CN110907363A - Laser-ultrasound-based crack detection system and detection method for high-speed rail contact line - Google Patents

Laser-ultrasound-based crack detection system and detection method for high-speed rail contact line Download PDF

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CN110907363A
CN110907363A CN201811080701.5A CN201811080701A CN110907363A CN 110907363 A CN110907363 A CN 110907363A CN 201811080701 A CN201811080701 A CN 201811080701A CN 110907363 A CN110907363 A CN 110907363A
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wave
crack
laser
energy detector
detection
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CN110907363B (en
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杜宏伟
赵亮
陆诗雨
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Changzhou Tiance Electronic Technology Co ltd
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Changzhou Yueqian Internet Of Things Technology Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
    • 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
    • G01N29/2418—Probes using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics
    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
    • G01N2021/1706—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids in solids

Abstract

The invention relates to a laser ultrasound-based crack detection system for a high-speed rail contact line, which is provided with a contact line following device and a laser ultrasound detection device; the contact line following device comprises a lifting bow, a transmission mechanism and a half-section cavity; the lifting bow is arranged on the top of the detection train, and two sides of the lifting bow are connected with the semi-section cavity through two corresponding groups of same transmission mechanisms; the laser ultrasonic detection device is arranged in the semi-section cavity and comprises a control processing unit, a laser ultrasonic excitation device and an ultrasonic receiving device; the laser ultrasonic excitation device and the ultrasonic receiving device are arranged on the laser ultrasonic detection adjusting mechanism. The invention provides a contact wire following device, which solves the problem that the contact wire cannot be followed and detected in running due to the 'Y' -shaped and nonlinear laying of the contact wire.

Description

Laser-ultrasound-based crack detection system and detection method for high-speed rail contact line
Technical Field
The invention relates to the field of laser ultrasonic flaw detection, in particular to a detection system and a detection method for fatigue cracks or other possible cracks on the surface of a contact wire giving high-speed rail electricity.
Background
Railway safety has always been the most interesting issue in rail transportation, and especially today's safety issues for higher speed railcars and high-speed railways are more compelling. The contact wire in the contact network system for supplying power to the high-speed rail is a very sensitive system and bears the comprehensive effects of high voltage, large current, high-speed friction, large suspension tension and the like. In long-term operation, fatigue cracks or other possible fine cracks are easy to generate on the contact surface of the contact line, the cracks can gradually extend inwards due to tension, the contact line can be broken when the cracks are serious, and the driving safety is damaged, so that the reinforcement of nondestructive inspection of the contact line which can generate the fine cracks is important.
At present, the wear detection of railway contact lines is carried out by erecting a high-frequency camera at the top of a train to photograph the contact lines, simulating the complete structure of the contact lines through an algorithm space, and finally comparing the worn part of the contact lower surface to judge the wear condition. In the aspect of crack detection of contact lines, the contact lines are suspended in the space above the train in a zigzag manner, so that following is difficult during flaw detection, and the traditional contact ultrasonic flaw detection method cannot meet the practical requirement, so that a better solution is not provided at present.
Since the high-speed rail is opened, an accident due to a pantograph-catenary (pantograph-catenary) system may occur. The contact line in the overhead line system supplying power to the high-speed rail is a very sensitive system and bears the comprehensive effects of high voltage, large current, high-speed friction, large suspension tension and the like.
At present, the contact line is mostly aimed at the research and detection in the aspect of abrasion, or the influence of vibration between high-speed rail running and the contact line. But the contact wire is in addition subjected to a large suspension tension. When a high-speed rail runs, the contact pressure between a pantograph and a contact net is about 100N, the relative speed reaches 80m/s, and the condition that macroscopic or invisible fine cracks appear on the surface and inside of the contact line can exist for a long time. In the high-speed rail mileage of 2.5 kilometres, the damage of the contact line makes the cardinal number of the potential safety hazard huge, difficult to perceive and difficult to maintain. And the high-speed rail is shut down for maintenance at night, so that the detection of the contact line is reserved and possible.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a crack detection system and a crack detection method of a high-speed rail contact line based on laser ultrasound, which rely on a contact line following device, complete the stable following and non-contact alignment of elements such as a laser emitting head, a detection probe and the like of a laser ultrasonic detection device in the running process of a detection vehicle, can keep a detection system capable of stably following the contact line and carrying out detection, detect whether cracks exist on the lower surface of the contact line, judge the depth and the angle of the cracks and finally judge dangers.
The technical scheme for realizing the purpose of the invention is as follows: a crack detection system of a high-speed rail contact line based on laser ultrasound comprises a contact line following device and a laser ultrasound detection device; the contact line following device comprises a lifting bow, a transmission mechanism and a half-section cavity; the lifting bow is arranged on the top of the detection train, and two sides of the lifting bow are connected with the semi-section cavity through two corresponding groups of same transmission mechanisms; the laser ultrasonic detection device is arranged in the semi-section cavity and comprises a control processing unit, a laser ultrasonic excitation device and an ultrasonic receiving device; the control processing unit is positioned in a compartment of the detection vehicle; the laser ultrasonic excitation device and the ultrasonic receiving device are arranged on the laser ultrasonic detection adjusting mechanism.
According to the technical scheme, the lifting bow comprises a long side of a suspension beam, a wide side of the suspension beam, an upper arm, an upper guide rod, a lower arm, a lower guide rod, a pneumatic control box, a bow lifting device and a bottom frame which is fixed on the top of a detection train through a fastening piece; the long side of the suspension beam and the wide side of the suspension beam form a suspension beam bow head; one end of the lower arm is connected with the underframe through a rotating shaft, the other end of the lower arm is hinged with the upper arm, a steel cable guide rail is arranged on the lower arm and is connected with the pantograph device through the steel cable guide rail, an air pipeline is arranged in the lower arm, and the end part of the upper end of the lower arm is connected to the air pipeline in the upper arm through a hose; the pantograph device is fixed on the underframe and drives the lower arm to rotate around the shaft, and comprises a pantograph gas source pump, an air bag type cylinder and a guide disc; the inflation inlet of the pantograph rising air source pump is connected with the air inlet of the air bag type air cylinder; the guide disc is connected with a push rod of the air bag type air cylinder, and a tensioned steel cable for driving the lower arm to move upwards around the shaft to lift the bow is arranged between the guide disc and the steel cable guide rail; two ends of the lower guide rod are respectively connected with one end of the upper arm and the bottom frame; one end of the upper guide rod is connected with the lower arm, and the other end of the upper guide rod is connected with the wide edge of the suspension beam; a carbon slide bar is attached to the friction contact position of the long edge of the suspension beam and the contact line; an air cavity connected with an air pipeline at one end of the upper arm is formed in the carbon slide bar, and compressed air is filled in the whole air pipeline; the pneumatic control box is arranged on the bottom frame, the air inlet end of the pneumatic control box is connected to the pantograph ascending air source pump through an air outlet of the three-way joint, the air outlet end of the pneumatic control box is connected with the air pipeline and the air cavity in the carbon slide bar, and the other air outlet of the three-way joint is connected with the air bag type air cylinder; the air bag type air cylinder is connected with a quick exhaust valve arranged in the pneumatic control box;
the transmission mechanism comprises four pairs of double-rod transmission structures, each two double-rod transmission structures are arranged on one side, and two ends of each double-rod transmission structure are respectively connected with the wide edge of the suspension beam and the outer wall of the half-section cavity; a pull rod spring is arranged at the center of the inward bending side of each pair of double-rod transmission structures;
a pair of obliquely arranged support rods pointing to the central axis of the contact line are fixed on the front and the back of the inner side wall of the half-section cavity respectively, a rectangular groove is formed in the center of the bottom of the half-section cavity, and a laser ultrasonic detection adjusting mechanism is embedded in the rectangular groove; the front end of the supporting rod is provided with a concave barrel roller, and a vibration damping spring is arranged between the inner rear end of the supporting rod and the half-section cavity; the concave curve of the concave drum roller is attached to the outline of the contact line and is in rolling contact with the contact line, and the wheel height of the concave drum roller and the long edge of the suspension beam are maintained at the same horizontal height.
The laser ultrasonic detection adjusting mechanism in the technical scheme comprises 5 sliding bases with adjustable positions; the lower half part of the sliding base is cylindrical and penetrates through a slotted hole at the bottom of the rectangular groove, threads for matching and fixing with a nut are arranged on the outer side of the sliding base, a round hole which penetrates through the whole sliding base and is used for a lead or an optical fiber to penetrate through the bottom is arranged in the center of the sliding base, the upper half part of the sliding base is in a convex shape, and the step position of the sliding base is flush with the slotted hole of the rectangular groove of the half-section cavity; corresponding scale strips with scales are fixed on two sides of a notch of the rectangular groove in the center of the bottom of the half-section cavity respectively, and the axial line end of the two scale strips close to the half-section cavity clamps the sliding base; the top plane of the sliding base is provided with an identification arrow.
The control processing unit comprises a laser control module for controlling the opening and closing of the optical fiber laser and various parameters emitted by the pulse laser of the optical fiber laser;
the data analysis module is used for processing the data signals transmitted back by the three electromagnetic sound energy detectors, judging whether the defects exceeding the alarm threshold value occur or not and judging whether the dangerous level exists or not, and positioning the defects by combining the position recording module;
the data analysis module comprises a storage unit for receiving and storing all data signals of the electromagnetic sound energy detectors and a processor of an operation unit for performing high-speed operation processing on the data signals returned by each electromagnetic sound energy detector, determining whether to trigger the position recording module to leave a current geographical position mark according to an operation result, judging the danger level according to the crack amplitude and giving priority maintenance prompt to the high-danger crack amplitude according to the preset condition;
the display module is used for displaying a real-time interface for receiving the waveform signal and the map;
the position recording module is used for positioning the current position of the detection vehicle in real time;
and a security module for system security and data protection;
the laser ultrasonic excitation device comprises a fiber laser, a fiber collimator and a linear focusing unit; the optical fiber laser is positioned at the top of the detection vehicle, is close to the underframe of the lifting bow, is connected with the optical fiber collimator in the semi-section cavity through optical fibers, and leads of the optical fibers and the detectors are attached to the upper arm and the lower arm of the lifting bow; the tail end of the optical fiber collimator is embedded and fixed on a circular hole in the center of a sliding base, and the rest part of the optical fiber collimator is arranged in the linear focusing pedestal;
the ultrasonic receiving device comprises a photoelectric detector, a first transverse wave-electromagnetic sound energy detector, a second transverse wave-electromagnetic sound energy detector, a surface acoustic wave-electromagnetic sound energy detector, a high-speed data acquisition device and a data acquisition device, wherein the high-speed data acquisition device is used for acquiring signals of the surface acoustic wave-electromagnetic sound energy detector, the first transverse wave-electromagnetic sound energy detector and the second transverse wave-electromagnetic sound energy detector and receiving trigger signals of the photoelectric detector.
In the technical scheme, a linear focusing pedestal is arranged on the third sliding base, and the other four sliding bases are fixed with right mounting pedestals; the top of each sliding base is provided with a double-guide-rail chute, the direction of the double-guide-rail chute is vertical to the axis direction of the half-section cavity, the double-guide-rail chute is matched with an inwards concave chute at the bottom of the mounting pedestal, the chutes are equal in length and width and are provided with screw holes; the surface acoustic wave-electromagnetic sound energy detector, the second transverse wave-electromagnetic sound energy detector, the photoelectric detector and the first transverse wave-electromagnetic sound energy detector are sequentially arranged on the corresponding mounting pedestal; the linear focusing unit is arranged on the linear focusing pedestal and is positioned on the central line of the half-section cavity; the direction of the photoelectric detector is aligned with the position of the laser line light source pre-irradiated on the contact line, and the photoelectric detector comprises a photosensitive resistor and a modulator; the photoresistor converts the detected weak optical signal on the surface of the object to be detected into an electric signal; the modulator modulates the converted electric signal, matches the characteristics of the linear light source optical signal, provides the converted electric signal for a trigger signal of the high-speed data acquisition unit to carry out data acquisition, and also provides the converted electric signal for a safety guarantee module of the control unit to obtain a determination signal.
According to the technical scheme, wind shields are mounted at two axial ends of the half-section cavity through fasteners; the front end of a protruding platform in the middle of the wind shield is provided with a pair of screw holes, the positions of the screw holes are aligned with two screw holes on a protruding beam at the bottom end of a rectangular groove in the center of the half-section cavity, and the screw holes are fixed through screws.
According to the technical scheme, the four mounting pedestals are flat on planes on two sides vertical to the axis direction of the half-section cavity, two pairs of adjusting knobs are arranged on two sides parallel to the axis direction of the half-section cavity, and the front sections in the adjusting knobs are rubber patches which are attached to and extrude the detector;
according to the technical scheme, the guide rails are arranged on the two inner walls of the linear focusing pedestal, which are parallel to the axial direction of the half-section cavity, and the two optical benches on one side can penetrate through the slotted holes and adjust the height up and down according to the scales on the outer side wall.
A detection method for a crack detection system of a high-speed rail contact line based on laser ultrasound comprises the following steps:
s1: the data analysis module of the control processing unit controls the high-speed data acquisition unit to only receive the data signal of the first transverse wave-electromagnetic sound energy detector; the method specifically comprises the following steps: the distance between a laser line light source and a first transverse wave-electromagnetic sound energy detector arranged in front of the laser line light source is 35-60 mm, when any value a in the range is selected, the advancing distance d' of the detection vehicle in the interval time of two pulses is required to be less than or equal to a, and the condition that the missing detection of broken joints of contact lines does not exist is judged; when a linear light source scans to be close to a crack, the pulse laser excites sound waves including surface acoustic waves, transverse waves and longitudinal waves on the surface of an object, and at the moment, a first wave peak is detected by the time domain waveform of the first transverse wave-electromagnetic sound energy detector; when the surface acoustic wave passes through the metal surface and reaches the bottom of the crack, the surface acoustic wave is superposed at the bottom of the crack and mode conversion is carried out, a part of energy is converted into diffracted transverse wave to be transmitted outwards, at the moment, a second wave peak is detected by a first transverse wave-electromagnetic acoustic energy detector in front of a laser line light source, a data analysis module of a control processing unit sends a signal to a high-speed data acquisition unit after judging the crack, the data acquisition unit triggers and receives all data signals of the electromagnetic acoustic energy detector, so that specific numerical values are further obtained when the surface acoustic wave is excited by the next laser pulse, and the crack depth and the orientation are calculated; meanwhile, the data analysis module triggers a signal to the position recording module, marks the position information at the next moment, and whether the stored information is stored or not is determined again in the second step;
s2: after the high-speed data acquisition unit is triggered to receive all the data signals of the electromagnetic sound energy detector and before the laser line light source moves to the crack, the fiber laserThe device (321) can generate the next laser pulse so as to excite and generate a new sound wave when the laser line light source moves to a position close to the left side of the crack under the condition that the specific crack data can be detected again; the method specifically comprises the following steps: firstly, laser pulse is excited to generate surface acoustic wave R, longitudinal wave L and transverse wave S, the surface acoustic wave R, the longitudinal wave L and the transverse wave S are propagated to the periphery of the metal surface, head waves are ignored, at the moment, a surface acoustic wave-electromagnetic acoustic energy detector detects that the surface acoustic wave-electromagnetic acoustic energy detector generates a first wave peak, and a data analysis module records the time point of the moment as TR0(ii) a Similarly, the time-domain waveform of the second shear wave-electromagnetic sound energy detector also detects the first peak, and records the time point T at this momentS0；
Then, when the surface acoustic wave R propagates rightward along the upper surface of the metal, i.e. in the detection forward direction, and is transmitted to the crack boundary, a part of the surface acoustic wave R is reflected at the boundary, i.e. a reflected wave propagates on the upper surface in the direction opposite to the original propagation direction, the surface acoustic wave-electromagnetic acoustic energy detector detects a second wave peak, and the time point at this time is recorded as TR1(ii) a The other part is diffracted along the crack boundary and is propagated to the other side of the crack, namely a transmitted wave which can be transmitted to a first transverse wave-electromagnetic acoustic energy detector; when the other part of the energy propagates to the bottom end of the crack along the inner wall of the crack, the energy is superposed at the bottom end and undergoes mode conversion, and part of the energy propagates from the bottom end of the groove to the periphery in the form of transverse wave and is a transverse wave component SR converted from the surface acoustic wave mode; the other part of energy is continuously transmitted along the inner surface of the groove in the form of surface acoustic wave, and is surface acoustic wave component RR;
as the ultrasonic wave continues to propagate in the test block, the part of the transverse wave SR is transmitted to the surface of the test block and finally a second peak is detected by the second transverse wave-electromagnetic acoustic energy detector, and the time point of the moment is recorded as TS1(ii) a In addition, the surface acoustic wave component RR which propagates along the surface of the groove and then along the surface of the metal test piece is also detected by a surface acoustic wave-electromagnetic sound energy detector after the transverse wave component SR signal, a third wave peak is generated, and the time T of the moment is recordedR2；
When the detection vehicle continues to advance, the laser line light source scans the right side of the crack, at the moment, the surface acoustic wave-electromagnetic acoustic energy detector only detects two wave crests, the first wave crest is a transmitted wave which winds from the right side to the left side of the surface acoustic wave groove, and the second wave crest is a surface acoustic wave component RR transmitted back from the bottom of the groove; in this case, the crack depth h cannot be calculated, and only the presence or absence of cracks can be determined.
S3 software calculation; the method specifically comprises the following steps: firstly, the propagation velocities of the surface acoustic wave and the transverse wave in the copper-magnesium alloy contact line are obtained, and are respectively expressed as VRAnd VSThen, the time taken for the ultrasonic wave of the transverse wave component SR and the surface wave component RR mode returning from the bottom of the groove to reach the detection point from the transmission of the sound wave from the pulse excitation point is set as
Figure BDA0001801869140000061
And
Figure BDA0001801869140000062
the time point of the laser pulse emitted by the linear light source generating ultrasonic waves on the metal surface is T; then
Figure BDA0001801869140000063
TR＝TR0-tR1,TS＝TS0-tS1……………(2)
Figure BDA0001801869140000064
Calculating a time point T during pulse excitation, and taking an average value of ultrasonic excitation time points obtained by the surface acoustic waves and the transverse waves; wherein t isR1、tS1The time spent for theoretically carrying out crack-free clock pulse excitation on the first wave peak detected by the surface acoustic wave-electromagnetic acoustic energy detector and the transverse wave-electromagnetic acoustic energy detector is a fixed value; d1For a known fixed distance of the second shear wave-electromagnetic acoustic energy detector from the laser line light source, d3A fixed distance of the known SAW-EM detector from the second shear wave-EM acoustic detector; in this case, the reflection of the surface acoustic wave is usedJudging that the receiving distance is not less than the first wave peak receiving distance:
t2×VR＝d≥d1+d3……………(4)
wherein t is2＝TR1-T, determining whether the formula is satisfied, if yes, indicating that the line light source excites a pulse on the left side of the crack or on the crack, and performing the next operation; if not, the linear light source is excited on the right side of the crack, and at the moment, two wave crests of the surface acoustic wave-electromagnetic acoustic energy detector are determined, the crack is directly judged to exist, and the next operation is not carried out;
Figure BDA0001801869140000065
wherein d is divided in the equation2Besides, the distance d between the position point of the laser line light source excitation pulse and the groove can be obtained by using the known values of other parameters2The value of (d);
Figure BDA0001801869140000071
Figure BDA0001801869140000072
the following equations (6) and (7) yield:
Figure BDA0001801869140000073
the depth h of the crack on the metal surface of the test block can be obtained;
Figure BDA0001801869140000074
Figure BDA0001801869140000075
solving the numerical value of the linear distance a from the bottom end of the groove to the surface acoustic wave-electromagnetic acoustic energy detector;
the left edge of the surface groove forms an angle of α with the upper surface of the metal test block,
according to the theory of trigonometric cosine, there are
Figure BDA0001801869140000076
The orientation angle α of the crack can be obtained, and then the correctness of the numerical value is judged and the crack danger level is given;
and after the data analysis module finishes grading the dangerous cracks, storing the position information marked by the S1 position recording module, the crack grade and the numerical value in a storage unit for the viewing and displaying module to display. When the cracks of the surface acoustic wave detector and the two transverse wave detectors are both lossless crack waveforms in two periodic pulses, the data analysis module only leaves the first transverse wave-electromagnetic sound energy detector for standby data acquisition again to wait for the next crack to appear.
The step S3 of the above technical solution is specifically that when the angle is equal to or less than 50 degrees and equal to or less than α degrees and equal to or less than 140 degrees, each ultrasonic component is easy to identify and the characteristic that the transverse wave component SR changes along with the change of α angle is obvious, so by using the change of the signal components along with the change of α angle, the orientation and depth information of the surface crack can be easily calculated by combining the above formulas (1) to (11);
when α is 140 degrees or α is less than 50 degrees, the information of the angle and the depth of the surface groove extracted by the arrival time of the transverse wave component SR and RR is difficult to be utilized, and the current calculation result α value and h value are abandoned;
if the crack depth and angle values calculated by detection are abandoned and are determined to be cracks, the data analysis module gives moderate dangerous crack grades; reserving a crack operation result, presetting a division value according to the crack depth, giving a risk rating, and setting the category as a single crack;
when two or more cracks with interval of more than millimeter level exist, the sound wave can form various reflected, vibrated and superposed waveforms between the cracks, which are obviously different from single-crack waveforms and are not beneficial to value calculation, but the existence of crack types can be confirmed at the moment, and the high-risk level is given under the condition that the types are multi-crack.
After the technical scheme is adopted, the invention has the following positive effects:
(1) the invention provides a contact line following device, which solves the problem that the contact line cannot be followed and detected in driving caused by the zigzag and nonlinear laying of the contact line. The contact line following device is simple in structure, high in feasibility and reliability and lower in cost compared with an electric device, can be optimized in the directions of reducing weight, vibration and the like continuously, and can be improved in a large space.
(2) The laser ultrasonic detection device provided by the invention is based on a contact line following device, solves the problems of detection, analysis, danger assessment, position recording and the like of cracks of a contact line, does not need excessive detection personnel to participate, can detect when a detection vehicle runs forwards, and has high automation level and labor saving by presetting a system.
(3) The detection design of the laser ultrasonic detection device realizes two times of detection on the same crack in one detection, the first laser pulse can judge whether the crack exists in a certain distance after exciting the ultrasonic wave, and the next laser pulse can confirm more information of the crack and is used for calculating the depth and the angle of the crack, carrying out primary prejudgment and secondary confirmation, reducing the false detection rate and having higher reliability; when a plurality of cracks are not concentrated, the depth and the angle of a single crack can be calculated, and more information about the crack can be obtained; when a plurality of cracks are concentrated, the cracks can be confirmed at millimeter-scale intervals and in a concentrated manner, high-risk judgment is given, and when the cracks are concentrated at intervals and in a high concentration within hundred-micron-scale intervals, measures for adjusting the line width of a laser line light source are also attached to reduce the probability of missed detection.
(4) The laser ultrasonic detection device is combined with the contact line following device, mechanical and electrical safety is comprehensively considered, safety protection of following separation is considered, and fault safety protection of electrical problems and the like is considered, so that the device has good safety consideration.
(5) The invention considers energy-saving measures, only one detector is reserved for standby and data is collected when no crack appears in the detection process, and the storage pressure and the electric energy loss are reduced.
(6) The device of the laser ultrasonic detection device is reasonably selected, the reasonable matching intervals among the laser parameters, the detector position and the detection vehicle speed are listed, the relation calculation can be carried out, the device can be matched and used according to different requirements, and the application range is wide; the whole system can also meet the requirement that the detection vehicle can increase the detection speed to hundreds of kilometers per hour.
Drawings
In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings, in which
FIG. 1 is a flow chart of the acoustic detection process of the present invention;
FIG. 2 is a schematic view of the position of the lifting bow of the present invention;
fig. 3 is a top view of a suspension beam bow of the present invention;
FIG. 4 is a cross-sectional view of the position of a support bar of the half-section cavity of the present invention;
FIG. 5 is a schematic view of a contact line suspension point connection and crack of the present invention;
FIG. 6 is a cross-sectional view of a half-section cavity of the present invention;
FIG. 7 is a block diagram of the slider base, mounting stage and linear focus stage of the present invention;
FIG. 8 is a top view of a half-section cavity structure of the present invention;
FIG. 9 is a block diagram of the windshield of the present invention;
FIG. 10 is a 3D block diagram and a detector mounting diagram of the contact line following device of the present invention;
FIG. 11 is a structural view of the impact force-spring buffer of the present invention;
FIG. 12 is a schematic diagram of the broken-line loop generating/detecting SAW in accordance with the present invention;
FIG. 13 is a time domain waveform of shear wave detection according to the present invention;
FIG. 14 is a diagram of a metal surface acoustic wave propagation process of the present invention;
FIG. 15 is a diagram of the SAW detection time domain waveform of the present invention;
FIG. 16 is a simplified schematic of crack parameter calculation according to the present invention;
the reference numbers in the drawings are as follows: the train 101, a contact wire following device 200, a contact wire 201, a suspension node 202, a crack 203, a lifting bow 210, a long side 211 of a suspension beam, a wide side 212 of the suspension beam, an upper arm 213, an upper guide rod 214, a lower arm 215, a lower guide rod 216, a pneumatic control box 217, a bow lifting device 218, a bottom frame 219, a transmission mechanism 220, a pull rod spring 221, a half-section cavity 230, a support rod 240, a concave drum roller 241, a shock absorption spring 242, a laser ultrasonic detection adjusting mechanism 250, a sliding base 251, a nut 252, a scale bar 253, an installation base 254, a linear focusing base 255, a wind shield 260, a projection table 261, a projection beam 262, a control processing unit 310, an optical fiber laser 321, an optical fiber collimator 322, a linear focusing unit 323, an optical bench 324, an ultrasonic receiving device 330, a photoelectric detector 331, a first transverse wave-electromagnetic acoustic energy detector 332, a second transverse wave-electromagnetic acoustic energy detector 333, a saw-to-electromagnetic acoustic energy detector 334.
Detailed Description
(example 1)
A crack detection system of a high-speed rail contact line based on laser ultrasound comprises a contact line following device 200 and a laser ultrasound detection device; the contact wire following device 200 comprises a lifting bow 210, a transmission mechanism 220 and a half-section cavity 230; the lifting bow 210 is arranged on the roof of the detection train 101, and two sides of the lifting bow 210 are connected with the half-section cavity 230 through two corresponding groups of same transmission mechanisms 220; the laser ultrasonic detection device is arranged in the half-section cavity 230 and comprises a control processing unit 310, a laser ultrasonic excitation device and an ultrasonic receiving device 330; the control processing unit 310 is located in the compartment of the detection vehicle, facilitates the control operation of operators, and comprises a laser control module, a data analysis module, a display module, a position recording module and a safety guarantee module. The laser ultrasonic excitation device and the ultrasonic receiving device 330 are installed on the laser ultrasonic detection adjusting mechanism 250.
Referring to fig. 1, the pantograph 210 is configured and positioned to control a pantograph, such as a high-speed rail, on the roof of the train 101. The lifting bow 210, as shown in fig. 10, includes a long side 211 of the suspension beam, a wide side 212 of the suspension beam, an upper arm 213, an upper guide rod 214, a lower arm 215, a lower guide rod 216, a pneumatic control box 217, a pantograph device 218, and a bottom frame 219 fixed to the roof of the test train 101 by fasteners, wherein the long side 211 of the suspension beam, the wide side 212 of the suspension beam, the upper arm 213, and the lower arm 215 are made of a light aluminum alloy material. The pantograph lifting device 218 comprises a pantograph lifting air source pump, an air bag type air cylinder and a guide disc, wherein the pantograph lifting air source pump inflates the air bag type air cylinder, the air bag type air cylinder expands to push the guide disc to move forwards, and a steel cable tensioned between the guide disc and a steel cable rail drives the lower arm 215 to move upwards around a shaft to lift a pantograph; when exhausting, the air bag type air cylinder retracts, and the lifting bow 210 falls. One end of the lower arm 215 is connected with the bottom frame 219, the other end is hinged with the upper arm 213, and a cable guide rail is arranged on the lower arm, and is connected with the pantograph device 218 through the cable guide rail, so that the pantograph device 218 can drive the lower arm 215 to rotate around the shaft; an air line is also provided in the lower arm 215, and the end is connected to an air line in the upper arm 213 via a hose, as a whole, as an air line of the automatic pantograph device. Two ends of the lower guide rod 216 are respectively connected to one end of the upper arm 213 and the bottom frame 219 for adjusting the maximum pantograph height. The upper guide rod 214 is connected with the lower arm 215 at one end and connected with the wide edge 212 of the suspension beam at the other end, and is used for adjusting the suspension beam to be in a horizontal position during movement. The carbon sliding strip is attached to the part, in friction contact with the contact line 201, of the long edge 211 of the cantilever beam, an air cavity is formed in the carbon sliding strip, the carbon sliding strip is connected to an air pipeline at one end of an upper arm 213, compressed air is filled in the whole air pipeline, and if the carbon sliding strip is worn to the limit or is broken, the automatic pantograph lowering device works to rapidly lower the pantograph.
The automatic bow lowering device mainly comprises a pneumatic control box 217, a carbon slide block and a corresponding air path pipe, wherein a bow raising air source passes through a three-way joint, one path of the bow raising air source enters an air bag type air cylinder for bow raising, the other path of the bow raising air source enters the pneumatic control box 217 and enters air cavities in the air path pipe and a carbon slide bar after coming out of the pneumatic control box 217, when the air pressure in the air path is lowered due to abrasion limit of the slide bar, breakage air leakage or impact, the automatic bow lowering device is triggered, a quick exhaust valve in the pneumatic control box 217 works to quickly exhaust the air in the air bag type air cylinder of the bow raising device 218, and the bow 210 is separated from contact by self weight to protect the safety of equipment.
Meanwhile, a protection mechanism that the half-section cavity 230 is separated from the following contact line is also used for triggering the quick exhaust valve to work, and the protection mechanism is used for detecting whether the half-section cavity 230 is separated from the following contact line.
In order to buffer the impact force during operation, referring to fig. 10, the four corners where the suspension beam wide edge 212 and the suspension beam long edge 211 are connected are provided with transverse springs (in the suspension beam wide edge direction), as shown in fig. 11 (a); the axle seat at the bottom in the middle of the wide side 212 of the suspension beam is connected with an upper arm 213 through a rotating shaft, the end of the upper arm 213 is connected to a bearing outer ring outside the rotating shaft, and a longitudinal spring (in the long side direction of the suspension beam) is arranged between one end of the wide bearing at the end of the two upper arms 213 and the axle seat at the bottom in the middle of the wide side 212 of the suspension beam, as shown in fig. 11 (b); the two structures enable the slide bar to flexibly move in the running direction of the detection vehicle, and can buffer impact force in all directions so as to maintain stable following of the contact line following device 200.
The broad sides 212 of the suspension beams of the lifting bow 210 are connected to a half-section chamber 230 by a transmission mechanism 220. The transmission mechanism 220 includes four pairs of double-rod transmission structures, each pair of which is disposed on one side and connects the beam-hanging broad edge 212 and the outer wall of the half-section cavity 230. In addition, a pull rod spring 221 is arranged at the center of the inward bending side of each pair of double rods, as shown in fig. 3 and fig. 10, so that the half-section cavity 230 can have a quick return function when flexibly following the swing, and the half-section cavity 230 can return to the middle initial position due to the average action of the four pull rod springs 221 when the work stops. In addition, the pull rod spring 221 can also counteract a portion of the back-and-forth inertial swing and unnecessary shaking of the transmission mechanism 220. In order to ensure the flexibility of the whole following mechanism, the half-section cavities of the transmission mechanisms 220 and 230 can be made of other non-metal materials with light weight, good toughness and high strength.
Four support rods 240 are fixed in the half-section cavity 230, as shown in the cross-sectional view of the support rods in fig. 4, the front ends of the support rods are concave barrel rollers 241, the concave curves are attached to the outer contour of the contact wire 201 and are in rolling contact with the contact wire 201 when a train runs, and the four support rods are made of insulating rubber materials and can also reduce impact force when a part of the support rods is in contact steering. The support rods 240 are respectively positioned in front of and behind the inner side wall of the half-section cavity 230 in a pair, and are inclined downwards by 45 degrees or other proper angles to be aligned with the central axis of the contact wire 201, so as not to scratch the upper suspension node 202 of the contact wire 201, as shown in fig. 5. In addition, a damping spring 242 is disposed between the rear end of the support rod 3 and the half-section cavity 230, so as to provide a damping force for the roller at the front end of the support rod 240 to follow the contact line 201 during traveling. In addition, the wheel height of the concave drum roller 241 at the top end of the support rod 240 is maintained at the same level as the long side 211 of the suspension beam. In conclusion, the disturbance on the horizontal direction and the vertical direction brought to the following device when the detection vehicle travels is comprehensively reduced.
As shown in FIG. 4, the bottom center of the half-section cavity 230 has a rectangular groove, as shown in FIG. 6, and 5 sliding bases 251 are embedded in the sectional view along the axial direction (length direction) of the half-section cavity. The lower half part of the sliding base 251 is cylindrical, penetrates through a slotted hole at the bottom of the rectangular groove, and is provided with threads at the outer side and a round hole at the center. The round hole penetrates through the whole sliding base and is used for a lead or an optical fiber to pass through the bottom; the outer threads are adapted to cooperate with nuts 252 to secure slide mount 251. The upper half of the slide base 251 is in a shape of a letter "convex", which is flush with the cross-sectional direction of the half-section cavity 230 and is contracted inward in both sides in the axial direction, as shown in fig. 4 and (a) and (b) of fig. 7. The distance of the constricted part is covered and blocked by the lower edge of the inverted trapezoid-shaped dimension bar 253, and the two dimension bars 253 are fixed on the two sides of the top of the rectangular groove at the bottom center of the half-section cavity 230, thereby clamping the sliding base 251. In addition, referring to fig. 8, scales are marked on the upper side of the inverted trapezoid of the dimension bar 253, and are used together with the identification arrow on the top plane of the sliding bases 251, so that the distance between the position of each sliding base 251 and each other can be displayed.
In addition, in fig. 7 (a), (b), (d) and (e), the top of each sliding base 251 has a dual-rail chute, and the direction of the chute is perpendicular to the axial direction of the half-section chamber 230. The chute is matched with an inward concave chute at the bottom of the mounting pedestal 254, and the chute has equal length and equal width and is provided with screw holes, so that the mounting and the fixing are convenient. Four installation pedestal 254 levels on the plane of the perpendicular both sides of half section cavity 230 axis direction, then has two pairs of four adjust knob on the plane of other both sides, and the inside anterior segment of knob is different shape rubber paster, and the laminating detector does not damage, and the outside is the knob, and rotatory propulsion extrudees the fixed inside detector that needs the installation. As shown in fig. 7 (c), a linear focusing stage 255, which is similar in size and structure to the four mounting stages 254, differs in that: the first, wall thickness is strengthened, the second, two pairs of adjusting knobs on the two sides parallel to the axial direction of the half-section cavity 230, change into two inner walls to install guide rails additionally, and wherein two optical benches 324 on one side can adjust the height up and down at the outer wall according to the scale through the slotted hole.
Five sliding bases 251, nuts 252, dimension bars 253, four mounting bases 254 and one linear focusing base 255 form the laser ultrasonic detection adjustment mechanism 250. In FIG. 6, five slide mounts 251 are shown from left to right, four being fixed mounting blocks 254, except for the third mounting linear focus block 255; on the mounting stage 254 or the linear focusing stage 255, from left to right, a saw-em detector 334, a second shear wave-em detector 333, a linear focusing unit 323, a photo detector 331, and a first shear wave-em detector 332 are mounted, respectively, as shown in fig. 10. And the detection direction is from left to right.
Fig. 9(a) and (b) are a cross-sectional view and a top view, respectively, of a wind deflector 260 having a width equal to the width of the half-section cavity 230 and a height such that it covers the tightened nut 252 up to the bottom end of the concave barrel roller 241 of the support rod 240. The front end of the protruding platform 261 in the middle of the wind deflector 260 has a pair of screw holes, which are aligned with the two screw holes on the protruding beam 262 at the bottom end of the rectangular groove in the center of the half-section cavity 230, and fixed in front of and behind the half-section cavity 230 by screws, as shown in the position of the wind deflector 260 in fig. 3, please refer to fig. 6 and 8 for the protruding beam 262.
The power density I of the laser must reach a value to excite a detectable acoustic fluctuation in the material, i.e. a locally detectable strain of the sample due to local thermal expansion caused by an increase in temperature, when the value of I is referred to as the initial threshold. An increase in I-value with excitation of detectable acoustic vibrations leads to an increase in lattice kinetic energy, but also within the elastic limits of the sample, all known as thermo-elastic mechanism excitation ultrasound. Then, the value I is increased continuously, so that when the kinetic energy of the crystal lattice exceeds the elastic limit, the irradiated part of the sample is melted and eroded, and the phenomenon of plasma flying out is accompanied, which is called as an erosion mechanism to excite the ultrasound. At this time, the temperature of the material surface rises to the melting point suddenly due to the absorption of laser, so that slight damage to the material surface is caused and should be avoided.
For metals, the threshold for the absorption laser power density of materials that generally distinguish between the two mechanisms is about 10MW/cm2. The initial threshold I is generally WM/cm2The critical I0 value of the laser, which is of such a magnitude that the sample is ablated, is called the ablation threshold, and is typically a few tens of WM/cm2Or higher and is related to material properties and light wavelength.
When the laser excitation ultrasonic is controlled in a thermal bomb mechanism, the process is as follows: when laser light with a power density I in the thermoelastic range is irradiated on a metal surface, a part of the light energy is reflected and a part is absorbed (generally, the ratio of laser light absorbed by a metal material is low). If the absorbed light pulse can be totally changed into a heat pulse (also called heat wave), the local temperature of the surface is increased. After local heating for about 400ns by laser irradiation in the metal material, the thermal wave disappears. The arrival rate of the heat pulse is less than 1MHz, so the heat wave and the acoustic wave can be considered independent.
The thermal wave generated by the metal absorbing the light pulse is divided into two parts. On the one hand, thermal energy propagates to other parts due to the thermal conductivity of the sample. As the frequency f increases, the heat transfer rate is much less than the acoustic velocity, so that the thermal conductivity is negligible for pulsed laser excitation ultrasound on the order of nanoseconds, especially on the order of picoseconds. On the other hand, a strain stress field is generated at the temperature rise position due to thermal expansion, so that the material is locally subjected to rapid thermal expansion, and broadband ultrasonic waves are generated.
However, the amplitude of the excited ultrasonic signal is low under the thermoelastic mechanism, the detection signal-to-noise ratio is poor, and the signal-to-noise ratio is usually improved through the spatial modulation of the pulse laser. Therefore, by modulating the laser point light source into a line light source, the amplitude of the signal generated by the line source is much stronger (about 5-10 times stronger) than that generated by the point source on the premise of the same incident energy of the laser. Meanwhile, the energy of the line source is distributed along the long direction, and the surface acoustic wave amplitude of the near field region is attenuated very little along with the increase of the receiving distance under the condition of the line source, so that the energy density is reduced, and the scanning range can be enlarged. In addition, in the near-field range, the linear light source is used for exciting the ultrasonic wave without considering the influence of the detection position on the signal amplitude.
Secondly, the installation position and the working mode of the laser ultrasonic detection device are as follows:
as shown in fig. 7 (a) and (c), the optical fiber collimator 322 emits a circular light spot, the illumination is uniform and collimated, the illumination area can be adjusted, and the required range of the diameter of the circular light spot is 0.6-2.5 mm. The linear focusing unit 323 includes a pair of cylindrical lenses, the axes of the two cylindrical lenses are perpendicular to each other, the axis of the former cylindrical lens coincides with the optical axis (the direction of the light emitted from the fiber collimator 322), the light is incident along the optical axis, the latter lens is a concave cylindrical lens, the concave surface faces inward (downward), the axis of the concave cylindrical lens is parallel to the cross section of the contact line 201 and is also perpendicular to the optical axis, the two cylindrical lenses are fixed on the two optical bases 324, and the distance is finely adjusted in the vertical direction. The two positions are related in that the tail end of the optical fiber collimator 322 is embedded and fixed in a circular hole in the center of a sliding base 251, the rest part is arranged in the linear focusing pedestal 255, and after the diameter of the circular light spot is adjusted, the top end of the optical fiber collimator 322 needs to be attached to the bottom end of the cylindrical lens. And a linear focus stage 255 is positioned on the third slide mount 251 from left to right in fig. 6.
The laser beam passing through the linear focusing unit 323 can adjust a linear light source with the linear length of 5-10 mm and the line width of 0.6-2.5 mm, the linear length direction is still in Gaussian distribution, the linear length center is aligned to the bottom center position of the contact line 201, and the direction is parallel to the cross section of the contact line 201.
The fiber laser 321 is positioned at the roof of the detection vehicle, is close to the chassis 219 of the lifting bow 210, is connected with the fiber collimator 322 in the half-section cavity 230 through optical fibers, and the optical fibers and leads of each detector are attached to the upper arm 213 and the lower arm 215 of the lifting bow 210;
the fiber laser 321 is one of pulse fiber lasers, and a Q-switched fiber laser (pulse width is ns magnitude) can be selected. The optical fiber detection device comprises a machine body and an optical fiber, wherein the machine body is arranged on the top of a detection vehicle or other vehicle body positions to enable the machine body to be stable and not to shake, the optical fiber is tightly attached to the upper arm and the lower arm of the lifting bow 210, and finally penetrates through a nut 252, a bottom slotted hole of the half-section cavity 230 and a sliding base 251 to be connected onto an optical fiber collimator 322. The single pulse energy of the fiber laser 321 is 0.1-50 mJ, the repetition frequency is 100-5 kHz, the wavelength can be S-band (1460-1530 nm) or C-band (1530-1565 nm), the embodiment can be 1.4um, and the pulse width is nanosecond level and is about 2-80 ns. The linear light source obtained by spatial modulation of the optical fiber and the linear focusing unit 323 excites the ultrasonic surface wave to have a bandwidth of 0.5-5 MHz, the main sound beam can longitudinally propagate along the surface of the object at a certain half diffusion angle, and the main sound beam can transversely and fully cover the whole surface of the object to be measured after propagating for a certain distance. In addition, the optical fiber is selected to have a suitable length to satisfy the requirement of the lifting bow 210 for the lifting operation and the following of the horizontal swinging of the half-section cavity 230. In addition, the outer layer of the optical fiber is covered with a protective layer, so that the flexibility and the toughness are ensured, and the optical fiber is durable.
The photoelectric detector 331 is installed in the installation pedestal 254 in front of the fiber collimator 322, and is also located on the central line in the half-section cavity 230, the direction is aligned with the position of the laser line light source pre-irradiated on the contact line 201, the angle required by the probe can be adjusted by four adjusting knobs on two sides of the installation pedestal 254, and the rubber patches in different shapes are further fixed.
The photo detector 331 includes a high-sensitivity photo resistor and a modulator, the photo resistor converts the detected weak optical signal on the surface of the object to be detected into an electrical signal, and the modulator modulates the converted electrical signal to match with the characteristics of the optical signal of the line light source, so as to provide a trigger signal with fast response, high gain and small noise for the high-speed data acquisition device, and also provide a determination signal for the safety guarantee module of the control processing unit 310. When the safety guarantee module confirms that the system is started, laser excitation and the train runs, the photoelectric detector 331 lasts for more than 1 second, and no light signal with the same intensity as that normally reflected on the contact line 201 is fed back all the time, the safety guarantee module of the control processing unit 310 judges that the laser line light source does not irradiate the contact line, the half-section cavity 230 is not followed, a sound lamp warning is given, the safety guarantee module sends a command to a pneumatic control box of the lifting bow 210, the quick exhaust valve works, air in the air bag type air cylinder is rapidly exhausted, and the lifting bow is lowered.
The saw-em detector 334 is located on the first sliding base 251 from left to right in fig. 6, and is installed at a position about 30-80 mm from the point where the laser line light source irradiates on the contact line 201, as shown in fig. 14. The surface acoustic wave-electromagnetic acoustic energy detector 334 can receive the surface acoustic wave which is within about 100mm of the distance and propagates on the surface of an object, actually keeps a distance of about 3-10 mm from the bottom surface of the contact line 201, and keeps the sensitivity of ultrasonic detection. The flaw detection coil, the multistage amplifier, the filtering detector and the analog-to-digital conversion module are electrically connected in sequence. The sensing probe is used as a detector, namely, the reverse process of generating sound waves by the electromagnetic acoustic energy transducer EMAT is realized (the electromagnetic acoustic energy transducer generally consists of a coil and a strong magnetic field, when high-frequency current flows through the coil, eddy current is induced on a conductor and an adjacent surface, and if the conductor is simultaneously influenced by the static magnetic field, the eddy current and the static magnetic field interact to generate Lorentz force, so that the sound waves are generated). The flaw detection coil of the surface acoustic wave-electromagnetic acoustic energy detector 334 is close to the surface of the object in a short distance and is used for detecting a surface acoustic wave signal; the multistage amplifier is used for amplifying the signal; the filter detector is used for carrying out filter detection on the amplified surface acoustic wave signal, filtering out interference clutter and other unobvious waveforms of longitudinal waves or transverse waves which can be detected possibly, and leaving surface acoustic wave characteristic signals.
Referring to fig. 12, the flaw detection coil is a folded rf coil, the magnetic field of the permanent magnet is parallel to the surface of the object, and the magnetic lines of force are along the tangential direction of the coil and perpendicular to the wires, thereby forming an electromagnetic acoustic energy transducer that enhances the sensitivity of surface acoustic wave detection. In addition, the detector also comprises a protective casing, and electronic components such as a multistage amplifier, a filter detector and an analog-to-digital conversion module of the surface acoustic wave-electromagnetic acoustic energy transducer 334 are arranged in the protective casing and are used for shielding electromagnetic interference in the flaw detection process and protecting the surface acoustic wave-electromagnetic acoustic energy transducer.
The first shear wave-electromagnetic sound energy detector 332, the second shear wave-electromagnetic sound energy detector 333, and the saw-electromagnetic sound energy detector 334 are installed at positions similar to those of the structure, and are installed on the fifth and second sliding bases 251 from left to right in fig. 6. Since the main beam of the laser line light source excited ultrasound spreads throughout the contact line 201,a distance is required, see figure 5, where the contact line 201 has an area of about 150mm across the street2And the distance d is minimum more than half of the width of the contact line 201, and the distance d is about 14mm of the width of the contact line 201 in consideration of the problems of sufficient propagation and installation spacing of the surface acoustic wave under the condition of the opposite running speed of the vehicle with the detection. Therefore, as shown in fig. 14, the second shear wave-electromagnetic sound energy detector 333 is installed 15-30 mm behind the laser line light source and in front of the saw-electromagnetic sound energy detector. The first transverse wave-electromagnetic sound energy detector 332 is 35-60 mm in front of the laser line light source, and the distance is the first condition that the laser ultrasonic detection device needs to meet detection. The second shear wave-electromagnetic sound energy detector 333 is spaced apart from the saw-electromagnetic sound energy detector 334 by a distance that does not disturb the magnetic field of the respective detectors and does not affect the detection operation. If not desired, a sheet metal foil may be added between the two acoustic detectors within the half-section cavity 230 to isolate electromagnetic interference between the detectors. The first shear wave-electromagnetic sound energy detector 332 and the second shear wave-electromagnetic sound energy detector 333 both also include a flaw detection coil, a permanent magnet, a multistage amplifier, a filter detector, an analog-to-digital conversion module, and a protective case, and are different in that: the permanent magnet magnetic fields of the first transverse wave-electromagnetic sound energy detector 332 and the second transverse wave-electromagnetic sound energy detector 333 are perpendicular to the surface of the object, and the flaw detection coil is a pcb butterfly coil for enhancing the transverse wave detection sensitivity. The mounting position of each detector is as shown in fig. 10.
The high-speed data acquisition unit is used for acquiring signals of the surface acoustic wave-electromagnetic acoustic energy detector 334, the first transverse wave-electromagnetic acoustic energy detector 332 and the second transverse wave-electromagnetic acoustic energy detector 333, and receiving a trigger signal of the photoelectric detector 331. The photodetector 331 generates a signal for triggering the high-speed data collector to collect data after detecting the pulse laser signal. The high-speed data acquisition device can be realized based on an FPGA and ARM9 architecture, the maximum sampling rate can reach 100M SPS, and the acquisition of signals in a high-speed motion state can be realized.
The control processing unit 310 includes a laser control module, a data analysis module, a display module, a position recording module, and a security module. The laser control module is used for controlling the on and off of the fiber laser 321 and various parameters of the pulse laser emission of the fiber laser 321. The data analysis module is used for processing the data signals transmitted back by the three electromagnetic sound energy detectors, judging whether the defects exceeding the alarm threshold value occur or not and judging whether the dangerous level exists or not, and positioning the defects by combining the position recording module; the data analysis module comprises a storage unit and a processor of an arithmetic unit, wherein the storage unit is used for receiving and storing all data signals of the electromagnetic sound energy detectors, the arithmetic unit carries out high-speed arithmetic processing on the data signals transmitted back by each electromagnetic sound energy detector, determines whether to trigger the position recording module to leave a current geographical position mark or not according to an arithmetic result, judges the dangerous grade according to the crack amplitude, and gives a priority maintenance prompt for the high-dangerous crack amplitude according to the preset condition. The specific crack algorithm is judged as follows. The position recording module is used for positioning the current position of the detection vehicle in real time, is started when the detection vehicle is started, comprises a GPS or Beidou navigation module, and is combined with the existing railway trunk map to provide a more accurate position mark. The safety guarantee module is used for system safety and data protection, and comprises a warning red light and a prompting horn, except for judging that the half-section cavity 230 is separated from following, a sound light warning is given, and the lifting bow 210 is lowered, the system is also protected from working abnormity, halt, power failure, short circuit or overload and other condition data and safety protection, data protection can be realized by using a flash memory for caching data, safety protection can be completed by using a contactor, a circuit breaker and a relay combination, the contactor is only controlled, the thermal relay realizes overload protection by disconnecting the contactor, and the circuit breaker is short-circuit protection. The display module includes a liquid crystal display or an oscilloscope, and is configured to display a real-time interface for receiving the waveform signal and a map, and a specific type of the display module is not limited in the embodiment of the present invention.
(1) The repetition frequency f of the optical fiber laser 321 is 100-5 kHz, laser emitted by the optical fiber laser is spatially modulated into a line light source, the line width Lw of the line light source is 0.6-2.5 mm, and the line length Ll is 5-10 mm. The distance d between the first transverse wave-electromagnetic acoustic energy transducer 332 and the irradiation point of the laser line light source on the contact line 201 is about35-60 mm. Therefore, if the crack detection speed of the contact line 201 is about V ═ f × d, then f is 1kHz and d is 50mm, which is generally selected to be 1000 × 50 × 10-3The speed of the detection vehicle can reach hundreds of kilometers per hour, namely 50m/s and about 180 km/h. In actual detection, in order to avoid unnecessary harmful vibration caused by too high speed of the transmission mechanism 220, the half-section cavity 230 and the contact line 201 of the following structure 200, the speed of the detection vehicle needs to be reduced as appropriate.
(2) The main objects of the detection are microcracks and cracks. The metal cracks are generated as follows: microcracks, with a length less than 2mm and a width less than 0.2 mm; cracking: the length is 2-5 mm, and the width is 0.2-0.5 mm; the length of the crack is more than 5mm, and the width of the crack is more than 0.5 mm; cracking-cracking over the full width. Wherein the metal wire has a high probability of micro-cracks and cracks.
The depth of the main object of the target detection, namely the supplement range of the crack, is not more than 5mm, the orientation angle of the crack is not less than 50 degrees and not more than α degrees and not more than 140 degrees, the line width of the laser line source is taken as at least one time of the width of the crack so as to cover and exceed the width of the crack, the crack is prevented from being densely appeared (the interval between two cracks is less than hundred micrometers), when the laser irradiates on the upper part of the first crack, the probability is that the sound wave can be arranged on the right side (the detection advancing direction) and the inner wall of the crack or on both sides and the inner wall of the crack, the sound wave can be propagated along the inner wall of the crack and the metal surface, the current crack can be detected, the next crack can not be detected, and finally the probability of the crack can be detected is reduced.
(3) The transverse wave and the surface acoustic wave propagate in metal at a speed of about 0m/s, the transverse wave is slightly faster than the surface acoustic wave, and the longitudinal wave has a speed about twice that of the transverse wave and about 6000 m/s. For example: in metallic aluminum, the longitudinal wave velocity 6010m/s, the transverse wave velocity 3160m/s and the surface acoustic wave velocity 2975 m/s. Therefore, the maximum possible propagation distance from the linear light source to the crack to the echo surface wave-electromagnetic acoustic energy detector can be estimated by the surface acoustic wave velocity, the maximum possible propagation distance is about 110mm (30+80mm), the time spent by the surface acoustic wave is about 30 mu s, if the detection vehicle runs at the speed of about 100km/h, the advancing distance of the detection vehicle in the time is 0.834mm or less, and the laser linear light source and the detector in the half-section cavity following the contact line 201 are smaller and can be ignored due to nonlinear advancing. It can be considered that the detector and the laser line light source are in a relatively stationary state with respect to the contact line 201 from the time the line light source excites the acoustic wave to the time the detection is completed (time of tens of microseconds to tens of microseconds).
(4) The laser ultrasonic detection device needs to meet a first detection condition: the detection progress process has no fault detection and omission of the contact line 201. The repetition frequency of the fiber laser also needs to satisfy a second condition: after the high-speed data acquisition unit is triggered to receive all the data signals of the electromagnetic sound energy detector and before the laser line light source moves to the crack, the fiber laser can generate the next laser pulse so as to participate in software calculation by using specific data for detecting the crack again. For example: the repetition frequency of the optical fiber laser is 800Hz, which is denoted as F, a first transverse wave-electromagnetic sound energy detector for constant standby detection is installed at a position 40mm in front of the laser line light source, which is denoted as D, the advancing speed V of the detection vehicle is about 27.8m/s (100km/h), and then the advancing distance of the detection vehicle in the time interval between two laser pulses is D' ═ V ÷ F < D, that is, 27.8 ÷ 800 ÷ 0.03475m ═ 34.75mm < 40 mm. That is, before the distance of the detection vehicle reaches the distance of 40mm detectable by one pulse, the fiber laser generates the next laser pulse,
the first condition is met, and the advancing distance in the time interval between two laser pulses can not exceed the effective distance D detectable by one pulse due to the fact that the speed of the detection vehicle is too high.
In addition, when the detection direction is rightward, the high-speed data collector triggered after the crack is detected by the first pulse can collect data required by software calculation through the second transverse wave and the surface acoustic wave detector, and the data is effective data generated and detected after the sound wave is excited on the left side of the crack by the second pulse. This satisfies the second condition.
If the speed of the detection vehicle is to be increased, the repetition frequency of the optical fiber pulser needs to be increased correspondingly. Otherwise, it is decreased. Therefore, the calculation method can roughly determine that the first transverse wave-electromagnetic sound energy detector 332 is arranged 35-60 mm in front of the laser line light source, and the distance value is appropriate.
The acoustic detection working process is as follows:
as shown in FIG. 5, the crack 203 on the contact surface of the contact wire 201 is a groove with a length and width of 3mm 200 μm 1mm instead of the actual crack, and a metal test block with a length and width of 100mm 12mm instead of the schematic cross-sectional area of 150mm, so as to describe how to detect the crack2As shown in fig. 6.
The first step is as follows: the data analysis module of the control processing unit 310 controls the high-speed data collector to receive only the data signal of the first shear wave-electromagnetic acoustic energy detector 332. The transverse wave time domain waveform diagram in the detection process is shown in fig. 13, and the specific sound wave propagation process is shown in the second step.
The distance between a laser line light source and a first transverse wave-electromagnetic sound energy detector 332 arranged in front of the laser line light source is 35-60 mm, when any value a in the range is selected, the advancing distance d' of the detection vehicle in the interval time of two pulses is required to be less than or equal to a, and the condition that the missing detection of broken joints of contact lines does not exist is judged; when the linear light source scans the object near the crack, the pulsed laser excites acoustic waves including surface acoustic waves, transverse waves and longitudinal waves on the surface of the object, and at this time, the time-domain waveform of the first transverse wave-electromagnetic acoustic energy detector 332 detects a first peak. When the acoustic expression wave passes through the metal surface and reaches the bottom of the crack again, the acoustic expression wave is superposed at the bottom of the crack and mode conversion is carried out, a part of energy is converted into diffraction transverse wave (namely shear wave) to be transmitted outwards, at the moment, a first transverse wave-electromagnetic acoustic energy detector 332 in front of a laser line light source detects a second wave peak, a data analysis module of the control processing unit 310 sends a signal to a high-speed data acquisition unit after judging the crack, and triggers and receives all data signals of the electromagnetic acoustic energy detector, so that specific numerical values are further obtained when the acoustic surface wave is re-excited by the next laser pulse, and the depth and the orientation of the crack are calculated. Meanwhile, the data analysis module triggers a signal to the position recording module, marks the position information at the moment, and determines whether to store the reserved information or not again in the second step.
In addition, when the ultrasonic wave is excited near the crack, the energy scattered at the bottom of the crack has a small specific gravity in the total energy and is attenuated in the propagation process, so that the transverse wave component generated by mode conversion at the bottom of the crack is not easy to perceive. Therefore, the first transverse wave-electromagnetic acoustic energy detector 332 is arranged in front of the laser line light source, and the first transverse wave-electromagnetic acoustic energy detector 332 is closer to the crack during forward detection, so that the receiving distance of transverse waves can be reduced, and meanwhile, the signal amplitude is increased and the detection signal-to-noise ratio is improved by the laser output line light source; the line width of the line light source is increased, and the amplitude of the central frequency is increased; ultimately enhancing the detectability of the transverse wave component. The second shear wave-electromagnetic energy detector 333 is also so configured that, when the next pulse-excited ultrasound is performed, the receiving distance of the shear wave component is reduced because the detection vehicle moves a short distance of several tens of millimeters closer to the crack.
The second step is that: when the first condition and the second condition are met, when the laser line light source moves to the left side of the crack to be closer, new sound waves are generated by excitation.
At this time, the propagation process of the surface acoustic wave is as follows, please refer to fig. 14:
first, laser pulse excitation generates a surface acoustic wave R, a longitudinal wave L, and a transverse wave S (ignoring a head wave). And propagates to the periphery of the metal surface, at this time, the SAW-EM acoustic energy detector 334 detects that a time domain waveform diagram is shown in FIG. 15, which will generate a first peak, and the data analysis module records the time point of this moment as TR0. Similarly, the time-domain waveform of the second shear wave-electromagnetic sound energy detector 333 also detects the first peak, and records the time point T at this timeS0。
Then, when the surface acoustic wave R propagates rightward (i.e., in the detection proceeding direction) along the metal upper surface (solid line) and passes to the boundary of the crack (i.e., groove), a part of the surface acoustic wave R is reflected at the boundary, that is, a part of the surface acoustic wave R is reflected at the boundaryThe reflected wave propagates on the top surface in the opposite direction of the original propagation direction (dashed line), and the SAW-EM detector 334 detects a second peak, noting that this time TR1(ii) a The other part is diffracted along the crack boundary and propagated to the other side (the double-dot chain line) of the crack, namely the transmitted wave, which can be transmitted to the first transverse wave-electromagnetic acoustic energy detector 332, and the content of the received waveform and data is not repeated herein because the detected data does not participate in the calculation; when the other part of the energy propagates to the bottom end of the crack along the inner wall of the crack, the energy is superposed at the bottom end and undergoes mode conversion, and part of the energy propagates to the periphery from the bottom end of the groove in the form of transverse wave (dotted line), which is called transverse wave component SR converted from the surface acoustic wave mode; another portion of the energy continues to propagate along the inner surface of the groove in the form of a surface acoustic wave (dash-dot line), referred to as surface acoustic wave component RR.
As the ultrasonic wave continues to propagate inside the test block, the portion of the transverse wave SR propagates to the surface of the test block and is finally detected as a second peak by the second transverse wave-electromagnetic acoustic energy detector 333, and the time point at this time is recorded as TS1. In addition, the surface acoustic wave RR (dot-dash line) propagating along the groove surface and then along the metal test piece surface is also detected by the surface acoustic wave-electromagnetic acoustic energy detector 334 after the SR signal, a third peak is generated, and the time TR2 at this time is noted. When the detection vehicle continues to advance, and when the laser line light source scans the right side of the crack, the surface acoustic wave-electromagnetic acoustic energy detector 334 only detects two wave crests, wherein the first wave crest is a transmitted wave which winds from the right side to the left side of the surface acoustic wave groove, and the second wave crest is a surface acoustic wave component RR which returns from the bottom of the groove. In this case, the crack depth h cannot be calculated, and only the presence or absence of cracks can be determined.
And thirdly, software calculates that in the whole detection process, the detector and the laser line light source can be considered to be in a relative static state relative to the contact line 201, and the operation process is simplified, as shown in FIG. 16, a schematic surface diagram containing grooves (representing cracks) is given on a test block, the depth of the cracks on the metal surface is h, the width is less than 0.5mm, the distance d2 from the position point of the laser line light source excitation pulse to the groove is unknown, the fixed distance d1 from the second transverse wave-electromagnetic acoustic energy detector 333 is known, the fixed distance d3 from the surface acoustic wave-electromagnetic acoustic energy detector 334 to the second transverse wave-electromagnetic acoustic energy detector 333 is known, the distance d1+ d2 is far greater than the width of the groove, so that the left edge of the groove can be approximately seen to be tightly close together, the surface acoustic waves can independently propagate on the two sides, the left edge of the surface groove and the upper surface of the metal test block form an angle α, and for further simplifying the calculation, because the change of the angle between the neglected 6725 in a certain range (50 degrees and 140 degrees) and the bottom ends of the grooves are considered to be approximately changed with the change of the linear grooves.
Firstly, the propagation velocities of the surface acoustic wave and the transverse wave in the copper-magnesium alloy contact line 201 are obtained and are respectively denoted as VR and VS, and then the time spent by the ultrasonic waves of the transverse wave component SR and the surface acoustic wave component RR modes returning from the bottom end of the groove from the sound wave propagation point to the detection point is respectively set as
Figure BDA0001801869140000201
And
Figure BDA0001801869140000202
the time point of the laser pulse emitted by the linear light source generating the ultrasonic wave on the metal surface is T. Then
Figure BDA0001801869140000211
TR＝TR0-tR1,TS＝TS0-tS1……………(2)
Figure BDA0001801869140000212
And calculating a time point T during pulse excitation, and taking an average value of ultrasonic excitation time points obtained by the surface acoustic wave and the transverse wave. Wherein t isR1、tS1The first peak is detected by the theoretical crack-free clock pulse ultrasonic-to-surface acoustic wave-electromagnetic acoustic energy detector 334 and the transverse wave-electromagnetic acoustic energy detector 333The time spent is a fixed value. At this time, the judgment is that the reflected wave receiving distance of the acoustic surface wave is not less than the first peak receiving distance:
t2×VR＝d≥d1+d3……………(4)
wherein t is2＝TR1-T, determining whether the formula is satisfied, if yes, indicating that the line light source excites a pulse on the left side of the crack or on the crack, and performing the next operation; if not, the linear light source is excited at the right side of the crack, and at this time, the acoustic surface wave-electromagnetic acoustic energy detector 334 is determined to have only two wave crests, the crack is directly judged to exist, and the next operation is not carried out.
Figure BDA0001801869140000213
Wherein d is divided in the equation2In addition, the distance d2 can be determined by using known parameters.
Figure BDA0001801869140000214
Figure BDA0001801869140000215
Figure BDA0001801869140000216
The crack depth can be determined.
Figure BDA0001801869140000217
Figure BDA0001801869140000218
The value of the hypotenuse a is determined. According to the theory of trigonometric cosine, there are
Figure BDA0001801869140000219
The orientation angle α of the crack can be determined.
And then judging the correctness of the numerical value and giving a crack danger level.
When 50 DEG- α DEG-140 DEG, each ultrasonic component is easy to recognize and the characteristic that the signal SR changes along with the change of the angle α is obvious, so the orientation and depth information of the surface crack can be easily calculated by using the change of the signal components along with the change of the angle α through combining the above formula, when α is more than 140 DEG or α <50 DEG, the angle and depth information of the surface groove extracted by the arrival time of the signal SR and RR is difficult to use, and the current calculation result α value and h value are abandoned.
The detected crack depth h should not exceed 5mm, the arrival time of the signals SR and RR will both have linear delay trend with the increase of the surface crack depth, and the amplitudes of both signals will also be attenuated and widened with the increase of the surface crack depth. Therefore, if the crack depth h is about 4-5 mm or exceeds the calculated value, the calculated value is not accurate enough and is discarded.
If the crack depth and angle values calculated by detection are abandoned and are determined to be cracks, the data analysis module gives moderate dangerous crack grades; the method includes the steps that a crack operation result is kept, a risk rating is given according to a preset division value of the crack depth, the crack depth h is less than 0.2mm and is rated as a mild dangerous crack, and the crack depth h is rated as a medium-low dangerous crack in the range of 0.2-0.4 mm; 0.4-0.6 mm is a moderate dangerous crack; 0.6-0.8 mm is a medium-high dangerous crack; 0.8mm or more is a highly dangerous crack, and the category is the first: and (4) single crack.
With this calculation method, only one in the front-rear range of the crack to be detected (the distance between the surface acoustic wave-electromagnetic acoustic energy detector 334 and the first transverse wave-electromagnetic acoustic energy detector 332) is required. Two or more than two near cracks (the interval is more than millimeter level), the sound wave can form reflection, oscillation, superposition of various forms between the cracks, the waveform is complicated, is obviously different from the waveform of a single crack, is not beneficial to value calculation, but the existence of the crack category can be confirmed at the moment. This situation gives a high risk rating, and the category is the second: and (4) multiple cracks.
And finishing the dangerous crack rating of the data analysis module, and storing the position information marked by the first-step position recording module, the crack rating and the numerical value in a storage unit for viewing and displaying by a display module. When the cracks of the surface acoustic wave and the two transverse wave detectors are both lossless crack waveforms in the two periodic pulses, the data analysis module only leaves the first transverse wave-electromagnetic acoustic energy detector 332 again for standby data acquisition to wait for the next crack to appear.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. The laser ultrasound-based crack detection system for the high-speed rail contact line is characterized in that: the device comprises a contact line following device (200) and a laser ultrasonic detection device; the contact line following device (200) comprises a lifting bow (210), a transmission mechanism (220) and a half-section cavity (230); the lifting bow (210) is arranged on the roof of the detection train (101), and two sides of the lifting bow (210) are connected with the half-section cavity (230) through two corresponding groups of same transmission mechanisms (220); the laser ultrasonic detection device is arranged in the half-section cavity (230), and comprises a control processing unit (310), a laser ultrasonic excitation device and an ultrasonic receiving device (330); the control processing unit (310) is positioned in a compartment of the detection vehicle; the laser ultrasonic excitation device and the ultrasonic receiving device (330) are arranged on the laser ultrasonic detection adjusting mechanism (250).
2. The laser ultrasound-based crack detection system for high-speed rail contact lines according to claim 1, wherein: the lifting bow (210) comprises a long side (211) of the suspension beam, a wide side (212) of the suspension beam, an upper arm (213), an upper guide rod (214), a lower arm (215), a lower guide rod (216), a pneumatic control box (217), a bow lifting device (218) and an underframe (219) which is fixed on the roof of the detection train (101) through fasteners; the long side (211) and the wide side (212) of the suspension beam form a suspension beam bow head; one end of the lower arm (215) is connected with the bottom frame (219) through a rotating shaft, the other end of the lower arm is hinged with the upper arm (213), a steel cable guide rail is arranged on the lower arm (215) and is connected with the pantograph device (218) through the steel cable guide rail, an air pipeline is arranged in the lower arm (215), and the end position of the upper end of the lower arm is connected to the air pipeline in the upper arm (213) through a hose; the pantograph device (218) is fixed on the bottom frame (219) and drives the lower arm (215) to rotate around a shaft, and the pantograph device (218) comprises a pantograph gas source pump, an air bag type cylinder and a guide disc; the inflation inlet of the pantograph rising air source pump is connected with the air inlet of the air bag type air cylinder; the guide disc is connected with a push rod of the air bag type air cylinder, and a tensioned steel cable for driving the lower arm (215) to move upwards around the shaft to lift the bow is arranged between the guide disc and the steel cable guide rail; two ends of the lower guide rod (216) are respectively connected to one end of the upper arm (213) and the underframe (219); one end of the upper guide rod (214) is connected with the lower arm (215), and the other end of the upper guide rod is connected with the wide edge (212) of the suspension beam; a carbon sliding strip is attached to the friction contact position of the long side (211) of the suspension beam and the contact line (201); an air cavity connected with an air pipeline at one end of the upper arm (213) is arranged in the carbon slide bar, and compressed air is filled in the whole air pipeline; the pneumatic control box (217) is arranged on the bottom frame (219), the air inlet end of the pneumatic control box (217) is connected to the pantograph gas source pump through one air outlet of the three-way joint, the air outlet end of the pneumatic control box is connected with the air pipeline and the air cavity in the carbon slide bar, and the other air outlet of the three-way joint is connected with the air bag type air cylinder; the air bag type cylinder is connected with a quick exhaust valve arranged in a pneumatic control box (217);
the transmission mechanism (220) comprises four pairs of double-rod transmission structures, every two double-rod transmission structures are arranged on one side, and two ends of each double-rod transmission structure are respectively connected with the wide edge (212) of the suspension beam and the outer wall of the half-section cavity (230); a pull rod spring (221) is arranged at the center of the inward bending side of each pair of double-rod transmission structures;
a pair of supporting rods (240) which are obliquely arranged and point to the central axis of the contact line (201) are respectively fixed in front and at the back of the inner side wall of the half-section cavity (230), a rectangular groove is formed in the center of the bottom of the half-section cavity (230), and a laser ultrasonic detection adjusting mechanism (250) is embedded in the rectangular groove; the front end of the supporting rod (240) is provided with a concave barrel roller (241), and a damping spring (242) is arranged between the rear end of the inside of the supporting rod (240) and the half-section cavity (230); the concave curve of the concave drum roller (241) is attached to the outer contour of the contact line (201) and is in rolling contact with the contact line (201), and the wheel height of the concave drum roller (241) and the long side (211) of the suspension beam are maintained at the same horizontal height.
3. The laser ultrasound-based crack detection system for high-speed rail contact lines according to claim 2, wherein: the laser ultrasonic detection adjusting mechanism (250) comprises 5 sliding bases (251) with adjustable positions; the lower half part of the sliding base (251) is cylindrical and penetrates through a slotted hole at the bottom of the rectangular groove, threads for matching and fixing with a nut (252) are arranged on the outer side of the sliding base, a round hole which penetrates through the whole sliding base and is used for a lead or an optical fiber to penetrate through the bottom is arranged in the center of the sliding base, the upper half part of the sliding base (251) is in a convex shape, and the step position of the sliding base is flush with the notch of the rectangular groove of the half-section cavity (230); corresponding scale strips (253) with scales are fixed on two sides of a notch of a rectangular groove in the center of the bottom of the half-section cavity (230), and the axial line end of the half-section cavity (230) close to the two scale strips (253) clamps the sliding base (251); the top plane of the sliding base (251) is provided with an identification arrow.
4. The laser ultrasound-based crack detection system for high-speed rail contact lines according to claim 1, wherein: the control processing unit (310) comprises a laser control module for controlling the on and off of the fiber laser (321) and parameters of pulse laser emission of the fiber laser (321);
the data analysis module is used for processing the data signals transmitted back by the three electromagnetic sound energy detectors, judging whether the defects exceeding the alarm threshold value occur or not and judging whether the dangerous level exists or not, and positioning the defects by combining the position recording module;
the data analysis module comprises a storage unit for receiving and storing all data signals of the electromagnetic sound energy detectors and a processor of an operation unit for performing high-speed operation processing on the data signals returned by each electromagnetic sound energy detector, determining whether to trigger the position recording module to leave a current geographical position mark according to an operation result, judging the danger level according to the crack amplitude and giving priority maintenance prompt to the high-danger crack amplitude according to the preset condition;
the display module is used for displaying a real-time interface for receiving the waveform signal and the map;
the position recording module is used for positioning the current position of the detection vehicle (101) in real time;
and a security module for system security and data protection;
the laser ultrasonic excitation device comprises a fiber laser (321), a fiber collimator (322) and a linear focusing unit (323); the fiber laser (321) is positioned at the roof of the detection vehicle, is close to the chassis (219) of the lifting bow (210), is connected with the fiber collimator (322) in the half-section cavity (230) through optical fibers, and leads of the optical fibers and the detectors are attached to the upper arm (213) and the lower arm (215) of the lifting bow (210); the tail end of the optical fiber collimator (322) is embedded and fixed on a round hole in the center of a sliding base (251), and the rest part is arranged in the linear focusing pedestal (255);
the ultrasonic receiving device (330) comprises a photoelectric detector (331), a first transverse wave-electromagnetic acoustic energy detector (332), a second transverse wave-electromagnetic acoustic energy detector (333), a surface acoustic wave-electromagnetic acoustic energy detector (334), a high-speed data acquisition device and a data processing device, wherein the high-speed data acquisition device is used for acquiring signals of the surface acoustic wave-electromagnetic acoustic energy detector (334), the first transverse wave-electromagnetic acoustic energy detector (332) and the second transverse wave-electromagnetic acoustic energy detector (333), and receiving a trigger signal of the photoelectric detector (331).
5. The laser ultrasound-based crack detection system for high-speed rail contact lines according to claim 3, wherein: a linear focusing pedestal (255) is arranged on the third sliding base (251), and the other four pedestals are fixed with a right mounting pedestal (254); the top of each sliding base (251) is provided with a double-guide-rail chute, the direction of the double-guide-rail chute is vertical to the axial direction of the half-section cavity (230), the double-guide-rail chute is matched with an inwards concave chute at the bottom of the mounting pedestal (254), and the chutes are equal in length and width and are provided with screw holes; the surface acoustic wave-electromagnetic acoustic energy detector (334), the second transverse wave-electromagnetic acoustic energy detector (333), the photoelectric detector (331) and the first transverse wave-electromagnetic acoustic energy detector (332) are sequentially arranged on corresponding mounting pedestals (254); the linear focusing unit (323) is arranged on the linear focusing pedestal (255) and is positioned on the central line of the half-section cavity (230); the direction of the photoelectric detector (331) is aligned with the position where the laser line light source pre-irradiates on the contact line (201), and the photoelectric detector (331) comprises a photosensitive resistor and a modulator; the photoresistor converts the detected weak optical signal on the surface of the object to be detected into an electric signal; the modulator modulates the converted electric signal, matches the characteristics of the linear light source optical signal, provides the converted electric signal to a high-speed data acquisition unit for data acquisition by a trigger signal, and provides the converted electric signal to a safety guarantee module of the control unit (310) by a determination signal.
6. The laser ultrasound-based crack detection system for high-speed rail contact lines according to any one of claims 1 to 5, wherein: wind shields (260) are mounted at two axial ends of the half-section cavity (230) through fasteners; the front end of a protruding table (261) in the middle of the wind shield (260) is provided with a pair of screw holes, and the positions of the screw holes are aligned with two screw holes on a protruding beam (262) at the bottom end of a rectangular groove in the center of the half-section cavity (230) and fixed through screws.
7. The laser ultrasound-based crack detection system for high-speed rail contact lines according to claim 5, wherein: the four mounting pedestals (254) are flat on two side planes vertical to the axial direction of the half-section cavity (230), two pairs of adjusting knobs are arranged on two side planes parallel to the axial direction of the half-section cavity (230), and the front sections in the adjusting knobs are rubber patches which are attached to and extrude the detector;
8. the laser ultrasound-based crack detection system for high-speed rail contact lines according to claim 5, wherein: the linear focusing pedestal (255) and two inner walls of the half-section cavity (230) are provided with guide rails in parallel in the axial direction, and the two optical benches (324) on one side can penetrate through the slotted holes and adjust the height up and down according to the scales on the outer side wall.
9. A detection method for the laser ultrasound based crack detection system for the high-speed rail contact line according to claim 1, characterized by comprising the following steps:
s1: the data analysis module of the control processing unit (310) controls the high-speed data acquisition unit to only receive the data signal of the first transverse wave-electromagnetic sound energy detector (332);
the method specifically comprises the following steps: the distance between a laser line light source and a first transverse wave-electromagnetic sound energy detector (332) arranged in front of the laser line light source is 35-60 mm, when any value a in the range is selected, the advancing distance d' of the detection vehicle in the interval time of two pulses is required to be less than or equal to a, and the detection is judged to be free of contact line broken joint missing detection; when the linear light source scans to be close to the crack, the pulse laser excites sound waves including surface acoustic waves, transverse waves and longitudinal waves on the surface of the object, and at the moment, a first wave peak is detected by the time domain waveform of the first transverse wave-electromagnetic sound energy detector (332); when the surface acoustic wave reaches the bottom of the crack through the metal surface, the surface acoustic wave is superposed at the bottom of the crack and mode conversion is carried out, a part of energy is converted into diffraction transverse wave to be transmitted outwards, at the moment, a first transverse wave-electromagnetic acoustic energy detector (332) in front of a laser line light source detects a second wave peak, a data analysis module of a control processing unit (310) sends a signal to a high-speed data acquisition unit after judging the crack, and triggers and receives all data signals of the electromagnetic acoustic energy detector so as to further obtain specific numerical values when the surface acoustic wave is re-excited by the next laser pulse, and the depth and the orientation of the crack are calculated; meanwhile, the data analysis module triggers a signal to the position recording module, marks the position information at the next moment, and whether the stored information is stored or not is determined again in the second step;
s2: after the high-speed data acquisition unit is triggered to receive all the data signals of the electromagnetic sound energy detector and before the laser line light source moves to the crack, the fiber laser (321) can generate next laser pulse so as to excite and generate new sound waves when the laser line light source moves to a position close to the left side of the crack under the condition that the specific data of the crack can be detected again;
the method specifically comprises the following steps: firstly, laser pulse is excited to generate surface acoustic wave R, longitudinal wave L and transverse wave S, the surface acoustic wave R, the longitudinal wave L and the transverse wave S propagate to the periphery of the metal surface, head waves are ignored, at the moment, a surface acoustic wave-electromagnetic acoustic energy detector (334) detects that the surface acoustic wave-electromagnetic acoustic energy detector generates a first wave peak, and a data analysis module records the time point of the moment as TR0(ii) a Similarly, the time-domain waveform of the second shear wave-electromagnetic acoustic energy detector (333) detects the first peak, and records the time point T at this timeS0；
Then, when the surface acoustic wave R propagates rightwards along the upper surface of the metal, namely, propagates along the detection advancing direction and is transmitted to the crack boundary, a part of the surface acoustic wave R is reflected at the boundary, namely, a reflected wave propagates on the upper surface along the reverse direction of the original propagation direction, a surface acoustic wave-electromagnetic acoustic energy detector (334) detects a second wave peak, and the time point at the moment is recorded as TR1(ii) a The other part is diffracted along the crack boundary and is propagated to the other side of the crack, namely a transmitted wave which can be transmitted to a first transverse wave-electromagnetic acoustic energy detector (332); when the other part of the energy propagates to the bottom end of the crack along the inner wall of the crack, the energy is superposed at the bottom end and undergoes mode conversion, and part of the energy propagates from the bottom end of the groove to the periphery in the form of transverse wave and is a transverse wave component SR converted from the surface acoustic wave mode; the other part of energy is continuously transmitted along the inner surface of the groove in the form of surface acoustic wave, and is surface acoustic wave component RR;
as the ultrasonic wave continues to propagate inside the test block, the part of the transverse wave SR is transmitted to the surface of the test block and finally a second peak is detected by a second transverse wave-electromagnetic sound energy detector (333), and the time point of the moment is recorded as TS1(ii) a In addition, the surface acoustic wave component RR which propagates along the groove surface and then along the metal test piece surface is also detected by a surface acoustic wave-electromagnetic acoustic energy detector (334) after the transverse wave component SR signal, a third peak is generated, and the time T of the moment is recordedR2；
When the detection vehicle continues to advance, the laser line light source scans the right side of the crack, at the moment, the surface acoustic wave-electromagnetic acoustic energy detector (334) only detects two wave crests, the first wave is a transmitted wave which winds from the right side to the left side of the surface acoustic wave groove, and the second wave crest is a surface acoustic wave component RR transmitted back from the bottom of the groove; in this case, the crack depth h cannot be calculated, and only the presence or absence of cracks can be determined.
S3 software calculation; the method specifically comprises the following steps:
firstly, the propagation velocities of the surface acoustic wave and the transverse wave in the copper-magnesium alloy contact line (201) are obtained, and are respectively expressed as VRAnd VSThen, the time taken for the ultrasonic wave of the transverse wave component SR and the surface wave component RR mode returning from the bottom of the groove to reach the detection point from the transmission of the sound wave from the pulse excitation point is set as
Figure FDA0001801869130000051
And
Figure FDA0001801869130000052
the time point of the laser pulse emitted by the linear light source generating ultrasonic waves on the metal surface is T; then
Figure FDA0001801869130000053
TR＝TR0-tR1,TS＝TS0-tS1……………(2)
Figure FDA0001801869130000061
Calculating a time point T during pulse excitation, and taking an average value of ultrasonic excitation time points obtained by the surface acoustic waves and the transverse waves; wherein t isR1、tS1The time spent for theoretically carrying out crack-free clock pulse ultrasonic to the surface acoustic wave-electromagnetic acoustic energy detector (334) and the transverse wave-electromagnetic acoustic energy detector (333) to detect the first peak is a fixed value; d1A known fixed distance of the second shear wave-electromagnetic acoustic energy detector (333) from the laser line light source, d3Is a known SAW-EM acoustic energy detector (334) spaced from the second shear wave-EMA fixed distance of the acoustic energy detector (333);
at this time, the judgment that the reflected wave receiving distance of the surface acoustic wave is not less than the first peak receiving distance is that:
t2×VR＝d≥d1+d3……………(4)
wherein t is2＝TR1-T, determining whether the formula is satisfied, if yes, indicating that the line light source excites a pulse on the left side of the crack or on the crack, and performing the next operation; if not, the linear light source is excited at the right side of the crack, and at the moment, the acoustic surface wave-electromagnetic acoustic energy detector (334) is determined to have only two wave crests, the crack is directly judged to exist, and the next operation is not carried out;
Figure FDA0001801869130000062
wherein d is divided in the equation2Besides, the distance d between the position point of the laser line light source excitation pulse and the groove can be obtained by using the known values of other parameters2The value of (d);
Figure FDA0001801869130000063
Figure FDA0001801869130000064
the following equations (6) and (7) yield:
Figure FDA0001801869130000065
the depth h of the crack on the metal surface of the test block can be obtained;
Figure FDA0001801869130000066
Figure FDA0001801869130000067
calculating the linear distance a between the bottom end of the groove and the surface acoustic wave-electromagnetic acoustic energy detector (334);
the left edge of the surface groove forms an angle of α with the upper surface of the metal test block,
according to the theory of trigonometric cosine, there are
Figure FDA0001801869130000071
The orientation angle α of the crack can be determined,
then judging the correctness of the numerical value and giving a crack danger level;
and after the data analysis module finishes grading the dangerous cracks, storing the position information marked by the S1 position recording module, the crack grade and the numerical value in a storage unit for the viewing and displaying module to display. When the cracks of the acoustic surface wave and the two transverse wave detectors are both in the waveform of the nondestructive crack in the two periodic pulses, the data analysis module only leaves the first transverse wave-electromagnetic acoustic energy detector (332) for standby data acquisition again to wait for the next crack to appear.
10. The method for detecting cracks on a laser-ultrasonic-based high-speed rail contact line as claimed in claim 9, wherein the step S3 is characterized in that when the angle is 50 ° ≦ α ≦ 140 °, each ultrasonic component is easily recognized and the variation of the transverse wave component SR with the α angle is obvious, so that the orientation and depth information of the surface crack can be easily calculated by using the variation of the signal components with the α angle by combining the above equations (1) to (11);
when α is 140 degrees or α is less than 50 degrees, the information of the angle and the depth of the surface groove extracted by the arrival time of the transverse wave component SR and RR is difficult to be utilized, and the current calculation result α value and h value are abandoned;
if the crack depth and angle numerical values calculated by detection are abandoned and are determined to be cracks, the data analysis module gives moderate dangerous crack grades; reserving a crack operation result, presetting a division value according to the crack depth, giving a risk rating, and setting the category as a single crack;
when two or more cracks with interval of more than millimeter level exist, the sound wave can form various reflected, vibrated and superposed waveforms between the cracks, which are obviously different from single-crack waveforms and are not beneficial to value calculation, but the existence of crack types can be confirmed at the moment, and the high-risk level is given under the condition that the types are multi-crack.
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