阅读说明：本技术 一种基于脉冲反射法的材料缺陷检测系统及其检测方法 (Material defect detection system based on pulse reflection method and detection method thereof ) 是由 涂一航 程锦 李恩 赵建华 吴君豪 张云鹏 李吉 于 2020-12-21 设计创作，主要内容包括：本发明提供一种基于脉冲反射法的材料缺陷检测系统及其检测方法,属于无损检测技术领域。本发明检测系统采用逆向思路,利用定向耦合器输入端与耦合端具有一定的耦合度,输出端与耦合端具有高隔离度的传输特性,将信号源端接输出端、超声探头端接输入端、示波器端接耦合端,从而实现探头反射信号被示波器获取；并对检测信号采用小波分析方法进行分析,实现了对缺陷深度的精确判定,提升了材料无损检测能力范围、关键部位无损检测效率和准确度,为材料工艺改进提供无损检测技术保障。(The invention provides a material defect detection system based on a pulse reflection method and a detection method thereof, belonging to the technical field of nondestructive detection. The detection system adopts a reverse thought, utilizes the transmission characteristic that the input end and the coupling end of the directional coupler have certain coupling degree and the output end and the coupling end have high isolation degree, and connects a signal source with the output end, an ultrasonic probe with the input end and an oscilloscope with the coupling end, thereby realizing that a probe reflection signal is acquired by the oscilloscope; and the detection signals are analyzed by adopting a wavelet analysis method, so that the defect depth is accurately judged, the nondestructive testing capability range of the material, the nondestructive testing efficiency and accuracy of key parts are improved, and the nondestructive testing technical guarantee is provided for the improvement of the material process.)

1. A material defect detection system based on a pulse reflection method is characterized by comprising a pulse modulation signal source, a directional coupler, an ultrasonic probe and a signal processing module;

the pulse modulation signal source is connected with the output end of the directional coupler, the ultrasonic probe is connected with the input end of the directional coupler, and the signal processing module is connected with the coupling end of the directional coupler;

the pulse modulation signal source generates an electric signal which is transmitted to the ultrasonic probe through the directional coupler, the ultrasonic probe converts the electric signal into an ultrasonic signal and then acts on a sample to be detected, and then the ultrasonic probe receives a reflected signal and is coupled to the signal processing module through the directional coupler.

2. The material defect detection system of claim 1, further comprising a power amplifier disposed between the pulsed signal source and the directional coupler.

3. The material defect detection system of claim 1, wherein the signal processing module comprises a limiter, a low noise amplifier, an oscilloscope, and an industrial personal computer; the amplitude limiter is connected with the coupling end of the directional coupler and used for limiting the surface reflection signals of the sample to be detected, which are higher than a threshold value; the low-noise amplifier is connected with the amplitude limiter and is used for amplifying weak signals; the oscilloscope is connected with the low noise amplifier and is used for displaying signals detected by the ultrasonic probe; and the industrial personal computer is connected with the oscilloscope and is used for performing wavelet denoising treatment.

4. The material defect detecting system of claim 1, wherein the ultrasonic probe is 0.5-1 cm away from the sample to be detected, and a thinner air gap between the sample to be detected and the probe is filled with a coupling agent in order to remove air between the sample to be detected and the probe.

5. The material defect detection system of claim 4, wherein the couplant is glycerol or an ultrasonic couplant.

6. The material defect detection system of claim 1, wherein the number of ports of the directional coupler is equal to or greater than 3.

7. The material defect detection system of claim 1, wherein the directional coupler is replaceable with a three-port power splitter.

8. A detection method based on the material defect detection system of any claim 1 to 7, characterized by comprising the following steps:

step 1, testing the similar material of a sample to be tested without defects by using a material defect detection system to obtain a reflected signal, then testing the thickness of the sample, obtaining the propagation time of ultrasonic waves according to a surface echo signal and a bottom echo signal, and further obtaining the transmission speed of the ultrasonic waves;

step 2, detecting a sample to be detected to obtain a defect signal;

step 3, processing the defect signals obtained in the step 2 by adopting a wavelet analysis method to obtain the back-and-forth time t of the ultrasonic waves between the upper surface and the lower surface of the defect₁And t₂Further obtaining a time interval delta t;

and 4, calculating to obtain the defect depth according to the ultrasonic transmission speed calculated in the step 1 and the time interval delta t obtained in the step 3.

9. The method for detecting a material defect detecting system according to claim 8, wherein the step 3 using a wavelet analysis method comprises the following steps:

step 3.1: wavelet decomposition of the defect signal, selecting a wavelet and determining a decomposition level N, and then performing decomposition calculation;

step 3.2: threshold quantization of wavelet decomposition high-frequency coefficients, namely selecting one threshold for high-frequency coefficients under each decomposition scale to perform threshold quantization processing;

step 3.3: and performing one-dimensional wavelet reconstruction according to the lowest layer low-frequency coefficient and each layer high-frequency coefficient of the wavelet decomposition to obtain a defect signal subjected to noise reduction.

10. The method for detecting a material defect detecting system according to claim 9, wherein the threshold value of the threshold value quantization in step 3.2 is a default value or a given threshold value.

Technical Field

The invention belongs to the technical field of nondestructive testing, and particularly relates to a material defect detection system based on a pulse reflection method and a detection method thereof.

Background

The nondestructive testing is a method for inspecting and testing the structure, the property, the state and the type, the property, the quantity, the shape, the position, the size, the distribution and the change of the defects inside and on the surface of a test piece by taking a physical or chemical method as a means and by means of modern technology and equipment and by utilizing the change of the reaction of heat, sound, light, electricity, magnetism and the like caused by the abnormal structure or the existence of the defects of a material on the premise of not damaging or not influencing the service performance of the tested object and not damaging the internal tissue of the tested object. Nondestructive testing is an indispensable effective tool for industrial development, reflects the industrial development level of a country to a certain extent, and has been acknowledged to be important. The current nondestructive testing methods mainly comprise four methods, namely Ray Testing (RT), Ultrasonic Testing (UT), magnetic powder testing (MT) and liquid Penetration Testing (PT).

Ray detection (RT) is observed by exposing a negative film to images of different blackness, using the transmission properties of various radiation sources to the material and the difference in the attenuation degree of different materials to the radiation. The ray detection can be used for detecting the three-dimensional defects such as air holes, slag inclusion, casting cavities and the like in the product. The method has the advantages that the detection result can be recorded as archival data for long-term storage, the detection image is visual, and the judgment on the size and the property of the defect is easy; the defect is that the crack surface is difficult to detect when the crack surface is nearly vertical to the ray, and the detection sensitivity to the micro crack is low, the production cost is high, the micro crack is harmful to human bodies, and protective equipment is needed. Magnetic particle testing (MT) utilizes the phenomenon that after a ferromagnetic material is magnetized, when magnetic lines of force meet defects such as cracks, the defects are bypassed, and magnetic leakage is generated, so that the defects are discovered. The magnetic powder detection equipment is simple, the operation is convenient, the sensitivity for detecting surface defects is high, and the defects are more visual; the disadvantage is that it is not sensitive to internal defects of the object. The magnetic powder inspection is suitable for detecting the discontinuity which is difficult to be seen visually when the surface and near surface of the ferromagnetic material are small in size and the gap is extremely narrow (for example, cracks with the length of 0.1mm and the width of micron order can be detected); the weld joints welded with the austenitic stainless steel material and the electrode cannot be detected, and the nonmagnetic materials such as copper, aluminum, magnesium, titanium, etc. cannot be detected. It is difficult to find shallow scratches on the surface, buried deeper holes, and delamination and folding at angles less than 20 ° to the workpiece surface. The penetration test (P T) is a test method which uses the physical property of liquid penetration, firstly, the colored penetrating liquid or fluorescent penetrating liquid is injected into the cracks of the surface opening, then the residual liquid on the surface is removed, and the penetrating liquid in the cracks is sucked out by the absorbent, thereby displaying the defect image. The defects that the internal defects of the product cannot be detected, and the reagent pollutes the environment and has certain toxicity; since only the surface distribution of the defects can be detected, it is difficult to determine the actual depth of the defects, and thus it is difficult to make a quantitative evaluation of the defects, and the detection results are greatly affected by the operator.

The principle of Ultrasonic Testing (UT) is a technique that studies reflected, transmitted and scattered waves by interaction of ultrasonic waves with a test piece, performs macroscopic defect detection, geometric characteristic measurement, detection and characterization of changes in tissue structure and mechanical properties of the test piece, and further evaluates the specific applicability thereof. The detection method is suitable for nondestructive detection of various test pieces such as metal, nonmetal, composite materials and the like; the method can be used for detecting the internal defects of the test piece in a large thickness range, for example, for metal materials, thin-walled pipes and plates with the thickness of 1-2 mm can be detected, and steel forgings with the length of several meters can also be detected; the defect positioning is accurate, and the detection rate of area type defects is high; the sensitivity is high, and the defect of small internal size of a test piece can be detected; and the detection cost is low, the speed is high, the equipment is portable, the device is harmless to human bodies and environment, and the field use is convenient.

Therefore, how to build a system to realize ultrasonic detection becomes an urgent problem to be solved.

Disclosure of Invention

In view of the problems in the background art, the present invention is directed to a system and a method for detecting material defects based on a pulse reflection method. The detection system adopts a reverse thought, utilizes the transmission characteristic that the input end and the coupling end of the directional coupler have certain coupling degree and the output end and the coupling end have high isolation degree, and connects a signal source with the output end, an ultrasonic probe with the input end and an oscilloscope with the coupling end, thereby realizing the acquisition of a probe reflection signal by the oscilloscope.

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

a material defect detection system based on a pulse reflection method comprises a pulse modulation signal source, a directional coupler, an ultrasonic probe and a signal processing module;

the pulse modulation signal source is connected with the output end (OUT) of the directional coupler, the ultrasonic probe is connected with the input end (IN) of the directional coupler, and the signal processing module is connected with the coupling end (CPL) of the directional coupler;

the pulse modulation signal source generates an electric signal which is transmitted to the ultrasonic probe through the directional coupler, the ultrasonic probe converts the electric signal into an ultrasonic signal and then acts on a sample to be detected, and then the ultrasonic probe receives a reflected signal and is coupled to the signal processing module through the directional coupler.

Further, the material defect detection system may further include a power amplifier disposed between the pulse modulation signal source and the directional coupler for amplifying the microwave signal.

Furthermore, the signal processing module comprises an amplitude limiter, a low noise amplifier, an oscilloscope and an industrial personal computer; the amplitude limiter is connected with a coupling end (CPL) of the directional coupler and is used for limiting a surface reflection signal of the sample to be detected, which is higher than a threshold value; the low-noise amplifier is connected with the amplitude limiter and is used for amplifying weak signals; the oscilloscope is connected with the low noise amplifier and is used for displaying signals detected by the ultrasonic probe; and the industrial personal computer is connected with the oscilloscope to perform wavelet denoising treatment.

Furthermore, the distance between the ultrasonic probe and the sample to be detected is 0.5-1 cm, and in order to eliminate air between the sample to be detected and the probe, a thinner air gap is filled with a coupling agent, so that the ultrasonic transmission is facilitated.

Further, the coupling agent is preferably glycerin or an ultrasonic coupling agent.

Further, the number of ports of the directional coupler should be greater than or equal to 3, and a three-port directional coupler is preferred.

Further, the directional coupler may be replaced with a three-port power splitter.

A detection method of a material defect detection system based on a pulse reflection method comprises the following steps:

step 1, testing the similar material of a sample to be tested without defects by using a material defect detection system to obtain a reflected signal, then testing the thickness of the sample, obtaining the propagation time of ultrasonic waves according to a surface echo signal and a bottom echo signal, and further obtaining the transmission speed of the ultrasonic waves;

step 2, detecting a sample to be detected to obtain a defect signal;

step 3, processing the defect signals obtained in the step 2 by adopting a wavelet analysis method to obtain the back-and-forth time t of the ultrasonic waves between the upper surface and the lower surface of the defect₁And t₂Further obtaining a time interval delta t;

and 4, calculating to obtain the defect depth according to the ultrasonic transmission speed calculated in the step 1 and the time interval delta t obtained in the step 3.

Further, the specific implementation steps of the wavelet analysis method adopted in the step 3 are as follows:

step 1: wavelet decomposition of the defect signal, selecting a wavelet and determining a decomposition level N, and then performing decomposition calculation;

step 2: threshold quantization of wavelet decomposition high-frequency coefficients, namely selecting one threshold for high-frequency coefficients under each decomposition scale to perform threshold quantization processing;

and step 3: and performing one-dimensional wavelet reconstruction according to the lowest layer low-frequency coefficient and each layer high-frequency coefficient of the wavelet decomposition to obtain a defect signal subjected to noise reduction.

Further, the threshold value of the threshold quantization in step 2 is a default value or a given threshold value.

The mechanism of the invention is as follows: the ultrasonic defect detection research is carried OUT based on the working principle of a directional coupler, wherein the working principle of the directional coupler is that signals are input from an IN port, output from an OUT port, and CPL is a coupling end and couples partial signals from the IN port; the OUT port has high isolation from the CPL port, and ideally, the signal of the OUT port is not coupled to the CPL port. By utilizing the working characteristics of the directional coupler, the detection system adopts a reverse thought, a transmitting signal is input from an OUT port, and an IN port is output to the ultrasonic probe; when the probe receives the reflected signal, the probe can be coupled to the CPL end from the IN port, and the CPL port is connected with an oscilloscope so as to receive the ultrasonic reflected signal. Because the OUT port and the CPL port have high isolation, a transmitting signal generated by the signal source cannot be coupled to the CPL port, and further a receiving signal of the oscilloscope cannot be influenced by the transmitting signal, so that the acquisition and analysis of a defective signal are facilitated, and the influence of source signal noise is reduced to a certain extent.

In addition, for the non-stationary process, the fourier transform has limitations, and only components of which frequencies are contained in a section of signal as a whole can be obtained, but the occurrence time of each component is unknown; two signals with very different time domains may be identical in spectrogram. The fourier transform is a superposition of the signal decomposed into a series of sine waves of different frequencies, and the wavelet transform is a superposition of the signal decomposed into a series of wavelet functions, wherein the wavelet functions are obtained by shifting and scaling a wavelet mother function. Clearly, approximating a sharply varying signal with an irregular wavelet function is superior to approximating it with a smooth sinusoid. Therefore, when the designed detection method is used for analysis, the wavelet analysis method is adopted to extract the defect echo signals, and the purpose is mainly to reduce or eliminate the noise mixed in the signals, so that the required defect echo signals are extracted. In ultrasonic detection, an echo signal received by a receiving probe contains useful signal components and noise components, and most of the noise signal is contained in details with high frequency, so wavelet coefficients obtained by decomposition can be processed by using forms of a threshold, a threshold and the like, and then the signal is subjected to wavelet reconstruction, so that the effect of denoising the signal is realized, and meanwhile, the detail part of the signal is also stored.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. when the directional coupler is used, a reverse thought is adopted as a core building detection system, the system adopts a single-probe form, electrical signals are converted into ultrasonic signals, meanwhile, a signal processing module is designed to filter noise signals and isolate interference of transmitted signals on received signals, and the whole test system is simple and easy to operate.

2. The detection system is adopted for detection, and the detection signals are analyzed by adopting a wavelet analysis method, so that the accurate judgment of the defect depth is realized, the nondestructive detection capability range of the material and the nondestructive detection efficiency and accuracy of key parts are improved, and the nondestructive detection technical guarantee is provided for the improvement of the material process.

3. The detection system can also realize the test of the material with larger loss, such as the composite material, solves the problem that the composite material is difficult to measure due to larger loss in the nondestructive detection of the composite material, and improves the capability of the nondestructive detection of the composite material.

Drawings

FIG. 1 is a schematic diagram of a material defect detection system according to the present invention.

FIG. 2 is a schematic diagram of the detection system according to the present invention in which probe reflection signals are acquired by an oscilloscope.

FIG. 3 is a schematic block diagram of a wavelet analysis method in the detection method of the present invention.

FIG. 4 is a waveform diagram of a reflected signal of the detection system of the present invention,

wherein, the upper graph is a waveform graph of the reflected signal without defects; the lower graph is a waveform of the reflected signal when defective.

FIG. 5 is a waveform diagram of the result of the detection method of the present invention after processing the reflected signal by wavelet analysis,

wherein, the upper graph is processed by adopting a default threshold value; the lower graph employs a given threshold process.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the following embodiments and accompanying drawings.

A material defect detection system based on a pulse reflection method is shown in a schematic diagram of fig. 1 and comprises a pulse modulation signal source, a power amplifier, a high-isolation directional coupler, an ultrasonic probe and a signal processing module; the signal processing module comprises an amplitude limiter, a low noise amplifier, an oscilloscope, an industrial personal computer and an AD (analog-to-digital) sampling; the pulse modulation signal source is connected with the output end (OUT) of the directional coupler through the power amplifier, the ultrasonic probe is connected with the input end (IN) of the directional coupler, and the amplitude limiter IN the signal processing module is connected with the coupling end (CPL) of the directional coupler; the amplitude limiter, the low noise amplifier, the oscilloscope, the AD sampling and the industrial personal computer are connected in sequence.

The detection system adopts a single probe form, the probe transmits and receives signals and is positioned on the upper side of the surface of a sample to be detected, the probe is in direct contact with the sample to be detected, and in order to eliminate air between the sample to be detected and the probe, a thinner air gap between the sample to be detected and the probe is filled with a coupling agent, so that the transmission of ultrasonic waves is facilitated.

The pulse signal source in the detection system adopts a signal generator with model number 33220A manufactured by Agilent. The signal source can generate waveforms such as sine waves, square waves, triangular waves and the like, and the maximum frequency is 6 MHz; AM, FM, PM, FSK and PW M modulation are supported; linear and logarithmic scan and burst modes; the signal amplitude ranges from 10mVpp to 10 Vpp.

The signal amplifier adopts a power amplifier, the frequency is 1MHz-700MHz, and the gain is 35 dB. The amplifier is mainly used for amplifying signals of a front-end signal generator, and is beneficial to transmission of ultrasonic signals, but the defect is obvious, namely noise signals are also amplified, so that noise reduction measures need to be taken in the system.

The model of the ultrasonic probe is GAB462, the working frequency is 5MHz, and the bandwidth can cover 1 MHz. The probe is used for converting the electric signal into an ultrasonic signal for ultrasonic defect detection.

The type of the amplitude limiter is HP 5086-. When the defect signal is weak, the reflection signal of the sample to be detected is too large, and the oscilloscope is not easy to display the defect signal, so that the amplitude limiter can be adopted to limit the surface reflection signal of the sample to be detected; when the signal is below the slicer threshold, the signal remains intact and above the threshold becomes the threshold voltage. By which defect signal discrimination is facilitated. Because the IN end of the directional coupler is coupled to the CPL end and has certain energy attenuation, the back end of the directional coupler needs to adopt low-noise amplification. The low-noise amplifier is used for a CPL port of the directional coupler, has the main function of amplifying signals, has a low noise coefficient, is suitable for amplifying weak signals and has a higher signal-to-noise ratio.

The oscilloscope model is HANTEK 6000BD, is a portable programmable oscilloscope, can communicate with P C computer through USB interface, and is controlled by C + + program and API function provided by the oscilloscope. The sampling rate of the oscilloscope is 1GSa/s, and the analog bandwidth is 70 MHz.

Fig. 2 is a schematic diagram of a probe reflected signal of the detection system of the present invention obtained by an oscilloscope, and as shown IN fig. 2, the present invention utilizes the operating characteristics of a directional coupler and adopts a reverse concept, a signal source transmits a signal to be input from an OUT port and output from an IN port to an ultrasonic probe. When the probe receives the reflected signal of the sample to be detected, the probe can be coupled to the CPL end from the IN port, the CPL port is connected with the oscilloscope, so that the ultrasonic reflected signal can be received, and meanwhile, because the signal source transmits a signal and has the function of high isolation from the reflected signal, the detection system can remove the influence of the source signal, is beneficial to acquiring and analyzing a defect signal, and simultaneously reduces the influence of noise of the source signal to a certain degree.

In the ultrasonic detection process, instrument factors such as fluctuation of power supply voltage, electrostatic interference, poor grounding and the like and scattering and reflection echoes caused by the fact that ultrasonic waves meet a heterogeneous interface and crystal grains when propagating in a detected object can affect defect echoes, and noise signals generally show a flat broadband characteristic, so that the noise signals can be considered as additive white Gaussian noise in research. Thus, the output signal of the receiving transducer is the echo signal plus additive noise. After the ultrasonic echo signal is mixed with noise, the waveform of the ultrasonic echo signal is expanded on a time axis, and the frequency band becomes wider. One of the important applications of wavelet time-frequency analysis is to reduce or eliminate noise mixed in signals, and in ultrasonic detection, echo signals received by a receiving probe contain useful signal components and noise components. Useful signals in the engineering field are usually low frequency signals or some relatively stationary signals, while noise appears as high frequency signals. In order to reduce the noise effect, we can apply the following method to perform noise reduction processing on the signal: the method comprises the steps of firstly carrying out wavelet decomposition on signals, processing wavelet coefficients obtained by decomposition by using forms of threshold, threshold and the like because most of noise signals are contained in details with high frequency, and then carrying out wavelet reconstruction on the signals, thus achieving the effect of denoising the signals.

A detection method of a material defect detection system based on a pulse reflection method comprises the following steps:

step 1, testing the similar material of a sample to be tested without defects by using a material defect detection system to obtain a reflection signal, then testing the thickness of the sample, obtaining the propagation time of ultrasonic waves according to a surface echo signal and a bottom surface echo signal, and further obtaining the transmission speed of the transmitted sound waves, wherein the reflection signal is shown in an upper graph of FIG. 4;

step 2, detecting the sample to be detected to obtain a defect signal, wherein the reflected signal is shown in the lower graph of FIG. 4;

step 3, processing the defect signals obtained in the step 2 by adopting a wavelet analysis method to obtain the back-and-forth time t of the ultrasonic waves between the upper surface and the lower surface of the defect₁And t₂And further obtaining a time interval Δ t, wherein a schematic block diagram of the wavelet analysis method is shown in fig. 3, and the specific process is as follows:

step 3.1, wavelet decomposition of the one-dimensional signal, selecting a wavelet and determining a decomposition level N, and then performing decomposition calculation;

step 3.2, threshold quantization of wavelet decomposition high-frequency coefficients, namely selecting one threshold for high-frequency coefficients under each decomposition scale to carry out threshold quantization processing;

3.3, performing one-dimensional wavelet reconstruction according to the lowest layer low-frequency coefficient and each layer high-frequency coefficient of the wavelet decomposition;

and 4, calculating to obtain the defect depth according to the ultrasonic transmission speed obtained by the calculation in the step 1 and the round-trip time obtained in the step 3.

The signal is denoised by wavelet analysis, and three methods of default threshold denoising treatment, given threshold denoising treatment and forced denoising treatment can be selected. The default threshold denoising method is to generate a default value of a signal by using a one-dimensional wavelet function ddencmp for signal denoising in an MATLAB wavelet analysis tool box, and then denoise by using another function wdencmp; the given value denoising method needs to obtain an actual threshold value through an empirical formula; the forced denoising method is to set all high-frequency coefficients in the wavelet decomposition structure to 0, i.e. to filter all high-frequency parts, and then to reconstruct the signal, which is easy to lose useful components in the signal, so the operability is not high, and the former two denoising methods are mainly adopted in the processing of ultrasonic detection defect echo signals. In order to determine a more suitable threshold denoising method, on the premise that the sym8 wavelet is selected as the wavelet basis and 6 layers are decomposed, denoising processing is performed on a noisy ultrasonic detection echo signal by adopting two methods, namely a default value method and a given threshold value method, respectively, and the obtained result is shown in fig. 5.

The C-C composite material is a composite material obtained by reinforcing carbon with carbon fibers, has the advantages of high specific strength, high specific modulus, fatigue resistance, high temperature resistance, stable structure size, strong designability and the like, is a structure and functional material widely applied in the field of aerospace, and the detection and research on the interface performance of the material are the key for realizing the process optimization and performance prediction of the composite material.

Example 1

A method for detecting an arc-shaped C-C composite material by a material defect detection system based on a pulse reflection method comprises the following steps:

step 1, testing an arc-shaped C-C composite material without defects by using a material defect detection system to obtain a reflection signal, then testing the thickness of a sample to be 6.5mm, obtaining the propagation time of ultrasonic waves under 5MHz and 10V output signals according to a surface echo signal and a bottom echo signal to be 2.517 mu s, and calculating the transmission speed of the ultrasonic waves to be 5164.8m/s because the propagation path of the ultrasonic waves inside is twice the thickness;

step 2, detecting a sample to be detected, and respectively obtaining defect signals at two positions;

step 3, processing the two defect signals obtained in the step 2 by adopting a wavelet analysis method to obtain the time interval delta t of the ultrasonic wave at two different positions₁1.582. mu.s and Δ t₂1.262 mu s;

step 4, calculating the ultrasonic transmission speed obtained in step 1 and the time interval delta t obtained in step 3₁And Δ t₂And the defect depths of the material to be detected at the two defect positions are calculated to be 4.085mm and 3.259mm respectively.

Example 2

The rectangular shaped C-C composite was tested for defects according to the procedure of example 1.

The test results of example 1 and example 2 show that the shape of the material does not affect the defect test results of the inspection system of the present invention.

Example 3

And (3) grooving test: and (3) carrying out slotting treatment on the C-C composite material, wherein the slots are defects, the three positions are marked as numbers 1, 2 and 3, and the actual measurement of the depth of the slot defect is 1mm, 2.09mm and 3.1mm respectively. The depth of the defect is known in this example for position No. 1, where the inspection is performed to obtain the ultrasonic propagation velocity, and then the other two defect positions are verified.

The testing system provided by the invention is used for detecting the slotted C-C composite material, and comprises the following steps:

step 1, testing the No. 1 position of the C-C composite material to obtain a defect signal, and processing the defect signal by using a wavelet analysis method to obtain the time interval delta t of the No. 1 position of ultrasonic waves under the output signals of 5MHz and 10V₁0.408 mus, the speed of sound of the ultrasound in the material is about 4902m/s due to the 2 defect depth positions of the ultrasound stroke;

step 2, continuously detecting the No. 2 position and the No. 3 position of the sample to be detected to obtain the defect signals of the No. 2 position and the No. 3 position;

step 3, processing the defect signals obtained in the step 2 by adopting a wavelet analysis method to obtain the time interval delta t of the ultrasonic waves at the No. 2 position and the No. 3 position₂Is 0.808 μ s, Δ t₃1.328 μ s;

and 4, calculating to obtain the defect depth of the No. 2 position as 1.98mm and the defect depth of the No. 3 position as 3.259mm according to the ultrasonic transmission speed obtained in the step 1 and the time interval obtained in the step 3.

According to the test result, the error between the detected defect depth of the No. 2 position and the actual measurement value is about 0.1 mm; the error between the detected defect depth of the No. 3 position and the actual measurement value is about 0.2mm, which shows that the defect detection system has higher detection accuracy.

While the invention has been described with reference to specific embodiments, any feature disclosed in this specification may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise; all of the disclosed features, or all of the method or process steps, may be combined in any combination, except mutually exclusive features and/or steps.