correlation coefficient of each acquisition point, and perform a time delay analysis on the translation distance corresponding to the correlation coefficient of each acquisition point. Combine the positive and negative analysis results with the time delay analysis results to extract the phase feature data of each acquisition point. The phase feature data of each acquisition point is mapped to the spatial position corresponding to the multi-layer structure interface grid model, and the multi-layer structure interface delamination defect detection image is output.

[0017] When defects such as interfacial debonding or cracks occur inside a composite material, it is generally believed that an air layer is introduced into the composite material, and there is a large difference in acoustic impedance between the air and the materials on both sides. According to the sound pressure reflection coefficient formula when the ultrasonic wave is incident vertically, it can be concluded that the sound pressure reflection coefficient (R) is ultimately determined by the density (ρ) and sound velocity (c) of the materials on both sides of the interface:

[0018] in, is the reflected sound pressure, is the incident sound pressure, Z is the acoustic impedance, and the subscripts 1 and 2 refer to the incident side and the transmission side, respectively. In the potting material, the acoustic impedance of the potting compound is usually smaller than the acoustic impedance of the matrix material, while the acoustic impedance of the air is much smaller than that of the potting compound and the matrix. The R between the potting compound and the matrix is ​​greater than zero, while the R between the potting compound and the air is less than zero, which means that the initial phase of the reflected wave is opposite, as shown in Figure 2 shown.

[0019] In this embodiment, the multi-layer structure interface is constructed by using the first fixed material as the upper propagation medium and the second fixed material as the lower propagation medium. At the same time, the air layer is selected as the stratification defect according to the upper propagation medium and the lower propagation medium to form the multi-layer structure interface.

[0020] like Figure 3 As shown, in order to verify whether the phase reversal phenomenon occurs at the interface, this embodiment uses finite element simulation software to establish a two-dimensional acoustic simulation model. In the model, organic glass is used as the upper propagation medium to replace the potting glue material; aluminum is used as the lower propagation medium to replace the matrix material, and air is located between organic glass and aluminum to replace the delamination defect. At the same time, this embodiment uses a single sine function modulated by a Hanning window as an excitation signal, and its direction is perpendicular to the upper surface of the organic glass. The center frequency is set to 2 MHz and the length is 0.3 mm. In addition, perfect matching layers are arranged on both sides to reduce the interference of reflected echoes. Echoes are generated when ultrasonic waves encounter discontinuous interfaces inside the composite material. When there is a delamination defect at the interface, the phase of the echo changes significantly.

[0021] like Figure 4 As shown in the figure, in the specific case, the longitudinal acceleration is used to characterize the signal, and the order of the positive and negative extreme values ​​in the echo is extracted to characterize the phase change. When the width is not less than 0.7 mm and the thickness is not less than 0.09 mm, the phase of the echo can be stably flipped. This size is about half the wavelength of the longitudinal wave of the plexiglass (1.35 mm). This conclusion is consistent with the principle of the reflection coefficient method.

[0022] Furthermore, the acquisition of the original echo signal of each acquisition point and the aggregation to form the original echo signal set further includes a preprocessing process, which is specifically: De-noise and filter the original echo signal of each acquisition point; Align the original echo signal of each acquisition point to the same start time, perform energy analysis on the original echo signal of each acquisition point, define the time range according to the energy analysis result, and determine the time window of the effective echo signal: The original echo signal is intercepted based on the time window of the effective echo signal and normalized to obtain the effective echo signal of each acquisition point, which are summarized to form a set of effective echo signals.

[0023] like Figure 5 As shown, in the specific application of the embodiment, in actual testing, the echo does not have the same short oscillation duration as the analog signal, which means that the small gap between the positive and negative extreme values ​​is prone to extraction errors under the influence of test conditions. Therefore, there is an urgent need for a method that can extract phase features from the entire signal. Correlation calculation has always been a powerful means of signal processing, which explains the degree of correlation between two sets of discrete values ​​in a mathematical way. The calculation formula is as follows, where A and B are two sets of signals, μ and σ are the mean and standard deviation respectively, and N is the total amount of data.

[0024]

[0025] Where r is the correlation coefficient, A and B are two groups of signals, μ and σ are the mean and standard deviation, i is a positive integer, and N is the total amount of data. When the two groups of signals are only opposite in phase, the correlation coefficient r is -1; otherwise, the correlation coefficient r is 1. Based on this principle, this embodiment uses the correlation coefficient method based on the translation window signal to extract the phase and time information of the echo.

[0026] Specifically, the signal analysis and benchmark determination are performed on the original echo signal set, wherein the signal analysis is performed on the original echo signal set, and the specific process is as follows: Perform oscillation time analysis on the valid echo signal set; Determine the echo range of the effective echo signal according to the oscillation time; The translation window length is determined according to the echo range of the effective echo signal, and the translation window length represents the translation window parameter.

[0027] More specifically, the original echo signal set is benchmarked, and the specific process is as follows: Selecting one or more valid echo signals based on a known defect-free area in the valid echo signal set; If multiple valid echo signals are selected, the average value of the multiple valid echo signals is calculated; The selected or resolved valid echo signal is used as the reference signal.

[0028] Based on the above, the specific steps of this embodiment are: (1) Based on the oscillation time of the two groups of signals, the specific range of the echo signal is defined, and the length of the translation window is determined based on this.

[0029] (2) The reference signal needs to be selected from all signals, or a group of average signals in the same area (usually the echo signal of the intact area is selected).

[0030] (3) Calculate the correlation between the echo signal and the reference signal of the corresponding position and length in the scanning area to obtain the sequence ( Distance related). The positive or negative value represents the phase difference between it and the reference signal, and the corresponding It represents the time difference.

[0031] (4) After all signal processing is completed, imaging is performed according to the location of the acquisition point, and the initial image is median filtered to enhance robustness.

[0032] In the specific case application based on the above embodiment, in order to verify the detection ability of this method in solid delamination defects, three potting material test blocks containing different types of defects (planar strip defects, planar circular defects and arc surface defects) were made and tested with an ultrasonic probe. At the same time, in order to ensure the acoustic coupling effect, deionized water was applied to the surface of the test block.

[0033] Based on the above implementation verification, the above three defects can be accurately identified through the phase reversal phenomenon. This is because the longitudinal wave half-wavelength of the potting material and the longitudinal wave half-wavelength of the matrix material both meet the phase reversal condition.

[0034] In the specific implementation, in order to eliminate the subjective measurement error introduced by manual measurement, a micro-displacement control platform was built to accurately control the relative position of the ultrasonic device and the test block. The ultrasonic device and the structure to be tested were placed in water. During the test, the test block was scanned point by point in the self-transmitting and self-receiving mode, with a displacement step of 0.2 mm. Each sampling point was sampled once, and finally the echo data of each sampling point was processed and imaged using the correlation coefficient method.

[0035] The displacement platform was used to test a 1 mm wide planar strip defect, a 2 mm diameter planar circular defect, and a 2 mm wide arc surface defect. The imaging results of the 1 mm wide planar strip defect are shown in Figure 2. Figure 6 As shown in the figure, the calculated width is about 1.2 mm. The imaging results in the test results are consistent with the morphology and width of the actual defect, and the measurement error is about 0.2 mm. In the imaging results, the black part represents the defective position, and the blank part represents the non-defective position. The above test results prove that the detection method has high detection accuracy and certain reliability in solid flaw detection on different surfaces.

[0036] More specifically, the phase feature data of each acquisition point is mapped to the spatial position corresponding to the multi-layer structure interface grid model, and also includes applying interpolation algorithm, image enhancement, median filtering and contrast enhancement for processing, and outputting the processed multi-layer structure interface delamination defect detection image.

[0037] In summary, this embodiment targets multi-layer structures, combined with the differences in acoustic impedance distribution within the components (the acoustic impedance of air is less than the acoustic impedance of the potting compound, and the acoustic impedance of the potting compound is less than the acoustic impedance of the base material), and the study found that when the width of the interface delamination defect is greater than half a wavelength and the thickness is greater than 1 / 10 of the wavelength, the reflected echo signal will produce an acoustic phase reversal phenomenon. Based on the acoustic phase reversal phenomenon, this embodiment proposes a correlation coefficient method based on a translation window signal to extract the phase difference information between the reference signal and the detection signal, which can easily and accurately identify whether an interface delamination defect occurs at the interface. At the same time, this embodiment combines the correlation coefficient method, and at the same time, in order to solve the problem of large blind spots in solid ultrasonic detection technology, a set of underwater ultrasonic scanning and imaging devices is built, which can achieve full-surface, high-precision scanning and imaging of composite materials with different curved surfaces.

[0038] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An ultra-high resolution multi-layer structure interface delamination ultrasonic detection method, characterized in that: The steps of the method include: Construct a multi-layer structure interface, and perform translation scanning on the multi-layer structure interface based on a scanning unit to build a multi-layer structure interface mesh model; Each grid point in the multi-layer structure interface grid model is used as a collection point, an excitation signal is configured for each grid point, and a specific angle is selected to perform ultrasonic excitation and reception on each grid point, and the original echo signal of each collection point is obtained, and the original echo signal set is aggregated; Perform signal analysis and benchmark determination on the original echo signal set to obtain benchmark signals and translation window parameters; For the original echo signal of each acquisition point, the translation window is moved within the entire time range of the signal, and the correlation coefficient between the signal in the window and the reference signal is calculated to generate the correlation coefficient and corresponding translation distance of each acquisition point; Perform a positive and negative analysis on the correlation coefficient of each acquisition point, and perform a time delay analysis on the translation distance corresponding to the correlation coefficient of each acquisition point. Combine the positive and negative analysis results with the time delay analysis results to extract the phase feature data of each acquisition point. The phase feature data of each acquisition point is mapped to the spatial position corresponding to the multi-layer structure interface grid model, and the multi-layer structure interface delamination defect detection image is output.

2. The ultra-high resolution multi-layer structure interface delamination ultrasonic detection method according to claim 1, characterized in that: The multi-layer structure interface is constructed by specifically using the first fixed material as the upper layer propagation medium and the second fixed material as the lower layer propagation medium. At the same time, an air layer is selected as a stratification defect according to the upper layer propagation medium and the lower layer propagation medium to form the multi-layer structure interface.

3. The ultra-high resolution multi-layer structure interface delamination ultrasonic detection method according to claim 2, characterized in that: The configuration of the excitation signal for each grid point and the selection of a specific angle for ultrasonic excitation and reception at each grid point are specifically as follows: A single sine function based on Hanning window modulation is perpendicular to the upper propagation medium in the multi-layer structure interface. The center frequency and length are set to excite and receive ultrasonic waves at each grid point.

4. The ultra-high resolution multi-layer structure interface delamination ultrasonic detection method according to claim 3, characterized in that: After obtaining the original echo signal of each acquisition point and aggregating it to form an original echo signal set, a preprocessing process is further included, which is specifically: De-noise and filter the original echo signal of each acquisition point; Align the original echo signal of each acquisition point to the same start time, perform energy analysis on the original echo signal of each acquisition point, define the time range according to the energy analysis result, and determine the time window of the effective echo signal: The original echo signal is intercepted based on the time window of the effective echo signal and normalized to obtain the effective echo signal of each acquisition point, which are summarized to form a set of effective echo signals.

5. The ultra-high resolution multi-layer structure interface delamination ultrasonic detection method according to claim 4, characterized in that: The signal analysis and benchmark determination are performed on the original echo signal set, wherein the signal analysis is performed on the original echo signal set, and the specific process is as follows: Perform oscillation time analysis on the valid echo signal set; Determine the echo range of the effective echo signal according to the oscillation time; The translation window length is determined according to the echo range of the effective echo signal, and the translation window length represents the translation window parameter.

6. The ultra-high resolution multi-layer structure interface delamination ultrasonic detection method according to claim 5, characterized in that: The original echo signal set is benchmarked, and the specific process is as follows: Selecting one or more valid echo signals based on a known defect-free area in the valid echo signal set; If multiple valid echo signals are selected, the average value of the multiple valid echo signals is calculated; The selected or resolved valid echo signal is used as the reference signal.

7. The ultra-high resolution multi-layer structure interface delamination ultrasonic detection method according to claim 6, characterized in that: The correlation coefficient between the signal in the calculation window and the reference signal is specifically calculated as follows: Where r is the correlation coefficient, A and B are two groups of signals, μ and σ are the mean and standard deviation, i is a positive integer, and N is the total amount of data.

8. The ultra-high resolution multi-layer structure interface delamination ultrasonic detection method according to claim 7, characterized in that: The phase feature data of each acquisition point is mapped to the spatial position corresponding to the multi-layer structure interface grid model, and also includes applying interpolation algorithm, image enhancement, median filtering and contrast enhancement for processing, and outputting the processed multi-layer structure interface delamination defect detection image.

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