CN108088913B - Piezoelectric ultrasonic guided wave probe for flaw detection of steel rail bottom and flaw detection method thereof - Google Patents

Piezoelectric ultrasonic guided wave probe for flaw detection of steel rail bottom and flaw detection method thereof Download PDF

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CN108088913B
CN108088913B CN201810018322.7A CN201810018322A CN108088913B CN 108088913 B CN108088913 B CN 108088913B CN 201810018322 A CN201810018322 A CN 201810018322A CN 108088913 B CN108088913 B CN 108088913B
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piezoelectric
guided wave
frequency
wafer
rail
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CN108088913A (en
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林荣
马宏伟
温宇立
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Dongguan University of Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/24—Probes
    • G01N29/2437—Piezoelectric probes
    • G01N29/245—Ceramic probes, e.g. lead zirconate titanate [PZT] probes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/449—Statistical methods not provided for in G01N29/4409, e.g. averaging, smoothing and interpolation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/023—Solids
    • G01N2291/0234—Metals, e.g. steel
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/028—Material parameters
    • G01N2291/0289—Internal structure, e.g. defects, grain size, texture
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/26—Scanned objects
    • G01N2291/262—Linear objects
    • G01N2291/2623—Rails; Railroads
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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    • Y02E30/30—Nuclear fission reactors

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  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

The invention discloses a piezoelectric ultrasonic guided wave probe for flaw detection of a rail bottom of a steel rail and a flaw detection method thereof, wherein the probe comprises an outer layer shell, a plurality of piezoelectric units and at least one interface, each piezoelectric unit comprises a piezoelectric wafer, a cable, a damping block, a sound absorption filler, an elastic element and an inner layer shell, the piezoelectric wafer is a piezoelectric ceramic wafer in a length direction vibration mode, the piezoelectric ceramic wafer is arranged at the bottom of the outer layer shell, the vibration direction is parallel to a horizontal plane, one surface of the piezoelectric wafer, which is parallel to the vibration direction, is close to the damping block, the damping block is arranged in the inner layer shell, the sound absorption filler is filled between the damping block and the inner layer shell, the elastic element is arranged between the inner layer shell and the outer layer shell, and the interface is arranged at the top of the outer layer shell and is connected with the piezoelectric wafer through the cable. The piezoelectric wafer in the vibration mode in the length direction is high in sensitivity, long in single detection distance and high in signal to noise ratio, small damage can be detected, and meanwhile, the piezoelectric wafer is low in cost and convenient to popularize.

Description

Piezoelectric ultrasonic guided wave probe for flaw detection of steel rail bottom and flaw detection method thereof
Technical Field
The invention relates to a flaw detection device and a flaw detection method thereof, in particular to a piezoelectric ultrasonic guided wave probe for flaw detection of a rail bottom of a steel rail and a flaw detection method thereof, and belongs to the technical field of nondestructive detection.
Background
Rail flaw detection is one of the key works for ensuring the safe operation of trains. Current rail inspection generally uses ultrasonic technology to detect damage by transmitting pulsed sound waves from the rail head tread surface into the rail and receiving their reflected waves by an ultrasonic probe. The ultrasonic flaw detection technology only can detect local areas around the probe each time when pulse sound waves are emitted, and large-area flaw detection blind areas exist in areas on two sides of the rail bottom of the steel rail. Although rail head damage remains a major factor in causing rail breakage, in recent years, the number of rail break events or accidents due to rail bottom damage has also tended to rise due to the increase in speed and heavy duty trains.
Nondestructive testing methods such as eddy current, rays and magnetic powder are difficult to apply to rail flaw detection due to various factors such as environmental influence, low reliability, insufficient technical maturity and the like. The ultrasonic guided wave detection technology has unique technical advantages in nondestructive detection of long-distance uniform-section components, so that the rail flaw detection method based on ultrasonic guided waves becomes a research hot spot in recent years.
The rail damage detection method based on magnetostriction and longitudinal ultrasonic guided waves in Chinese patent publication No. CN102520068A uses a magnetostriction transducer to excite longitudinal ultrasonic guided waves in a rail to detect rail damage, but the magnetostriction-based ultrasonic guided waves have low signal-to-noise ratio and are difficult to apply in the field conveniently. In addition, the technique disclosed in this patent is mainly applicable to rail head flaw detection.
Ultrasonic guided wave flaw detection of a steel rail is performed by a hammering method, such as I Bartoli, J Zhang, and lu superb, but in a guided wave signal obtained by the hammering method, the recognition degree of a guided wave mode is low, so that a guided wave receiving transducer is required to be close to a damage point, which is often difficult to realize in actual detection. In addition, the hammer method is not suitable for production practice.
In recent years, non-contact ultrasonic guided wave flaw detection based on laser ultrasonic and air coupling is also developed, but the method still has obvious defects in the aspects of signal-to-noise ratio, precision and popularization.
Disclosure of Invention
The invention aims to provide a piezoelectric ultrasonic guided wave probe for flaw detection of a steel rail bottom, which adopts a piezoelectric wafer in a length direction vibration mode, has high sensitivity, long single detection distance and high signal to noise ratio, can detect smaller damage, has lower cost and is convenient to popularize.
The invention further aims to provide a flaw detection method based on the piezoelectric ultrasonic guided wave probe.
The aim of the invention can be achieved by adopting the following technical scheme:
a piezoelectric ultrasonic guided wave probe for rail end of rail flaw detection, including outer shell, a plurality of piezoelectricity unit and at least one interface, every piezoelectricity unit includes piezoelectricity wafer and cable conductor, piezoelectricity wafer is the piezoelectricity ceramic wafer of length direction vibration mode, and piezoelectricity wafer sets up in the bottom of outer shell, and vibration direction is parallel with the horizontal plane, the interface sets up at the top of outer shell to be connected with piezoelectricity wafer through the cable conductor.
Further, each piezoelectric unit further comprises a damping block, the damping block is arranged in the outer shell, a protective film is coated on one surface of the piezoelectric wafer, which is parallel to the vibration direction, and one surface of the piezoelectric wafer, which is parallel to the vibration direction, is clung to the damping block.
Further, each piezoelectric unit further includes an inner-layer housing disposed in the outer-layer housing, and the damper block is disposed in the inner-layer housing.
Further, each piezoelectric unit further comprises a sound absorption filler, and the sound absorption filler is filled between the damping block and the inner shell.
Further, each piezoelectric unit further includes an elastic element disposed between the inner and outer shells.
Further, the plurality of piezoelectric units are divided into at least one piezoelectric unit group, the at least one piezoelectric unit group is arranged in a longitudinal direction parallel to the vibration direction of the piezoelectric wafer, and all piezoelectric units in each piezoelectric unit group are arranged side by side in a transverse direction perpendicular to the vibration direction of the piezoelectric wafer.
Further, the outer side surface of the bottom of the outer shell forms a curved surface which can be attached to the upper surface of one side of the rail bottom of the steel rail, and the piezoelectric wafers of the piezoelectric units are arranged on the curved surface.
Further, when the interface is one, the piezoelectric wafers of the piezoelectric units are connected with the interface through cables; when the number of the interfaces is two or more, each interface is connected with the piezoelectric wafer of one piezoelectric unit or the piezoelectric wafers of a plurality of piezoelectric units.
The other object of the invention can be achieved by adopting the following technical scheme:
the flaw detection method based on the piezoelectric ultrasonic guided wave probe comprises the following steps:
when detecting one side of the rail bottom of the steel rail, placing a piezoelectric ultrasonic guided wave probe on the upper surface of the side of the rail bottom of the steel rail, so that the vibration direction of a piezoelectric wafer is parallel to the length direction of the steel rail, and when detecting, applying a certain pressure above the piezoelectric ultrasonic guided wave probe, so that the piezoelectric wafer at the bottom of the piezoelectric ultrasonic guided wave probe can be tightly attached to the upper surface of the side of the rail bottom of the steel rail;
when detecting the two sides of the rail bottom of the steel rail, respectively placing piezoelectric ultrasonic guided wave probes on the upper surfaces of the two sides of the rail bottom of the steel rail, so that the vibration direction of the piezoelectric wafer is parallel to the length direction of the steel rail, and when detecting, applying a certain pressure above the piezoelectric ultrasonic guided wave probes, so that the piezoelectric wafer at the bottom of the piezoelectric ultrasonic guided wave probes can be tightly attached to the upper surfaces of the two sides of the rail bottom of the steel rail;
and connecting the piezoelectric ultrasonic guided wave probe with external equipment, and selecting proper detection frequency to perform ultrasonic guided wave rail flaw detection by combining the piezoelectric ultrasonic guided wave probe and the selected piezoelectric wafer.
Further, selecting a proper detection frequency for ultrasonic guided wave rail flaw detection specifically comprises:
selecting an ultrasonic guided wave detection frequency upper limit and a ultrasonic guided wave detection frequency lower limit according to detection requirements;
a plurality of frequency points are separated from the frequency range between the upper frequency limit and the lower frequency limit at equal intervals to serve as measuring points;
the measuring points are used as excitation frequencies to conduct guided wave detection respectively;
respectively carrying out time-frequency analysis on the guided wave receiving signals of each measuring point to obtain a time-frequency analysis result of the guided wave receiving signals of each measuring point;
spreading the upper frequency limit, the lower frequency limit and the time-frequency analysis result of each detection in the frequency range by taking time and frequency as axes respectively, adding the values of the corresponding time points and the frequency points respectively, and drawing a guided wave time-frequency analysis chart of the excitation frequency corresponding to the frequency range in guided wave detection;
according to the guided wave time-frequency analysis chart, the ultrasonic guided wave rail flaw detection is preferably carried out by adopting the proper guided wave excitation center frequency and the guided wave flaw detection analysis frequency/frequency band.
Compared with the prior art, the invention has the following beneficial effects:
1. the piezoelectric ultrasonic guided wave probe is convenient to use and easy to popularize, each piezoelectric unit in the piezoelectric ultrasonic guided wave probe adopts a piezoelectric wafer in a length direction vibration mode (LE mode), has good response in a frequency range of ten kilohertz to hundreds of kilohertz, overcomes the defect that the traditional ultrasonic steel rail flaw detection technology has a large-area flaw detection blind area in the two side areas of the steel rail bottom, has long single detection distance, can reach ten meters to tens meters, has high flaw detection efficiency, and has higher sensitivity and signal-to-noise ratio and can detect smaller damage when being used for flaw detection of the rail bottom compared with the traditional ultrasonic guided wave probe.
2. The piezoelectric wafers in each piezoelectric unit are covered with the protective film on the surface which is parallel to the outer side of the vibration direction, the surface which is parallel to the inner side of the vibration direction is clung to the damping block, the protective film can protect the piezoelectric wafers from being damaged in the use process, and the damping block can provide damping for the vibration of the piezoelectric wafers so as to reduce the pulse width, improve the resolution and provide supporting effect for the piezoelectric wafers.
3. The sound absorption filler in each piezoelectric unit is filled between the damping block and the inner shell, and can absorb sound waves transmitted by the piezoelectric wafer to the back surface (the surface parallel to the inner side of the vibration direction) so as to reduce pulse clutter.
4. The elastic element in each piezoelectric unit is arranged between the inner layer shell and the outer layer shell, can provide the functions of transmitting and balancing external pressure, and can enable the outer layer shell and the inner layer shell to relatively move in a small range so as to ensure that the piezoelectric wafer can be in perfect contact with the upper surface of one side of the rail bottom during detection.
5. The outer side surface of the bottom of the outer shell forms a curved surface which can be attached to the upper surface of one side of the rail bottom of the steel rail, and piezoelectric wafers of all piezoelectric units are arranged on the curved surface so as to achieve better contact effect.
6. In order to select proper detection frequency, the invention uses a time-frequency analysis technology, can obtain the propagation characteristic of guided waves in the whole relevant frequency domain range, so that the time-frequency characteristics of a plurality of actual signals can be conveniently and intuitively utilized to optimize the guided wave detection excitation frequency, the problem that the theoretical analysis based on a dispersion curve is not matched with the actual guided wave detection when the guided wave excitation frequency is selected can be avoided, and the analysis frequency of the guided wave detection can be conveniently obtained.
Drawings
Fig. 1 is a cross-sectional view of a piezoelectric ultrasonic guided wave probe of embodiment 1 of the present invention parallel to the vibration direction of a piezoelectric wafer.
Fig. 2 is a cross-sectional view of the piezoelectric ultrasonic guided wave probe of embodiment 1 of the present invention perpendicular to the vibration direction of the piezoelectric wafer.
Fig. 3 is an axial side view of the piezoelectric ultrasonic guided wave probe of embodiment 1 of the present invention showing the top of the outer layer housing.
Fig. 4 is an axial side view showing the bottom of the outer housing of the piezoelectric ultrasonic guided wave probe of embodiment 1 of the present invention.
Fig. 5 is an isometric view of a piezoelectric wafer in a piezoelectric ultrasonic guided wave probe according to embodiment 1 of the present invention.
Fig. 6 is a front view of a piezoelectric wafer in a piezoelectric ultrasonic guided wave probe according to embodiment 1 of the present invention.
Fig. 7 is a plan view of a piezoelectric wafer in the piezoelectric ultrasonic guided wave probe of embodiment 1 of the present invention.
Fig. 8 is a side view of a piezoelectric wafer in a piezoelectric ultrasonic guided wave probe according to embodiment 1 of the present invention.
Fig. 9 is a schematic plan view of a piezoelectric ultrasonic guided wave probe of embodiment 1 of the present invention placed on an upper surface of one side of a rail foot of a steel rail.
Fig. 10 is a three-dimensional schematic view of a piezoelectric ultrasonic guided wave probe of embodiment 1 of the present invention placed on one side upper surface of a rail foot of a steel rail.
Fig. 11 is an enlarged view at a in fig. 10.
Fig. 12 is a schematic diagram of connection between a piezoelectric ultrasonic guided wave probe and an external device with signal excitation and reception functions integrated in one channel according to embodiment 1 of the present invention.
Fig. 13 is a schematic diagram of connection between two piezoelectric ultrasonic guided wave probes of embodiment 2 of the present invention and an excitation channel and a receiving channel of an external device, respectively.
Fig. 14 is a schematic diagram of two piezoelectric ultrasonic guided wave probes according to embodiment 3 of the present invention connected to an external excitation device and an external receiving device, respectively.
Fig. 15 is a schematic plan view of the piezoelectric ultrasonic guided wave probe of embodiment 4 of the present invention placed on the upper surfaces of both sides of the rail bottom of the steel rail.
Fig. 16 is a schematic diagram of the piezoelectric ultrasonic guided wave probe according to embodiment 5 of the present invention in which each interface is connected to a piezoelectric wafer of one piezoelectric unit.
Fig. 17 is a cross-sectional view of the piezoelectric ultrasonic guided wave probe of embodiment 6 of the present invention parallel to the vibration direction of the piezoelectric wafer.
Fig. 18 is a schematic diagram of connection between two interfaces of the piezoelectric ultrasonic guided wave probe according to embodiment 6 of the present invention and an excitation channel and a receiving channel of an external device, respectively.
Fig. 19 is a schematic diagram of two interfaces in the piezoelectric ultrasonic guided wave probe according to embodiment 7 of the present invention connected to an external excitation device and an external receiving device, respectively.
The device comprises a 1-outer shell, a 2-interface, a 3-piezoelectric wafer, a 4-cable, a 5-damping block, a 6-sound absorption filler, a 7-elastic element, an 8-inner shell, a 9-piezoelectric ultrasonic guided wave probe, a 10-steel rail, 11-external equipment, 12-external excitation equipment and 13-external receiving equipment.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but embodiments of the present invention are not limited thereto.
Example 1:
the embodiment provides a piezoelectric ultrasonic guided wave probe which can be used for flaw detection of a steel rail bottom, overcomes the defect that a large-area flaw detection blind area exists in two side areas of the steel rail bottom in the traditional ultrasonic steel rail flaw detection technology, is long in single detection distance, can reach ten meters to tens of meters in typical single detection distance, and is high in flaw detection efficiency.
As shown in fig. 1 to 4, the piezoelectric ultrasonic guided wave probe of the present embodiment includes an outer layer housing 1, five piezoelectric units, each of which includes a piezoelectric wafer 3, a cable 4, a damping block 5, a sound absorption filler 6, an elastic element 7, and an inner layer housing 8, and an interface 2.
As shown in fig. 5 to 8, the piezoelectric wafer 3 is a piezoelectric ceramic wafer in a longitudinal vibration mode (LE mode), specifically a piezoelectric ceramic wafer in a PZT-5 type longitudinal vibration mode, and the vibration mode can be seen from fig. 5 and 6; the negative pole of piezoelectric wafer 3 bordures, its total length L is 16mm, effective length L is 14mm, width w is 4mm, thickness d is 1mm, this piezoelectric wafer 3 has good response in 10kHz ~ 300 kHz's within range, can satisfy the excitation and the receipt of guided wave in the common frequency range, during the encapsulation, the vibration direction of piezoelectric wafer 3 is parallel with the horizontal plane, and be parallel to the vibration direction and cover on the one side outside, be parallel to the vibration direction and hug closely with damping piece 5, the protection film is made by sound transmission performance and wear resistance's material, have better rigidity in order to protect piezoelectric wafer 3 not to receive the damage in the use simultaneously.
The cable 4 is preferably a coaxial cable for connecting five piezoelectric wafers 3 to the interface 2.
The damping block 5 is disposed in the inner housing 8, and in this embodiment, since the inner side of the piezoelectric wafer 3 parallel to the vibration direction is closely attached to the damping block 5, a part of the piezoelectric wafer 3 is also disposed in the inner housing 8, and the damping block 5 can provide damping for the vibration of the piezoelectric wafer 3 to reduce the pulse width, improve the resolution, and provide a supporting effect for the piezoelectric wafer 3.
The sound absorption filler 6 is filled between the damping block 5 and the inner shell 8, and is mainly used for absorbing sound waves transmitted by the piezoelectric wafer 3 to the back surface (the surface parallel to the inner side of the vibration direction) so as to reduce pulse clutter.
The elastic element 7 is arranged between the inner shell 8 and the outer shell 1, the elastic element 7 can be a spring, a spring piece or an elastic filler, preferably a spring is adopted, the action of transmitting and balancing external pressure is provided, and the outer shell 1 and the inner shell 8 can relatively move in a small range so as to ensure that the piezoelectric wafer 3 can be in perfect contact with the upper surface of one side of the rail bottom during detection.
The inner shell 8 is arranged in the outer shell 1 and is used for packaging the piezoelectric crystal plate 3, the damping block 5 and the sound absorption filler 6.
The interface 2 can be a BNC or MCX interface and can be connected with the cable 4, namely, the connection with five piezoelectric wafers 3 through the cable 4 is realized.
In the present embodiment, the five piezoelectric units are divided into one piezoelectric unit group, that is, only one piezoelectric unit group in the longitudinal direction parallel to the vibration direction of the piezoelectric wafer 3, as can be seen from fig. 1; in the transverse direction perpendicular to the vibration direction of the piezoelectric wafer 3, five piezoelectric units in the group of piezoelectric units are arranged side by side and are packaged in the inner part and the bottom of the outer shell 1, as can be seen from fig. 2; in order to attach to the upper surface of one side of the rail bottom of the steel rail, the piezoelectric ultrasonic guided wave probe of this embodiment forms a curved surface on the outer side of the bottom of the outer shell 1, which can attach to the upper surface of one side of the rail bottom of the steel rail, and after the piezoelectric unit group is packaged, five piezoelectric wafers 3 are transversely arranged on the curved surface, so as to achieve a better contact effect, as can be seen from fig. 4.
In the embodiment, one side of the rail bottom of the steel rail is detected, as shown in fig. 9-11, a piezoelectric ultrasonic guided wave probe 9 is placed on the upper surface of the side of the rail bottom of the steel rail 10, so that the vibration direction of a piezoelectric wafer 3 is parallel to the length direction of the steel rail 10, in fig. 9, the projection of the piezoelectric ultrasonic guided wave probe 9 on the cross section of the steel rail 10 can be seen, and when the detection is performed, a certain pressure is applied above the piezoelectric ultrasonic guided wave probe 9, so that the piezoelectric wafer 3 at the bottom of the piezoelectric ultrasonic guided wave probe 9 can be tightly attached to the upper surface of the side of the rail bottom of the steel rail 10; as shown in fig. 12, the interface 2 of the piezoelectric ultrasonic guided wave probe 9 is connected to an external device 11, and the external device 11 may be an ultrasonic guided wave flaw detector or other devices with signal excitation and/or receiving functions, and the external device 11 of this embodiment is specifically an external device with signal excitation and receiving functions integrated in one channel, and in the detection, the piezoelectric wafer 3 of the piezoelectric ultrasonic guided wave probe 9 realizes excitation of guided waves by the inverse piezoelectric effect and reception of guided waves by the piezoelectric effect.
In this embodiment, after the interface 2 of the piezoelectric ultrasonic guided wave probe 9 is connected to the external device 11, the piezoelectric ultrasonic guided wave probe 9 and the selected piezoelectric wafer 3 are combined, and an appropriate detection frequency is selected to perform ultrasonic guided wave rail flaw detection.
The method for ultrasonic guided wave rail flaw detection by selecting proper detection frequency specifically comprises the following steps:
1) Selecting an ultrasonic guided wave detection frequency upper limit and a frequency lower limit according to detection requirements, wherein the frequency upper limit is marked as f U The lower frequency limit is denoted as f L The frequency range between them is denoted as [ f ] L ，f U ]。
2) A frequency range [ f ] between an upper frequency limit and a lower frequency limit L ，f U ]A plurality of frequency points are separated according to the equal interval delta f to serve as measuring points, and the plurality of frequency points are f L +Δf，f L +2*Δf，f L +3*Δf，……，f U 。
3) And carrying out guided wave detection by taking the measuring points as excitation frequencies.
In order to facilitate data processing, in this embodiment, before the guided wave detection is performed by using the measurement points as excitation frequencies, the detected trigger time and the guided wave signal sampling frequency may be set, so that the time labels of the guided wave excitation times in the guided wave receiving signals of each measurement point are the same, and the guided wave receiving signal sampling frequencies of each guided wave detection are consistent.
If the triggering time of detection and the sampling frequency of the guided wave signal are not set before the guided wave detection is performed by taking the measuring point as the excitation frequency, the time axis of the guided wave receiving signal is shifted after the guided wave detection is performed by taking the measuring point as the excitation frequency, so that the time labels of the guided wave excitation time in all the guided wave receiving signals are the same, the guided wave receiving signals with high sampling frequency are downsampled, the sampling frequencies of all the guided wave receiving signals are consistent, and the lowest sampling frequency meets the requirement of the sampling theorem.
4) Respectively carrying out time-frequency analysis T (f, T) on the guided wave receiving signals of each measuring point to obtain a time-frequency analysis result A of the guided wave receiving signals of each measuring point i (i＝1,2,3,…)。
5) Upper frequency limit f U Lower frequency limit f L And said frequency range [ f L ，f U ]Time-frequency analysis result A of each detection i (i=1, 2,3, …) in time and frequency, respectivelyAnd (3) expanding the frequency as an axis, respectively adding the values of the corresponding time point and the frequency point, and drawing a guided wave time-frequency analysis chart of the excitation frequency corresponding to the frequency range in guided wave detection.
6) Judging whether further analysis is needed to be carried out on the sub-frequency bands in the frequency range according to the guided wave mode of the guided wave time-frequency analysis chart, if so, entering the step 7), otherwise, entering the step 8).
In this step, if the guided wave mode of the guided wave time-frequency analysis chart is too complex, further analysis of the sub-bands in the frequency range is required.
7) Selecting a sub-frequency band, and respectively taking the upper limit and the lower limit of the sub-frequency band as the upper limit and the lower limit of the frequency, returning to the step 2) so as to re-draw the guided wave time-frequency analysis chart.
8) According to the guided wave time-frequency analysis chart, the ultrasonic guided wave steel rail flaw detection is preferably carried out at a proper guided wave excitation frequency and analysis frequency/frequency band, specifically: the guided wave time-frequency analysis chart can intuitively show the distribution, intensity and dispersion characteristics of different guided wave modes in each frequency band, and the proper guided wave excitation frequency and analysis frequency/frequency band are optimized for ultrasonic guided wave rail flaw detection according to the quantity of the guided wave modes, whether the guided wave modes are easy to identify and the amplitude displayed by the guided wave time-frequency analysis chart, and the principles of less quantity of comprehensive guided wave modes, easy identification, ideal amplitude and the like.
After the treatment of the steps, 62kHz is preferably used as the central frequency of guided wave excitation, and 20-220 kHz is preferably used as the guided wave flaw detection analysis frequency, so that the ultrasonic guided wave flaw detection of the rail bottom of the steel rail is completed.
Example 2:
the main characteristics of this embodiment are: the structure of the piezoelectric ultrasonic guided wave probe is the same as that of the embodiment 1, as shown in fig. 13, one side of the rail bottom of the steel rail is detected, but two piezoelectric ultrasonic guided wave probes 9 are arranged on the upper surface of the side of the rail bottom of the steel rail 10, so that the vibration direction of the piezoelectric wafer 3 is parallel to the length direction of the steel rail 10, and when in detection, a certain pressure is applied above the piezoelectric ultrasonic guided wave probes 9, so that the piezoelectric wafer 3 at the bottom of the piezoelectric ultrasonic guided wave probes 9 can be clung to the upper surface of the side of the rail bottom of the steel rail 10; the interfaces 2 of the two piezoelectric ultrasonic guided wave probes 9 are respectively connected to an excitation channel and a receiving channel of the external equipment 11, the piezoelectric ultrasonic guided wave probes 9 connected with the excitation channel of the external equipment 11 realize the excitation of guided waves through the inverse piezoelectric effect on the piezoelectric wafer 3 in detection, and the piezoelectric ultrasonic guided wave probes 9 connected with the receiving channel of the external equipment 11 realize the reception of guided waves through the piezoelectric effect on the piezoelectric wafer 3 in detection.
Example 3:
the main characteristics of this embodiment are: the structure of the piezoelectric ultrasonic guided wave probe is the same as that of the embodiment 1, as shown in fig. 14, two piezoelectric ultrasonic guided wave probes 9 are placed on the upper surface of one side of the rail bottom of the steel rail 10 to detect one side of the rail bottom of the steel rail, but the external equipment comprises an external excitation device 12 and an external receiving device 13, namely, the excitation and receiving functions of signals are realized by different external equipment, the interfaces 2 of the two piezoelectric ultrasonic guided wave probes 9 are respectively connected to the external excitation device 12 and the external receiving device 13, the piezoelectric ultrasonic guided wave probes 9 connected with the external excitation device 12 realize the excitation of guided waves through inverse piezoelectric effect on the piezoelectric wafer 3 during detection, and the piezoelectric ultrasonic guided wave probes 9 connected with the external receiving device 13 realize the reception of guided waves through piezoelectric effect on the piezoelectric wafer 3 during detection.
Example 4:
the main characteristics of this embodiment are: the structure of the piezoelectric ultrasonic guided wave probe is the same as that of the embodiment 1, and the two sides of the rail bottom of the steel rail are detected, as shown in fig. 15, the piezoelectric ultrasonic guided wave probe 9 is respectively placed on the upper surfaces of the two sides of the rail bottom of the steel rail 10, so that the vibration direction of the piezoelectric wafer 3 is parallel to the length direction of the steel rail 10, in fig. 15, the projection of the piezoelectric ultrasonic guided wave probe 9 on the cross section of the steel rail 10 can be seen, and when in detection, a certain pressure is applied above the piezoelectric ultrasonic guided wave probe 9, so that the piezoelectric wafer 3 at the bottom of the piezoelectric ultrasonic guided wave probe 9 can be tightly attached to the upper surfaces of the two sides of the rail bottom of the steel rail 10, and a person skilled in the art can know that the two sides of the rail bottom of the steel rail 10 can be detected simultaneously, or sequentially.
Example 5:
the main characteristics of this embodiment are: as shown in fig. 16, the number of the interfaces 2 in the piezoelectric ultrasonic guided wave probe is five, and each interface 2 is connected with one piezoelectric wafer 3 through a cable 4.
As can be appreciated by those skilled in the art, the number of the interfaces 2 in the piezoelectric ultrasonic guided wave probe can be four, wherein three interfaces 2 are respectively connected with three piezoelectric wafers 3 in a one-to-one correspondence manner through cables 4, and the other interface 2 is connected with one piezoelectric wafer 3 through the cables 4; the number of the interfaces 2 in the piezoelectric ultrasonic guided wave probe can be three, the first interface 2 is connected with two piezoelectric wafers 3 through a cable 4, the second interface 2 is connected with two piezoelectric wafers 3 through the cable 4, and the third interface is connected with one piezoelectric wafer 3 through the cable 4; the number of the interfaces 2 in the piezoelectric ultrasonic guided wave probe can be two, the first interface 2 is connected with three piezoelectric wafers 3 through a cable 4, and the second interface 2 is connected with two piezoelectric wafers 3 through the cable 4. The remainder are as in examples 1,2,3 or 4.
Example 6:
the main characteristics of this embodiment are: the number of piezoelectric units in the piezoelectric ultrasonic guided wave probe is ten, the ten piezoelectric units are divided into two groups of piezoelectric units, namely, each group of piezoelectric units is provided with five piezoelectric units, as shown in fig. 17, the two groups of piezoelectric units are arranged in a longitudinal direction parallel to the vibration direction of the piezoelectric wafers 3, the two groups of piezoelectric units are packaged in the inner part and the bottom of the outer shell 1, the five piezoelectric units in each group of piezoelectric units are arranged side by side in a transverse direction perpendicular to the vibration direction of the piezoelectric wafers 3, correspondingly, the number of interfaces 2 in the piezoelectric ultrasonic guided wave probe in the embodiment is two, wherein the five piezoelectric wafers 3 in one group of piezoelectric units are connected with one interface 2, and the five piezoelectric wafers 3 in the other group of piezoelectric units are connected with the other interface 2.
As shown in fig. 18, in the present embodiment, one side of the rail bottom of the rail 10 is inspected, the piezoelectric ultrasonic guided wave probe 9 is placed on the upper surface of the side of the rail bottom of the rail 10 so that the vibration direction of the piezoelectric wafer 3 is parallel to the length direction of the rail 10, and when inspecting, a certain pressure is applied above the piezoelectric ultrasonic guided wave probe 9 so that the piezoelectric wafer 3 at the bottom of the piezoelectric ultrasonic guided wave probe 9 can be closely attached to the upper surface of the side of the rail bottom of the rail 10; the two interfaces 2 of the piezoelectric ultrasonic guided wave probe 9 are respectively connected to an excitation channel and a receiving channel of the external device 11, five piezoelectric units connected with the excitation channel of the external device 11, the piezoelectric wafer 3 realizes the excitation of guided waves through the inverse piezoelectric effect in detection, and five piezoelectric units connected with the receiving channel of the external device 11, and the piezoelectric wafer 3 realizes the reception of guided waves through the piezoelectric effect in detection.
Example 7:
the main characteristics of this embodiment are: the structure of the piezoelectric ultrasonic guided wave probe is the same as that of example 6, as shown in fig. 19, the piezoelectric ultrasonic guided wave probe 9 is placed on the upper surface of one side of the rail bottom of the rail 10, but the external equipment comprises an external excitation device 12 and an external receiving device 13, namely, the excitation and receiving functions of signals are realized by different external equipment, two interfaces 2 of the piezoelectric ultrasonic guided wave probe 9 are respectively connected to five piezoelectric units connected with the external excitation device 12, the piezoelectric wafer 3 realizes the excitation of guided waves through the inverse piezoelectric effect in detection, and the piezoelectric wafer 3 realizes the reception of guided waves through the piezoelectric effect in detection.
In the above embodiments 1 to 7, the piezoelectric ultrasonic guided wave probe may be mounted in an external jig or other external mechanical device to facilitate the implementation of detection; in addition, under the condition of allowing, the number of the piezoelectric units is increased in the transverse direction perpendicular to the length direction of the steel rail, so that the excitation and the reception of guided waves are facilitated.
In summary, the piezoelectric ultrasonic guided wave probe is convenient to use and low in cost, the piezoelectric ultrasonic guided wave probe is easy to popularize, each piezoelectric unit in the piezoelectric ultrasonic guided wave probe adopts a piezoelectric wafer in a length direction vibration mode (LE mode), the piezoelectric ultrasonic guided wave probe has good response in a frequency range of ten kilohertz to hundreds of kilohertz, the defect that a large-area flaw detection blind area exists in two side areas of a rail bottom of a steel rail in the traditional ultrasonic steel rail flaw detection technology is overcome, the single detection distance is long, the typical single detection distance can reach ten meters to tens meters, the flaw detection efficiency is high, and compared with the traditional ultrasonic guided wave probe, the sensitivity and the signal-to-noise ratio are higher when the piezoelectric ultrasonic guided wave probe is used for rail bottom flaw detection, the single detection distance is longer, and less damage can be detected.
The above-mentioned embodiments are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can equally substitute or change the technical solution and the inventive concept of the present invention, including using the characteristics of relative independence of the guided wave excitation and the guided wave receiving process of the ultrasonic guided wave flaw detection, and using the present invention to separately implement the guided wave excitation or separately implement the guided wave receiving, which falls within the protection scope of the present invention.

Claims (8)

1. The utility model provides a flaw detection method based on piezoelectricity supersound guided wave probe, piezoelectricity supersound guided wave probe is used for rail foot to detect a flaw, includes outer casing, a plurality of piezoelectricity unit and at least one interface, and every piezoelectricity unit includes piezoelectricity wafer and cable conductor, piezoelectricity wafer is length direction vibration mode's piezoelectricity potsherd, and piezoelectricity wafer sets up in the bottom of outer casing, and vibration direction is parallel with the horizontal plane, the interface sets up at the top of outer casing to be connected with piezoelectricity wafer through the cable conductor, its characterized in that: the method comprises the following steps:
when detecting one side of the rail bottom of the steel rail, placing a piezoelectric ultrasonic guided wave probe on the upper surface of the side of the rail bottom of the steel rail, so that the vibration direction of a piezoelectric wafer is parallel to the length direction of the steel rail, and when detecting, applying a certain pressure above the piezoelectric ultrasonic guided wave probe, so that the piezoelectric wafer at the bottom of the piezoelectric ultrasonic guided wave probe can be tightly attached to the upper surface of the side of the rail bottom of the steel rail;
when detecting the two sides of the rail bottom of the steel rail, respectively placing piezoelectric ultrasonic guided wave probes on the upper surfaces of the two sides of the rail bottom of the steel rail, so that the vibration direction of the piezoelectric wafer is parallel to the length direction of the steel rail, and when detecting, applying a certain pressure above the piezoelectric ultrasonic guided wave probes, so that the piezoelectric wafer at the bottom of the piezoelectric ultrasonic guided wave probes can be tightly attached to the upper surfaces of the two sides of the rail bottom of the steel rail;
connecting a piezoelectric ultrasonic guided wave probe with external equipment, and selecting a proper detection frequency to perform ultrasonic guided wave rail flaw detection by combining the piezoelectric ultrasonic guided wave probe and a selected piezoelectric wafer;
the method for ultrasonic guided wave rail flaw detection by selecting proper detection frequency specifically comprises the following steps:
selecting an ultrasonic guided wave detection frequency upper limit and a ultrasonic guided wave detection frequency lower limit according to detection requirements;
a plurality of frequency points are separated from the frequency range between the upper frequency limit and the lower frequency limit at equal intervals to serve as measuring points;
the measuring points are used as excitation frequencies to conduct guided wave detection respectively;
shifting the time axis of the guided wave receiving signals so that the time labels of the guided wave excitation moments in all the guided wave receiving signals are the same, and downsampling the guided wave receiving signals with high sampling frequency so that the sampling frequencies of all the guided wave receiving signals are consistent, and the lowest sampling frequency meets the requirement of a sampling theorem;
respectively carrying out time-frequency analysis on the guided wave receiving signals of each measuring point to obtain a time-frequency analysis result of the guided wave receiving signals of each measuring point;
spreading the upper frequency limit, the lower frequency limit and the time-frequency analysis result of each detection in the frequency range by taking time and frequency as axes respectively, adding the values of the corresponding time points and the frequency points respectively, and drawing a guided wave time-frequency analysis chart of the excitation frequency corresponding to the frequency range in guided wave detection;
according to the guided wave time-frequency analysis chart, the ultrasonic guided wave rail flaw detection is preferably carried out by adopting the proper guided wave excitation center frequency and the guided wave flaw detection analysis frequency/frequency band.
2. The flaw detection method according to claim 1, characterized in that: each piezoelectric unit further comprises a damping block, the damping block is arranged in the outer shell, a protective film is coated on one surface of the piezoelectric wafer, which is parallel to the vibration direction, and one surface of the piezoelectric wafer, which is parallel to the vibration direction, is clung to the damping block.
3. The flaw detection method according to claim 2, characterized in that: each piezoelectric unit further comprises an inner layer shell, the inner layer shell is arranged in the outer layer shell, and the damping blocks are arranged in the inner layer shell.
4. A flaw detection method according to claim 3, wherein: each piezoelectric unit further comprises a sound absorption filler, and the sound absorption filler is filled between the damping block and the inner-layer shell.
5. A flaw detection method according to claim 3, wherein: each piezoelectric unit further includes an elastic element disposed between the inner and outer shells.
6. The flaw detection method according to claim 1, characterized in that: the piezoelectric units are divided into at least one group of piezoelectric unit groups, the at least one group of piezoelectric unit groups are arranged in a longitudinal direction parallel to the vibration direction of the piezoelectric wafer, and all piezoelectric units in each group of piezoelectric unit groups are arranged side by side in a transverse direction perpendicular to the vibration direction of the piezoelectric wafer.
7. The flaw detection method according to claim 1, characterized in that: the outer side surface of the bottom of the outer shell forms a curved surface which can be attached to the upper surface of one side of the rail bottom of the steel rail, and the piezoelectric wafers of the piezoelectric units are arranged on the curved surface.
8. The flaw detection method according to any one of claims 1 to 7, characterized in that: when the interface is one, the piezoelectric wafers of the piezoelectric units are connected with the interface through cables; when the number of the interfaces is two or more, each interface is connected with the piezoelectric wafer of one piezoelectric unit or the piezoelectric wafers of a plurality of piezoelectric units.
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