CN117630174A - Plate-type concrete multichannel-multi-degree-of-freedom pulse wave nondestructive testing method - Google Patents
Plate-type concrete multichannel-multi-degree-of-freedom pulse wave nondestructive testing method Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 51
- 238000009659 non-destructive testing Methods 0.000 title claims abstract description 16
- 238000001228 spectrum Methods 0.000 claims abstract description 33
- 238000003384 imaging method Methods 0.000 claims abstract description 21
- 238000009499 grossing Methods 0.000 claims abstract description 7
- 238000001514 detection method Methods 0.000 claims description 16
- 230000001052 transient effect Effects 0.000 claims description 14
- 238000010304 firing Methods 0.000 claims description 10
- 230000005284 excitation Effects 0.000 claims description 6
- 238000005259 measurement Methods 0.000 claims description 3
- 238000000059 patterning Methods 0.000 claims description 3
- 230000009466 transformation Effects 0.000 claims description 3
- 230000007547 defect Effects 0.000 description 5
- 230000035939 shock Effects 0.000 description 5
- 238000012360 testing method Methods 0.000 description 4
- 238000010276 construction Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000005553 drilling Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 229910001294 Reinforcing steel Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 239000004035 construction material Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
Abstract
The invention discloses a plate-type concrete multichannel-multi-degree-of-freedom pulse wave nondestructive testing method, which comprises the following steps: s1, acquiring pulse wave data of each measuring point according to the designed position of the observation system to obtain multi-channel pulse wave data; s2, carrying out Fourier transform on the multi-channel pulse wave data to obtain a frequency-space spectrum, and carrying out slight smoothing treatment on the frequency-space spectrum; s3, carrying out weighted superposition on the frequency-space spectrum curve according to the distance between the detector position and the measuring point position; s4, picking up and storing amplitude maximum value points and corresponding frequency values on the superimposed frequency-space spectrum curves, and arranging the amplitude maximum value points and the corresponding frequency values in sequence from large to small; s5, performing layer stripping imaging on the saved frequency value and the relative amplitude value based on the multi-degree-of-freedom model, and performing imaging by using the thickness of each layer and the corresponding relative amplitude value; and S6, calibrating and interpreting the imaging result. The method has strong anti-interference capability, high signal-to-noise ratio and more reliable extracted resonance frequency.
Description
Technical Field
The invention relates to the field of plate-type concrete structure detection, in particular to a plate-type concrete multichannel-multi-degree-of-freedom pulse wave nondestructive detection method.
Background
In the railway engineering construction process, concrete is one of main construction materials of main structures such as track slabs, bridges, tunnel linings and the like, so that the quality of the concrete is critical to the safety of a train running at a high speed, but the concrete is affected by a construction process, and the concrete member is inevitably subjected to defects such as uneven thickness, incompact inside and the like; in addition, the defects of train load, wind and rain erosion and temperature and humidity change can further cause corrosion of reinforcing steel bars of the concrete structure, so that durability and strength are poor, and potential safety hazards are formed. Therefore, the quality detection work of the prepared concrete structure has very important significance for railway construction and safe operation.
The existing methods for detecting and identifying concrete mainly comprise a core drilling method and an impact echo method.
As the name suggests, the core drilling method is to collect concrete samples deep into the concrete structure and directly perform internal defect inspection and rigidity detection, and the method has certain destructiveness on the concrete structure and is generally not welcome by industry owners.
The impact echo method is a nondestructive testing method for the thickness and compactness of a concrete structure based on stress waves, and the principle is as follows: the short-time mechanical shock wave is reflected for many times in the structure body to generate transient resonance, and the position and the range of the member defect are determined by using the resonance frequency. The existing impulse echo method is based on a single degree of freedom model, firstly, an effective signal is selected from time domain pulse signals, then only one maximum amplitude value and a corresponding frequency value are picked up to perform thickness calculation and strength estimation, the principle of the method is simple and easy to process, but the method has the following defects:
(1) The short-time shock wave is received in a single channel, the data is easily influenced by the outside, and the signal-to-noise ratio is low;
(2) The data processing process is based on a single degree of freedom model, the picked resonant frequency is often the main frequency of the sensor, and great uncertainty exists in effective signal selection and resonant frequency pickup, so that an error result is further caused.
Disclosure of Invention
Aiming at the current situation and the deficiency of the impact echo technology, the invention provides a plate-type concrete multichannel-multi-degree-of-freedom pulse wave nondestructive testing method which has strong anti-interference capability and high signal-to-noise ratio and does not need to identify effective signals of original signals.
The invention adopts the following technical scheme:
a plate-type concrete multichannel-multi-degree-of-freedom pulse wave nondestructive testing method comprises the following steps:
s1, designing a concrete detection area and measuring point positions, and acquiring pulse wave data of each measuring point by using a short-time transient mechanical wave triggering and array acquisition device according to the designed observation system positions to obtain multi-channel pulse wave data;
during acquisition, the positions of the excitation points of the short-time transient mechanical wave triggering and array acquisition device and the midpoints of detectors adjacent to the excitation points coincide with the positions of the measurement points;
s2, carrying out Fourier transformation on the multi-channel pulse wave data of each measuring point acquired in the S1 to obtain a frequency-space spectrum of the position of the measuring point, carrying out slight smoothing on the frequency-space spectrum, and carrying out the following steps:
，
wherein the method comprises the steps ofSmoothRepresenting smoothing operators, subscriptssRepresenting the smoothed spectrum;representing the frequency spectrum of the pulse signal of each channel,iwhich represents the number of the channel and,i=1,2,3…；
s3, according to the distance between the detector position and the measuring point position, weighting and superposing the frequency-space spectrum curve obtained in the S2:
，
s4, picking up and storing the amplitude maximum point and the corresponding frequency value on the frequency-space spectrum curve after the superposition of S3,
the frequency values are arranged in sequence from big to small:、/>、/>、/>the method comprises the steps of carrying out a first treatment on the surface of the Preserving the relative amplitude values corresponding to the different frequency values +.>、/>、/>、/>The method comprises the steps of carrying out a first treatment on the surface of the Wherein,nthe number of detectors;
s5, performing layer stripping imaging on the frequency value and the relative amplitude value stored in the step S4 based on the multi-degree-of-freedom model:
；
；
；
；
wherein,for concrete speed, < >>Thickness for each layer;
patterning using the thickness of each layer and the corresponding relative amplitude value;
and S6, calibrating and interpreting the imaging result of the step S5.
In step S3, when the frequency-space spectrum curves are weighted and superimposed, weighting coefficients of each channelThe distance between the detector and the measuring point is selected, the weighting coefficient of the position of the measuring point is large, the weighting coefficient of the position of the measuring point is small, and the method comprises the following steps:
。
preferably, in step S1, the distance between the short-time transient mechanical wave firing and the detector of the array acquisition device is 5-20 cm.
Preferably, the distance between the measuring points in step S1 is 0.5-1 m.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention designs a nondestructive testing method of the impact echo, which utilizes the multi-channel superposition effect to enhance the signal to noise ratio of effective signals, and compared with a single-channel data acquisition and processing mode, the method has strong anti-interference capability, high signal to noise ratio and can extract reliable resonance frequency;
2. the method adopts a multi-degree-of-freedom model imaging method, directly picks up the frequency values corresponding to all maximum amplitude values in the frequency spectrum curve, and has no possibility of losing effective information; the influence of invalid information is effectively eliminated through the integral calibration of the imaging result;
3. in the imaging principle aspect, the invention is based on a multi-degree-of-freedom resonance model, does not need to identify effective signals of original signals, the method can perform layer-by-layer stripping imaging on all the picked resonant frequencies one by one, and can be further expanded to multi-layer concrete structure detection.
Drawings
FIG. 1 is a schematic cross-sectional view of a device for triggering and collecting array in a transient mechanical wave in a short time in embodiment 1;
FIG. 2 is a schematic top view of the bracket of FIG. 1;
FIG. 3 is a schematic diagram of a state of the short-time transient mechanical wave firing and array acquisition device applied to the surface of a detected object;
FIG. 4 is a schematic diagram of the connection structure of the receiver and the bracket in the short-time transient mechanical wave firing and array acquisition device;
FIG. 5 is a flow chart of a method of slab concrete multi-channel-multi-degree of freedom pulse wave nondestructive testing;
FIG. 6 is an imaging result of the multi-channel-multi-degree of freedom pulse wave nondestructive testing method in example 1;
fig. 7 is an imaging result of a conventional shock echo technique.
In the figure:
1. the trigger switch 2, the guide rod 3, the impact spring 4, the heavy hammer 5, the buffer spring 6, the detector 7, the shell 8.U type clamping groove
9. Scale 10, top opening 11, trigger support 12, receiver support 13, receiver
Detailed Description
The following describes the plate-type concrete multichannel-multi-degree-of-freedom pulse wave nondestructive testing method in detail by referring to the drawings and the embodiments.
The invention discloses a plate-type concrete multichannel-multi-degree-of-freedom pulse wave nondestructive testing method, which adopts a short-time transient mechanical wave firing and array acquisition device shown in fig. 1-4 to acquire pulse wave data, wherein the acquisition device comprises a firing switch 1, a guide rod 2, an impact spring 3, a heavy hammer 4, a firing device support 11 and a receiver support 12, the firing device support 11 is used for installing a firing device, the receiver support 12 is used for installing a receiver array, and a graduated scale 9 is further arranged on at least one side of an opening 10 at the top of the receiver support 12. In this embodiment the receiver array consists of a plurality of receivers (only 3 are shown in the figure), each receiver 13 comprising a housing 7, a detector 6 and a buffer spring 5, the detector 6 being arranged to collect stress waves. A U-shaped clamping groove 8 is arranged on the top surface of the shell 7.
In use, the measurement point (the position corresponding to the midpoint position 15 between the falling point 14 of the weight 4 and the falling point of the detector 6 nearest to the excitation point (i.e. the contact point with the object to be measured)) is aligned with the acquisition point of the object to be measured (e.g. a track plate or a cement block), and is pressed with force, and the state of the device in the pressed state is shown in fig. 3. The trigger switch 1 is pulled upwards to the vertex position, and at the moment of releasing the hand, the heavy hammer 4 rapidly impacts the surface of the detected object under the drive of the impact spring 3 and the self weight to generate transient mechanical shock waves; the shock wave is recorded by the detector array after multiple bounces in the detection object. The device ensures the pressure equalization of each detector 6 through the buffer action of the buffer spring, and further obtains the multichannel stress wave record of energy equalization.
And sequentially testing and collecting all points on the test line according to the method.
Referring to fig. 5, the plate-type concrete multi-channel-multi-degree-of-freedom pulse wave nondestructive testing method of the invention comprises the following steps:
s1, firstly, designing a concrete detection area and a measuring point position, and acquiring pulse wave data of each measuring point by adopting the short-time transient mechanical wave triggering and array acquisition device according to the designed observation system position. Referring to FIG. 3, during acquisition, the midpoint position 15 between the falling point 14 of the weight 4 in the short-time transient mechanical wave firing and array acquisition device and the falling point (i.e. the contact point with the object to be measured) of the nearest detector 6 from the excitation point coincides with the measuring point position, and the distance between the detectorsdxThe smaller the detection accuracy is, the higher the detection accuracy is;
s2, collecting each measuring pointFourier transforming the multi-channel pulse wave data to obtain the frequency-space of the measuring point positionf-x) A spectrum;
in order to enhance the identification degree of characteristic frequency in a concrete structure and eliminate the influence of noise frequency on a detection result, the method needs to be carried outf-xSmoothing the spectrum:
wherein the method comprises the steps ofSmoothRepresenting smoothing operators, subscriptssRepresenting the smoothed spectrum;representing the frequency spectrum of the pulse signal of each channel,irepresentative channel number [ (]i=1,2,3……），
S3, carrying out weighted superposition on the spectrum-space spectrum curve of the multi-channel pulse wave data:
the weighting coefficient of each channel needs to be selected according to the distance between the detector and the measuring point, the weighting coefficient of the position of the measuring point is large, the weighting coefficient of the position of the measuring point is small, and a selection mode is provided:
wherein,mthe number of detectors.
The signal to noise ratio of the frequency spectrum-space spectrum data can be effectively enhanced through superposition of frequency spectrum-space spectrum curves, and the stability of subsequent characteristic frequency extraction is improved.
S4, picking up amplitude maxima on a spectrum-space spectrum curve and corresponding frequency values, wherein the frequency values are sequentially arranged from large to small as follows:、/>、/>、/>；
to enhance discrimination, the relative amplitude values (difference between absolute amplitude value and amplitude mean) corresponding to different frequency values are saved:、/>、/>、/>。
s5, performing layer stripping imaging on the frequency value and the relative amplitude value stored in the step S4 based on the multi-degree-of-freedom model:
；
；
；
......
；
wherein,for the propagation speed of elastic waves in concrete structures, < >>Is the thickness of the n-th layer.
Finally, the thickness of each layer is utilizedAnd corresponding relative amplitude valueA n A graph was formed (n=1, 2,3 …).
The layer stripping imaging mainly embodies the imaging principle aspect: based on the multi-degree-of-freedom resonance model, all resonance frequencies are picked up, the number of the resonance frequencies represents the number of layers, and the formula is adopted when the thickness of the 1 st layer is calculated:the method comprises the steps of carrying out a first treatment on the surface of the After calculating the nth (n>1) When the layer thickness is calculated as +.>I.e. the thickness of the 1 st to (n-1) th layers needs to be stripped off one by one, so that the method is called layer stripping imaging, and can be further expanded to the detection of a multi-layer concrete structure.
The signal to noise ratio of the frequency spectrum curve can be effectively enhanced through superposition of the frequency spectrum curve, and the extraction stability of the subsequent characteristic frequency is improved.
And S6, calibrating and interpreting the imaging result.
Example 1
In order to test the application effect of the method, application test is carried out in the detection of a certain tunnel lining, the layout length of the measuring line is 119m, the distance between the measuring points is 0.5m, and the total number of the measuring points is 239.
S1, observing and collecting pulse wave signals of each measuring point by using the device shown in FIG. 1, and keeping the collecting point coincident with the marked measuring point in FIG. 3 in the collecting process.
S2, carrying out Fourier transformation on multi-channel pulse wave data acquired by 239 measuring points to obtain frequency-space of all measuring point positionsf-x) Spectrum, and pairf-xThe spectra were slightly smoothed;
s3, carrying out weighted superposition on the multi-channel data spectrum-space spectrum curves of each measuring point;
s4, picking up and storing amplitude maximum points on the superimposed spectrum-space spectrum curve and corresponding frequency values;
s5, performing layer stripping imaging on the frequency and amplitude values stored in the step 4 based on a multi-degree-of-freedom model, wherein the multi-degree-of-freedom imaging result is shown in fig. 6, and a broken line in the drawing shows a lining thickness change curve. Compared with the result of the traditional detection method shown in fig. 7, the detection result of the invention is more clear;
and S6, calibrating and interpreting the imaging result.
Claims (4)
1. A plate-type concrete multichannel-multi-degree-of-freedom pulse wave nondestructive testing method is characterized by comprising the following steps of:
s1, designing a concrete detection area and measuring point positions, and acquiring pulse wave data of each measuring point by using a short-time transient mechanical wave triggering and array acquisition device according to the designed observation system positions to obtain multi-channel pulse wave data;
during acquisition, the positions of the excitation points of the short-time transient mechanical wave triggering and array acquisition device and the midpoints of detectors adjacent to the excitation points coincide with the positions of the measurement points;
s2, carrying out Fourier transformation on the multi-channel pulse wave data of each measuring point acquired in the S1 to obtain a frequency-space spectrum of the position of the measuring point, carrying out slight smoothing on the frequency-space spectrum, and carrying out the following steps:
，
wherein the method comprises the steps ofSmoothRepresenting smoothing operators, subscriptssRepresenting the smoothed spectrum;representing the frequency spectrum of the pulse signal of each channel,iwhich represents the number of the channel and,i=1,2,3…；
s3, according to the distance between the detector position and the measuring point position, weighting and superposing the frequency-space spectrum curve obtained in the S2:
，
s4, picking up and storing the amplitude maximum point and the corresponding frequency value on the frequency-space spectrum curve after the superposition of S3,
the frequency values are arranged in sequence from big to small:、/>、/>、/>the method comprises the steps of carrying out a first treatment on the surface of the Preserving relative amplitude values corresponding to different frequency values、/>、/>、/>The method comprises the steps of carrying out a first treatment on the surface of the Wherein,nthe number of detectors;
s5, performing layer stripping imaging on the frequency value and the relative amplitude value stored in the step S4 based on the multi-degree-of-freedom model:
；
；
；
.........
；
wherein, the concrete speed is the thickness of each layer;
patterning using the thickness of each layer and the corresponding relative amplitude value;
wherein, the concrete speed is the thickness of each layer;
patterning using the thickness of each layer and the corresponding relative amplitude value;
and S6, calibrating and interpreting the imaging result of the step S5.
2. The method for the nondestructive testing of the plate-type concrete multi-channel-multi-degree-of-freedom pulse waves according to claim 1, which is characterized by comprising the following steps of: s3, when the frequency-space spectrum curves are subjected to weighted superposition, the weighting coefficients of each channelThe distance between the detector and the measuring point is selected, the weighting coefficient of the position of the measuring point is large, the weighting coefficient of the position of the measuring point is small, and the method comprises the following steps:
。
3. the slab concrete multi-channel-multi-degree-of-freedom pulse wave nondestructive testing method according to claim 1, wherein the method comprises the following steps of: and S1, the distance between the short-time transient mechanical wave firing and the detector of the array acquisition device is 5-20 cm.
4. The slab concrete multi-channel-multi-degree-of-freedom pulse wave nondestructive testing method according to claim 1, wherein the method comprises the following steps of: the interval between each measuring point in the S1 is 0.5-1 m.
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