阅读说明：本技术 一种针对薄层压式电介质复合材料的超声检测装置及方法 (Ultrasonic detection device and method for thin-laminated dielectric composite material ) 是由 刘向东 王韦玉 聂靓靓 韩佳轩 黄明浩 王若丞 蒋军 金海云 陶诗迪 肖畅 柳艳 于 2021-09-17 设计创作，主要内容包括：本发明公开了一种针对薄层压式电介质复合材料的超声检测装置与方法,该装置包括载物台、数字超声波探伤仪、超声探头、机械臂组件、示波器以及计算机。计算机通过信号传输线给步进电机驱动器指令操控三自由度机械臂组件,数字超声波探伤仪产生超声信号并通过与之相连的超声探头穿过载物台中的耦合剂传输至待测薄层压式电介质复合材料的上表面,数字超声波探伤仪通过BNC传输线与示波器相连,并通过网线将波形数据传输至计算机。本发明能够对作为部分电力设备主绝缘的薄层压式电介质复合材料进行超声无损检测,进行超声声速、超声频谱和缺陷超声形貌分析,研究在长时运行状况下材料的缺陷分布与老化状态。(The invention discloses an ultrasonic detection device and method for a thin-laminated dielectric composite material. The computer gives an instruction to the stepper motor driver through a signal transmission line to control the three-degree-of-freedom mechanical arm assembly, the digital ultrasonic flaw detector generates an ultrasonic signal and transmits the ultrasonic signal to the upper surface of the thin laminated dielectric composite material to be detected through an ultrasonic probe connected with the digital ultrasonic flaw detector, the ultrasonic probe penetrates through a coupling agent in the objective table and transmits the ultrasonic signal to the upper surface of the thin laminated dielectric composite material to be detected, and the digital ultrasonic flaw detector is connected with the oscilloscope through a BNC transmission line and transmits waveform data to the computer through a network cable. The invention can carry out ultrasonic nondestructive detection on the thin laminated dielectric composite material serving as the main insulation of part of power equipment, carry out ultrasonic sound velocity, ultrasonic frequency spectrum and defect ultrasonic morphology analysis, and research the defect distribution and aging state of the material under the long-term operation condition.)

1. An ultrasonic testing apparatus for a thin laminated dielectric composite, comprising:

an object stage (1) as a placement surface for a thin laminated dielectric composite material; during detection, a coupling agent is placed in the objective table (1) and submerges the thin-layer laminated dielectric composite material;

a digital ultrasonic flaw detector (11) for generating an ultrasonic signal and receiving an echo signal;

the ultrasonic probe (3) is connected with the digital ultrasonic flaw detector (11) so as to transmit ultrasonic signals generated by the ultrasonic flaw detector (11) into the couplant and penetrate through the couplant to reach the upper surface of the thin-laminated dielectric composite material; and an echo signal generated after the ultrasonic signal reaches the thin laminated dielectric composite material;

the mechanical arm assembly is used for driving the ultrasonic probe (3) to move in multiple degrees of freedom;

the oscilloscope (14) is connected with the digital ultrasonic flaw detector (11) and is used for receiving and displaying an echo signal of the digital ultrasonic flaw detector (11);

and the computer (11) is connected with the oscilloscope (14) and is used for carrying out data processing and analysis on the echo signals received by the oscilloscope (14) and carrying out nondestructive testing on the thin-laminated dielectric composite material sample by adopting multiple ways of ultrasonic velocity, ultrasonic frequency spectrum and defect ultrasonic morphology.

2. The ultrasonic testing device for a thin laminated dielectric composite material according to claim 1, wherein the robot arm assembly comprises a Z-direction robot arm (4), a Y-direction robot arm (7) and an X-direction robot arm (9), a Y-Z converting table (6-1), an X-Y converting table (6-2); the Z-direction mechanical arm (4) is connected with the Y-direction mechanical arm (7) through a Y-Z conversion table (6-1), and the Z-direction mechanical arm (4) realizes displacement in the Z direction through a Z-direction knob (5); the Y-direction mechanical arm (7) is connected with the X-direction mechanical arm (9) through an X-Y conversion table (6-2), and the Y-direction mechanical arm (7) realizes displacement in the Y direction through a Y-direction knob (8); the X-direction mechanical arm (9) realizes displacement in the X direction through an X-direction knob (10).

3. The ultrasonic testing device for the thin laminated dielectric composite material according to claim 2, wherein the robot arm assembly is connected to a stepping motor driver (12), the stepping motor driver (12) is connected to a computer (13), and the computer (13) issues a control command to the stepping motor driver (12) to control the movements of the Z-direction robot arm (4), the Y-direction robot arm (7), the X-direction robot arm (9), the Y-Z conversion table (6-1), and the X-Y conversion table (6-2) to realize displacements in the X-direction, the Y-direction, and the Z-direction of the ultrasonic probe (3) fixed to the Z-direction robot arm (4) by a jig.

4. The ultrasonic testing apparatus for a thin laminated dielectric composite material according to claim 3, wherein the stage (1), the ultrasonic probe (3), the Z-direction robot arm (4), the Y-direction robot arm (7), the X-direction robot arm (9), the Y-Z converting stage (6-1), the X-Y converting stage (6-2), the digital ultrasonic flaw detector (11), the stepping motor driver (12), the computer (13) and the oscilloscope (14) are all placed on the same horizontal stage.

5. The ultrasonic testing device for thin laminated dielectric composites of claim 3, wherein the data processing employs digital filters to filter the collected data, data windowing is performed using a Hanning window, and a 64-order low-pass FIR filter is used with 60dB stop band attenuation and 5MHz cut-off frequency.

6. The ultrasonic testing device for a thin laminated dielectric composite of claim 1, wherein the echo generated after the ultrasonic signal reaches the thin laminated dielectric composite comprises: the surface wave is an echo of a pulse wave reaching an interface between the couplant and the upper surface of the thin-laminated dielectric composite material to be detected, the defect wave is an echo of a pulse wave reaching an internal defect of the thin-laminated dielectric composite material to be detected, and the bottom wave is an echo of the pulse wave reaching the lower surface of the thin-laminated dielectric composite material to be detected.

7. The ultrasonic testing device for a thin laminated dielectric composite of claim 6, wherein the ultrasonic speed of sound is calculated by a surface wave and bottom surface wave time difference; the ultrasonic frequency spectrum is realized by carrying out Fourier transform on an original ultrasonic signal; and the defect ultrasonic morphology is used for coding the defect wave amplitude value and then drawing a color map corresponding to the color RGB value.

8. The ultrasonic testing apparatus for a thin laminated dielectric composite of claim 7, wherein the ultrasonic speed of sound is calculated by a surface wave and bottom surface wave time difference comprising:

carrying out ultrasonic sound velocity analysis on the recorded ultrasonic original data, recording the time difference delta t between the surface wave and the bottom wave by searching the amplitude position of the surface wave and the bottom wave, measuring the thickness d of the sample, and obtaining the thickness d of the sample by a formulaCalculating the internal sound velocity v of the thin laminated dielectric composite material;

the ultrasonic frequency spectrum is realized by carrying out Fourier transform on an original ultrasonic signal, and comprises the following steps:

and carrying out ultrasonic spectrum analysis on the recorded ultrasonic original data, carrying out Fourier transform on the filtered ultrasonic data, and intercepting the frequency spectrum within the frequency range of 0-10 MHz for analysis.

9. The ultrasonic inspection apparatus for thin laminated dielectric composites of claim 7 wherein the ultrasonic characterization of defects by encoding the amplitude of the defect waves and plotting the color map against the RGB values of the colors comprises:

performing defect ultrasonic topography analysis on recorded ultrasonic original data, recording two-dimensional coordinates (x, y) of each ultrasonic detection point in a scanning area and amplitude characteristic values A (x, y) of each point, constructing a characteristic value matrix according to the amplitude characteristic values corresponding to each ultrasonic detection point (x, y) after an ultrasonic probe finishes scanning along a preset path, performing pixel grouping on the ultrasonic detection points according to imaging precision F, wherein each group comprises F multiplied by F ultrasonic detection points, respectively calculating the average value of the characteristic values of all the ultrasonic detection points of each group, taking the average value as the characteristic value A' (i, j) of a corresponding imaging pixel point, reconstructing an F pixel point characteristic value matrix, and averagely dividing all the characteristic values of the pixel point characteristic value matrix into 256 intervals from small to large in the range, respectively corresponding to integers 0-255 by formulaCalculating 8bit gray value G (x, y) of each pixel point; and finally, converting the gray value into an RGB value to realize color image drawing of the defect ultrasonic imaging.

10. An ultrasonic testing method for a thin laminated dielectric composite material, characterized by being carried out using the ultrasonic testing apparatus for a thin laminated dielectric composite material according to claim 3, comprising the steps of:

s1, opening the computer (13) and the stepping motor driver (12), giving a zeroing instruction through the computer (13), and indicating the stepping motor driver (12) to control the Z-direction mechanical arm (4), the Y-direction mechanical arm (7) and the X-direction mechanical arm (9) to return to the original positions;

s2, placing the thin-layer laminated dielectric composite material (2) at the bottom of an objective table (1), pouring a coupling agent into the objective table (1) until the coupling agent submerges the thin-layer laminated dielectric composite material (2) and can contact the lower surface of the ultrasonic probe (3) when the zero point position to be scanned is opposite to the ultrasonic probe (3);

s3, setting parameters of the scanning step through a computer (13), and setting storage parameters to record real-time waveform of the oscilloscope;

s4, opening the digital ultrasonic flaw detector (11) and the oscilloscope (14), clicking a start button on the computer (13) after the waveform is checked to be correct on the oscilloscope (14), scanning according to the parameters of the scanning step in S3, and recording the waveform of the oscilloscope in real time according to the storage parameters in S3;

and S5, performing data processing and data analysis on the oscilloscope real-time parameters stored in the S4, performing filtering processing on the data through a filtering algorithm, and calculating the ultrasonic sound velocity, the ultrasonic frequency spectrum and the defect morphology by using MATLAB writing software.

Technical Field

The invention belongs to the field of research on dielectric and electrical insulation, and particularly relates to an ultrasonic detection device and method for a thin-layer-pressure type dielectric composite material.

Background

Based on the requirements of power equipment manufacturing process and insulation structure design in actual engineering, laminated dielectric composite materials prepared by using paper or fiber cloth as a substrate, impregnating adhesive, and performing hot pressing and the like widely exist in a power equipment insulation system, and have good insulation performance, mechanical property, heat resistance, electric arc resistance, corrosion resistance and the like. The epoxy laminated glass cloth plate has stable dielectric property and high mechanical strength under high temperature and high humidity, and is widely used for main insulation of a high-voltage motor; the laminated phenolic paper board has good mechanical property and is used in transformer oil and insulating structural parts for electrical equipment; the laminated phenolic glass cloth plate has good water resistance and heat resistance, and is suitable for a circuit breaker junction edge structural member; the organic silicon epoxy glass cloth plate is used for an electric insulating part in a damp and hot area due to heat resistance and mildew resistance; the main insulation of the coil bar in the pumped storage generator is an epoxy mica powder glass cloth laminated composite material reinforced by mica powder as a base, epoxy glue as an adhesive and glass cloth. For the laminated dielectric composite material with compact structure, electric heating aging can occur in the long-term use process, local defects such as bubbles, layering, impurities, uneven distribution and the like are easily generated inside the laminated dielectric composite material, and therefore the service life of the material and the safe and stable operation of power equipment are greatly influenced. The ultrasonic detection technology has the advantages of low cost, convenient use, contribution to on-site nondestructive detection and the like, can realize the positioning and imaging of the internal defects of the material and reflect the change of the local performance of the material. Ultrasonic detection technology for homogeneous insulating materials is mature, but ultrasonic detection research for laminated dielectric composite materials is less, and accurate measurement is difficult due to the fact that a sample is thin and sound attenuation in multilayer media is large, and an ultrasonic detection device and method for the laminated dielectric composite materials need to be provided, so that accurate positioning and measurement analysis of faults are achieved.

The ultrasonic detection device in the existing literature is mostly used for thick dielectric materials, is mostly single dielectric materials such as silicon rubber, polyethylene and the like, cannot be directly used for thin-layer pressure type dielectric composite materials, and has the problems of low resolution, overlarge sound signal attenuation, incapability of measurement and the like; the existing ultrasonic detection methods in the literature mostly use single parameter analysis, and few ultrasonic detection methods simultaneously carry out ultrasonic sound velocity, ultrasonic frequency spectrum and defect ultrasonic shape analysis, so that the defect characteristics and the aging state of a sample are difficult to be comprehensively evaluated.

Disclosure of Invention

In order to solve at least one technical problem in the background art, the present invention provides an ultrasonic testing apparatus and method for a thin laminated dielectric composite material.

In order to achieve the purpose, the technical scheme of the invention is as follows:

an ultrasonic testing apparatus for a thin laminated dielectric composite, comprising:

an object stage (1) as a placement surface for a thin laminated dielectric composite material; during detection, a coupling agent is placed in the objective table (1) and submerges the thin-layer laminated dielectric composite material;

a digital ultrasonic flaw detector (11) for generating an ultrasonic signal and receiving an echo signal;

the ultrasonic probe (3) is connected with the digital ultrasonic flaw detector (11) so as to transmit ultrasonic signals generated by the ultrasonic flaw detector (11) into the couplant and penetrate through the couplant to reach the upper surface of the thin-laminated dielectric composite material; and an echo signal generated after the ultrasonic signal reaches the thin laminated dielectric composite material;

the mechanical arm assembly is used for driving the ultrasonic probe (3) to move in multiple degrees of freedom;

the oscilloscope (14) is connected with the digital ultrasonic flaw detector (11) and is used for receiving and displaying an echo signal of the digital ultrasonic flaw detector (11);

and the computer (11) is connected with the oscilloscope (14) and is used for carrying out data processing and analysis on the echo signals received by the oscilloscope (14) and carrying out nondestructive testing on the thin-laminated dielectric composite material sample by adopting multiple ways of ultrasonic velocity, ultrasonic frequency spectrum and defect ultrasonic morphology.

Further, the mechanical arm assembly comprises a Z-direction mechanical arm (4), a Y-direction mechanical arm (7), an X-direction mechanical arm (9), a Y-Z conversion table (6-1) and an X-Y conversion table (6-2); the Z-direction mechanical arm (4) is connected with the Y-direction mechanical arm (7) through a Y-Z conversion table (6-1), and the Z-direction mechanical arm (4) realizes displacement in the Z direction through a Z-direction knob (5); the Y-direction mechanical arm (7) is connected with the X-direction mechanical arm (9) through an X-Y conversion table (6-2), and the Y-direction mechanical arm (7) realizes displacement in the Y direction through a Y-direction knob (8); the X-direction mechanical arm (9) realizes displacement in the X direction through an X-direction knob (10).

Furthermore, the mechanical arm assembly is connected with a stepping motor driver (12), the stepping motor driver (12) is connected with a computer (13), and the computer (13) sends a control command to the stepping motor driver (12) to control the movement of the Z-direction mechanical arm (4), the Y-direction mechanical arm (7), the X-direction mechanical arm (9), the Y-Z conversion table (6-1) and the X-Y conversion table (6-2), so that the displacement of the ultrasonic probe (3) fixed on the Z-direction mechanical arm (4) through the clamp in the X direction, the Y direction and the Z direction is realized.

Furthermore, the object stage (1), the ultrasonic probe (3), the Z-direction mechanical arm (4), the Y-direction mechanical arm (7), the X-direction mechanical arm (9), the Y-Z conversion table (6-1), the X-Y conversion table (6-2), the digital ultrasonic flaw detector (11), the stepping motor driver (12), the computer (13) and the oscilloscope (14) are all placed on the same horizontal table.

Further, the data processing adopts a digital filter, the acquired data is filtered, a Hanning window is used for windowing the data, a 64-order low-pass FIR filter is used, the stopband attenuation is 60dB, and the cut-off frequency is 5 MHz.

Furthermore, the echo generated after the ultrasonic signal reaches the thin-laminated dielectric composite material includes an echo in which a surface wave is an echo in which a pulse wave reaches an interface between the coupling agent and the upper surface of the thin-laminated dielectric composite material to be detected, a defect wave is an echo in which a pulse wave reaches an internal defect of the thin-laminated dielectric composite material to be detected, and a bottom wave is an echo in which a pulse wave reaches the lower surface of the thin-laminated dielectric composite material to be detected.

Further, the ultrasonic sound velocity is calculated by a time difference between the surface wave and the bottom wave; the ultrasonic frequency spectrum is realized by carrying out Fourier transform on an original ultrasonic signal; and the defect ultrasonic morphology is used for coding the defect wave amplitude value and then drawing a color map corresponding to the color RGB value.

Further, the ultrasonic sound velocity calculation by the surface wave and bottom surface wave time difference includes:

the recorded ultrasonic original data is subjected to ultrasonic sound velocity analysis, and by searching the amplitude positions of the surface wave and the bottom surface wave,recording the time difference delta t between the two and measuring the thickness d of the sample by a formulaAnd calculating the internal sound velocity v of the thin laminated dielectric composite.

The ultrasonic frequency spectrum is realized by carrying out Fourier transform on an original ultrasonic signal, and comprises the following steps:

and carrying out ultrasonic spectrum analysis on the recorded ultrasonic original data, carrying out Fourier transform on the filtered ultrasonic data, and intercepting the frequency spectrum within the frequency range of 0-10 MHz for analysis.

Further, the step of drawing a color map corresponding to the color RGB values after the defect ultrasonic morphology is encoded by the defect amplitude value includes:

performing defect ultrasonic topography analysis on recorded ultrasonic original data, recording two-dimensional coordinates (x, y) of each ultrasonic detection point in a scanning area and amplitude characteristic values A (x, y) of each point, constructing a characteristic value matrix according to the amplitude characteristic values corresponding to each ultrasonic detection point (x, y) after an ultrasonic probe finishes scanning along a preset path, performing pixel grouping on the ultrasonic detection points according to imaging precision F, wherein each group comprises F multiplied by F ultrasonic detection points, respectively calculating the average value of the characteristic values of all the ultrasonic detection points of each group, taking the average value as the characteristic value A' (i, j) of a corresponding imaging pixel point, reconstructing an F pixel point characteristic value matrix, and averagely dividing all the characteristic values of the pixel point characteristic value matrix into 256 intervals from small to large in the range, respectively corresponding to integers 0-255 by formulaAnd calculating 8bit gray value G (x, y) of each pixel point. And finally, converting the gray value into an RGB value to realize color image drawing of the defect ultrasonic imaging.

Correspondingly, the invention provides an ultrasonic detection method for a thin laminated dielectric composite material, which is carried out by adopting the ultrasonic detection device for the thin laminated dielectric composite material, and comprises the following steps:

s1, opening the computer (13) and the stepping motor driver (12), giving a zeroing instruction through the computer (13), and indicating the stepping motor driver (12) to control the Z-direction mechanical arm (4), the Y-direction mechanical arm (7) and the X-direction mechanical arm (9) to return to the original positions;

s2, placing the thin-layer laminated dielectric composite material (2) at the bottom of an objective table (1), pouring a coupling agent into the objective table (1) until the coupling agent submerges the thin-layer laminated dielectric composite material (2) and can contact the lower surface of the ultrasonic probe (3) when the zero point position to be scanned is opposite to the ultrasonic probe (3);

s3, setting parameters of the scanning step through a computer (13), and setting storage parameters to record real-time waveform of the oscilloscope;

s4, opening the digital ultrasonic flaw detector (11) and the oscilloscope (14), clicking a start button on the computer (13) after the waveform is checked to be correct on the oscilloscope (14), scanning according to the parameters of the scanning step in S3, and recording the waveform of the oscilloscope in real time according to the storage parameters in S3;

s5, processing and analyzing the data of the oscilloscope real-time parameters stored in S4, filtering the data through a filtering algorithm, and calculating the ultrasonic sound velocity, the ultrasonic frequency spectrum and the defect appearance by using MATLAB writing software

Compared with the prior art, the invention has the beneficial effects that:

(1) the ultrasonic detection device for the thin laminated dielectric composite material has high scanning freedom degree and convenient operation, can realize XYZ three-direction scanning of a computer-controlled stepping motor in a measuring range by any required path through programming, has the minimum step length of 2.5 mu m, and simultaneously realizes measurement and analysis of ultrasonic sound velocity and sample defect ultrasonic morphology.

(2) According to the type, the size, the sound velocity, the sound attenuation coefficient and other parameters of the sample, the frequency, the shape and the model of the ultrasonic probe can be freely selected for replacement, the ultrasonic probe with the characteristic model can be selected for the thin laminated dielectric composite material, and the measurement problem caused by the excessively thin sample and the large sound attenuation of the laminated composite material is avoided.

(3) The computer programming is utilized, the nondestructive testing is carried out on the sample by adopting multiple ways of ultrasonic sound velocity, ultrasonic frequency spectrum and defect ultrasonic appearance, and the information such as the defect position, the aging degree and the like of the sample can be detected and analyzed in an all-round way; the ultrasonic sound velocity is calculated through the time difference between the surface wave and the bottom wave, the ultrasonic frequency spectrum is realized through Fourier transform on the original ultrasonic signal, and the defect ultrasonic morphology is used for drawing a color map corresponding to the RGB value after the defect wave amplitude value is coded.

(4) The acquired signals are filtered and analyzed, and a 64-order low-pass FIR filter is designed, so that high-frequency noise interference is avoided.

(5) The ultrasonic detection of the thin-laminated dielectric composite material is non-contact nondestructive detection, ultrasonic signals are transmitted and received through the coupling agent, damage to a sample caused by defect destructive measurement is avoided, and meanwhile, the influence of a contact state and contact pressure on the accuracy of a measurement result in contact measurement is also avoided.

Drawings

FIG. 1 is a schematic structural diagram of an ultrasonic testing device for a thin laminated dielectric composite material according to the present invention

FIG. 2 is a schematic diagram of a pulse echo method used in the present invention

In the figure: the initial pulse is a pulse wave emitted by the ultrasonic probe at the contact position of the ultrasonic probe and the couplant, the surface wave is an echo of the pulse wave reaching the interface of the upper surface of the couplant and the thin-layer-pressure type dielectric composite material to be detected, the defect wave is an echo of the pulse wave reaching the internal defect of the thin-layer-pressure type dielectric composite material to be detected, and the bottom wave is an echo of the pulse wave reaching the lower surface of the thin-layer-pressure type dielectric composite material to be detected.

FIG. 3 is a schematic diagram of the present invention for converting the ultrasonic detection point matrix into the pixel matrix during the defect ultrasonic topography detection

In the figure: the left image is an ultrasonic detection point matrix, and the right image is a converted pixel matrix

FIG. 4 is a diagram of the effect of a selected 64 th order low-pass FIR filter of the present invention

In the figure: the upper graph is the original waveform data, and the lower graph is the waveform data after passing through a 64-order low-pass FIR filter.

FIG. 5 is a diagram showing the result of ultrasonic sound velocity detection according to the present invention

In the figure: the left graph is a test result graph of the ultrasonic sound velocity of a single dielectric material, and the right graph is a test result graph of the ultrasonic sound velocity of a thin laminated dielectric composite material.

FIG. 6 is a diagram showing the results of ultrasonic spectrum detection according to the present invention

In the figure: the left graph is a test result graph of the ultrasonic frequency spectrum of a certain single dielectric material, and the right graph is a test result graph of the ultrasonic frequency spectrum of a certain thin laminated dielectric composite material.

Detailed Description

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted" and "connected" are to be interpreted broadly, e.g., as being either fixedly connected, detachably connected, or integrally connected; the connection can be mechanical connection, electrical connection and signal connection; they may be connected directly or indirectly through intervening media, so to speak, as communicating between the two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art. The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.

Referring to fig. 1, the ultrasonic testing apparatus for a thin laminated dielectric composite material provided in this embodiment mainly includes a stage 1, a digital ultrasonic flaw detector 11, an ultrasonic probe 3, a mechanical arm assembly, an oscilloscope 14, and a computer. In addition, for convenience of description of the positional relationship, cartesian coordinates are established in fig. 1.

The objective table 1 is used as a placing table surface of the thin laminated dielectric composite material, and the thin laminated dielectric composite material 2 at least comprises two materials, in the embodiment, the two materials are composed of a first material 2-1 and a second material 2-2; during detection, a couplant is placed in the objective table 1, and the couplant submerges the thin-layer laminated dielectric composite material but is not higher than the ultrasonic probe.

The digital ultrasonic flaw detector 11 is used for generating ultrasonic signals and receiving echo signals. Specifically, in this embodiment, the digital ultrasonic flaw detector 11 is of a type SIUI CTS-9006, a sampling rate of 240MHz, a measurement resolution of 0.1mm, and a working frequency range of 0.5 to 10MHz, and can generate a pulse repetition frequency of 20 to 2000 Hz.

The ultrasonic probe 3 is connected to the digital ultrasonic flaw detector 11 through a BNC transmission line to transmit an ultrasonic signal (i.e., a pulse wave) generated by the ultrasonic flaw detector 11 to the coupling agent, pass through the coupling agent to reach the upper surface of the thin laminated dielectric composite material, and receive an echo generated after the ultrasonic signal reaches the thin laminated dielectric composite material. Specifically, as shown in fig. 2, the start pulse is a pulse wave emitted from the ultrasonic probe at a position where the ultrasonic probe contacts the couplant, the surface wave is an echo of the pulse wave reaching an interface between the couplant and the upper surface of the thin-laminate dielectric composite material to be measured, the defect wave is an echo of the pulse wave reaching an internal defect of the thin-laminate dielectric composite material to be measured, and the bottom wave is an echo of the pulse wave reaching the lower surface of the thin-laminate dielectric composite material to be measured.

The digital ultrasonic flaw detector 11 inputs waveform data into the oscilloscope 14 through a BNC signal transmission line, the oscilloscope 14 transmits the waveform data to the computer 13 through a network cable for data processing and analysis, and nondestructive testing is carried out on the thin-laminated dielectric composite material sample by adopting multiple ways of ultrasonic sound velocity, ultrasonic frequency spectrum and defect ultrasonic morphology. The ultrasonic sound velocity is calculated through the time difference between the surface wave and the bottom wave, the ultrasonic frequency spectrum is realized through Fourier transform on an original ultrasonic signal, and the defect ultrasonic morphology is used for drawing a color map corresponding to a color RGB value after the defect wave amplitude value is coded.

The mechanical arm assembly is used for driving the ultrasonic probe 3 to realize multi-degree-of-freedom motion in the XYZ three directions.

Therefore, the ultrasonic detection device for the thin laminated dielectric composite material provided by the embodiment has high scanning freedom degree and convenient operation, XYZ three-direction scanning in a range can be carried out on any required path, the minimum step length can reach 2.5 mu m, and the ultrasonic sound velocity and the ultrasonic shape and appearance of the sample defect can be measured and analyzed.

Specifically, the mechanical arm assembly comprises a Z-direction mechanical arm 4, a Y-direction mechanical arm 7, an X-direction mechanical arm 9, a Y-Z conversion table 6-1 and an X-Y conversion table 6-2, wherein the Z-direction mechanical arm 4 is connected with the Y-direction mechanical arm 7 through the Y-Z conversion table 6-1, and the Z-direction mechanical arm 4 realizes displacement in the Z direction through a Z-direction knob 5; the Y-direction mechanical arm 7 is connected with the X-direction mechanical arm 9 through an X-Y conversion table 6-2, and the Y-direction mechanical arm 7 realizes displacement in the Y direction through a Y-direction knob 8; the X-direction mechanical arm 9 realizes displacement in the X direction through the X-direction knob 10; the control of the three-degree-of-freedom motion of the mechanical arm assembly is connected with a stepping motor driver 12 through a signal transmission line, the stepping motor driver 12 is connected with a computer 13 through an RS232 serial port, and the computer 13 controls the mechanical arm assembly through instructions of the RS232 serial port stepping motor driver 12 to realize the displacement of an ultrasonic probe (3) fixed on a Z-direction mechanical arm (4) through a clamp in the X direction, the Y direction and the Z direction. Meanwhile, the ultrasonic probe 3 can be detached and replaced with probes of different models according to use requirements, the frequency, the shape and the model of the ultrasonic probe can be freely selected and replaced according to parameters such as the type, the size, the sound velocity and the sound attenuation coefficient of a sample, the ultrasonic probe with the characteristic model can be selected for the thin laminated dielectric composite material, and the measurement problem caused by the fact that the sample is too thin and the laminated composite material is large in sound attenuation is avoided.

As a preferred embodiment of the present invention, in order to avoid vibration during use and ensure detection accuracy, the stage 1, the ultrasonic probe 3, the Z-direction robot 4, the Y-direction robot 7, the X-direction robot 9, the Y-Z conversion stage 6-1, the X-Y conversion stage 6-2, the digital ultrasonic flaw detector 11, the stepping motor driver 12, the computer 13, and the oscilloscope 14 are all placed on the same horizontal stage.

As another preferred embodiment of the present invention, the data processing employs a digital filter, the acquired waveform data signal is filtered to avoid the interference of high-frequency noise of the acquired signal, a hanning window is used for data windowing, and a 64-order low-pass FIR filter is used to reduce the stopband attenuation to 60dB and cut-off frequency to 5 MHz.

Specifically, in the embodiment, the stepping motor driver (12) is of a model of Zolix SC300-2B, the output frequency range of the driver is 200-20 KHz, and the pulse speed is 400 pps-18 Kpps; the oscilloscope (14) adopts 2207B model of Pico company, the sampling frequency is 125MS/s, and the bandwidth is 70MHz

When the ultrasonic detection device carries out ultrasonic detection on the thin laminated dielectric composite material, the process is as follows:

s1, opening the computer 13 and the stepping motor driver 12, giving a zeroing instruction through the computer 13, and instructing the stepping motor driver 12 to control the Z-direction mechanical arm 4, the Y-direction mechanical arm 7 and the X-direction mechanical arm 9 to return to the original positions;

s2, placing the thin-layer laminated dielectric composite material 2 at the bottom of the objective table 1, pouring a coupling agent into the objective table 1 until the coupling agent submerges the thin-layer laminated dielectric composite material 2 and can contact the lower surface of the ultrasonic probe 3, wherein the zero point position to be scanned is opposite to the ultrasonic probe 3;

s3, setting parameters of the scanning step through the computer 13, and setting storage parameters to record real-time waveform of the oscilloscope;

s4, opening the digital ultrasonic flaw detector 11 and the oscilloscope 14, clicking a start button on the computer 13 after the oscilloscope 14 checks that the waveform is correct, scanning according to the parameters of the scanning step S3, and recording the oscilloscope waveform in real time by the storage parameters S3;

and S5, performing data processing and data analysis on the oscilloscope real-time parameters stored in the S4, performing filtering processing on the data through a filtering algorithm, and calculating the ultrasonic sound velocity, the ultrasonic frequency spectrum and the defect morphology by using MATLAB writing software.

The ultrasonic testing device for the thin laminated dielectric composite material is further described with reference to an application scenario as follows:

the laminated dielectric composite material prepared by using paper or fiber cloth as a substrate, impregnating an adhesive and performing hot pressing and the like widely exists in an insulation system of power equipment, and has the characteristics of good insulation performance, mechanical property, heat resistance, electric arc resistance, corrosion resistance and the like. For the laminated dielectric composite material with compact structure, electric heating aging can occur in the long-term use process, local defects such as bubbles, layering, impurities, uneven distribution and the like are easily generated inside the laminated dielectric composite material, and therefore the service life of the material and the safe and stable operation of power equipment are greatly influenced.

Taking epoxy mica glass cloth as an example of a main insulating material of a pumped storage motor wire rod, the material structure is epoxy impregnated mica glass silk cloth, the thin-layer laminated dielectric composite material is prepared by a VPI impregnation baking process, the thickness of the whole insulating layer material is about 5mm, and the thickness of the single-layer mica glass silk cloth is about 0.1 mm. The pumped storage motor needs to be frequently started and stopped due to the peak-shaving frequency-modulation working characteristic, so that the temperature in the epoxy mica glass cloth insulating layer changes alternately, and the materials age and deteriorate gradually under the action of long-term high voltage, mechanical vibration and the surrounding environment, and even breakdown and stop accidents in operation occur. At present, in the existing research, a destructive detection means is mostly used for detecting the electrothermal aging characteristic of the material, the existing nondestructive ultrasonic detection research is also mostly limited to the measurement of single ultrasonic sound velocity, and the defect state and the aging degree of the epoxy mica glass cloth insulating layer are difficult to visually and comprehensively represent.

The ultrasonic detection device for the thin laminated dielectric composite material can be used for ultrasonic detection of epoxy mica glass cloth, and the process flow is as follows:

firstly, opening a computer 13 and a stepping motor driver 12, giving a zeroing instruction through the computer 13, and indicating the stepping motor driver 12 to control a Z-direction mechanical arm 4, a Y-direction mechanical arm 7 and an X-direction mechanical arm 9 to return to the original positions;

then placing the epoxy mica glass cloth material at the bottom of the objective table 1, wherein the position of the zero point to be scanned is opposite to the ultrasonic probe 3, and pouring the coupling agent into the objective table 1 until the coupling agent submerges the epoxy mica glass cloth and can contact the lower surface of the ultrasonic probe 3;

the scanning step parameters are then set by the computer 13 where the scanning area is chosen to be 2mm x 2 mm. Setting storage parameters, and recording real-time waveform of the oscilloscope at each grid point position in a scanning area, wherein the scanning precision is 2.5 mu m;

opening the digital ultrasonic flaw detector 11 and the oscilloscope 14, clicking a start button on the computer 13 after the waveform is checked to be correct on the oscilloscope 14, scanning according to the scanning step parameters, and storing the parameters to record the waveform of the oscilloscope in real time;

the stored real-time data of the oscilloscope is filtered through a filtering algorithm, a Hanning window is adopted to window the data, a 64-order low-pass FIR filter is used, the attenuation of a stop band is 60dB, the cut-off frequency is 5MHz, the filtering effect is shown in figure 4, and the high-frequency noise is effectively filtered out through the filtered ultrasonic waveform.

Carrying out ultrasonic sound velocity analysis on the recorded ultrasonic original data, recording the time difference delta t between the surface wave and the bottom wave by searching the amplitude position of the surface wave and the bottom wave, measuring the thickness d of the sample, and obtaining the thickness d of the sample by a formulaAnd calculating the sound velocity v inside the sample, and as shown in FIG. 5, comparing the ultrasonic sound velocity results of the pure epoxy and the epoxy mica glass cloth, wherein the sound velocity in the epoxy is 2500m/s, and the sound velocity in the epoxy mica glass cloth is 2778 m/s.

And performing ultrasonic frequency spectrum analysis on recorded ultrasonic original data, performing Fourier transform on the filtered ultrasonic data, intercepting a frequency spectrum in a frequency range of 0-10 MHz for analysis, and as shown in fig. 6, obtaining an ultrasonic sound velocity result comparison graph of pure epoxy and epoxy mica glass cloth, wherein the ultrasonic characteristic frequency of the pure epoxy measured by the ultrasonic detection equipment is 1.2MHz, and the ultrasonic characteristic frequency of the epoxy mica glass cloth is 1.2MHz and 3.6 MHz.

And carrying out defect ultrasonic morphology analysis on the recorded ultrasonic original data. And recording two-dimensional coordinates (x, y) of each ultrasonic detection point in the scanning area and amplitude characteristic values A (x, y) of each point, and constructing a characteristic value matrix according to the amplitude characteristic values corresponding to each ultrasonic detection point (x, y) after the ultrasonic probe finishes scanning along a preset path. In view of the fact that the number of detection points is large and the eigenvalues of the adjacent points are not very different, in order to reduce the data storage pressure and the color image imaging pressure, the ultrasonic detection points are grouped into pixels according to the imaging precision F, each group comprises F x F ultrasonic detection points, the average value of the eigenvalues of all the ultrasonic detection points of each group is respectively calculated and is used as the eigenvalue A' (i, j) of the corresponding imaging pixel point, and an F pixel point eigenvalue matrix is reconstructed, wherein the principle schematic diagram is shown in fig. 3.

Taking the maximum value max (A '(i, j)) and the minimum value min (A' (i, j)) in the pixel characteristic value matrix, dividing all the characteristic values of the pixel characteristic value matrix into 256 intervals from small to large in the range,respectively corresponding to integers 0-255 by formulaAnd calculating 8bit gray value G (x, y) of each pixel point. And finally, converting the gray value into an RGB value to realize color image drawing of the defect ultrasonic imaging. Bubble defects and delamination defects are introduced into the epoxy mica glass fiber cloth in advance, and the defects introduced in advance are found through defect ultrasonic imaging.

In summary, compared with the prior art, the invention has the following technical advantages:

(1) the ultrasonic detection device for the thin laminated dielectric composite material has high scanning freedom degree and convenient operation, can realize XYZ three-direction scanning of a computer-controlled stepping motor in a measuring range by any required path through programming, has the minimum step length of 2.5 mu m, and simultaneously realizes measurement and analysis of ultrasonic sound velocity and sample defect ultrasonic morphology.

(2) According to the type, the size, the sound velocity, the sound attenuation coefficient and other parameters of the sample, the frequency, the shape and the model of the ultrasonic probe can be freely selected for replacement, the ultrasonic probe with the characteristic model can be selected for the thin laminated dielectric composite material, and the measurement problem caused by the excessively thin sample and the large sound attenuation of the laminated composite material is avoided.

(3) The computer programming is utilized, the nondestructive testing is carried out on the sample by adopting multiple ways of ultrasonic sound velocity, ultrasonic frequency spectrum and defect ultrasonic appearance, and the information such as the defect position, the aging degree and the like of the sample can be detected and analyzed in an all-round way; the ultrasonic sound velocity is calculated through the time difference between the surface wave and the bottom wave, the ultrasonic frequency spectrum is realized through Fourier transform on the original ultrasonic signal, and the defect ultrasonic morphology is used for drawing a color map corresponding to the RGB value after the defect wave amplitude value is coded.

(4) The acquired signals are filtered and analyzed, and a 64-order low-pass FIR filter is designed, so that high-frequency noise interference is avoided.

(5) The ultrasonic detection of the thin-laminated dielectric composite material is non-contact nondestructive detection, ultrasonic signals are transmitted and received through the coupling agent, damage to a sample caused by defect destructive measurement is avoided, and meanwhile, the influence of a contact state and contact pressure on the accuracy of a measurement result in contact measurement is also avoided.

The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention accordingly, and not to limit the protection scope of the present invention accordingly. All equivalent changes or modifications made in accordance with the spirit of the present disclosure are intended to be covered by the scope of the present disclosure.