CN112858466B - Quantitative evaluation method for cracks on inner surface of metal pipeline - Google Patents
Quantitative evaluation method for cracks on inner surface of metal pipeline Download PDFInfo
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Abstract
The invention discloses a quantitative evaluation method for cracks on the inner surface of a metal pipeline, which is 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 for generating an alternating 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 performing operation and processing. According to the invention, the magnetic induction intensity change when the detected pipeline is cracked is obtained through the magnetic field sensor, so that quantitative evaluation of the crack shape is realized, and the problem that quantitative analysis on the crack is difficult in the prior art is solved.
Description
Technical Field
The invention relates to the technical field of material surface physical property characterization evaluation methods, in particular to a non-contact detection and evaluation method for cracks 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 periodic inspection is of great importance to ensure the integrity of the metal pipeline. The most adopted nondestructive testing technology in the current engineering is ultrasonic testing. Ultrasonic detection is a nondestructive detection method for detecting internal defects of a material by utilizing the energy change of the acoustic performance difference of the material and the defects thereof on the reflection condition and the penetration time of ultrasonic wave propagation waveforms. The ultrasonic detection has the advantages of high speed, high sensitivity and no harm to human body, and can realize the quantitative analysis of defects. However, ultrasonic testing requires a certain finish on the surface being inspected and a couplant filling the gap between the probe and the surface being tested to ensure adequate acoustic coupling. In addition, because of the tendency to generate spurious reflection waves, it is difficult to apply the device, and an experienced inspector is required to perform the operation and judge the detection result.
By adopting the detection method based on the electromagnetic principle, the limitation of complex ultrasonic detection process can be solved, and the metal surface is not required to be cleaned. The eddy current detection is a nondestructive detection method which uses electromagnetic induction phenomenon as a basic principle and detects the change condition of the induced eddy current in the detected object so as to implement nondestructive evaluation of the physical property of the material or detect the internal defect of the material. Impedance analysis is a very widely used method in eddy current testing. The method is an analysis means for identifying the influence factor effect based on the close relation between the impedance and the phase change of the detection coil caused by the eddy current effect. The eddy current detection has the advantages of no need of direct contact, no need of coupling medium, high speed and easy automation realization.
The eddy current detection is the most common detection means in the current online detection application, but the eddy current detection has certain defects, more interference factors and large lift-off effect. In particular, the conventional impedance analysis method can only be used to determine whether a defect exists in the conductor, and cannot intuitively describe information such as the shape, size, and position of the defect. In the flaw detection process, the type and shape of the flaw are difficult to judge, and quantitative analysis of the flaw is difficult to implement. Modern nondestructive testing does not meet the requirement of detecting defects, and quantitative assessment of defects has very important significance for ensuring the state stability of institutions, ensuring production safety operation and assessing the life cycle of equipment. In order to obtain more obvious characteristic quantities to improve the defect detection capability, the conventional eddy current detection must be improved and innovated in detection means and analysis methods.
Disclosure of Invention
Therefore, it is necessary to provide a quantitative evaluation method for cracks on the inner surface of a metal pipeline, so as to solve the problems that the type and shape of crack defects are difficult to judge and quantitative analysis of the cracks is difficult to realize in the conventional eddy current detection.
In order to achieve the above object, the present invention provides a quantitative evaluation method of cracks on an inner surface of a metal pipe, which is applied to a data analysis processing unit of an evaluation test device including a data analysis processing unit, a mechanical motion control unit, a transmission device connected to the mechanical motion control unit, and a detection probe provided at the transmission device, the detection probe including an excitation coil for generating an alternating magnetic field signal and a magnetic field sensor provided at an outer surface of the excitation coil, the data analysis processing unit being connected to the mechanical motion control unit and the magnetic field sensor, the mechanical motion control unit being configured to transmit positional information to the data analysis processing unit, the data analysis processing unit being configured to synthesize the positional information and magnetic induction intensity information transmitted by the magnetic field sensor and perform operation and processing, the mechanical motion control unit realizing driving of the transmission device, the method comprising a crack cross-sectional shape evaluation step:
Driving a transmission device to move in a crack-free pipeline to obtain radial or axial magnetic induction intensity of a detection probe at different positions;
Driving a transmission device to move in a detected pipeline to obtain radial or axial magnetic induction intensities of a detection probe at different positions, and comparing the magnetic induction intensities with magnetic induction intensities without cracks to obtain a radial or axial magnetic induction intensity difference value;
And comparing the obtained radial or axial magnetic induction intensity difference with a preset magnetic induction intensity disturbance curve model to obtain the crack cross-sectional area.
Further, the preset magnetic induction intensity disturbance curve model is obtained through the following steps:
carrying out numerical solution on a space magnetic field near cracks with different shapes according to physical and structural parameters of the detection probe and the detected pipeline by utilizing finite element analysis software;
And (3) according to radial or axial magnetic induction intensity of cracks with different sectional areas obtained by numerical solution, establishing a magnetic induction intensity disturbance curve model by adopting a mathematical fitting method.
Further, the method further comprises a crack circumference length evaluation step:
The driving device is driven to enable the detection probe to be arranged in the detected pipeline, so that the axis of the exciting coil and the axis of the pipeline are kept concentric;
driving the transmission device to move back and forth so that the detection probe moves back and forth in the axis direction inside the detected pipeline to obtain the axial magnetic induction intensity of the magnetic field sensor, and recording the position of the detection probe as the axis reference point position when the axial magnetic induction intensity change of the magnetic field sensor reaches the maximum value;
The position of the detection probe at the axis reference point is kept unchanged, the transmission device is driven to rotate the probe at a constant speed, the axial magnetic induction intensity change condition of the magnetic field sensor is obtained, and when the axial magnetic induction intensity changes, the rotation angle at the moment is recorded as a first angle;
Continuing rotating the probe at a constant speed, acquiring the change condition of the axial magnetic induction intensity of the magnetic field sensor, and recording the rotation angle at the moment as a second angle when the axial magnetic induction intensity is changed again;
And calculating the length of the pipe 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 transmission device is driven to enable the detection probe to extend into the detected pipeline and move in the axial direction of the detected pipeline, and when the axial magnetic induction intensity changes, the position and the angle of the detection probe are recorded;
the detection probe is moved out of the detected pipeline by the driving transmission device and rotated for a certain angle;
Repeating the steps for a plurality of times, taking the obtained maximum position of the 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;
the angle is kept unchanged, and the transmission device is driven to enable the detection probe to move along the axis direction of the detected pipeline, so that the maximum value of the y component variation of the magnetic induction intensity is obtained;
and calculating the azimuth angle of the crack according to the maximum value and a preset azimuth relation model.
Further, the detection probe comprises a magnetic field sensor in both axial and radial detection directions.
Further, the evaluation test device further comprises a probe auxiliary device, wherein 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 connected to the excitation coil, the signal generator being configured to generate a sinusoidal alternating current such that the coil generates an alternating current magnetic field signal.
Compared with the prior art, the quantitative evaluation of the crack shape is realized by adopting the evaluation testing device and acquiring the magnetic induction intensity change of the detected pipeline when the crack appears through the magnetic field sensor, and the problem that the crack is difficult to quantitatively analyze in the prior art is solved.
Drawings
FIG. 1 is a schematic structural diagram of an evaluation test device for quantitatively evaluating pipeline cracks;
FIG. 2 is a schematic structural view of a detection probe according to the present invention;
FIG. 3 is a schematic diagram of a model of a pipe and crack under test according to the present invention;
FIG. 4 is a graph showing the magnetic field distribution under the action of a crack of different shape according to the present invention;
FIG. 5 is a schematic view of the longitudinal and cross-sectional structures of the tested pipeline and the crack circumferential distribution of the invention;
FIG. 6 is a schematic cross-sectional structure of crack orientation detection of the present invention;
FIG. 7 is a schematic view showing the distribution of cracks in different directions according to the present invention.
Reference numerals illustrate:
1. the test device is evaluated in such a way that,
10. A data analysis processing unit, 11, a mechanical motion control unit,
12. The transmission device, 13 and the detection probe,
130. The excitation coil, 131 the magnetic field sensor,
132. A coil former, 133, a spacer ring,
134. The outer shell, 135, protective sleeve of the probe,
136. A leading-out terminal 137, a signal wire,
14. A probe auxiliary device, 15, a signal generator,
2. A pipeline to be tested;
20. And (5) cracking.
Detailed Description
In order to describe the technical content, constructional features, achieved objects and effects of the technical solution in detail, the following description is made in connection with the specific embodiments in conjunction with the accompanying drawings.
Referring to fig. 1 to 7, the present embodiment provides a quantitative evaluation method for cracks on the 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 exciting coil 130 for generating alternating magnetic field signals and a magnetic field sensor 131 arranged on the outer surface of the cylindrical exciting 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 operation and processing, the mechanical motion control unit 11 is used for driving the transmission device 12, and the data analysis processing unit 10 can acquire the telescopic position and the rotating angle of the transmission device 12 through the mechanical motion control unit 11 so as to acquire the position and the angle of the detection probe. In certain embodiments, the evaluation test device 1 further comprises a probe aid 14, the probe aid 14 being used to connect the transmission means with the test probe 13. The evaluation test arrangement 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 magnetic field signals disturbed by cracks and sending the magnetic field signals 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 motions in the detected pipeline, and transmitting 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 transmission part of mechanical motion control and is used for executing command signals sent by the mechanical motion control unit.
In order to fix the structure of the detection probe 13, the detection probe 13 may further include a coil bobbin 132, an isolating ring 133, a probe housing 134, a protective sleeve 135, or a lead-out terminal 136, and the detection probe is connected to the data analysis processing unit 10 through a signal line 137.
The invention can realize quantitative evaluation of the crack section shape, quantitative evaluation of the crack circumference length and quantitative evaluation of the crack orientation, and each quantitative evaluation process is analyzed and described below.
1. Quantitative assessment of crack section shape:
In performing the quantitative evaluation of the crack cross-sectional shape, the method includes the crack cross-sectional shape evaluation step of: driving a transmission device to move in a crack-free pipeline to obtain radial or axial magnetic induction intensity of a detection probe at different positions; driving a transmission device to move in a detected pipeline to obtain radial or axial magnetic induction intensities of a detection probe at different positions, and comparing the magnetic induction intensities with magnetic induction intensities without cracks to obtain a radial or axial magnetic induction intensity difference value; and comparing the obtained radial or axial magnetic induction intensity difference with a preset magnetic induction intensity disturbance curve model to obtain the crack cross-sectional area. 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: carrying out numerical solution on a space magnetic field near cracks with different shapes according to physical and structural parameters of the detection probe and the detected pipeline by utilizing finite element analysis software; and (3) according to radial or axial magnetic induction intensity of cracks with different sectional areas obtained by numerical solution, establishing a magnetic induction intensity disturbance curve model by adopting a mathematical fitting method. Firstly, obtaining different radial or axial magnetic induction intensities for cracks with different sectional areas according to actual structures and physical parameters in a simulation mode, so as to establish a magnetic induction intensity disturbance curve model.
The embodiment can realize quantitative evaluation of the crack shape by acquiring the change condition of the space magnetic field near the crack, in particular 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 embodiments can be summarized as follows:
1. Numerical solution of the space magnetic field: and carrying out numerical solution on the space magnetic field near the cracks with different shapes according to the physical and structural parameters of the adopted detection probe and the detected pipeline by utilizing COMSOL Multiphysics finite element analysis software.
2. Establishing a relation expression of crack shape and magnetic field: and establishing an input mathematical relation expression and an output mathematical relation expression by adopting a mathematical fitting method according to the magnetic field values under the cracks with different cross sections obtained by numerical solution.
3. Measurement of magnetic induction: in the actual operation process, the magnetic field sensor is used for measuring the axial magnetic induction intensity at the radial magnetic induction intensity peak value and the zero point under the condition of no crack.
4. Obtaining a magnetic field change value under the action of cracks: and (3) the magnetic sensor is close to the vicinity of the crack, and the axial magnetic induction intensity at the radial magnetic induction intensity peak value or the zero point at the moment is obtained. The value is compared with the value in the case of no crack, and the difference value of the radial or axial magnetic field, namely the change value, is obtained.
5. Obtaining crack shape: and according to the change value of the radial or axial magnetic field around the actual detected pipeline crack, reversely pushing to obtain the sectional area of the crack according to the relation between the established crack shape and the magnetic field.
To verify the effect of the above embodiment, a pipeline model shown in fig. 3 was established. A circumferential crack is formed on the inner surface of the metal pipe, 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 that all three types of cracks selected are full-circle cracks in a plane perpendicular to the axis. In addition, the exciting coil adopts a cylindrical coil coaxial with the metal pipeline to be tested. The measurement point is selected to be in place between the excitation coil and the crack in the pipe. For the convenience of analysis and comparison, specific parameters are selected as follows, the opening of the crack section is 4mm, and the depth is 2mm. Excitation coil inner diameter r c1 =8 mm, outer diameter r c2 =12 mm and height h=6 mm. The radial measurement point of the magnetic field takes r=13.5 mm.
Fig. 4 shows the radial and axial magnetic induction disturbance curves under three different cross-sectional shape cracks, respectively. The curve represented by circles is the radial and axial magnetic induction distribution at the r=13.5 mm position in the crack-free condition. Analysis shows that the crack cross-sectional shape does not affect the overall distribution of magnetic induction intensity, but has a certain effect on radial and axial magnetic induction intensity values. The radial and axial magnetic induction intensity changes caused by the cracks of the rectangular cross section are most obvious, the second is a semicircular cross section, and the influence degree is not obvious, namely a triangular cross section. This feature confirms that the effect of the crack cross-section on the external magnetic field is different. From the finite element analysis results, it can be concluded that the larger the crack cross-sectional area, the more pronounced the effect on the external magnetic field. I.e. the cross-sectional area of the crack 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 cross-sectional area of the crack.
2. Quantitative assessment of crack circumferential length:
In performing the quantitative assessment of the crack circumference length, the method further comprises the step of assessing the crack circumference length: the driving device is driven to enable the detection probe to be arranged in the detected pipeline, so that the axis of the exciting coil and the axis of the pipeline are kept concentric; driving the transmission device to move back and forth so that the detection probe moves back and forth in the axis direction inside the detected pipeline to obtain the axial magnetic induction intensity of the magnetic field sensor, and recording the position of the detection probe as the axis reference point position when the axial magnetic induction intensity change of the magnetic field sensor reaches the maximum value; the position of the detection probe at the axis reference point is kept unchanged, the transmission device is driven to rotate the probe at a constant speed, the axial magnetic induction intensity change condition of the magnetic field sensor is obtained, and when the axial magnetic induction intensity changes, the rotation angle at the moment is recorded as a first angle; continuing rotating the probe at a constant speed, acquiring the change condition of the axial magnetic induction intensity of the magnetic field sensor, and recording the rotation angle at the moment as a second angle when the axial magnetic induction intensity is changed again; and calculating the length of the pipe 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 into a rotary scanning mode, rotates at the same certain angle interval in a clockwise direction, and the data analysis processing unit automatically records the magnetic induction intensity value at each angle position after the scanning is completed. The length of the crack in the circumferential direction can be determined according to the numerical comparison of the axial magnetic induction intensity at different circumferential positions. The above embodiments can be summarized as follows:
1. the exciting coil in the detection probe is placed inside the detected pipeline together with the magnetic sensor, and the concentricity of the exciting coil and the axis of the detected pipeline is ensured.
2. The detection probe moves back and forth in the axial direction inside the pipeline, and when the output change of the magnetic field sensor reaches the maximum value, the position is set as an axial reference point position, namely the axial position of the crack;
3. the position of the axis direction of the detection probe is kept unchanged, the probe is rotated at a constant speed, and the change condition of the output value of the magnetic field sensor is detected. If the rotation is to a certain position, the data analysis processing unit detects that the sensor value changes at the moment (if the change is larger than a preset ratio, the change is generated), namely the rotation angle at the moment is recorded as a first angle.
4. And continuing to rotate the detection probe and detecting the output value of the sensor. When the sensor value changes again, the data analysis processing unit records that the rotating angle is the second angle.
5. Through the difference (the second angle minus the first angle) and analysis, the length of the crack in the circumferential direction can be accurately and conveniently obtained.
To verify the effect of the above embodiment, six assemblies of metal pipe inner diameters of 14mm, but with different lengths of cracks were respectively built in COMSOL Multiphysics finite element analysis software. The height and depth of the crack cross section were both 2mm, i.e. the cross section of the crack was square. The only change in the six assemblies is the circumferential length of the crack. The different lengths in the circumferential direction are represented by the central angles corresponding to the circular arcs, which are respectively 0 °,60 °,120 °,180 °,270 ° and 360 °, as shown in fig. 5. Here, four special measurement points are selected as the positions for magnetic field comparison, the magnetic field measurement points P1 to P4 are respectively selected at four positions of 0 °,90 °,180 °,270 °, and the radial measurement position r=13.5 mm.
Comparing the changes in magnetic field at the four measurement points, it can be found that:
1) When no crack exists, namely when the central angle of the crack is 0 DEG, the axial magnetic induction intensities Bz at the positions of the four observation points P1-P4 are completely equal.
2) When a crack with the central angle of 60 degrees appears, the axial magnetic induction intensity at the observation point P1 changes and is obviously weakened in the four observation points. Bz at the other three observation points was substantially unchanged. Therefore, by comparing the axial magnetic induction intensities at the positions P1 and P2, the length of the crack in the circumferential direction can be qualitatively judged to be between 0 and 90 degrees.
3) When the crack is increased to 120 degrees from the central angle 60 degrees, the magnetic induction intensity at the observation point P2 is weakened in the four observation points, and Bz at the other two observation points P3 and P4 is basically unchanged. Therefore, by comparing the axial magnetic induction intensities at the positions P2 and P3, the length of the crack in the circumferential direction can be qualitatively judged to be between 90 degrees and 180 degrees.
4) When the crack increases from the central angle 120 ° to 180 °, the magnetic induction intensity at the observation point P3 is weakened. At this time, only the axial magnetic induction intensity at P4 is unchanged among the four observation points. Therefore, the length of the crack in the circumferential direction can be qualitatively judged to be 180-270 degrees.
5) When the crack increases from 180 ° to 270 °, the magnetic induction intensity at the observation point P4 is weakened. Therefore, the length of the crack in the circumferential direction can be qualitatively judged to be 270-360 degrees.
6) When the crack increases from the central angle 270 ° to 360 °, the magnetic induction at the observation points P1 and P4 slightly decreases. Because the model becomes an axisymmetric structure, the axial magnetic induction intensity at the positions of the four observation points P1-P4 remains completely equal. The distribution of magnetic induction intensity at the four observation points is similar to that of the case without the crack, except that the values of magnetic fields measured by the circumferential crack are smaller than those measured by the case without the crack.
The results shown in Table 1 below were obtained, in which "+.f. shows a significant decrease in magnetic induction," ↘ "shows a certain decrease in magnetic induction, and" - "shows no change in magnetic induction.
TABLE 1 four measurement points, bz variation with crack circumferential length
It can be seen that the Bz peaks at the four detection points P1 to P4 gradually decrease as the circumferential length of the crack increases. Therefore, the above-described embodiment can quantitatively evaluate the length of the crack in the circumferential direction by adding the measurement points in the circumferential direction and utilizing the change in the axial magnetic induction strength Bz of each measurement point.
3. Quantitative evaluation of crack orientation:
in performing the quantitative crack orientation assessment, the method further comprises a crack orientation assessment step: the transmission device is driven to enable the detection probe to extend into the detected pipeline and move in the axial direction of the detected pipeline, and when the axial magnetic induction intensity changes, the position and the angle of the detection probe are recorded; the detection probe is moved out of the detected pipeline by the driving transmission device and rotated for a certain angle; repeating the steps for a plurality of times (for example, enabling the detection probe to complete half cycle or one cycle of rotation), taking the acquired maximum position of the 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; the angle is kept unchanged, and the transmission device is driven to enable the detection probe to move along the axis direction of the detected pipeline, so that the maximum value of the y component variation of the magnetic induction intensity is obtained; 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 detection directions, namely an axial direction and a radial direction. The above embodiment may take the steps in specific operations:
1) The detection probe with the magnetic field sensors in two sensitive directions is driven to extend into the pipeline to be detected, and the detection probe and the pipeline are ensured to be coaxial. By detecting the movement of the probe in the detected pipeline along the axial direction, the axial coordinate z 1 (namely the telescopic position of the transmission device) at the moment when the axial magnetic induction intensity changes is recorded.
2) And (3) removing the detection probe from the pipeline, rotating the detection probe by a certain angle clockwise (or anticlockwise), and adopting the same method operation of the step (1) to respectively record the axial coordinate z 2、z3……zn of the change of the axial magnetic induction intensity.
3) The position at the maximum in the above axial coordinate values is defined as the start position of the crack, and the magnetic field sensor is repositioned thereto as shown in fig. 6.
4) The magnetic field sensor is ensured to be unchanged at the angle position, the detection probe is axially moved, and the maximum value B ym of the change of the y component of the magnetic induction intensity is recorded.
5) The cracks with different azimuth correspond to different B ym, and the azimuth angle of the crack can be calculated through the change value of the y component of the magnetic induction intensity.
6) Since the method starting position is defined as the deepest position of the crack in the axial direction, the azimuth angle of the crack measured should be between-90 ° and +90°. An azimuth of 0 ° represents a crack in a horizontal state, where B ym was measured to be more pronounced than cracks in other orientations. B ym are positive and negative, which represent both sides of the crack in different directions of the starting position.
To verify the effect of the above embodiment, five cracks were created in different orientations, each of which was semicircular in cross-sectional shape, and remained unchanged all the time, their positions in the metal pipe were as shown in FIG. 7 at ①-⑤. Wherein ① is a circumferential crack placed in the xy plane, ② is a crack ① rotated clockwise by a certain angle (e.g., 45 °), ③ is a crack placed coaxially with the metal tube, ④ is a crack ③ rotated clockwise by a certain angle, and ⑤ is another circumferential crack placed in the xy plane, which corresponds to a crack ① rotated clockwise by 180 °. The lengths of all the cracks are kept to be 8.796mm, and the distance between the magnetic field measuring point and the circle center is 13.5mm. With the change of the crack orientation, the magnetic induction intensity distribution in the y direction is obviously changed. The specific variation is as follows:
1) When the crack is in the xy plane, that is, the crack ①, by is distributed in the axial direction with an approximate odd symmetry, z >0, the magnetic induction value is negative, and when z <0, the magnetic induction value is positive. The magnetic induction in the y direction reaches a maximum value B ym at a certain position in the axis direction.
2) When the crack is rotated clockwise by an angle, the magnetic induction intensity value in the y direction is weakened, including a maximum value B ym.
3) When the crack rotates again clockwise, coaxial with the pipe, the y-direction magnetic induction value is always zero, and the maximum value B ym does not occur, i.e. B ym =0.
4) When the crack rotates clockwise again, symmetrical to the crack ②, the y-direction magnetic induction intensity distribution is exactly opposite to the crack ②, and the values are the same.
5) When the crack rotates clockwise again, i.e. crack ⑤, the y-direction magnetic induction distribution is exactly opposite to that of crack ①, which is the same value.
According to the analysis, the magnetic induction intensity value in the y direction, particularly the maximum value B ym, has obvious quantitative relation with the crack orientation, can be used as the characteristic quantity of crack orientation evaluation, and can realize quantitative evaluation of the crack orientation.
When the evaluation test device is specifically adopted to quantitatively evaluate the crack, the following steps can be adopted:
1) Firstly, three physical parameters of the shape, the circumference length and the azimuth of the crack are selected, and the measured parameters are obtained by the evaluation and test device. And selecting different measurement parameters, and then, the evaluation testing device enters a corresponding working mode.
2) Under the corresponding working mode, the mechanical motion control unit drives the detection probe to perform a corresponding detection process in the detected pipeline, and obtains the magnetic induction intensity in the corresponding direction.
3) The data analysis and processing unit obtains the state of the measured parameter according to the mutual mapping relation between the measured parameter and the magnetic induction intensity amplitude based on the obtained information such as the magnetic induction intensity and the motion position of the detection probe.
The method provides the magnetic induction intensities with different dimensions as three measured parameters, avoids mutual interference between signals to a certain extent, and improves the capability of quantitative crack evaluation.
4) In an embodiment, the mechanical motion control unit and the data analysis and processing unit may be centrally controlled by a unified-unified unit.
It should be noted that, although the foregoing embodiments have been described herein, the scope of the present invention is not limited thereby. Therefore, based on the innovative concepts of the present invention, alterations and modifications to the embodiments described herein, or equivalent structures or equivalent flow transformations made by the present description and drawings, apply the above technical solution, directly or indirectly, to other relevant technical fields, all of which are included in the scope of the invention.
Claims (6)
1. The quantitative evaluation method for the cracks on the inner surface of the metal pipeline is characterized by being 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 exciting coil for generating alternating magnetic field signals and a magnetic field sensor arranged on the outer surface of the exciting 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 calculating and processing the magnetic induction intensity information, and the mechanical motion control unit is used for driving the transmission device, and the method comprises the steps of evaluating the section shapes of the cracks:
Driving a transmission device to move in a crack-free pipeline to obtain radial or axial magnetic induction intensity of a detection probe at different positions;
Driving a transmission device to move in a detected pipeline to obtain radial or axial magnetic induction intensities of a detection probe at different positions, and comparing the peak value of a spatial radial magnetic field in the magnetic induction intensities and the axial magnetic field intensity at a zero point with corresponding magnetic induction intensities without cracks to obtain a radial or axial magnetic induction intensity difference value;
comparing the obtained radial or axial magnetic induction intensity difference with a preset magnetic induction intensity disturbance curve model to obtain a crack cross-sectional area;
The preset magnetic induction intensity disturbance curve model is obtained through the following steps:
Carrying out numerical solution on a space magnetic field near cracks with different shapes according to physical and structural parameters of the detection probe and the detected pipeline by utilizing finite element analysis software; according to radial or axial magnetic induction intensity of cracks with different sectional areas obtained by numerical solution, a mathematical fitting method is adopted to establish a magnetic induction intensity disturbance curve model;
Firstly, using a magnetic field sensor to measure the axial magnetic induction intensity at a radial magnetic induction intensity peak value and a zero point under the condition of no crack; the magnetic sensor is close to the vicinity of the crack, and the axial magnetic induction intensity at the radial magnetic induction intensity peak value or the zero point at the moment is obtained; comparing the value with the condition without crack, and obtaining the difference value of the radial or axial magnetic field, namely the variation value;
And according to the change value of the radial or axial magnetic field around the actual detected pipeline crack, reversely pushing to obtain the sectional area of the crack according to the relation between the established crack shape and the magnetic field.
2. A method for quantitatively evaluating cracks on the inner surface of a metal pipe according to claim 1, further comprising the step of evaluating the circumferential length of the crack:
The driving device is driven to enable the detection probe to be arranged in the detected pipeline, so that the axis of the exciting coil and the axis of the pipeline are kept concentric;
driving the transmission device to move back and forth so that the detection probe moves back and forth in the axis direction inside the detected pipeline to obtain the axial magnetic induction intensity of the magnetic field sensor, and recording the position of the detection probe as the axis reference point position when the axial magnetic induction intensity change of the magnetic field sensor reaches the maximum value;
The position of the detection probe at the axis reference point is kept unchanged, the transmission device is driven to rotate the probe at a constant speed, the axial magnetic induction intensity change condition of the magnetic field sensor is obtained, and when the axial magnetic induction intensity changes, the rotation angle at the moment is recorded as a first angle;
Continuing rotating the probe at a constant speed, acquiring the change condition of the axial magnetic induction intensity of the magnetic field sensor, and recording the rotation angle at the moment as a second angle when the axial magnetic induction intensity is changed again;
And calculating the length of the pipe crack in the circumferential direction according to the angle difference between the first angle and the second angle.
3. A method for quantitatively evaluating cracks on the inner surface of a metal pipe according to claim 1, further comprising the step of evaluating crack orientation:
The transmission device is driven to enable the detection probe to extend into the detected pipeline and move in the axial direction of the detected pipeline, and when the axial magnetic induction intensity changes, the position and the angle of the detection probe are recorded;
the detection probe is moved out of the detected pipeline by the driving transmission device and rotated for a certain angle;
Repeating the steps for a plurality of times, taking the obtained maximum position of the 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;
the angle is kept unchanged, and the transmission device is driven to enable the detection probe to move along the axis direction of the detected pipeline, so that the maximum value of the y component variation of the magnetic induction intensity is obtained;
and calculating the azimuth angle of the crack according to the maximum value and a preset azimuth relation model.
4. A method for quantitatively evaluating cracks on the inner surface of a metal pipe according to claim 3, wherein the detection probe comprises magnetic field sensors in both axial and radial directions.
5. The method for quantitatively evaluating cracks on the inner surface of a metal pipeline according to claim 1, wherein the evaluation and test device further comprises a probe auxiliary device, and the probe auxiliary device is used for connecting the transmission device and the detection probe.
6. The method of claim 1, wherein the evaluation test device further comprises a signal generator, the signal generator being connected to the excitation coil, the signal generator being configured to generate a sinusoidal alternating current such that the coil generates an alternating current magnetic field signal.
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| CN114002316B (en) * | 2021-10-28 | 2023-12-22 | 江苏信息职业技术学院 | Crack and corrosion hole flaw detection method for induction eddy magnetic field detection |
| CN114088808B (en) * | 2021-11-15 | 2024-05-24 | 无锡学院 | Pipeline crack visual detection method and system for three-dimensional induced eddy magnetic field cloud picture |
| CN117893553B (en) * | 2024-03-15 | 2024-05-31 | 宝鸡鼎钛金属有限责任公司 | Image processing titanium metal segmentation method and system |
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