A method for nondestructive ultrasonic testing of pipeline pressure outside the pipeline

Abstract

The present invention relates to the field of detection, and specifically to a method for off-pipe ultrasonic non-destructive detection of pipeline pressure. The method comprises the following steps: fixing two ultrasonic guided wave transmitting probes on the outer wall of the pipeline, a detection system issuing a test command, the ultrasonic guided wave transmitting probe outputting a pulse signal which is incident on the pressure pipeline, the incident ultrasonic signal undergoing waveform conversion at the probe-pipe wall medium interface, the ultrasonic guided wave receiving probe receiving refracted shear waves propagating along the pipe diameter into the pipeline wall and reflected longitudinal waves propagating along the fluid direction of the inner and outer pipe walls, and sending the received ultrasonic signal which has undergone multiple waveform conversions from reflected shear waves to reflected longitudinal waves into the detection system, establishing an ultrasonic-based pressure measurement model, and calculating the fluid pressure and fluid medium flow rate. This off-pipe non-destructive detection of pipeline pressure based on the ultrasonic principle not only has no pressure loss and does not destroy the fluid flow field, but is also highly practical and overcomes the shortcomings of previous contact measurement. It is also easy for on-site workers to operate and is convenient to carry.

Description

Technical Field

[0001] The invention relates to the field of measurement and detection of ultrasonic signal processing, in particular to a method for ultrasonic non-destructive detection of pipeline pressure outside the pipeline. Background Art

[0002] Pressure is one of the key parameters reflecting the operating status of liquid and gas pipeline systems. Pressure measurement is crucial for the safe operation and real-time monitoring of pipeline systems. Pressure pipelines are tubular structures that withstand internal and external pressure and are assembled from numerous pressure-bearing and supporting components. With the increasing scale of modern engineering construction, steel pressure pipelines are widely used. They are used to varying degrees in various industries, including chemical, petroleum, pharmaceutical, energy, aviation, environmental protection, steel, and public works. They are considered the fifth mode of transportation in modern society, alongside roads, railways, aviation, and shipping. The current number of pressure pipelines is enormous. According to incomplete statistics, industrial pipelines in various production facilities at domestic industrial enterprises span hundreds of thousands of kilometers. The water pipe network is like the human body's vascular system. It is complex and must be protected from blockage or damage, otherwise it will cause significant problems. Similarly, pipe ruptures and blockages can affect the smooth flow of industrial drainage and potentially cause serious accidents. In the safety management of pressure pipelines, inspection is one of the most direct and effective methods to prevent accidents such as leaks, explosions, and instability. With the accelerated pace of urban modernization, the number of pressure pipelines in various industries is increasing exponentially. This has also led to an increase in the application of pipeline equipment, and at the same time, for pressure pipeline safety accidents. The hydraulic system, which is currently widely used in various mechanical equipment and automatic control systems, has the characteristics of large power transmission, small structure, and fast response. However, since all components and working fluids in the system work in a closed oil circuit, it is generally not allowed to drill holes on it to install measuring equipment. There is no reserved detection interface during manufacturing, which brings great difficulties to the system status detection and fault repair. At present, my country's pipelines are facing increasingly complex and harsh service conditions, and there are many hidden dangers in the pressure pipelines in use. Because the working conditions and installation environment of the pipeline are generally harsh, pipeline corrosion is inevitable. For example, due to the influence of factors such as the erosion of the conveying medium, surrounding environmental factors, and unreasonable installation, internal and external corrosion of the pipeline, collision and friction, and medium leakage accidents caused by them occur frequently. There are many difficulties in pipeline detection:

[0003] (1) Many pipes have insulation layers, and accurate inspection cannot be performed without removing the insulation layers, which is very expensive.

[0004] (2) The pipeline inspection operation distance is long, the line changes are complex, the installation and burial environment changes a lot, there are many obstacles and shielding along the pipeline, and many places cannot be touched or approached;

[0005] (3) Visual inspection is limited. The interior of most pipelines is inaccessible and the exterior has anti-corrosion or insulation layers.

[0006] The cost of removing and installing insulation is typically several times the cost of inspection, significantly increasing testing costs and preventing access to critical, inaccessible areas. Currently, conventional non-destructive testing methods such as radiography and ultrasound are primarily used for inspecting steel pressure pipelines in my country. These methods cannot achieve 100% inspection, are prone to missed detections and misjudgments, and suffer from low accuracy and efficiency. Furthermore, the complete removal of insulation is required, resulting in significant losses and prolonged repair time. Traditional pressure testing methods mostly rely on invasive pressure measurement, which compromises pipeline integrity and poses safety risks under high pressure. In this context, non-invasive testing methods have become the best solution. Currently, non-invasive pressure testing methods primarily include resistance strain gauge and ultrasonic methods. The resistance strain gauge method typically involves installing a pressure sensor at the test point. The pressure sensing element directly contacts the measured medium, converting the pressure value into an electrical signal and transmitting it via a method suitable for the site, including wired or wireless methods. This method offers the advantages of simplicity and directness, as the sensor directly senses pressure changes. However, when using this method to measure, the pressure sensor must be installed at the measured point, which is not allowed in many situations. Another disadvantage of this method is that the flow field of the fluid in the pipeline will be disturbed.

[0007] Nondestructive testing (NDT) technology is widely used in routine inspections of pressure pipelines, ensuring their safety and performance. NDT refers to structural inspection and testing methods that employ advanced technology and equipment to determine the internal and surface properties and conditions of pipelines without damaging the test piece, using physical or chemical methods. It involves testing materials or components without damaging them or affecting their performance or future use. Common NDT methods include ultrasonic testing (UT), penetrating testing (PT), radiographic testing (X-ray), and magnetic particle testing (MT). Key testing items include thickness measurement and crack detection. Within ultrasonic testing, the ultrasonic out-of-pipe measurement method obtains oil pressure information by detecting ultrasonic echoes. It offers advantages such as non-destructive flow field detection, lack of mechanical inertia, fast transient response, strong dynamic measurement capabilities, and easy installation. Ultrasonic waves propagate in fluid media such as gases and liquids as longitudinal waves. The propagation speed of ultrasonic waves in oil is affected by the oil pressure, allowing oil pressure to be measured by measuring the ultrasonic propagation time. Ultrasonic nondestructive testing (NDT) uses ultrasound to collect defect information from thin to thick, from the surface to the inside, to inspect the internal quality of welds. If the measured wall thickness is less than the minimum wall thickness of the container, a strength recalibration should be performed, and pressure reduction or repair measures should be proposed. Ultrasonic NDT allows for rapid quantitative defect assessment, facilitates on-site inspection, is convenient for analysis, and has a high degree of automation. When ultrasonic waves propagate in hydraulic pipelines, the pressure increases, causing the oil density to increase and the compressibility to decrease, thereby increasing the speed of sound. Furthermore, at a certain temperature, the speed of sound increases linearly with increasing hydraulic oil pressure. By using the change in ultrasonic wave propagation time to represent the change in sound wave propagation speed, the change in ultrasonic wave propagation time can be used to deduce the change in ultrasonic wave velocity in the fluid, and thus determine the change in fluid pressure. When ultrasonic waves propagate in a fluid, the fluid pressure affects the propagation speed of the ultrasonic wave. Therefore, by converting the sound velocity measurement into pressure, the pressure can be obtained. This is a non-contact ultrasonic pressure testing method. Compared to traditional contact testing methods, it offers advantages such as flexible installation and no changes to the fluid state. However, a large amount of data indicates that research on non-contact ultrasonic pressure parameter detection is still in the exploratory stage. At a certain temperature, the speed of sound increases linearly with increasing oil pressure. This linear relationship is particularly stable under high pressure and within a narrow temperature range, so the fluid pressure can be calculated by detecting changes in the speed of sound. However, directly measuring the velocity of ultrasound in oil is difficult. This is because ultrasonic pulse reflection testing has blind spots, and defect orientation affects detection sensitivity. Surface and near-surface defects parallel to the workpiece surface are relatively difficult to detect. Complex specimen shapes also present implementation challenges for ultrasonic testing.Due to certain internal structures of materials, such as grain size, phase composition, non-uniformity, and non-compactness, the detection sensitivity and signal-to-noise ratio of small defects will be reduced. When qualitative or quantitative characterization of material defects is required, experienced personnel are required to operate the test, otherwise the detection accuracy will be reduced.

[0008] In order to solve the technical problem of rapid detection of corrosion defects in pressure pipelines, existing technologies usually adopt Figure 8 The following figure illustrates the propagation mechanism of ultrasound within a pipe. These propagation mechanisms are generally categorized as through-beam and horizontal oblique-incidence. In the through-beam method, ultrasonic straight probes (ultrasonic probes 1 and 2) transmit and receive ultrasonic signals, or probe 1 serves as both the transmitter and receiver. Installation of the through-beam method is relatively simple and straightforward, but multiple reflections of ultrasound within the pipe can lead to significant signal overlap, making extraction difficult. In practice, the horizontal oblique-incidence ultrasonic excitation and receiving probes (ultrasonic probes 1 and 3) are fixed parallel to each other on the outside of the pipe wall. Pulse straight probes are used and symmetrically mounted on the side of the pipe using a clamp. The frequency of the ultrasound wave must be determined based on the medium and operating environment. High frequencies produce a narrow beam, concentrated energy, and high resolution, but they also exhibit significant attenuation. This is particularly true when testing rough pipe surfaces. Ultrasonic waves within certain frequency ranges, which can propagate over long distances within tubular metal materials or components, scatter significantly and are difficult to penetrate. Since the detection time delay characteristics have a nonlinear relationship with pipeline pressure, and this relationship changes with changes in system pressure, pipeline diameter, wall thickness and material, fluid type, and temperature; at the same time, the nonlinear relationship model is unclear, and currently only an approximation of the original model is obtained.

[0009] In recent years, with the continuous advancement of science and technology, nondestructive testing (NDT) has become a primary method for pressure pipeline inspection. Ultrasonic guided wave (UGW) testing (UTT) has become a new favorite in this field. Ultrasonic guided wave testing (UGW) technology has been continuously refined and its accuracy has increased significantly in pressure pipeline inspections. Ultrasonic guided waves are capable of propagating ultrasound waves of a specific frequency range over long distances in tubular metal materials or components. Ultrasonic guided waves in pipes typically include four waveform types: longitudinal, torsional, flexural, and circumferential. Flow device calibration standards are also diverse. Theoretically, many methods for generating guided waves exist, including normal ultrasound incidence, electromagnetic transducers, comb transducers (transducer arrays), and oblique longitudinal wave transducers (with an incident angle of longitudinal waves) with oblique incident conversion. Oblique longitudinal wave transducers offer a precise and effective method for generating guided waves. In pipes, guided waves can exist in various waveforms, including longitudinal, torsional, and flexural waves, and their propagation behavior is complex. Domestic research on guided wave inspection technology is still primarily in the theoretical research stage. While there has been some exploratory study of pipeline dispersion curves, there are no domestically developed probes and instruments suitable for practical pipeline ultrasonic guided wave inspection. The development of ultrasonic guided wave probes and equipment is still in the laboratory development stage. The main challenges in probe development lie in the impact of background noise and wave scattering on the inspection process, as well as the energy attenuation of guided waves during propagation. Due to dispersion, the signal's time domain width increases while its amplitude decreases with increasing propagation distance. This signal broadening makes it difficult to extract characteristic signals, and the reduction in wave packet peak value significantly reduces detection sensitivity. These two factors significantly impact the effectiveness and accuracy of flaw detection. Ultrasonic guided wave testing (UGW) differs significantly from traditional ultrasonic testing. The key difference lies in that traditional ultrasonic testing can only inspect a single test point. Conventional methods typically involve performing ultrasonic thickness measurements and spot checks on the surface of a cleaned pipe. In contrast, UGW can inspect 100% of the material quality of a long, extended pipeline from a single test point, and can quickly detect internal and external corrosion and other defects. Guided wave testing is particularly effective in difficult-to-inspect pipeline sections compared to conventional ultrasonic testing. Furthermore, UGW outperforms traditional ultrasonic testing in detecting cracks and metal loss (greater than 3% of the cross-section). UGW uses a probe to detect corrosion without removing the surface paint. UGW can inspect onshore and offshore pipelines, even in densely populated areas, overhead pipelines, underground pipelines, and various insulated pipelines. UGW can inspect hundreds of meters per day, achieving 100% inspection in a single test. However, UGW also has its limitations in pipeline inspection. First of all, ultrasonic guided wave testing is a fast and large-scale preliminary detection method that can evaluate the safety of the pipeline system and determine normal and suspicious areas.However, it cannot conduct a qualitative analysis of the detected defects. The defect location is to determine the approximate range of the defect, and then use other detection methods to make a final comprehensive evaluation. Secondly, guided wave detection is more sensitive to defects that cause large metal defect areas on the annular section of the pipeline, while defects with small circumferential metal defect areas, such as single point defects and axial strip defects, as well as axial cracks, are more difficult to detect. Then, the changing structure of the annular section of the pipeline will also affect the detection accuracy and the length of one-time detection. The weld excess height and the shape of the elbow will affect the detection of defects in the location. Defects in the tee are more difficult to detect, and guided wave transmission cannot pass through the flange. It is difficult to interpret the detection results of complex pipeline systems.

[0010] Ultrasonic nondestructive testing of pipelines requires not only detecting the presence of defects but also locating them. Accurately calculating the arrival time and diffraction transit time of ultrasonic echoes is key to solving this problem. The ultrasonic echo signals received by ultrasonic sensors are affected by the detection system's time response and noise, resulting in reduced resolution. Although echoes from small defects can be detected through filtering, if a near-surface defect exists within the pipeline, the echoes from the near-surface defect will be mixed with the echo from the pipe wall. The acquired time domain signal will only show echoes from the inner and outer surfaces, with no clear echo between them. In this case, traditional methods are unable to detect the defect echo from the received ultrasonic echo signal, making it easy to miss defects. The prevalence of near-surface defects in pipelines is far higher than that of other types of defects. Detecting near-surface defects is a key task in pipeline defect detection. The ultrasonic signal collected by pipeline ultrasonic testing can be viewed as the convolution of the system time response and the ultrasonic reflection sequence. If the reflection sequence can be recovered from the measured ultrasonic signal or an optimal estimate of the reflection sequence can be found, then the arrival time and reflection coefficient of the ultrasonic echo can be given by the reflection sequence, thereby separating the near-surface defect echo, solving the problem of difficult detection of near-surface defects. The application of deconvolution technology can effectively restore the ultrasonic reflection sequence. Typical deconvolution methods include least squares deconvolution, predictive deconvolution, homomorphic deconvolution, and minimum entropy deconvolution. Since predictive deconvolution and homomorphic deconvolution have the properties of inverse filtering, the deconvolution problem is not difficult to solve when the system is linear and in minimum phase. When the system is non-minimum phase or nonlinear, it is more difficult to apply these two methods for deconvolution, and sometimes pathological phenomena will occur. While least-squares deconvolution can be used for both minimum-phase and non-minimum-phase systems, it generally requires the derivation of a linear system with a Toeplitz matrix. While this can often be solved using methods such as matrix inversion, Levison recursion, and the conjugate gradient method, the condition number of the Toeplitz matrix can be very large, leading to ill-posed problems, poor numerical stability, and even inability to solve the problem. Because ultrasonic signals exhibit both nonlinearity and non-minimum-phase characteristics, conventional deconvolution algorithms are difficult to obtain the desired solution. If two ultrasonic echoes are very close, minimum entropy deconvolution fails. This result is due to the inherent properties of minimum entropy deconvolution. Summary of the Invention

[0011] In response to the shortcomings of the existing technology, the present invention provides a pipeline detection method that has no pressure loss, does not destroy the fluid flow field, has strong anti-interference ability, is highly practical, is simple and flexible to operate, is easy to use, has a fast detection speed, accurate results, and is low-cost and highly efficient.

[0012] To achieve the above technical effects, the technical solutions of this application are as follows:

[0013] A method for nondestructive ultrasonic testing of pipeline pressure outside the pipeline comprises the following steps:

[0014] The ultrasonic guided wave transmitting probe 1 and the ultrasonic guided wave receiving probe 2 are fixed on the outer wall of the pipeline in a parallel installation manner, and a spacing distance is set between the ultrasonic guided wave transmitting probe 1 and the ultrasonic guided wave receiving probe 2. The detection system of the ultrasonic guided wave transmitting probe 1 and the ultrasonic guided wave receiving probe 2 is connected, and the detection software in the detection system is set. The internal pressure of the pipeline is adjusted by the standard pressure source of the connected pressure pipeline. The single-chip microcomputer of the detection system issues a test command. The ultrasonic guided wave transmitting probe 1 outputs a pulse signal with a frequency of 2.5MHz and an amplitude of 150V through the piezoelectric chip on the oblique inner pipe wall of the organic glass wedge, and incidents the ultrasonic signal into the pressure pipeline at an incident angle β. The incident ultrasonic signal undergoes waveform conversion at the probe-pipeline wall medium interface. The ultrasonic guided wave receiving probe 2 receives the refracted shear wave propagating along the pipe diameter into the pipeline wall and the reflected longitudinal wave propagating along the fluid direction of the inner and outer pipe walls, and transmits the received reflected shear wave to the reflection The ultrasonic signal with multiple waveform conversions of longitudinal waves is sent to the detection system, and an ultrasonic-based pressure measurement model is established to determine the pressure of the fluid and the flow velocity of the fluid medium. The instantaneous flow rate and cumulative flow rate of the fluid are calculated using known parameters. The detection delay characteristics have a nonlinear relationship with the pipeline pressure and are compared with the delay measurement value. The ultrasonic propagation delay is calculated using a sparse deconvolution algorithm. K static convolution kernels are adaptively aggregated, and multiple convolution kernels are dynamically aggregated into a convolution weight matrix. The network output results are used to evaluate the network performance, and a nonlinear mapping relationship between pressure and sound velocity is established. According to the narrowband and super-Gaussian properties of the ultrasonic signal, atoms in the complete atomic library are selected. The genetic algorithm is used to optimize the weights and thresholds of the BP-neural network for prediction, and the sound velocity of the ultrasonic wave in the fluid is obtained. The corresponding relationship between the sound velocity and pressure and the corresponding relationship between the acoustic parameters and pressure are found. Non-invasive pressure detection is achieved by measuring the time delay.

[0015] Furthermore, based on the real-time pressure inside the pipeline provided by the standard pressure source, the fluid pressure and the flow rate of the fluid medium are indirectly calculated using the time difference of ultrasonic wave propagation in the flowing medium, or the fluid pressure and the flow rate of the fluid medium are calculated based on the Doppler effect of ultrasonic wave in the fluid.

[0016] Furthermore, the ultrasonic guided wave transmitting probe 1 utilizes the piezoelectric effect based on the piezoelectric chip, and contacts the ultrasonic oblique single crystal probe at an excitation angle through the inner pipe wall of the organic glass wedge, excites the guided wave longitudinal wave, and is incident on the inner pipe wall of the pipe through the sound-transmitting oblique wedge, and is incident on the surface of the pipe workpiece at an incident angle and speed. The wave undergoes waveform conversion, reflection, and refraction at the interface of the inner pipe wall. According to the law of reflection and refraction of the wave, longitudinal waves, transverse waves or surface waves are generated in the pipe. After the emitted sound wave enters the pipe, it propagates along the axial direction of the pipe. A part of the incident longitudinal wave propagates axially along the outer surface of the pipe to form a critical refraction. The critical refracted longitudinal wave propagates in a straight line along the pipe wall at a certain incident depth, and continues to generate the first reflected longitudinal wave and the second reflected longitudinal wave on the outer wall similar to the critical refracted longitudinal wave, the first reflected longitudinal wave and the second reflected longitudinal wave received by the ultrasonic guided wave receiving probe 2, and the first inner wall reflected longitudinal wave and the second inner wall reflected longitudinal wave propagating along the inner pipe wall and being collected and received by the ultrasonic guided wave receiving probe 2 for guided wave data collection; the other part of the sound wave propagates along the pipe diameter and enters the pipe wall and is refracted into a refracted shear wave. The refracted shear wave takes the first inner wall reflected longitudinal wave and the second inner wall reflected longitudinal wave as the base, and is refracted along the refraction angle β. s The first reflected shear wave and the second reflected shear wave are connected end to end at an angle, and the third inner wall reflected shear wave and the fourth inner wall reflected shear wave are connected end to end, and triangular waveform propagation occurs in the pipe wall. Similarly, when reaching the inner pipe wall, waveform conversion occurs again to generate the first reflected shear wave, and after reaching the outer pipe wall, the second reflected shear wave is generated obliquely downward, and then the third reflected shear wave is generated upward, and the fourth reflected shear wave is generated obliquely downward, and so on. The ultrasonic guided wave receiving probe 2 receives the critical refracted longitudinal wave, the first reflected longitudinal wave, the second reflected longitudinal wave, ... in sequence.

[0017] Furthermore, the ultrasonic wave is incident from the ultrasonic guided wave transmitting probe 1 into the pressure pipe, the incident depth and the frequency are inversely proportional, and the propagation delay is directly proportional to the sensitivity of the pressure change and the frequency. After multiple waveform conversions, the critical refracted longitudinal wave propagates in a straight line along the pipe wall and is received by the ultrasonic guided wave receiving probe 2. The reflected longitudinal wave is converted into a shear wave and a longitudinal wave, and the propagation process of the reflected longitudinal wave is divided into two parts: propagation in the wall thickness in the form of a shear wave and propagation in the inner and outer surfaces of the pipe wall in the form of a longitudinal wave.

[0018] Furthermore, the relationship between time delay and pipeline pressure is:

[0019] Pressure change inside the pipeline

[0020]

[0021] The velocity of longitudinal waves at normal pressure is

[0022]

[0023] The acoustic elastic coefficient L1 of the longitudinal wave propagating in the pipe

[0024]

[0025] The acoustoelastic coefficient L2 of the shear wave propagating in the pipe

[0026]

[0027] The pressure change value Δp inside the pipeline,

[0028] Where, E is the elastic modulus of the pipe, d is the pipe wall thickness, and R is the average radius of the pipe. is the transit time change under the measured pressure, D is the ultrasonic propagation distance, is the transit time at normal pressure, is the transition thickness, Δt Lre is the change in the transit radius time, V L is the velocity of longitudinal wave under the measured pressure, t L is the transit time under the measured pressure condition, l is the signal length, λ is the wavelength, m is the mass density, P is the fluid pressure, μ is the proportional coefficient, v is the sound wave velocity, n is the number of ultrasonic guided wave receiving probes, β s is the refraction angle, Δt L is the time interval of the flight.

[0029] Furthermore, the detection system includes: a field programmable logic gate array FPGA module and a time-to-digital converter TDC module connected to each other, as well as an ultrasonic excitation module, a signal conditioning module for receiving ultrasonic guided wave probe signals, a data processing and display module, and a power supply module respectively connected to both sides of the time-to-digital converter TDC module.

[0030] Furthermore, the time-to-digital converter (TDC) module compensates for changes in temperature and voltage, and uses the propagation delay of signals through internal gate circuits to perform high-precision time interval measurements. The field-programmable gate array (FPGA) module displays the absolute interval time measured and transmits control and data to the time-to-digital converter (TDC) module.

[0031] The input signal of the ultrasonic excitation module to stimulate the ultrasonic guided wave transmitting probe 1 is generated by the time-to-digital converter TDC module, which contains multiple square wave pulse trigger signals with fixed duty cycles. After passing through the isolation and push-pull drive module, it acts on the ultrasonic guided wave receiving probe 2. The ultrasonic signal propagating in the pipe wall is received by the ultrasonic guided wave receiving probe 2 after a complex propagation and conversion process. After being processed by the signal conditioning circuit of the signal conditioning module, it is received by the time-to-digital converter TDC module, realizing the measurement of converting time into digital data, and realizing the communication calculation and storage of ultrasonic propagation delay inside the field programmable logic gate array FPGA module.

[0032] Furthermore, the power module generates charging and discharging waveforms, and the time-to-digital converter (TDC) module samples and counts the time range to be measured using a clock signal. The module calculates the time value based on the count value, performs relevant hardware debugging and experimental verification in a relatively short period of time, and completes the measurement of the time interval from the start signal to the end signal.

[0033] Furthermore, the detection system is powered on, and the system clock setting, pin function definition, time-to-digital converter (TDC) module timing function setting, and interrupt initialization are completed. The system enters a cyclic operation and waits for a timer interrupt. During the configuration process, the timer is set to interrupt once every 1 second, and the transit time is measured in the interrupt program. When the timer interrupt is entered, the control code is written through the serial peripheral interface (SPI) communication, and the time-to-digital converter (TDC) module starts working. The time-to-digital converter (TDC) module sends an excitation pulse and starts timing. The SPI communication reads the three transit time values stored in the three 32-bit result registers inside the time-to-digital converter (TDC) module, and the data format is processed in the SPI receive interrupt. The system returns to the cyclic operation and waits for the timer interrupt to perform the next measurement. The data processing and display module displays the measurement results and uploads the data to the host computer via the EtherCAT bus.

[0034] Furthermore, the detection system establishes an ultrasonic pressure measurement model based on the sound velocity relationship between pipeline pressure, strain and stress. Specifically, for thin-walled pipelines, ignoring the radial stress along the wall thickness direction, the relationship between strain and stress can be expressed by the circumferential and axial stresses, that is,

[0035]

[0036] The ultrasonic pressure measurement model uses two zero-phase filters. After the two ultrasonic signals χ1(t) and χ2(t) pass through the two zero-phase filters respectively, the time delay Δt of the two signals is calculated using the cross-correlation delay estimation module.

[0037] Among them, ε A , ε R , ε C are the three-dimensional strains in the axial direction A, radial direction R and circumferential direction C, E is the elastic modulus of the pipe, v is the wave velocity under the measured pressure, σ h represents the radial stress along the wall thickness direction, σ θ represents the transverse stress along the shear wave refraction angle, and θ represents the shear wave refraction angle.

[0038] Furthermore, the ultrasonic pressure measurement model constructs a more robust sparsity measurement function and a nonlinear transformation function based on the properties of sparsity. After nonlinear transformation, the sparse sequence becomes even sparser. Subsequently, a nonlinear minimum entropy deconvolution algorithm is designed based on the ultrasonic Gaussian properties of the ultrasonic signal. The ultrasonic pressure measurement model constructs a sparse compression atom library and a deconvolution atom library based on the obtained ultrasonic wavelet, ultrasonic echo mathematical model and nonlinear transformation function according to different requirements. On this basis, a sparse compression algorithm and a sparse deconvolution algorithm for ultrasonic signals are designed. The sparse sequence deconvolved by the sparse deconvolution algorithm and the nonlinear minimum entropy deconvolution algorithm realizes the two functions of ultrasonic signal compression and deconvolution for pipeline defect detection and precise positioning. The sparse deconvolution algorithm accurately calculates the time delay Δt through sparse deconvolution, obtains the sound velocity of the ultrasonic wave in the fluid, finds the corresponding relationship between the sound velocity and pressure, constructs the atom library with a Gaussian window function, selects r atoms to form the measurement matrix w, and establishes the atomic function of sparse decomposition:

[0039]

[0040] g(t) is a Gaussian function with a peak at t=u, where t is time, μ is the proportional coefficient, s is the scaling factor, vt is the carrier frequency, w is the carrier phase, and s is the modulation index.

[0041] Find the optimal atom α=[α1,α2,α3,...,] for each decomposition step. The atom with the largest inner product W between the signal and the sparse atom library is the optimal atom. Select the residual teromp when (r-1) atoms are selected. Perform Schmidt orthogonalization on the selected r atoms a1,a2,..., emp(i)=sum(a.*W(:,i)), and then calculate the residual B(:,I)=temp(I)*A(:,I).

[0042] Where I is the observation vector, i is the smoothed signal of the discontinuous point, and A is the sensing matrix.

[0043] The measurement matrix w = [g2, g0, g1], where g2, g0, and g1 are all 2000×2000 matrices.

[0044] The ultrasonic pressure measurement model selects an atom (that is, a column) that best matches the signal y, calculates the signal residual, assigns the residual to the input signal, and continues to find the next optimal atom. Then, the atom that best matches the signal residual is selected, the number of iterations is increased by 1, and the signal y of the linear combination of these atoms is repeatedly iterated to determine whether the iteration is terminated. If so, it ends, otherwise, the optimal atom is continued to be searched until the iteration is terminated. Then, based on the narrowband and super-Gaussian properties of the ultrasonic signal, atoms in the complete atom library are reasonably selected so that the selected atoms can match the structure of the ultrasonic signal χ to the maximum extent. The appropriate sparse decomposition algorithm and sparse decomposition coefficient are sought and introduced into the perception reconstruction. Multiple convolution kernels are dynamically aggregated into a convolution weight matrix W(χ). The final aggregated convolution kernel is k convolution kernels W(k) with highly concentrated energy. The dynamic convolution function based on the full dynamic matrix φ(χ) input is decomposed, and the ultrasonic signal is reconstructed using the sparse coefficients, thereby realizing the deconvolution of the ultrasonic signal.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1. Based on relevant knowledge of acoustics and fluid mechanics, the present invention utilizes the physical property that changes in fluid sound velocity due to changes in hydraulic system pressure. An ultrasonic guided wave transmitter probe 1 and an ultrasonic guided wave receiver probe 2 are mounted parallel to and fixed to the outer wall of a pipe. These probes are connected to a detection system. The ultrasonic guided wave transmitter probe 1 injects ultrasonic signals into the pressure pipe at a specific angle of incidence β via a piezoelectric chip attached to the oblique inner wall of a plexiglass wedge. This not only overcomes the influence of pipe wall thickness but also effectively eliminates system errors, achieving high accuracy. The incident ultrasonic signal undergoes waveform conversion at the probe-pipeline interface. The ultrasonic guided wave receiver probe 2 receives the refracted shear waves that propagate along the pipe diameter and into the pipe wall, as well as the reflected longitudinal waves that propagate along the inner and outer pipe walls. The received ultrasonic signal, which undergoes multiple waveform conversions from reflected shear waves to reflected longitudinal waves, is then fed into the detection system to establish an ultrasonic-based pressure measurement model. This ultrasonic-based nondestructive testing of pipeline pressure outside the pipe not only eliminates pressure loss and does not disrupt the fluid flow field, but is also highly practical, simple, flexible, and easy to use. It overcomes the shortcomings of previous contact-based measurement methods and is easy for field workers to operate and carry.

[0047] 2. The present invention uses the time difference to indirectly calculate the fluid pressure based on the real-time pressure inside the pipeline provided by the standard pressure source. The detection delay characteristic has a nonlinear relationship with the pipeline pressure and is compared with the time delay measurement value. This avoids the complexity of directly measuring the speed of sound and is less affected by external factors. It has the advantage of comprehensive coverage detection in non-destructive testing of pressure pipelines and can achieve efficient detection of the entire pipeline without omission. Its relatively sensitive sensing ability can even detect metal loss in the pipeline cross section. It has stability in pressure pipeline applications. Due to the fast propagation speed of guided waves, it can more sensitively detect the inner and outer surfaces of the pipeline. At the same time, it can also perform autonomous pressure pipeline detection along the direction of the transported fluid. Due to its advantage of achieving long-distance detection with single-point excitation, it can achieve rapid pressure pipeline detection without removing or dismantling local insulation layers. At the same time, it can achieve detection of some inaccessible areas, which well meets the above-mentioned detection needs.

[0048] 3. The present invention calculates the ultrasonic propagation delay through a sparse deconvolution algorithm, adaptively aggregates K static convolution kernels, uses the network output results to evaluate the network performance, establishes a nonlinear mapping relationship between pressure and sound speed, and in the process of single-mode waveguide transmission in a pressure pipeline, adaptively aggregates K static convolution kernels, and dynamically aggregates multiple convolution kernels into a convolution weight matrix, which can significantly improve the performance of the convolutional neural network (CNN). Once encountering pipe cracks, corrosion, surface pits, etc., corresponding reflected waves will be generated, achieving universal resolution improvement, overcoming the problem that traditional optical resolution is limited by the optical diffraction limit. The time delay is accurately calculated through the sparse deconvolution algorithm, the sound speed of the ultrasonic wave in the fluid is obtained, and the corresponding relationship between the sound speed and pressure is found. With higher sensitivity and spatial resolution than traditional sparse SIM, the sparse deconvolution algorithm has been proven to be able to achieve a stable spatial resolution improvement of nearly 2 times without paying additional hardware costs.

[0049] 4. Based on the narrowband and super-Gaussian nature of ultrasonic signals, the present invention rationally selects atoms from the complete set of atoms, ensuring that the selected atoms maximally match the structure of the ultrasonic signal. This method then seeks a suitable sparse decomposition algorithm to achieve high sparsity in the decomposition coefficients and highly concentrated energy. This allows for the construction of a highly accurate ultrasonic signal using only a few sparse coefficients, thus enabling deconvolution of the ultrasonic signal. This method further improves detection sensitivity by increasing the propagation distance of ultrasonic waves within the pipeline, while also eliminating signal overlap. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of the detection system for ultrasonic guided wave pressure detection of the present invention.

[0051] Figure 2 yes Figure 1 Schematic diagram of the ultrasonic propagation process in a pipeline and the propagation of ultrasonic signals.

[0052] Figure 3 It is a schematic structural diagram of the detection system of the present invention.

[0053] Figure 4 This is the ultrasonic pressure measurement model of the present invention.

[0054] Figure 5 yes Figure 4 Schematic diagram of the zero-phase filter delay estimation circuit used.

[0055] Figure 6 This is a flowchart of the sparse algorithm.

[0056] Figure 7 It is a flow chart based on feedforward BP-neural network.

[0057] Figure 8 It is a schematic diagram of the propagation path of the ultrasonic propagation mechanism in the pipeline. DETAILED DESCRIPTION

[0058] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process. However, the protection scope of the present invention is not limited to the following embodiment.

[0059] Example 1

[0060] A method for nondestructive ultrasonic testing of pipeline pressure outside the pipeline comprises the following steps:

[0061] The ultrasonic guided wave transmitting probe 1 and the ultrasonic guided wave receiving probe 2 are fixed on the outer wall of the pipeline in a parallel installation manner, and a spacing distance is set between the ultrasonic guided wave transmitting probe 1 and the ultrasonic guided wave receiving probe 2. The detection system of the ultrasonic guided wave transmitting probe 1 and the ultrasonic guided wave receiving probe 2 is connected, and the detection software in the detection system is set. The internal pressure of the pipeline is adjusted by the standard pressure source of the connected pressure pipeline. The single-chip microcomputer of the detection system issues a test command. The ultrasonic guided wave transmitting probe 1 outputs a pulse signal with a frequency of 2.5MHz and an amplitude of 150V through the piezoelectric chip on the oblique inner pipe wall of the organic glass wedge, and incidents the ultrasonic signal into the pressure pipeline at an incident angle β. The incident ultrasonic signal undergoes waveform conversion at the probe-pipeline wall medium interface. The ultrasonic guided wave receiving probe 2 receives the refracted shear wave propagating along the pipe diameter into the pipeline wall and the reflected longitudinal wave propagating along the fluid direction of the inner and outer pipe walls, and transmits the received reflected shear wave to the reflection The ultrasonic signal with multiple waveform conversions of longitudinal waves is sent to the detection system, and an ultrasonic-based pressure measurement model is established to determine the pressure of the fluid and the flow velocity of the fluid medium. The instantaneous flow rate and cumulative flow rate of the fluid are calculated using known parameters. The detection delay characteristics have a nonlinear relationship with the pipeline pressure and are compared with the delay measurement value. The ultrasonic propagation delay is calculated using a sparse deconvolution algorithm. K static convolution kernels are adaptively aggregated, and multiple convolution kernels are dynamically aggregated into a convolution weight matrix. The network output results are used to evaluate the network performance, and a nonlinear mapping relationship between pressure and sound velocity is established. According to the narrowband and super-Gaussian properties of the ultrasonic signal, atoms in the complete atomic library are selected. The genetic algorithm is used to optimize the weights and thresholds of the BP-neural network for prediction, and the sound velocity of the ultrasonic wave in the fluid is obtained. The corresponding relationship between the sound velocity and pressure and the corresponding relationship between the acoustic parameters and pressure are found. Non-invasive pressure detection is achieved by measuring the time delay.

[0062] Based on relevant knowledge of acoustics and fluid mechanics, the present invention utilizes the physical property that changes in fluid sound velocity due to changes in hydraulic system pressure. It employs an ultrasonic guided wave transmitter probe 1 and an ultrasonic guided wave receiver probe 2, mounted parallel to and fixed relative to the outer wall of a pipe. These probes are connected to a detection system. The ultrasonic guided wave transmitter probe 1 injects ultrasonic signals into the pressure pipe at a specific angle of incidence β via a piezoelectric chip attached to the oblique inner wall of a plexiglass wedge. This not only overcomes the influence of pipe wall thickness but also effectively eliminates system errors, achieving high accuracy. The incident ultrasonic signal undergoes waveform conversion at the probe-pipeline medium interface. The ultrasonic guided wave receiver probe 2 receives the refracted shear waves that propagate along the pipe diameter and into the pipe wall, as well as the reflected longitudinal waves that propagate along the inner and outer pipe walls. The received ultrasonic signal, which undergoes multiple waveform conversions from reflected shear waves to reflected longitudinal waves, is then fed into the detection system to establish an ultrasonic-based pressure measurement model. This ultrasonic-based nondestructive testing method for pipeline pressure outside the pipe not only eliminates pressure loss and does not disrupt the fluid flow field, but is also highly practical, simple, flexible, and easy to use. It overcomes the shortcomings of previous contact-based measurement methods and is easy for field workers to operate and carry.

[0063] Example 2

[0064] See Figures 1 to 3. According to the present invention, an ultrasonic guided wave transmitting probe 1 and an ultrasonic guided wave receiving probe 2 are relatively fixed on the outer wall of the pipeline in a parallel installation manner, connected to the detection system of the probes, and detection software is set in the detection system. The pressure pipeline adjusts the internal pressure of the pipeline through a standard pressure source. The detection system single-chip microcomputer issues a test command. The ultrasonic guided wave transmitting probe 1 outputs a pulse signal with a frequency of 2.5MHz and an amplitude of 150V through the piezoelectric chip on the oblique inner pipe wall of the organic glass wedge. The ultrasonic signal is incident into the pressure pipeline at a certain incident angle β. The incident ultrasonic signal undergoes waveform conversion at the probe-pipeline wall medium interface. The ultrasonic guided wave receiving probe 2 receives the refracted shear wave propagating along the pipe diameter into the pipeline wall and the reflected longitudinal wave propagating along the direction of the fluid on the inner and outer pipe walls. The received ultrasonic signal that has undergone multiple waveform conversions from the reflected shear wave to the reflected longitudinal wave is sent to the detection system to establish an ultrasonic-based pressure measurement model and provide real-time pressure measurement according to the standard pressure source. The pressure in the pipeline is measured, and the pressure and flow velocity of the fluid are indirectly calculated using the time difference of ultrasonic wave propagation in the flowing medium, or the flow velocity of the fluid medium is calculated based on the Doppler effect of ultrasonic wave in the fluid. The instantaneous flow rate and cumulative flow rate of the fluid are calculated using known parameters. The nonlinear relationship between the detection delay characteristics and the pipeline pressure is compared with the delay measurement value, and the ultrasonic wave propagation delay is calculated through the sparse deconvolution algorithm. K static convolution kernels are adaptively aggregated, and multiple convolution kernels are dynamically aggregated into a convolution weight matrix. The network output results are used to evaluate the network performance, and a nonlinear mapping relationship between pressure and sound speed is established. According to the narrowband and super-Gaussian properties of the ultrasonic signal, atoms in the complete atomic library are selected. The weights and thresholds of the BP-neural network are optimized by genetic algorithm for prediction, and the sound speed of ultrasonic wave in the fluid are obtained. The corresponding relationship between sound speed and pressure and the corresponding relationship between acoustic parameters and pressure are found. Non-intrusive pressure detection is achieved by measuring the time delay.

[0065] The ultrasonic guided wave transmitting probe 1 utilizes the piezoelectric effect based on the piezoelectric chip, contacts the ultrasonic oblique single crystal probe through the appropriate organic glass wedge inclined excitation angle, excites the guided wave longitudinal wave, and is incident on the inner wall of the pipe through the acoustically transparent oblique wedge, and is incident on the surface of the pipe workpiece at an incident angle and speed. The wave undergoes waveform conversion, reflection, and refraction at the interface. According to the law of wave reflection and refraction, longitudinal waves, shear waves or surface waves are generated in the pressure pipe workpiece. After the emitted sound wave enters the pipe, it propagates along the axial direction of the pipe. A part of the incident longitudinal wave propagates axially along the outer surface of the pipe to form a critical refraction longitudinal wave. Wave, the critical refracted longitudinal wave propagates in a straight line along the pipe wall at a certain incident depth, and continues to generate the first inner wall first reflected longitudinal wave received similar to the critical refracted longitudinal wave, and the second inner wall second reflected longitudinal wave received by the ultrasonic guided wave receiving probe 2, as well as the first inner wall reflected longitudinal wave and the second inner wall reflected longitudinal wave propagated along the inner pipe wall and received and collected by the ultrasonic guided wave receiving probe 2 for guided wave data collection; similarly, another part of the sound waves propagates along the pipe diameter and enters the pipe wall and is refracted into a refracted shear wave, and the refracted shear wave takes the first inner wall reflected longitudinal wave and the second inner wall reflected longitudinal wave as the base, and is refracted along the refraction angle β sThe first and second reflected shear waves are connected end to end at an angle of . The third and fourth inner wall reflected shear waves are connected end to end, and triangular waveforms propagate within the pipe wall. Similarly, upon reaching the inner pipe wall, waveform conversion occurs again, generating the first reflected shear wave. After reaching the outer pipe wall, the second reflected shear wave is generated obliquely downward, which in turn generates the third reflected shear wave upward, and the fourth reflected shear wave is generated obliquely downward, and so on. The ultrasonic guided wave receiving probe 2 sequentially receives the critical refracted longitudinal wave, the first reflected longitudinal wave, the second reflected longitudinal wave, and so on. In actual pipeline inspection, the curvature of the bottom surface of the wedge of the organic glass wedge corresponds one-to-one to the outer surface diameter of the pipe. After the excited sound waves enter the pipeline, they propagate along the pipeline's axis. As the spacing between ultrasonic guided wave probes changes, the number of received longitudinal waves changes accordingly. To improve measurement accuracy, the detection software examines the relationship between each longitudinal wave's time delay and pressure and temperature, analyzes the relationship between adjacent longitudinal wave delay intervals and pressure and temperature, and selects echo signals with a high signal-to-noise ratio. Therefore, in the experiment, the critical refracted longitudinal wave, the first reflected longitudinal wave, the second reflected longitudinal wave, the third reflected longitudinal wave, the fourth reflected longitudinal wave, and the fifth reflected longitudinal wave are primarily selected as the measured signals. A two-dimensional Fourier transform is performed on the multiple sets of collected data to obtain an actual wavenumber-frequency curve. This is compared with the theoretical wavenumber-frequency curve to verify the Ao guided wave mode excited in the pipeline. The Ao mode Lamb wave is used to detect defects in long pipelines. Other reflected longitudinal wave signals are not considered due to their weak amplitude and poor signal quality. The probe emits an ultrasonic pulse wave that permeates the pipe wall thickness and propagates axially along the pipe. When a defect is encountered during the waveguide transmission process, the waveguide returns a proportional reflected wave at the defect's radial cross-section, due to its finite area. Therefore, the probe can detect the return signal echo to identify and determine the defect's size. Any change in pipe wall thickness, whether inside or outside, generates a reflected signal that is picked up by the probe, allowing the detection of metal defects (defects) caused by corrosion or erosion on both the inner and outer walls of the pipe. The echo signal that appears between the initial pulse and the reference wave is the defect echo signal. The defect's location and approximate size are determined based on the echo's amplitude and distance from the reference wave.

[0066] from Figure 2 It can be seen that when the ultrasonic wave is incident from the ultrasonic guided wave transmitting probe 1 into the pressure pipe, the incident depth and frequency are inversely proportional, and the propagation delay is directly proportional to the sensitivity of the pressure change and the frequency. After multiple waveform conversions, the critical refracted longitudinal wave propagates in a straight line along the wall of the pressure pipe and is received by the ultrasonic guided wave receiving probe 2. The reflected longitudinal wave is converted into a shear wave and a longitudinal wave, and the propagation process of the reflected longitudinal wave is divided into two parts: propagation in the wall thickness as a shear wave and propagation on the outer surface of the pipe wall as a longitudinal wave.

[0067] The relationship between time delay and pipeline pressure is:

[0068]

[0069] The velocity of longitudinal waves at normal pressure is

[0070]

[0071] The acoustic elastic coefficient L1 of the longitudinal wave propagating in the pipe

[0072]

[0073] The acoustoelastic coefficient L2 of the shear wave propagating in the pipe

[0074]

[0075] The pressure change value Δp inside the pipeline,

[0076] Among them, E is the elastic modulus of the pressure pipe, L1 is the acoustic elastic coefficient of the longitudinal wave propagating in the pressure pipe, d is the pipe wall thickness, R is the average radius of the pipe, is the transit time change under the measured pressure, D is the ultrasonic propagation distance, is the transit time at normal pressure, is the transition thickness, Δt Lre is the change in the transit radius time, V L is the velocity of longitudinal wave under the measured pressure, t L is the transit time under the measured pressure condition, l is the signal length, λ is the wavelength, m is the mass density, P is the fluid pressure, μ is the proportional coefficient, v is the sound wave velocity, n is the number of ultrasonic guided wave receiving probes, β s is the refraction angle, Δt L is the transit time interval. In summary, the ultrasonic propagation delay Δt in a pipe is linearly related to pressure. When the pressure inside the pipe changes, the ultrasonic propagation delay will also change linearly. Therefore, non-invasive pressure detection can be achieved by measuring the delay.

[0077] like Figure 3 As shown in the figure, the entire detection system structure includes: a connected field programmable logic gate array FPGA module, a time-to-digital converter TDC module, an ultrasonic excitation module connected to both sides of the time-to-digital converter TDC module, a signal conditioning module for receiving ultrasonic guided wave probe signals, a data processing and display module, and a power supply module.

[0078] Control and data are transmitted between the field programmable logic gate array (FPGA) module and the time-to-digital converter (TDC) module. The input signal of the ultrasonic excitation module to stimulate the ultrasonic guided wave transmitting probe 1 is generated by the time-to-digital converter (TDC) module. The input signal, which contains multiple square wave pulse trigger signals with fixed duty cycles, passes through the isolation and push-pull drive module and acts on the ultrasonic guided wave receiving probe 2. The ultrasonic signal propagating in the pipe wall is received by the ultrasonic guided wave receiving probe 2 after a complex propagation and conversion process. After the signal is processed by the signal conditioning circuit of the signal conditioning module, it is received by the time-to-digital converter (TDC) module, and the calculation and storage of the ultrasonic propagation delay are realized inside the field programmable logic gate array (FPGA) module.

[0079] The power module generates charging and discharging waveforms, and the time-to-digital converter (TDC) module samples and counts the time range to be measured using a clock signal. The module calculates the time value based on the count value, performs relevant hardware debugging and experimental verification in a relatively short period of time, and completes the measurement of the time interval from the start signal to the end signal.

[0080] The detection software workflow: The detection system is powered on, and configurations such as system clock setting, pin function definition, time-to-digital converter (TDC) module function settings, and interrupt initialization are completed. The system then enters a loop, waiting for a timer interrupt. During the configuration process, the timer is set to interrupt every 1 second, and transit time measurements are performed in the interrupt routine. The timer interrupt is entered, and control codes are written via Serial Peripheral Interface (SPI) communication, causing the TDC module to begin operation. The TDC module sends an excitation pulse and begins timing. SPI communication reads the three transit time values stored in the TDC module's three 32-bit result registers, and the data format is processed in the SPI receive interrupt. The system then returns to a loop, waiting for a timer interrupt and performing the next measurement. The data processing and display module displays the measurement results and uploads the data to the host computer via the EtherCAT bus.

[0081] See Figure 4 Through the analysis of the relationship between ultrasonic wave velocity, pipeline stress and internal pressure of the pipeline, ultrasonic pressure measurement theory uses stress as a link to study the relationship between ultrasonic wave velocity and internal pressure of the pipeline, and detect the effect of fluid flow on ultrasonic pulses. The detection system establishes an ultrasonic pressure measurement model based on the relationship between pipeline pressure, strain and stress. For thin-walled pipelines, the radial stress along the wall thickness direction is ignored. The relationship between strain and stress can be expressed by circumferential and axial stress, that is,

[0082]

[0083] Among them, ε A , εR , ε C are the three-dimensional strains in the axial direction A, radial direction R and circumferential direction C, E is the elastic modulus of the pipe, v is the wave velocity under the measured pressure, σ h represents the radial stress along the wall thickness direction, σ θ represents the transverse stress along the shear wave refraction angle, and θ represents the shear wave refraction angle.

[0084] like Figure 5 As shown in the figure. When the ultrasonic propagation distance is long and the surface wave or critical refracted longitudinal wave signal attenuates significantly, resulting in a very low signal-to-noise ratio (SNR) of the ultrasonic echo signal, the ultrasonic pressure measurement model uses two zero-phase filters. The two ultrasonic signals χ1(t) and χ2(t) are respectively filtered through the two zero-phase filters, and then the time delay Δt of the two signals is calculated using the cross-correlation delay estimation module. Because the ultrasonic propagation delay is less sensitive to pressure changes and is easily affected by multiple factors, a single longitudinal wave is used to establish the measurement model. The measurement accuracy is easily affected by waveform selection and random measurement errors. Information fusion multivariate linear regression is used to combine the propagation delay of the critical refracted longitudinal wave and multiple reflected longitudinal waves, as well as temperature information, to improve measurement accuracy.

[0085] The above cross-correlation delay estimation method based on the zero-phase digital filter can not only effectively remove interference, but also keep the original signal phase undistorted and the phase shift zero.

[0086] See Figure 6 From a practical and theoretical perspective, the ultrasonic pressure measurement model constructs a more robust sparsity measurement function and a nonlinear transformation function based on the properties of sparsity. After nonlinear transformation, the sparse sequence becomes even more sparse. Subsequently, a nonlinear minimum entropy deconvolution algorithm is designed based on the ultrasonic Gaussian properties of the ultrasonic signal. The specific steps of the sparse algorithm can be found in Figure 6 As shown, no further details are given here.

[0087] According to different requirements, the ultrasonic pressure measurement model constructs a sparse compression atom library and a deconvolution atom library by using the obtained ultrasonic wavelet, ultrasonic echo mathematical model and nonlinear transformation function. On this basis, a sparse compression algorithm and a sparse deconvolution algorithm for ultrasonic signals are designed. The sparse sequence deconvolved by the sparse deconvolution algorithm and the nonlinear minimum entropy deconvolution algorithm can realize the two functions of ultrasonic signal compression and deconvolution for pipeline defect detection and precise positioning.

[0088] The sparse deconvolution algorithm accurately calculates the time delay Δt through sparse deconvolution, obtains the sound velocity of ultrasound in the fluid, finds the corresponding relationship between sound velocity and pressure, constructs the atomic library using the Gaussian window function, selects r atoms to form the measurement matrix w, and establishes the sparse decomposition atomic function:

[0089]

[0090] g(t) is a Gaussian function with a peak at t=u, where t is time, μ is the proportional coefficient, s is the scaling factor, vt is the carrier frequency, w is the carrier phase, and s is the modulation index.

[0091] Find the optimal atom α=[α1,α2,α3,...,] for each decomposition step. The atom with the largest inner product W between the signal and the sparse atom library is the optimal atom. Select the residual teromp when (r-1) atoms are selected. Perform Schmidt orthogonalization on the selected r atoms a1,a2,..., emp(i)=sum(a.*W(:,i)), and then calculate the residual B(:,I)=temp(I)*A(:,I).

[0092] Where I is the observation vector, i is the smoothed signal of the discontinuous point, and A is the sensing matrix.

[0093] The measurement matrix w = [g2, g0, g1], where g2, g0, and g1 are all 2000×2000 matrices.

[0094] The ultrasonic pressure measurement model selects an atom (i.e., a column) that best matches the signal y, calculates the signal residual, assigns the residual to the input signal, and continues to find the next optimal atom. The atom that best matches the signal residual is then selected, and the number of iterations is incremented by 1. The linear combination of these atoms, signal y, is iterated repeatedly. The iteration is determined to terminate. If so, the optimal atom is searched for until the iteration terminates. Based on the narrowband and super-Gaussian properties of the ultrasonic signal, atoms are rationally selected from the complete atom library to maximize the match between the selected atoms and the structure of the ultrasonic signal χ. A suitable sparse decomposition algorithm and sparse decomposition coefficients are then sought and introduced into the perceptual reconstruction. Multiple convolution kernels are dynamically aggregated into a convolution weight matrix W(χ). The resulting aggregated convolution kernels are k highly energy-concentrated convolution kernels W(k). Dynamic convolution is performed based on the χ function of the full dynamic matrix φ(χ) input. The ultrasonic signal is reconstructed using the sparse coefficients, thereby achieving deconvolution of the ultrasonic signal. A dynamic channel fusion mechanism is used to address the limitations of conventional dynamic convolution.

[0095] Through a large number of experiments, the ultrasonic pressure measurement model uses a weighted iterative sparse deconvolution algorithm to accurately calculate the wall thickness of the pipeline, accurately detect internal defects in the pipeline (mainly including slag inclusions, air holes, etc.), and at the same time detect near-surface defects of the pipeline that cannot be detected by traditional methods. Based on the ultrasonic sparse sequence obtained by deconvolution, the arrival time of the defect echo is accurately calculated, thereby accurately locating the defect.

[0096] In order to avoid establishing explicit model equations, the ultrasonic pressure measurement model has excellent nonlinear curve fitting capabilities based on the neural network. Samples of pressure, sound velocity, temperature, and characteristic signals in some samples are selected as training data to train the neural network. The neural network fully learns the pressure measurement results and saves them in the form of weights and thresholds. Then, samples of other samples are input into the neural network. The network performance is evaluated based on the output results of the neural network, and a nonlinear mapping relationship between pressure and sound velocity is established.

[0097] like Figure 7 As shown in the figure, the ultrasonic pressure measurement model preprocesses input data and uses a multi-layer feedforward network trained using the back propagation error algorithm. Based on this feedforward network, a BP neural network consisting of an input layer, hidden layer, and output layer is constructed. A single ultrasonic sensor receiving probe is used as a neural network node. These nodes are then used to build a multi-layer neural network structure. A genetic algorithm is used to optimize the BP network's weights and thresholds. After optimization, each individual in the population contains all the network's weights and thresholds. Individual fitness values are calculated using a fitness function, and the genetic algorithm is used to find the individual with the optimal fitness. The BP network uses the optimal individual obtained by the genetic algorithm to predict the neural network weights and thresholds. During input data preprocessing, the genetic algorithm encodes the initial values, and the error obtained from BP neural network training is used as the fitness value. Selection, crossover, and mutation operations are performed to calculate the fitness value. The algorithm then determines whether the termination condition is met. If so, the optimal weights and thresholds are obtained. Otherwise, the algorithm returns to the selection process and continues to determine whether the termination condition is met.

[0098] In the data preprocessing, the BP-neural network part determines the network topology, the initial BP-neural network weights and thresholds, obtains the optimal weights and thresholds, calculates the errors and updates the weight thresholds, and determines whether the end conditions are met. If so, the process ends; otherwise, the calculation error is returned and the determination of the end conditions continues until the end conditions are met. After training, the BP network predicts the output.

[0099] The genetic algorithm involves two processes: forward propagation of the signal and backward propagation of the error. This involves calculating the error output from input to output, adjusting the weights and thresholds in this direction, and continuously adjusting the weight input vector by minimizing the loss function. The weights are then adjusted layer by layer, working backward. All weights in the network are randomly initialized. Based on the input of an example, the algorithm calculates the output of each unit in the output layer from forward to backward, and then calculates the error term for each unit in each layer, starting from the output layer. For each unit k in the output layer, the error term is calculated, and each weight is updated to solve the weight vector, obtaining the eigenvector of the sampled signal. The perceptron input value is then obtained from the weight vector, and the sigmoid function is used to calculate the output of each perceptron. During forward propagation, the input signal passes through the hidden layer and acts on the output node, where it undergoes a nonlinear transformation to generate the output signal. If the actual output does not match the expected output, the algorithm proceeds to the backward propagation of the error.

[0100] It should be pointed out that all directional indications in the embodiments of the present invention (such as both sides, edges, up, down, left, right, front, back, middle, top, bottom, tail, axial, radial...) are only used to explain the relative position relationship, movement state, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0101] The present invention has been introduced in detail above. Specific implementation methods are used herein to illustrate the present invention. The description of the above embodiments is only used to help understand the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for nondestructive ultrasonic testing of pipeline pressure outside the pipeline, characterized by: The steps include: The ultrasonic guided wave transmitting probe 1 and the ultrasonic guided wave receiving probe 2 are fixed on the outer wall of the pipeline in a parallel installation manner, and a spacing distance is set between the ultrasonic guided wave transmitting probe 1 and the ultrasonic guided wave receiving probe 2. The detection system connects the ultrasonic guided wave transmitting probe 1 and the ultrasonic guided wave receiving probe 2, and adjusts the internal pressure of the pipeline through the standard pressure source of the connected pressure pipeline. The detection system issues a test command, and the ultrasonic guided wave transmitting probe 1 outputs a pulse signal with a frequency of 2.5MHz and an amplitude of 150V, and incidents the ultrasonic signal into the pressure pipeline at an incident angle β. The incident ultrasonic signal undergoes waveform conversion at the probe-pipeline wall medium interface, and the ultrasonic guided wave receiving probe 2 receives the refracted shear wave propagating along the pipe diameter into the pipeline wall and the reflected longitudinal wave propagating along the fluid direction of the inner and outer pipe walls, and sends the received ultrasonic signal that has undergone multiple waveform conversions from the reflected shear wave to the reflected longitudinal wave to the ultrasonic wave transmitting probe 1. A pressure measurement model based on ultrasound is established to obtain the pressure and flow velocity of the fluid medium, calculate the instantaneous flow rate and cumulative flow rate of the fluid, detect the nonlinear relationship between the time delay characteristics and the pipeline pressure, and compare them with the time delay measurement value. The ultrasonic propagation delay is calculated through the sparse deconvolution algorithm, K static convolution kernels are adaptively aggregated, and multiple convolution kernels are dynamically aggregated into a convolution weight matrix. The network output results are used to evaluate the network performance, and a nonlinear mapping relationship between pressure and sound speed is established. According to the narrowband and super-Gaussian properties of the ultrasonic signal, atoms in the complete atomic library are selected, and the genetic algorithm is used to optimize the weights and thresholds of the BP-neural network for prediction. The sound speed of ultrasound in the fluid is obtained, and the corresponding relationship between sound speed and pressure and the corresponding relationship between acoustic parameters and pressure are found. Non-invasive pressure detection is achieved by measuring the time delay.

2. The method for nondestructive testing of pipeline pressure by ultrasonic testing outside the pipeline according to claim 1, characterized in that: Based on the real-time pressure inside the pipeline provided by the standard pressure source, the fluid pressure and fluid medium flow rate are indirectly calculated using the time difference of ultrasonic wave propagation in the flowing medium, or the fluid pressure and fluid medium flow rate are calculated based on the Doppler effect of ultrasonic wave in the fluid.

3. The method for nondestructive testing of pipeline pressure by ultrasonic testing outside the pipeline according to claim 1, characterized in that: The ultrasonic guided wave transmitting probe 1 utilizes the piezoelectric effect based on the piezoelectric chip, and contacts the ultrasonic oblique single crystal probe at an angle through the inner wall of the organic glass wedge to stimulate the inner wall of the pipe, and excites the guided wave longitudinal wave. The wave is incident on the inner wall of the pipe at an angle and speed through the acoustically transparent oblique wedge, and is incident on the surface of the pipe workpiece at an incident angle and speed. The wave undergoes waveform conversion, reflection, and refraction at the interface of the inner pipe wall, generating longitudinal waves, transverse waves or surface waves in the pipe. After the emitted sound wave enters the pipe, it propagates along the axial direction of the pipe. A part of the incident longitudinal wave propagates axially along the outer surface of the pipe to form a critical refracted longitudinal wave. The critical refracted longitudinal wave At a certain incident depth, the sound waves propagate in a straight line along the pipe wall, and continue to generate the first reflected longitudinal wave and the second reflected longitudinal wave on the outer wall similar to the critical refracted longitudinal wave, the first reflected longitudinal wave and the second reflected longitudinal wave received by the ultrasonic guided wave receiving probe 2, as well as the first inner wall reflected longitudinal wave and the second inner wall reflected longitudinal wave propagating along the inner pipe wall and being collected and received by the ultrasonic guided wave receiving probe 2 for guided wave data collection; another part of the sound waves propagates along the pipe diameter and enters the pipe wall and is refracted into a refracted shear wave, which takes the first inner wall reflected longitudinal wave and the second inner wall reflected longitudinal wave as the base, and is refracted along the refraction angle β s The first reflected shear wave and the second reflected shear wave are connected end to end at an angle, and the third inner wall reflected shear wave and the fourth inner wall reflected shear wave are connected end to end, and triangular waveform propagation occurs in the pipe wall. Similarly, when reaching the inner pipe wall, waveform conversion occurs again to generate the first reflected shear wave, and after reaching the outer pipe wall, the second reflected shear wave is generated obliquely downward, and then the third reflected shear wave is generated upward, and the fourth reflected shear wave is generated obliquely downward, and so on. The ultrasonic guided wave receiving probe 2 receives the critical refracted longitudinal wave, the first reflected longitudinal wave, the second reflected longitudinal wave, ... in sequence.

4. The method for nondestructive testing of pipeline pressure by ultrasonic testing outside the pipeline according to claim 1, characterized in that: Ultrasonic waves are incident into the pressure pipe from the ultrasonic guided wave transmitting probe 1. The incident depth is inversely proportional to the frequency, and the propagation delay is directly proportional to the sensitivity of the pressure change and the frequency. After multiple waveform conversions, the critical refracted longitudinal wave propagates in a straight line along the pipe wall and is received by the ultrasonic guided wave receiving probe 2. The reflected longitudinal wave is converted into a shear wave and a longitudinal wave, and the propagation process of the reflected longitudinal wave is divided into two parts: propagation in the wall thickness as a shear wave and propagation in the inner and outer surfaces of the pipe wall as a longitudinal wave.

5. The method for nondestructive testing of pipeline pressure by ultrasonic testing outside the pipeline according to claim 4, characterized in that: The relationship between time delay and pipeline pressure is: Pressure change inside the pipeline The velocity of longitudinal waves at normal pressure is The acoustic elastic coefficient L1 of the longitudinal wave propagating in the pipe The acoustoelastic coefficient L2 of the shear wave propagating in the pipe The pressure change value Δp inside the pipeline, Where, E is the elastic modulus of the pipe, d is the pipe wall thickness, and R is the average radius of the pipe. is the transit time change under the measured pressure, D is the ultrasonic propagation distance, is the transit time at normal pressure, is the transition thickness, Δt Lre is the change in the transit radius time, V L is the velocity of longitudinal wave under the measured pressure, t L is the transit time under the measured pressure condition, l is the signal length, λ is the wavelength, m is the mass density, P is the fluid pressure, μ is the proportional coefficient, v is the sound wave velocity, n is the number of ultrasonic guided wave receiving probes, β s is the refraction angle, Δt L is the time interval of the flight.

6. The method for nondestructive testing of pipeline pressure by ultrasonic testing outside the pipeline according to claim 1, characterized in that: The detection system includes: an interconnected field programmable logic gate array FPGA module and a time-to-digital converter TDC module, as well as an ultrasonic excitation module connected to both sides of the time-to-digital converter TDC module, a signal conditioning module for receiving ultrasonic guided wave probe signals, a data processing and display module, and a power supply module.

7. The method for nondestructive ultrasonic testing of pipeline pressure outside the pipeline according to claim 6, characterized in that: The time-to-digital converter (TDC) module compensates for temperature and voltage changes, and uses the propagation delay of signals through internal gate circuits to perform high-precision time interval measurements. The field-programmable gate array (FPGA) module displays the absolute interval time measured and transfers control and data to the TDC module.

8. The method for nondestructive testing of pipeline pressure using ultrasonic technology outside the pipeline according to claim 7, characterized in that: The input signal of the ultrasonic excitation module to stimulate the ultrasonic guided wave transmitting probe 1 is generated by the time-to-digital converter TDC module, which contains multiple square wave pulse trigger signals with fixed duty cycles. After passing through the isolation and push-pull drive module, it acts on the ultrasonic guided wave receiving probe 2. The ultrasonic signal propagating in the pipe wall is received by the ultrasonic guided wave receiving probe 2 after the propagation and conversion process. After being processed by the signal conditioning circuit of the signal conditioning module, it is received by the time-to-digital converter TDC module, realizing the measurement of converting time into digital data, and realizing the communication calculation and storage of the ultrasonic propagation delay inside the field programmable logic gate array FPGA module.

9. The method for nondestructive testing of pipeline pressure using ultrasonic technology outside the pipeline according to claim 6, characterized in that: The power module generates charging and discharging waveforms, and the time-to-digital converter (TDC) module samples and counts the time range to be measured using a clock signal. The module calculates the time value based on the count value, performs relevant hardware debugging and experimental verification in a relatively short period of time, and completes the measurement of the time interval from the start signal to the end signal.

10. The method for nondestructive testing of pipeline pressure using ultrasonic technology outside the pipeline according to claim 9, characterized in that: The system is powered on, and configurations such as system clock setting, pin function definition, time-to-digital converter (TDC) module timing function setup, and interrupt initialization are completed. The system then enters a loop, waiting for a timer interrupt. During configuration, the timer is set to interrupt once every 1 second, and transit time is measured in the interrupt routine. Upon entering the timer interrupt, control codes are written via the serial peripheral interface (SPI) communication, and the TDC module begins operation. The time-to-digital converter (TDC) module sends an excitation pulse and starts timing. SPI communication reads the three transit time values stored in the three 32-bit result registers within the TDC module, processes the data format during the SPI receive interrupt, and then returns to the system to enter a loop, waiting for the timer interrupt to perform the next measurement. The data processing and display module displays the measurement results and uploads the data to the host computer via the EtherCAT bus.

11. The method for nondestructive testing of pipeline pressure using ultrasonic technology outside the pipeline according to claim 1, characterized in that: The detection system establishes an ultrasonic pressure measurement model based on the sound velocity relationship between pipeline pressure, strain and stress. Specifically, for thin-walled pipes, ignoring the radial stress along the wall thickness direction, the relationship between strain and stress can be expressed by the circumferential and axial stresses, that is, The ultrasonic pressure measurement model uses two zero-phase filters. After the two ultrasonic signals χ1(t) and χ2(t) pass through the two zero-phase filters respectively, the time delay Δt of the two signals is calculated using the cross-correlation delay estimation module. Among them, ε A , ε R , ε C are the three-dimensional strains in the axial direction A, radial direction R and circumferential direction C, E is the elastic modulus of the pipe, v is the wave velocity under the measured pressure, σ h represents the radial stress along the wall thickness direction, σ θ represents the transverse stress along the shear wave refraction angle, and θ represents the shear wave refraction angle.

12. The method for nondestructive testing of pipeline pressure using ultrasonic technology outside the pipeline according to claim 1, characterized in that: The ultrasonic pressure measurement model constructs a more robust sparsity measurement function and a nonlinear transformation function based on the properties of sparsity. After nonlinear transformation, the sparse sequence becomes even sparser. Subsequently, a nonlinear minimum entropy deconvolution algorithm is designed based on the ultrasonic Gaussian properties of the ultrasonic signal. The ultrasonic pressure measurement model constructs a sparse compression atom library and a deconvolution atom library based on the obtained ultrasonic wavelet, ultrasonic echo mathematical model and nonlinear transformation function according to different requirements. On this basis, a sparse compression algorithm and a sparse deconvolution algorithm for ultrasonic signals are designed. The sparse deconvolution algorithm and the nonlinear minimum entropy deconvolution algorithm deconvolute the sparse sequence. The sparse deconvolution algorithm accurately calculates the time delay Δt through sparse deconvolution to obtain the sound velocity of the ultrasonic wave in the fluid, finds the corresponding relationship between the sound velocity and pressure, constructs the atom library using a Gaussian window function, selects r atoms to form the measurement matrix w, and establishes the atomic function of sparse decomposition: g(t) is a Gaussian function with a peak at t = u, where t is time, μ is the proportional coefficient, s is the scaling factor, vt is the carrier frequency, w is the carrier phase, and s is the modulation index; Find the optimal atom α = [α1, α2, α3, ...,] for each decomposition step. The atom with the largest inner product W between the signal and the sparse atom library is the optimal atom. Select the residual teromp when (r-1) atoms are selected. Perform Schmidt orthogonalization on the selected r atoms a1, a2, ..., emp(i) = sum(a.*W(:,i)), and then calculate the residual B(:,I) = temp(I)*A(:,I); Where I is the observation vector, i is the smoothed signal of the discontinuous point, and A is the sensing matrix; The measurement matrix w = [g2, g0, g1], where g2, g0, and g1 are all 2000 × 2000 matrices; The ultrasonic pressure measurement model selects an atom that best matches the signal y, calculates the signal residual, assigns the residual to the input signal, continues to find the next optimal atom, and then continues to select the atom that best matches the signal residual. The number of iterations is increased by 1, and the signal y of the linear combination of these atoms is repeatedly iterated to determine whether the iteration is terminated. If so, it ends, otherwise it continues to search for the optimal atom until the iteration is terminated. Then, based on the narrowband and super-Gaussian properties of the ultrasonic signal, atoms in the complete atom library are reasonably selected so that the selected atoms can match the structure of the ultrasonic signal χ to the maximum extent. Appropriate sparse decomposition algorithms and sparse decomposition coefficients are sought and introduced into the perception reconstruction. Multiple convolution kernels are dynamically aggregated into a convolution weight matrix W(χ). The final aggregated convolution kernel is k convolution kernels W(k) with highly concentrated energy. Dynamic convolution is decomposed based on the χ function input by the full dynamic matrix φ(χ), and the ultrasonic signal is reconstructed using sparse coefficients, thereby realizing the deconvolution of the ultrasonic signal.

Images