CN112858466A - Quantitative evaluation method for inner surface cracks of metal pipeline - Google Patents
Quantitative evaluation method for inner surface cracks of metal pipeline Download PDFInfo
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- G01N27/83—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws by investigating stray magnetic fields
Abstract
The invention discloses a quantitative evaluation method of metal pipeline inner surface cracks, which is applied to a data analysis processing unit of an evaluation test device, wherein the evaluation test device comprises a data analysis processing unit, a mechanical motion control unit, a transmission device connected with the mechanical motion control unit and a detection probe arranged on the transmission device, the detection probe comprises an excitation coil used for generating an alternating current magnetic field signal and a magnetic field sensor arranged on the outer surface of the excitation coil, the mechanical motion control unit is used for transmitting position information to the data analysis processing unit, and the data analysis processing unit is used for integrating the position information and magnetic induction intensity information transmitted by the magnetic field sensor and carrying out operation and processing. According to the invention, the magnetic induction intensity change of the detected pipeline when the crack appears is obtained through the magnetic field sensor, so that the quantitative evaluation of the crack shape is realized, and the problem that the crack is difficult to quantitatively analyze in the prior art is solved.
Description
Technical Field
The invention relates to the technical field of material surface physical characteristic characterization and evaluation methods, in particular to a non-contact detection and evaluation method for a crack on the inner surface of a metal pipeline.
Background
The metal pipeline is widely applied in the fields of equipment manufacturing industry, petroleum and natural gas, nuclear power and the like, and has very important significance in periodic inspection to ensure the integrity of the metal pipeline. At present, most of nondestructive testing technologies adopted in engineering are ultrasonic testing. Ultrasonic inspection is a nondestructive inspection method for inspecting internal defects of a material by using the difference of acoustic properties of the material and the defects thereof to the energy change of the reflection condition and the penetration time of an ultrasonic propagation waveform. The ultrasonic detection has the advantages of high speed, high sensitivity and no harm to human body, and can realize quantitative analysis of defects. However, ultrasonic testing requires a certain finish of the surface being inspected and requires a couplant to fill the gap between the probe and the surface being tested to ensure adequate acoustic coupling. In addition, since spurious reflected waves are likely to be generated, the application is difficult, and a certain experience of an inspector is required to perform an operation and judge a detection result.
The detection method based on the electromagnetic principle can solve the limitation of complex ultrasonic detection process, and does not require cleaning of the metal surface. The eddy current detection is a nondestructive detection method which takes the electromagnetic induction phenomenon as the basic principle and implements nondestructive evaluation of the physical properties of materials or detects the internal defects of the materials by detecting the change condition of induced eddy current in a measured object. Impedance analysis is a method that is widely used in eddy current testing. It is an analysis means for identifying the effect of influencing factors based on the close relation between the impedance and phase change of the detection coil caused by the analysis of eddy current effect. The eddy current detection has the advantages of no need of direct contact and coupling medium, high speed and easy automation.
Eddy current inspection is the most common inspection means in the current online inspection application, but eddy current inspection has certain defects, more interference factors and large lift-off effect. In particular, the conventional impedance analysis method can only be used for judging whether a defect exists in the conductor, and cannot intuitively describe information such as the shape, size and position of the defect. The type and shape of the defect are difficult to judge in the flaw detection process, and quantitative analysis of the defect is difficult to implement. Modern nondestructive testing does not meet the problem that only defects can be detected, and quantitative evaluation of the defects has great significance for ensuring the state stability of mechanisms, ensuring safe production operation and evaluating the life cycle of equipment. In order to obtain more obvious characteristic quantities to improve the detection capability of the defects, the traditional eddy current detection must be improved and innovated in detection means and analysis methods.
Disclosure of Invention
Therefore, a quantitative evaluation method for the inner surface cracks of the metal pipeline is needed to be provided, and the problems that the type and the shape of the crack defects are difficult to judge and the quantitative analysis of the cracks is difficult to realize in the conventional eddy current test are solved.
In order to achieve the above object, the present invention provides a quantitative evaluation method for cracks on an inner surface of a metal pipe, which is applied to a data analysis processing unit of an evaluation test device, wherein the evaluation test device comprises a data analysis processing unit, a mechanical motion control unit, a transmission device connected with the mechanical motion control unit, and a detection probe arranged on the transmission device, the detection probe comprises an excitation coil for generating an alternating magnetic field signal and a magnetic field sensor arranged on an outer surface of the excitation coil, the data analysis processing unit is connected with the mechanical motion control unit and the magnetic field sensor, the mechanical motion control unit is used for transmitting position information to the data analysis processing unit, the data analysis processing unit is used for integrating the position information and magnetic induction intensity information transmitted by the magnetic field sensor and performing operation and processing, the mechanical motion control unit realizes driving of the transmission device, the method comprises a crack section shape evaluation step:
the driving transmission device moves in the crack-free pipeline to obtain the radial or axial magnetic induction intensity of the detection probe at different positions;
the driving transmission device moves in the measured pipeline to obtain the radial or axial magnetic induction intensity of the detection probe at different positions, and the magnetic induction intensity is compared with the magnetic induction intensity without cracks to obtain a radial or axial magnetic induction intensity difference value;
and comparing the obtained radial or axial magnetic induction difference value with a preset magnetic induction disturbance curve model to obtain the area of the cross section of the crack.
Further, the preset magnetic induction disturbance curve model is obtained through the following steps:
using finite element analysis software to carry out numerical solution on the space magnetic field near the cracks with different shapes according to the physical and structural parameters of the detection probe and the detected pipeline;
and (4) solving the radial or axial magnetic induction intensity of the cracks with different sectional areas according to the numerical value, and establishing a magnetic induction intensity disturbance curve model by adopting a mathematical fitting method.
Further, the method further comprises a crack circumferential length evaluation step:
the driving transmission device enables the detection probe to be arranged inside the detected pipeline, so that the axis of the exciting coil and the axis of the pipeline keep concentric;
the transmission device is driven to move back and forth, so that the detection probe moves back and forth in the detected pipeline along the axis direction, the axial magnetic induction intensity of the magnetic field sensor is obtained, and when the change of the axial magnetic induction intensity of the magnetic field sensor reaches the maximum value, the position of the detection probe is recorded as the position of an axis reference point;
keeping the position of the detection probe at the axis reference point unchanged, driving the transmission device to rotate the probe at a constant speed, acquiring the change condition of the axial magnetic induction intensity of the magnetic field sensor, and recording the rotating angle at the moment as a first angle when the axial magnetic induction intensity is changed;
continuously rotating the probe at a constant speed to obtain the change condition of the axial magnetic induction intensity of the magnetic field sensor, and recording the rotating angle at the moment as a second angle when the axial magnetic induction intensity changes again;
and calculating the length of the pipeline crack in the circumferential direction according to the angle difference between the first angle and the second angle.
Further, the method further comprises a crack orientation evaluation step:
the driving device enables the detection probe to extend into the detected pipeline and move along the axial direction of the detected pipeline, and the position and the angle of the detection probe are recorded when the axial magnetic induction intensity changes;
the driving transmission device moves the detection probe out of the detected pipeline and rotates a certain angle;
repeating the steps for multiple times, taking the maximum position of the obtained detection probe as the initial position of the crack, and re-driving the transmission device to position the detection probe to the initial position of the crack and rotate to a corresponding angle;
keeping the angle unchanged, and driving a transmission device to enable a detection probe to move along the axial direction of the detected pipeline to obtain the maximum value of the variation of the y component of the magnetic induction intensity;
and calculating the azimuth angle of the crack according to the maximum value and a preset azimuth relation model.
Further, the detection probe comprises magnetic field sensors in two detection directions, namely an axial direction and a radial direction.
Further, the evaluation test device further comprises a probe auxiliary device, and the probe auxiliary device is used for connecting the transmission device and the detection probe.
Further, the evaluation test device further comprises a signal generator, wherein the signal generator is connected with the exciting coil and is used for generating sine alternating current so that the coil generates an alternating current magnetic field signal.
Different from the prior art, the technical scheme adopts the assessment testing device, and the magnetic induction intensity change of the detected pipeline when the crack appears is obtained through the magnetic field sensor, so that the quantitative assessment of the shape of the crack is realized, and the problem that the crack is difficult to perform quantitative analysis in the prior art is solved.
Drawings
FIG. 1 is a schematic structural diagram of an evaluation test device for quantitative evaluation of pipeline cracks according to the present invention;
FIG. 2 is a schematic structural diagram of a test probe of the present invention;
FIG. 3 is a schematic view of a model of a pipe and a crack under test according to the present invention;
FIG. 4 is a magnetic field distribution diagram under the action of different-shape cracks according to the present invention;
FIG. 5 is a schematic diagram of the longitudinal and cross-sectional structures of the measured pipeline and the cracks distributed in the circumferential direction;
FIG. 6 is a cross-sectional structural schematic view of crack orientation detection of the present invention;
FIG. 7 is a schematic view of the distribution of different orientation cracks of the present invention.
Description of reference numerals:
1. the evaluation of the test device is carried out,
10. a data analysis and processing unit 11, a mechanical motion control unit,
12. a transmission device 13, a detection probe,
130. the magnetic field sensor of the excitation coil, 131,
132. a coil frame, 133, a spacer ring,
134. the probe shell is composed of a probe shell, a 135 protective sleeve,
136. a leading-out terminal 137, a signal wire,
14. a probe auxiliary device, 15, a signal generator,
2. a pipe to be tested;
20. and (4) cracking.
Detailed Description
To explain technical contents, structural features, and objects and effects of the technical solutions in detail, the following detailed description is given with reference to the accompanying drawings in conjunction with the embodiments.
Referring to fig. 1 to 7, the present embodiment provides a quantitative evaluation method for cracks on an inner surface of a metal pipe, which is applied to a data analysis processing unit 10 of an evaluation test device 1, wherein the evaluation test device 1 is used for detecting cracks 20 on a tested pipe 2. The evaluation test device 1 comprises a data analysis processing unit 10, a mechanical motion control unit 11, a transmission device 12 connected with the mechanical motion control unit, and a detection probe 13 arranged on the transmission device, wherein the detection probe 13 comprises an excitation coil 130 for generating an alternating current magnetic field signal and a magnetic field sensor 131 arranged on the outer surface of the cylindrical excitation coil 130, the data analysis processing unit 10 is connected with the mechanical motion control unit 11 and the magnetic field sensor 131, the mechanical motion control unit 11 is used for transmitting position information to the data analysis processing unit 10, the data analysis processing unit 10 is used for integrating the position information and magnetic induction intensity information transmitted by the magnetic field sensor 131 and performing calculation and processing, the mechanical motion control unit 11 drives the transmission device 12, and the data analysis processing unit 10 can acquire the telescopic position and the rotation angle of the transmission device 12 through the mechanical motion control unit 11, thereby acquiring the position and angle of the detection probe. In some embodiments, the evaluation test device 1 further comprises a probe aid 14, the probe aid 14 being used to connect the actuator with the test probe 13. The evaluation test device further comprises a signal generator 15 connected to the excitation coil for generating a sinusoidal alternating current such that the coil generates an alternating magnetic field signal.
The magnetic field sensor is used for detecting a magnetic field signal disturbed by the crack and sending the magnetic field signal to the data analysis processing unit 10. The mechanical motion control unit is used for controlling the transmission device so as to control the detection probe to generate axial and rotary motion in the detected pipeline, and transmits the real-time position to the data analysis and processing unit so as to record the magnetic induction intensity values corresponding to different positions. The transmission device is a mechanical motion control transmission part and is used for executing the command signal sent by the mechanical motion control unit.
In order to realize the structural fixation of the detection probe 13, the detection probe 13 may further include a coil bobbin 132, a spacer ring 133, a probe housing 134, a protective sleeve 135 or a leading end 136, and the detection probe is connected to the data analysis processing unit 10 through a signal line 137.
The method can realize quantitative evaluation of the shape of the section of the crack, the circumferential length of the crack and the orientation of the crack, and each quantitative evaluation process is analyzed and explained below.
Quantitative evaluation of crack section shape:
in the case of performing quantitative evaluation of the crack sectional shape, the method includes a crack sectional shape evaluation step of: the driving transmission device moves in the crack-free pipeline to obtain the radial or axial magnetic induction intensity of the detection probe at different positions; the driving transmission device moves in the measured pipeline to obtain the radial or axial magnetic induction intensity of the detection probe at different positions, and the magnetic induction intensity is compared with the magnetic induction intensity without cracks to obtain a radial or axial magnetic induction intensity difference value; and comparing the obtained radial or axial magnetic induction difference value with a preset magnetic induction disturbance curve model to obtain the area of the cross section of the crack. Namely, the invention can quantitatively analyze the shape and the size of the crack section according to the radial or axial magnetic induction intensity.
The preset magnetic induction intensity disturbance curve model can be obtained through the following steps: using finite element analysis software to carry out numerical solution on the space magnetic field near the cracks with different shapes according to the physical and structural parameters of the detection probe and the detected pipeline; and (4) solving the radial or axial magnetic induction intensity of the cracks with different sectional areas according to the numerical value, and establishing a magnetic induction intensity disturbance curve model by adopting a mathematical fitting method. Namely, in a simulation mode, different radial or axial magnetic induction intensities are obtained for different cross-section cracks according to actual structure and physical parameters, and therefore a magnetic induction intensity disturbance curve model is established.
In the embodiment, the quantitative evaluation of the crack shape can be realized by acquiring the change condition of the space magnetic field near the crack, particularly the dependency relationship between the crack section shape and the peak value of the space radial magnetic field and the axial magnetic field at the zero point. The above embodiment can be summarized as the following steps:
1. numerical solution of the spatial magnetic field: and (3) utilizing COMSOL Multiphysics finite element analysis software to carry out numerical solution on the space magnetic field near the cracks with different shapes according to physical and structural parameters of the adopted detection probe and the detected pipeline.
2. Establishing a relation expression of crack shape and magnetic field: and (4) solving the obtained magnetic field values under the cracks with different sectional areas according to the numerical values, and establishing an input and output mathematical relation expression by adopting a mathematical fitting method.
3. Measurement of magnetic induction: in the actual operation process, firstly, the magnetic field sensor is utilized to measure the radial magnetic induction peak value and the axial magnetic induction at the zero point under the condition of no crack.
4. And (3) solving the magnetic field change value under the action of the crack: and (4) enabling the magnetic sensor to be close to the crack, and obtaining the axial magnetic induction at the radial magnetic induction peak value or the zero point. The values are compared with those without cracks, and the difference value of the radial or axial magnetic field, i.e. the variation value, is obtained.
5. Obtaining the shape of the crack: and according to the change value of the radial or axial magnetic field around the actual detected pipeline crack, obtaining the size of the cross section of the crack by reverse estimation by referring to the established relation between the crack shape and the magnetic field.
To verify the effect of the above embodiment, a pipe model as shown in fig. 3 was established. A circumferential crack exists on the inner surface of the metal tube, and the cross section of the crack is respectively rectangular, semicircular and triangular. Only the influence of the cross-sectional shape is considered here, so the three types of cracks selected are all full-circumference cracks in a plane perpendicular to the axis. In addition, the exciting coil is a cylindrical coil coaxial with the metal pipeline to be tested. The measurement point is selected at a suitable location between the excitation coil and the crack in the pipe. For the purpose of analytical comparison, the parameters were chosen such that the crack cross section had an opening of 4mm and a depth of 2 mm. Inner diameter r of exciting coilc18mm, outer diameter rc212mm and a height h of 6 mm. The radial measurement point of the magnetic field is taken as r-13.5 mm.
FIG. 4 shows the radial and axial magnetic induction disturbance curves of three types of cracks with different cross-sectional shapes. The curve indicated by the circle is the radial and axial magnetic flux density distribution at the position where r is 13.5mm in the case of no crack. Analysis shows that the cross section shape of the crack does not influence the overall distribution of magnetic induction intensity, but has certain influence on radial and axial magnetic induction intensity values. The radial and axial magnetic induction intensity changes caused by the cracks with the rectangular cross section are most obvious, and then the cracks with the rectangular cross section are semicircular cross sections, so that the cross sections with the insignificant influence degree are triangular cross sections. This feature confirms that the influence of the crack cross-section on the external magnetic field is not the same. From the finite element analysis results, it can be concluded that the larger the cross-sectional area of the crack, the more significant the influence on the external magnetic field. I.e. the crack cross-sectional area will significantly influence the obtained radial or axial magnetic induction, the above-described embodiments of the invention may be used for quantitative analysis of the crack cross-sectional area.
Secondly, quantitative evaluation of the circumferential length of the crack:
in the case of performing a quantitative evaluation of the crack circumferential length, the method further comprises a crack circumferential length evaluation step of: the driving transmission device enables the detection probe to be arranged inside the detected pipeline, so that the axis of the exciting coil and the axis of the pipeline keep concentric; the transmission device is driven to move back and forth, so that the detection probe moves back and forth in the detected pipeline along the axis direction, the axial magnetic induction intensity of the magnetic field sensor is obtained, and when the change of the axial magnetic induction intensity of the magnetic field sensor reaches the maximum value, the position of the detection probe is recorded as the position of an axis reference point; keeping the position of the detection probe at the axis reference point unchanged, driving the transmission device to rotate the probe at a constant speed, acquiring the change condition of the axial magnetic induction intensity of the magnetic field sensor, and recording the rotating angle at the moment as a first angle when the axial magnetic induction intensity is changed; continuously rotating the probe at a constant speed to obtain the change condition of the axial magnetic induction intensity of the magnetic field sensor, and recording the rotating angle at the moment as a second angle when the axial magnetic induction intensity changes again; and calculating the length of the pipeline crack in the circumferential direction according to the angle difference between the first angle and the second angle.
In order to complete the quantitative evaluation, the detection probe is designed to rotate in a scanning mode and rotate clockwise at the same certain angle interval, and after the scanning is completed, the data analysis processing unit automatically records the magnetic induction intensity value at each angle position. The length of the crack in the circumferential direction can be determined from a numerical comparison of the axial magnetic induction at different circumferential positions. The above embodiments can be summarized as the following steps:
1. the exciting coil in the detection probe together with the magnetic sensor is placed inside the measured pipeline, and the concentricity of the exciting coil and the axis of the measured pipeline is ensured.
2. Moving the detection probe back and forth in the direction of the axis in the pipeline, and when the output change of the magnetic field sensor reaches the maximum value, setting the position as an axial reference point position, namely the axial position of the crack;
3. keeping the position of the detection probe in the axial direction unchanged, rotating the probe at a constant speed, and detecting the change condition of the output value of the magnetic field sensor. If the sensor rotates to a certain position, the data analysis processing unit detects that the value of the sensor changes (if the change is larger than a preset ratio, the change is generated), and the rotating angle at the moment is recorded as a first angle.
4. The detecting probe is continuously rotated and the output value of the sensor is detected. When the value of the sensor changes again, the data analysis processing unit records the rotating angle as a second angle.
5. Through the difference (the first angle is subtracted from the second angle), and analysis is carried out, the length of the crack in the circumferential direction can be accurately and conveniently obtained.
To verify the effect of the above embodiment, six metal pipe assemblies each having an inner diameter of 14mm but different lengths of cracks were created in the COMSOL Multiphysics finite element analysis software. The height and depth of the crack section are both 2mm, i.e. the crack section is square. The only change in the six components was the circumferential length of the crack. The different lengths in the circumferential direction are indicated by the central angles corresponding to the circular arcs, respectively 0 °,60 °, 120 °, 180 °,270 ° and 360 °, as shown in fig. 5. Four special measuring points are selected as the positions for magnetic field comparison, the magnetic field measuring points P1-P4 are respectively selected at four positions of 0 °, 90 °, 180 ° and 270 °, and the radial measuring position r is 13.5 mm.
Comparing the change in magnetic field at the four measurement points, it can be found that:
1) when no crack is present, i.e. the crack central angle is 0 °, the axial magnetic induction Bz at the position of the four observation points P1-P4 is exactly equal.
2) When the crack with the central angle of 60 degrees appears, the axial magnetic induction intensity at the observation point P1 in the four observation points is changed and is obviously weakened. The Bz is substantially unchanged at the other three observation points. Therefore, the length of the crack in the circumferential direction can be qualitatively judged to be between 0 and 90 degrees through comparison of the axial magnetic induction intensity at P1 and P2.
3) When the crack increases from 60 degrees to 120 degrees, the magnetic induction intensity at the observation point P2 is weakened in the four observation points, and the Bz at the other two observation points P3 and P4 is basically unchanged. Therefore, the length of the crack in the circumferential direction can be qualitatively judged to be between 90 and 180 degrees through comparison of the axial magnetic induction intensity at P2 and P3.
4) When the crack increases from 120 ° to 180 ° at the central angle, the magnetic induction at the observation point P3 decreases. At this time, only the axial magnetic induction at P4 was unchanged from the four observation points. Therefore, the length of the crack in the circumferential direction can be qualitatively judged to be between 180 and 270.
5) When the crack increases from 180 ° to 270 ° at the central angle, the magnetic induction at the observation point P4 decreases. Therefore, the length of the crack in the circumferential direction can be qualitatively judged to be between 270 and 360 degrees.
6) When the crack increases from 270 ° to 360 ° of the central angle, the magnetic induction at observation points P1 and P4 is slightly reduced. Since the model is an axisymmetric structure, the axial magnetic induction at the positions of the four observation points P1-P4 is kept completely equal. The magnetic induction intensity distribution of the four observation points is similar to that of the crack-free condition, except that the magnetic field values measured by the circumferential cracks are smaller than those measured by the crack-free condition.
From the above results, table 1 below was obtained, where "↓" indicated a significant decrease in magnetic induction intensity, "↘" indicated a certain decrease in magnetic induction intensity, and "-" indicated no change in magnetic induction intensity.
TABLE 1 four measurement points, Bz as a function of the circumferential length of the crack
From this, it can be seen that the Bz peak at the four detection points P1-P4 gradually decreased as the crack circumferential length increased. Therefore, the above-described embodiment can quantitatively evaluate the circumferential length of the crack by increasing the circumferential measurement points and using the variation of the axial magnetic induction Bz at each measurement point.
Thirdly, crack orientation quantitative evaluation:
in the case of quantitative evaluation of crack orientation, the method further comprises a crack orientation evaluation step of: the driving device enables the detection probe to extend into the detected pipeline and move along the axial direction of the detected pipeline, and the position and the angle of the detection probe are recorded when the axial magnetic induction intensity changes; the driving transmission device moves the detection probe out of the detected pipeline and rotates a certain angle; repeating the steps for multiple times (if the detection probe is rotated for a half-cycle or a cycle), taking the maximum position of the obtained detection probe as the initial position of the crack, and re-driving the transmission device to position the detection probe to the initial position of the crack and rotate the detection probe to a corresponding angle; keeping the angle unchanged, and driving a transmission device to enable a detection probe to move along the axial direction of the detected pipeline to obtain the maximum value of the variation of the y component of the magnetic induction intensity; and calculating the azimuth angle of the crack according to the maximum value and a preset azimuth relation model.
In order to realize the detection of the magnetic induction intensity in different directions, the detection probe comprises magnetic field sensors in two axial and radial detection directions. The above embodiment may adopt the following steps in specific operations:
1) a detection probe of a magnetic field sensor with two sensitive directions is driven to extend into a detected pipeline, and the detection probe and the pipeline are also ensured to be coaxial. The axial coordinate z of the change of the axial magnetic induction intensity at the moment is recorded through the movement of the detection probe along the axial direction in the detected pipeline1(i.e., the position in which the transmission telescopes).
2) Moving the detection probe out of the pipeline, rotating the detection probe at a certain angle clockwise (or anticlockwise), operating by the same method in the step 1, and respectively recording the axial coordinate z of the change of the axial magnetic induction intensity2、z3……zn。
3) The maximum position among the above axial coordinate values is defined as the starting position of the crack, and the magnetic field sensor is repositioned thereto as shown in fig. 6.
4) Ensuring the magnetic field sensor to be unchanged at the angle position, axially moving the detection probe, and recording the maximum value B of the variation of the y component of the magnetic induction intensityym。
5) Different azimuthal cracks correspond to different BymThe azimuth angle of the crack can be calculated from the variation value of the y-component of the magnetic induction.
6) Due to the fact thatThe normal starting position is defined as the deepest position of the crack in the axial direction, and therefore the azimuth angle of the crack measured should be between-90 ° and +90 °. An azimuth angle of 0 ° indicates that the crack is horizontal, and B is measuredymThe cracks are more pronounced than in other orientations. B isymThere are positive and negative, which represent the different directions on both sides of the crack at the starting position.
To verify the effectiveness of the above example, five different orientations of cracks were created, all of which were semi-circular in cross-sectional shape and remained constant throughout, and their positions in the metal pipe were shown in (r) -v of fig. 7. The cracks are arranged coaxially with the metal pipe, the cracks are arranged clockwise with a certain angle, and the cracks are arranged clockwise with another circumferential crack, which is equivalent to the cracks arranged clockwise 180 degrees. The lengths of all the cracks are kept 8.796mm, and the distance between the magnetic field measuring point and the center of the circle is 13.5 mm. The magnetic induction intensity distribution in the y direction is obviously changed along with the change of the crack orientation. The specific changes are as follows:
1) when the crack lies in the xy plane, i.e. the crack is distributed along the axial direction with an approximate odd symmetry, z>At 0, the magnetic induction intensity value is a negative value, z<At 0, the magnetic induction intensity value is positive. The magnetic induction intensity in the y direction reaches a maximum value B at a certain position in the axial directionym。
2) When the crack is rotated clockwise by an angle, the magnetic induction intensity value in the y direction is reduced, including the maximum value Bym。
3) When the crack rotates clockwise and is coaxial with the pipeline, the magnetic induction intensity value in the y direction is always zero, and the maximum value B does not appearymI.e. Bym＝0。
4) When the crack rotates clockwise again and is symmetrical to the crack II, the magnetic induction intensity distribution in the y direction is just opposite to that of the crack II, and the numerical value is the same.
5) When the crack rotates clockwise, i.e. the crack is a fifth direction, the magnetic induction intensity distribution in the y direction is just opposite to that of the crack, and the value is the same.
From the above analysis, the values of the magnetic induction intensity in the y-direction, in particular the maximum value B, were confirmedymThe crack orientation quantitative evaluation method has an obvious quantitative relation with the crack orientation, and can be used as a characteristic quantity for crack orientation evaluation.
When the evaluation test device is specifically adopted to carry out quantitative evaluation on the cracks, the following steps can be adopted:
1) firstly, three physical parameters of the measured parameters, namely the shape, the circumferential length and the orientation of the crack, are selected, and the measured parameters are obtained by evaluating a testing device. And selecting different measurement parameters, and then, evaluating the test device to enter a corresponding working mode.
2) Under the corresponding working mode, the mechanical motion control unit drives the detection probe to perform the corresponding detection process in the detected pipeline, and obtains the magnetic induction intensity in the corresponding direction.
3) The data analysis and processing unit can obtain the state of the measured parameter according to the mutual mapping relation between the measured parameter and the magnetic induction amplitude value based on the obtained information such as the magnetic induction intensity, the motion position of the detection probe and the like.
The method provides magnetic induction intensities with different dimensions as the measured values of three different parameters, avoids mutual interference among signals to a certain extent, and improves the capability of quantitative evaluation of cracks.
4) In an embodiment, the mechanical motion control unit and the data analysis and processing unit may be centrally controlled by a unified unit.
It should be noted that, although the above embodiments have been described herein, the invention is not limited thereto. Therefore, based on the innovative concepts of the present invention, the technical solutions of the present invention can be directly or indirectly applied to other related technical fields by making changes and modifications to the embodiments described herein, or by using equivalent structures or equivalent processes performed in the content of the present specification and the attached drawings, which are included in the scope of the present invention.
Claims (7)
1. The quantitative evaluation method of the metal pipeline inner surface crack is characterized by being applied to a data analysis processing unit of an evaluation testing device, wherein the evaluation testing device comprises a data analysis processing unit, a mechanical motion control unit, a transmission device connected with the mechanical motion control unit and a detection probe arranged on the transmission device, the detection probe comprises an excitation coil used for generating an alternating current magnetic field signal and a magnetic field sensor arranged on the outer surface of the excitation coil, the data analysis processing unit is connected with the mechanical motion control unit and the magnetic field sensor, the mechanical motion control unit is used for transmitting position information to the data analysis processing unit, the data analysis processing unit is used for integrating the position information and magnetic induction intensity information transmitted by the magnetic field sensor and carrying out operation and processing, the mechanical motion control unit realizes the driving of the transmission device, the method comprises a crack section shape evaluation step:
the driving transmission device moves in the crack-free pipeline to obtain the radial or axial magnetic induction intensity of the detection probe at different positions;
the driving transmission device moves in the measured pipeline to obtain the radial or axial magnetic induction intensity of the detection probe at different positions, and the magnetic induction intensity is compared with the magnetic induction intensity without cracks to obtain a radial or axial magnetic induction intensity difference value;
and comparing the obtained radial or axial magnetic induction difference value with a preset magnetic induction disturbance curve model to obtain the area of the cross section of the crack.
2. The method for quantitatively evaluating the cracks on the inner surface of the metal pipeline according to claim 1, wherein the preset magnetic induction disturbance curve model is obtained by the following steps:
using finite element analysis software to carry out numerical solution on the space magnetic field near the cracks with different shapes according to the physical and structural parameters of the detection probe and the detected pipeline;
and (4) solving the radial or axial magnetic induction intensity of the cracks with different sectional areas according to the numerical value, and establishing a magnetic induction intensity disturbance curve model by adopting a mathematical fitting method.
3. The method of claim 1, further comprising a crack circumferential length evaluation step of:
the driving transmission device enables the detection probe to be arranged inside the detected pipeline, so that the axis of the exciting coil and the axis of the pipeline keep concentric;
the transmission device is driven to move back and forth, so that the detection probe moves back and forth in the detected pipeline along the axis direction, the axial magnetic induction intensity of the magnetic field sensor is obtained, and when the change of the axial magnetic induction intensity of the magnetic field sensor reaches the maximum value, the position of the detection probe is recorded as the position of an axis reference point;
keeping the position of the detection probe at the axis reference point unchanged, driving the transmission device to rotate the probe at a constant speed, acquiring the change condition of the axial magnetic induction intensity of the magnetic field sensor, and recording the rotating angle at the moment as a first angle when the axial magnetic induction intensity is changed;
continuously rotating the probe at a constant speed to obtain the change condition of the axial magnetic induction intensity of the magnetic field sensor, and recording the rotating angle at the moment as a second angle when the axial magnetic induction intensity changes again;
and calculating the length of the pipeline crack in the circumferential direction according to the angle difference between the first angle and the second angle.
4. The method of claim 1, further comprising a crack orientation evaluation step of:
the driving device enables the detection probe to extend into the detected pipeline and move along the axial direction of the detected pipeline, and the position and the angle of the detection probe are recorded when the axial magnetic induction intensity changes;
the driving transmission device moves the detection probe out of the detected pipeline and rotates a certain angle;
repeating the steps for multiple times, taking the maximum position of the obtained detection probe as the initial position of the crack, and re-driving the transmission device to position the detection probe to the initial position of the crack and rotate to a corresponding angle;
keeping the angle unchanged, and driving a transmission device to enable a detection probe to move along the axial direction of the detected pipeline to obtain the maximum value of the variation of the y component of the magnetic induction intensity;
and calculating the azimuth angle of the crack according to the maximum value and a preset azimuth relation model.
5. The method of claim 4, wherein the detection probe comprises magnetic field sensors for both axial and radial detection directions.
6. The method of claim 1, wherein the evaluation test device further comprises a probe auxiliary device, and the probe auxiliary device is used for connecting the transmission device and the detection probe.
7. The method of claim 1, wherein the evaluation test device further comprises a signal generator connected to the excitation coil, the signal generator being configured to generate a sinusoidal alternating current to cause the coil to generate an alternating magnetic field signal.
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