CN114740093B - Ultrasonic guided wave defect quantitative detection method and application thereof - Google Patents
Ultrasonic guided wave defect quantitative detection method and application thereof Download PDFInfo
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Abstract
The invention discloses an ultrasonic guided wave defect quantitative detection method and application thereof, wherein the defect quantitative detection method comprises the following steps: obtaining the propagation speed of ultrasonic guided waves in a free section of the anchor rod without anchoring through ultrasonic guided wave detection; the propagation speed of the ultrasonic guided wave in the anchoring compact section of the anchor rod is obtained through ultrasonic guided wave detection; and processing a return signal obtained by ultrasonic guided wave detection by a ICEEMDAN method, acquiring reflection time parameters of different positions and defects of the anchor rod according to a peak value of an inherent mode function obtained by signal decomposition, and quantitatively detecting the length of the defect according to the propagation speed and the reflection time parameters. The detection method is efficient and accurate and is suitable for wide application.
Description
Technical Field
The invention relates to the technical field of ultrasonic guided wave for quality detection.
Background
The anchor rod is a reinforcing and supporting tool widely used in surface engineering such as side slopes, rock and soil deep foundation pits and underground engineering such as tunnels and stopes, the anchor rod is a part which extends into a support or a foundation and is used for carrying out stress transmission, and generally, the longer the anchor section in the anchor rod is, the better the reinforcing and supporting effect is.
In engineering application, the quality of the anchor rod is directly related to the safety of projects, and once the anchor rod fails, a huge threat is generated to the stability of a rock-soil structure, and serious site accidents and huge losses of projects can be generated. The failure of the bolt is typically caused by a variety of reasons, such as: the anchor rod has insufficient length; the anchoring agent is not effectively bonded with the rod body and the surrounding rock; the anchor rod is broken due to geological condition change or impact caused by blasting, heavy machinery and earthquake force; the stress state of the anchor rod is changed from axial tensile stress to transverse shear stress due to the transverse sliding of the surrounding rock, so that the anchor rod is sheared; because the working environment is worse, liquid such as water, moist air, rainwater and the like infiltrates into the anchor rod, the anchor rod is corroded to cause stress concentration, and then the anchor rod is broken from the stress concentration position and the like. These causes, in addition to strong external damage, mainly include mass defects of the bolt itself and mass defects resulting from small damage during long-term operation. One of the more common quality defects is debonding, which is that in the grouting process of an anchor rod, an unglued part appears in an anchoring section due to insufficient grouting pressure or gravity and the like, and the part is the debonding part. Whether such quality defect can timely and accurately identify has significant influence on the application safety of the anchor rod.
In the prior art, some nondestructive detection methods for the defects of the anchor rod, such as an acoustic stress wave method, are developed, wherein an excitation hammer is utilized to strike the end head of the free section of the anchor rod to generate stress waves, when the stress waves longitudinally propagate to the interface of the anchoring section along the anchor rod body, one part of the stress waves are reflected, and the other part of the stress waves are transmitted into the anchoring section to continue to propagate, and are reflected again when reaching the bottom end of the anchoring section, and the quality and the defect condition of the anchor rod are evaluated by detecting the time of the waves reflected from the bottom of the anchor rod and combining a consolidation wave velocity theory. However, these detection methods and other nondestructive detection of defects can simply determine the position of the defect, and cannot determine the form of the defect, particularly the length of the defect such as debonding.
Disclosure of Invention
The invention aims to provide an ultrasonic guided wave detection method capable of detecting the position and the form of the defect in an anchor rod and quantitatively determining the parameters of the defect, such as the debonding length.
The invention also aims at providing application of the detection method.
The invention firstly discloses the following technical scheme:
An ultrasonic guided wave defect quantitative detection method, which comprises the following steps:
obtaining the propagation speed Cf of the ultrasonic guided wave in the free section of the anchor rod without anchoring through ultrasonic guided wave detection;
acquiring the propagation speed Cb of the ultrasonic guided wave in the anchoring compact section of the anchor rod through ultrasonic guided wave detection;
the dimension of the anchor rod defect L 3 is obtained according to the following calculation model:
Wherein L 1 is the length of the free section of the anchor rod, L 21 and L 22 respectively represent the length from the upper interface of the anchor body to the upper interface of the defect and the length from the lower interface of the defect to the bottom of the anchor rod, t b is the reflection time of the ultrasonic guided wave at the upper interface of the anchor body, t r is the reflection time of the ultrasonic guided wave at the bottom of the anchor rod, t g is the excitation time of the excitation wave, t dd is the reflection time of the ultrasonic guided wave at the lower interface of the anchor defect, t ud is the reflection time of the ultrasonic guided wave at the upper interface of the anchor defect,
Wherein, each time parameter is obtained through the following processes:
Respectively transmitting ultrasonic guided waves to an anchor rod without anchoring and an anchor rod with dense anchoring, which have the length L, and respectively collecting returned ultrasonic guided wave signals;
identifying a reflected wave packet signal of the excitation wave signal and the bottom of the anchor rod on a time-amplitude spectrum generated by the returned ultrasonic guided wave signal, wherein the time corresponding to the peak value of the excitation wave signal is excitation time;
Decomposing the returned ultrasonic guided wave signal through improved self-adaptive noise complete set empirical mode decomposition to obtain a decomposed intrinsic mode function;
determining ultrasonic guided wave reflection time t corresponding to each of different positions and upper and lower interfaces of the defect according to different positions of an anchor rod in peak points of an envelope curve of an inherent mode function and peak points corresponding to the upper and lower interfaces of the defect;
Obtaining double-way travel time of ultrasonic guided waves to different positions of the anchor rod and the upper and lower interfaces of the defect through the difference value of the reflection time t and the excitation time, and further obtaining respective single-way travel time;
Wherein, the stock different positions include anchor body upper interface and stock bottom.
In some embodiments, the ultrasonic guided wave is a longitudinal ultrasonic guided wave of 20-100 kHz.
In some embodiments, the obtaining of the natural mode function includes:
adding a plurality of groups of Gaussian white noise into the returned ultrasonic guided wave signals to generate a plurality of groups of corresponding new signals;
performing empirical mode decomposition on the signal sequence added with Gaussian white noise to obtain a plurality of envelope mean values, and performing total average on the envelope mean values to obtain a current-order residual error;
subtracting a current order residual error from the returned ultrasonic signal to obtain a current order inherent mode function, adding new groups of Gaussian white noise to the current order residual error, performing empirical mode decomposition again to obtain a plurality of new envelope mean values, performing total average on the plurality of new envelope mean values to obtain a new residual error, and subtracting the new residual error from the current order residual error to obtain a new inherent mode function;
repeating the steps until the extremum of the current order residual is not more than two, and completing decomposition.
In some embodiments, the new signal is obtained by the following calculation model:
Si＝s+β0E1(ω·(i))，i＝1，2，...，I
Wherein s i represents the new signal, s represents the returned ultrasonic guided wave signal, ω (i) represents gaussian white noise with mean and unit variance of 0 and 1, respectively, I represents the number of added white noise, I represents the total number of added white noise, β 0 represents the white noise coefficient for adjusting the required signal-to-noise ratio between the added noise and the residual after the added noise, ε 0 represents the amplitude of the added noise, std (·) is a standard deviation operator; e 1 represents an operator of the 1 st natural mode function obtained by EMD decomposition;
and/or, the kth order residual r k and the kth natural mode function IMFk obtained in the obtaining of the natural mode function are obtained through the following calculation models:
βk＝ε0std(rk)，
Wherein M (& gt) represents an envelope local mean operator meeting the judgment condition of the intrinsic mode function, E k (& gt) represents an operator of a kth Intrinsic Mode Function (IMF) obtained by EMD decomposition, and beta k represents a white noise coefficient set when white noise is added for the kth-1 time.
In some embodiments, the obtaining of the propagation velocity C f of the ultrasonic guided wave in the free section without the anchor comprises:
Carrying out ultrasonic guided wave detection on a free anchor rod with a known length L and without an anchor section, and identifying an excitation wave signal and a reflected wave packet signal at the bottom of the anchor rod on a time-amplitude spectrum generated by a return signal of the free anchor rod;
According to the peak value method, the time corresponding to the peak value of the excitation wave on the time-amplitude spectrum and the peak value of the reflected wave packet at the bottom of the anchor rod are respectively used as the excitation time and the reflection time, and the difference between the two is the double-way travel time delta t p, so that the single-way travel time of the guided wave on the free anchor rod is obtained
By the length L of the free anchor rod and the single-pass propagation time of the guided wave on the free anchor rodIs used to obtain the general anchor free section wave speed C f.
In some embodiments, the obtaining of the propagation velocity C b of the ultrasonic guided wave in the anchored compact section of the bolt comprises:
ultrasonic guided wave detection is carried out on the full-length anchored compact anchor rod with the known length L, and an excitation wave signal and a reflected wave packet signal at the bottom of the anchor rod are identified on a time-amplitude spectrum generated by a return signal of the full-length anchored compact anchor rod;
According to the peak value method, the time corresponding to the peak value of the excitation wave on the time-amplitude spectrum and the peak value of the reflected wave packet at the bottom of the anchor rod are respectively used as the excitation time and the reflection time, the difference between the two is the double-way travel time delta t b, and the single-way travel time of the guided wave on the anchored dense anchor rod is obtained
Single pass propagation time through length L of the anchor rod and guided wave on the anchored dense anchor rodIs used to obtain the general anchoring compaction segment wave velocity C b.
The invention further discloses application of the defect detection method in determination of the debonding length of the anchor rod.
The invention has the following beneficial effects:
the detection method can rapidly and accurately extract weak reflection generated at the defect in the detected target.
The detection method can effectively solve the problem that the defect interface identification is affected by multiple reflections in the anchor body, and stable and effective information is extracted.
The detection method can use the low-frequency ultrasonic guided wave for detection, the attenuation of the guided wave to surrounding medium is less in the detection process, and the detection accuracy is high.
The invention can rapidly, accurately and quantitatively obtain the parameters of the target defect, such as the defect length, and the obtained result has high precision.
Drawings
FIG. 1 is a schematic diagram of an assembly of a detection system of the present invention;
FIG. 2 is a waveform diagram of the tip reflection of a defective anchor according to example 1;
FIG. 3 is a graph showing all IMF components of the defect bolt head reflection signal of example 1 after ICEEMDAN decomposition;
FIG. 4 is a waveform of the tip reflection of the free bolt of example 1;
FIG. 5 is a waveform of the reflection of the tip of the full length anchored solid bolt of example 1;
fig. 6 is an envelope diagram of the second order IMF component of the defect bolt head reflection signal of example 1 after ICEEMDAN decomposition.
Detailed Description
The present invention will be described in detail with reference to the following examples and drawings, but it should be understood that the examples and drawings are only for illustrative purposes and are not intended to limit the scope of the present invention in any way. All reasonable variations and combinations that are included within the scope of the inventive concept fall within the scope of the present invention.
The empty pulp detection is performed by the following process:
S1: and the ultrasonic guided wave transmitter is connected to excite the low-frequency ultrasonic guided wave, and the ultrasonic guided wave receiver is used for collecting the return signal of the low-frequency ultrasonic guided wave from the detected anchor rod.
The system is shown in figure 1, and comprises an ultrasonic guided wave transmitting and receiving instrument such as a pulse generating and receiving instrument 1 capable of transmitting and receiving low-frequency ultrasonic guided waves to an anchor rod sample 6, a collecting device such as a double-channel data collecting card 2 for collecting and storing output data of the pulse generating and receiving instrument 1, a data processing device such as a computer 3 for processing the collected data, an excitation sensor 4 arranged between a transmitting end of the pulse generating and receiving instrument 1 and a transmitting path of the anchor rod sample 6 and fixed at the end part of the anchor rod sample 6, and a receiving sensor 5 arranged between a receiving end of the pulse generating and receiving instrument 1 and a receiving path of the anchor rod sample 6 and fixed at the end part of the anchor rod sample 6; wherein the excitation sensor and/or the receiving sensor is preferably a piezoelectric sensor. The ultrasonic guided wave transmitter and the receiver can be connected with the anchor rod through a coaxial cable with good shielding effect, the excited low-frequency ultrasonic guided wave can be transmitted through an excitation sensor fixed at the end part of the anchor rod through an adhesive, after the sensor transmits the low-frequency ultrasonic guided wave to the anchor rod for anchoring, a receiving sensor fixed at the end part of the anchor rod receives the transmitted wave generated by the ultrasonic guided wave at the defect and an anchoring interface, the reflected wave signal is transmitted to an ultrasonic guided wave receiver through the coaxial cable of the receiving sensor, the ultrasonic guided wave receiver outputs the reflected wave signal to a signal data acquisition device, such as a double-channel data acquisition card, the acquisition device stores the signal data, and the signal data is input into a data processing device, such as a computer, various quality parameters of a target, such as the length of the anchor rod, the length of an anchoring section, the compactness of the anchor rod, the position of a debonding defect x, the abnormal degree of the defect and the like are accurately detected according to the processing result of the computer.
Wherein, the low-frequency ultrasonic guided wave selects a low-frequency longitudinal ultrasonic guided wave of 20kHz-100kHz, and the generation process can use the following processes:
A5-period sine function wave with the frequency of 20kHz is generated through Hanning window modulation, a wave packet formed by the sine function wave is excited by an ultrasonic transmitter to serve as an excitation signal, and the excitation signal is transmitted into an anchoring anchor rod through a sensor with the center frequency of 30kHz, namely, a low-frequency longitudinal ultrasonic guided wave with the frequency of 20kHz-100kHz is generated.
S2: and separating the return signal through improved adaptive noise complete set empirical mode decomposition (ICEEMDAD) to obtain a separated natural mode function.
The method can adopt the following processes:
S21: and adding I groups of Gaussian white noise omega i (t) subjected to Empirical Mode Decomposition (EMD) and multiplying the signal to noise ratio into the sequence s of the return signal to obtain I groups of new signals s i.
si＝s+β0EI(ω(i))
Wherein ω (i) represents gaussian white noise with mean and unit variance of 0 and 1, respectively, and i=1, 2,.; Representing a white noise figure for adjusting the required signal-to-noise ratio between the added noise and the residual after the added noise, ε 0 is typically set to 0.2, std (·) is the standard deviation operator; operator E k (. Cndot.) is the kth Intrinsic Mode Function (IMF) obtained by performing EMD decomposition.
S22: performing EMD decomposition on the s i times to obtain an envelope mean value meeting IMF determination conditions, performing addition average on the envelope mean values to obtain a first-order residual error r 1 of the return signal, and subtracting a current-order residual error from a sequence s of the return signal to obtain a first-order intrinsic mode function IMF 1, where:
r1＝<M(si))
IMF1＝s-r1
Wherein M (·) represents an operator of the local mean of the envelope satisfying the IMF decision condition; and </cndot > represents performing an average calculation.
S23: continuously adding I groups of Gaussian white noise into the first-order residual error, constructing a new signal r 1+β1E2(ω(i) to be decomposed), and calculating a local mean value through EMD decomposition to obtain a second-order residual error and IMF:
r2＝<M(r1+β1E2(ω(i))))
IMF2＝r1-r2
S24: similarly, for k=3..k, K can result in the K-th order residual:
rk＝<M(rk-1+βk-1Ek(ω(i)))>
wherein, beta k＝ε0std(rk).
S25: calculating the kth order IMF:
IMFk＝rk-1-rk
S26: steps S24 and S25 are repeated, and when the residual r k is a monotonic function, the calculation is stopped and the obtained IMF component is recorded.
S3: and according to the peak point of the envelope curve of the inherent mode function, combining the wave speed of the ultrasonic guided wave in the reinforcing steel bar and the anchoring compact section to obtain the debonding size.
The specific process can be as follows:
s31: the propagation speed C f of the ultrasonic guided wave in the steel bar is obtained.
The specific method can be as follows:
S310: and (3) carrying out ultrasonic guided wave detection on the free anchor rod with the known length L (i.e. the anchor rod without the anchor section) according to the process of the step S1, and identifying the excitation wave signal and the reflected wave packet signal at the bottom of the anchor rod on a time-amplitude spectrum generated by a return signal of the free anchor rod.
S311: according to the peak method, the peak value of the excitation wave on the time-amplitude spectrum and the time corresponding to the peak value of the reflected wave packet at the bottom of the anchor rod are respectively used as the excitation time and the reflection time, and the difference between the two is the double travel time delta t p, so that the single travel time of the guided wave on the free anchor rod and the anchor rod can be obtained
S312: the common anchor rod free section wave speed C f is obtained through the ratio of the length L of the free anchor rod to the single-pass propagation time of the guided wave on the free anchor rod.
S32: the propagation speed C b of the ultrasonic guided wave in the anchoring compaction section is obtained.
The specific method can be as follows:
S320: and (3) carrying out ultrasonic guided wave detection on the full-length anchored compact anchor rod with the known length L according to the process of the step S1, and identifying the excitation wave signal and the reflected wave packet signal at the bottom of the anchor rod on a time-amplitude spectrum generated by a return signal of the full-length anchored compact anchor rod.
S321: according to the peak value method, the time corresponding to the peak value of the excitation wave on the time-amplitude spectrum and the peak value of the reflected wave packet at the bottom of the anchor rod are respectively used as the excitation time and the reflection time, and the difference between the two is the double travel time delta t b, so that the single travel time on the guided wave anchoring dense anchor rod can be obtained
S322: the wave speed C b of the general anchoring dense section of the anchor rod is obtained through the ratio of the length L of the anchor rod to the single-pass propagation time of the guided wave on the anchoring dense anchor rod.
S33: and (3) determining the debonding size according to the peak point of the envelope curve of the natural mode function obtained in the step S3.
The method specifically comprises the following steps:
Finding out peak points of an envelope curve of the intrinsic mode function, analyzing peak points corresponding to upper and lower interfaces of the defect, determining respective corresponding reflection time t, and obtaining double-way travel time of the guided wave to different positions through difference values of the respective reflection time t and excitation time (namely, time corresponding to the peak value of the excitation wave on the time-amplitude spectrum), thereby obtaining respective single-way travel time. The total length of the anchor rod can be obtained by multiplying the reflection time corresponding to the anchoring dense section and the reflection time corresponding to the defect by the wave speed of the anchoring dense section and the wave speed of the free section of the anchor rod respectively:
Wherein L 1 is the length of the free section, L 3 is the length of the defect, L 21 and L 22 respectively represent the length of the anchor from the upper interface of the anchor to the upper interface of the defect and the length of the anchor from the lower interface of the defect to the bottom of the anchor, t b is the reflection time of the upper interface of the anchor, t r is the reflection time of the bottom of the anchor, and t g is the excitation time of the excitation wave. t dd is the reflection time of the interface under the anchoring defect, and t ud is the reflection time of the interface on the anchoring defect.
Thus, the size of the anchor defect can be obtained from the calculation result of L 3.
Example 1
Simulation experiments were performed by the above embodiments:
the detection target is an anchor rod with the total length of 3m and the diameter of 2cm, the length of the anchor body is 2.5m, a debonding defect exists in the middle part, and the defect length is 0.6m.
The return signal which is generated according to the above embodiment is shown in fig. 2.
The ICEEMDAN decomposition yields an IMF of order 10, as shown in fig. 3.
In order to obtain the wave velocity of ultrasonic guided waves in the reinforcing steel bars and the anchoring dense sections, ultrasonic guided wave detection is carried out on free anchor rods with the length of 3m (namely anchor rods without the anchoring sections) and full-length anchoring dense anchor rods according to the process of the step S1, and an envelope curve is obtained on the obtained reflected signals, as shown in fig. 4 and 5.
Fig. 4 is a waveform diagram of the reflection at the end of a free anchor, wherein the first wave packet is an excitation signal, the peak value thereof is 0.125ms, and the four wave packets are respectively the first, second, third and fourth reflection signals at the bottom of the anchor from left to right, and the first reflection wave packet is selected, and the peak value thereof is 1.285ms. Therefore, the double travel time of ultrasonic guided wave in the free anchor rod is 1.16ms, the single travel time is 0.58ms, and the wave speed in the steel bar is 5172m/s through the ratio of the anchor rod length of 3m to the single travel time.
Fig. 5 is a waveform diagram of the reflection at the end of a full length anchored dense bolt, wherein the first wave packet is an excitation signal with a peak value of 0.125ms, and the subsequent wave packet is a reflection wave packet at the bottom of the bolt with a peak value of 2.751ms. Therefore, the double-way travel time of ultrasonic guided waves in the anchoring dense anchor rod is 2.626ms, the single-way travel time is 1.313ms, and the wave speed of the anchoring dense section is 2285m/s through the ratio of the anchor rod length of 3m to the single-way travel time.
The first order IMF in fig. 3 is characterized by a waveform of the excitation signal with a peak value of 0.125ms. Characteristic reflected signals at the defect can be observed from the second-order IMF, and the third-to tenth-order IMFs contain too little physical information.
Therefore, the envelope curve of the second-order IMF is obtained, as shown in fig. 6, and the real positions corresponding to the upper anchor rod anchoring body interface, the upper defect interface, the lower defect interface and the anchor rod bottom are calculated according to the ultrasonic wave velocity and the geometric parameters of the detection target, and are identified in the figure as a broken line, B broken line, C broken line and D broken line respectively.
The ultrasonic guided wave is excited by the anchor rod end, firstly reaches the upper interface of the anchor body, and the guided wave is reflected back to the anchor rod end, so that the first wave packet represents a reflected signal of the upper interface of the anchor body, and the peak point of the reflected signal is a; the ultrasonic guided wave continues to propagate forwards and then reaches the upper interface and the lower interface of the defect, so that the second wave packet and the third wave packet respectively represent reflection signals of the upper interface and the lower interface of the defect, and the peak values of the reflection signals are b and c respectively; finally, the ultrasonic guided wave reaches the bottom of the anchor rod and is reflected back to the end head of the anchor rod, and the reflected wave packet of the bottom of the anchor rod can be judged according to the calculated true value of the bottom of the anchor rod, wherein the peak value of the reflected wave packet is d. There are a plurality of wave packets preceding the reflected signal at the interface under the defect and the reflected signal at the bottom of the anchor rod, which represent a plurality of echo signals of the repeated propagation of the ultrasonic guided wave between the defect and the anchor interface.
Based on the peak points, the corresponding times are obtained as 0.31ms,0.76ms,1.0ms and 2.29ms, respectively.
According to the time of the peak point and the ultrasonic wave velocity, the length of the free section of the anchor rod is calculated to be 0.48m, the length of the anchor rod is 3.08m, and the debonding size is 0.62m.
The relative error in testing for defects was 3.3%.
The above examples are only preferred embodiments of the present invention, and the scope of the present invention is not limited to the above examples. All technical schemes belonging to the concept of the invention belong to the protection scope of the invention. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be within the scope of the present invention.
Claims (5)
1. An ultrasonic guided wave defect quantitative detection method, which comprises the following steps:
Obtaining the propagation speed C f of the ultrasonic guided wave in the free section of the anchor rod without anchoring through ultrasonic guided wave detection;
Obtaining the propagation speed C b of the ultrasonic guided wave in the anchoring compaction section of the anchor rod through ultrasonic guided wave detection;
Obtaining the size of the anchor rod defect according to the following calculation model ：
；
Wherein L represents the total length of the anchor rod,For the length of the free section of the anchor rod,/>And/>Representing the anchor length from the upper interface of the anchor to the upper interface of the defect and the anchor length from the lower interface of the defect to the bottom of the anchor rod respectively,/>For the reflection time of ultrasonic guided wave at the interface of the anchoring body,/>Is the reflection time of ultrasonic guided wave at the bottom of the anchor rod, t g is the excitation time of excitation wave,/>For the ultrasonic guided wave reflection time of the interface under the anchoring defect,/>To anchor the ultrasonic guided wave reflection time of the interface on the defect,
Wherein, each time parameter is obtained through the following processes:
Respectively transmitting ultrasonic guided waves to an anchor rod without anchoring and an anchor rod with dense anchoring, which have the length L, and respectively collecting returned ultrasonic guided wave signals;
identifying a reflected wave packet signal of the excitation wave signal and the bottom of the anchor rod on a time-amplitude spectrum generated by the returned ultrasonic guided wave signal, wherein the time corresponding to the peak value of the excitation wave signal is excitation time;
Decomposing the returned ultrasonic guided wave signal through improved self-adaptive noise complete set empirical mode decomposition to obtain a decomposed intrinsic mode function;
determining ultrasonic guided wave reflection time t corresponding to each of different positions and upper and lower interfaces of the defect according to different positions of an anchor rod in peak points of an envelope curve of an inherent mode function and peak points corresponding to the upper and lower interfaces of the defect;
Obtaining double-way travel time of ultrasonic guided waves to different positions of the anchor rod and the upper and lower interfaces of the defect through the difference value of the reflection time t and the excitation time, and further obtaining respective single-way travel time;
wherein, the different positions of the anchor rod comprise an anchor upper interface and an anchor rod bottom;
The obtaining of the natural mode function comprises the following steps:
adding a plurality of groups of Gaussian white noise into the returned ultrasonic guided wave signals to generate a plurality of groups of corresponding new signals;
performing empirical mode decomposition on the signal sequence added with Gaussian white noise to obtain a plurality of envelope mean values, and performing total average on the envelope mean values to obtain a current-order residual error;
subtracting a current order residual error from the returned ultrasonic signal to obtain a current order inherent mode function, adding new groups of Gaussian white noise to the current order residual error, performing empirical mode decomposition again to obtain a plurality of new envelope mean values, performing total average on the plurality of new envelope mean values to obtain a new residual error, and subtracting the new residual error from the current order residual error to obtain a new inherent mode function;
repeating the steps until the extremum of the current order residual error is not more than two, and completing decomposition;
Wherein the new signal is obtained by the following calculation model:
，/>，
；
Wherein, Representing the new signal, s representing the returned ultrasonic guided wave signal,/>Gaussian white noise with mean and unit variance of 0 and 1 respectively is represented, I represents the number of added white noise, I represents the total number of added white noise,/>Representing a white noise figure for adjusting a desired signal-to-noise ratio between the added noise and the residual after the added noise,/>Representing the amplitude of the added noise,/>Is a standard deviation operator; /(I)An operator representing the 1 st natural mode function obtained by EMD decomposition;
And/or wherein the kth order residual obtained And the kth intrinsic mode function IMF k is obtained by the following calculation model:
rk＝<M(rk-1+βk-1Ek(ω(i))）>，，
，
，
Wherein, Envelope local mean operator representing satisfaction of natural mode function decision condition,/>Representing the averaging of the values,First/>, obtained for EMD decompositionOperators of intrinsic mode functions IMF,/>Representing the white noise figure set at the k-1 st addition of white noise.
2. The defect quantitative detection method according to claim 1, wherein: the ultrasonic guided wave is a longitudinal ultrasonic guided wave of 20-100 kHz.
3. The defect quantitative detection method according to claim 1, wherein: the obtaining of the propagation speed C f of the ultrasonic guided wave in the free section without anchoring comprises:
Carrying out ultrasonic guided wave detection on a free anchor rod with a known length L and without an anchor section, and identifying an excitation wave signal and a reflected wave packet signal at the bottom of the anchor rod on a time-amplitude spectrum generated by a return signal of the free anchor rod;
According to the peak value method, the time corresponding to the peak value of the excitation wave on the time-amplitude spectrum and the peak value of the reflected wave packet at the bottom of the anchor rod are respectively used as the excitation time and the reflection time, and the difference between the two is the double-way travel time delta t p, so that the single-way travel time of the guided wave on the free anchor rod is obtained
The common anchor rod free section wave speed C f is obtained through the ratio of the length L of the free anchor rod to the single-pass propagation time of the guided wave on the free anchor rod.
4. The defect quantitative detection method according to claim 1, wherein: the obtaining of the propagation speed C b of the ultrasonic guided wave in the anchoring compaction section of the anchor rod comprises the following steps:
ultrasonic guided wave detection is carried out on the full-length anchored compact anchor rod with the known length L, and an excitation wave signal and a reflected wave packet signal at the bottom of the anchor rod are identified on a time-amplitude spectrum generated by a return signal of the full-length anchored compact anchor rod;
According to the peak method, the time corresponding to the peak value of the excitation wave and the peak value of the reflected wave packet at the bottom of the anchor rod on the time-amplitude spectrum is respectively used as the excitation time and the reflection time, and the difference between the two is the double-journey travel time The single-pass propagation time/>, of the guided wave on the anchored dense anchor rod is obtained；
The common wave speed C b of the anchoring dense section is obtained through the ratio of the length L of the anchoring rod to the single-pass propagation time of the guided wave on the anchoring dense anchoring rod.
5. Use of the quantitative defect detection method according to any one of claims 1-4 in anchor rod debonding length measurement.
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