CN110230976B - Method for nondestructive testing of steel rail rolling contact fatigue crack propagation vertical depth - Google Patents
Method for nondestructive testing of steel rail rolling contact fatigue crack propagation vertical depth Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention discloses a method for nondestructively detecting the vertical depth of the rolling contact fatigue crack propagation of a steel rail. The method can solve the problem that the vertical depth of the crack is judged by experience or hypothesis in the process of maintaining and grinding the steel rail, provide quantitative theoretical analysis for the maintenance of the steel rail of a railway system, prolong the service life of the steel rail and reduce the running and maintenance cost of the railway. The method is based on the existing alternating current electromagnetic field measurement technology, a measuring probe needs to form an included angle of 45 degrees with the length direction of the surface of the crack to scan the crack, a Bz signal is obtained after passing through the length center point of the surface of the crack, the ratio of the Bz wave trough and the wave crest is obtained through calculation, the vertical angle relation between the ratio and the actual crack is researched, and the vertical depth of the crack is obtained through calculation by combining the depth of a crack pocket given by the Bx signal. And solving by using a finite element model to obtain the relation between the ratio of the cracks with different surfaces and vertical angles to the Bz wave trough and the wave crest, establishing a database, inputting the surface length of the cracks and the ratio of the Bz wave trough and the wave crest, and outputting the vertical depth of the cracks.
Description
Technical Field
The invention relates to the field of nondestructive inspection and rail transit, in particular to a method for representing the vertical depth of rolling contact fatigue crack propagation of a steel rail in an electromagnetic nondestructive way.
Background
Rolling contact fatigue cracks are one of the typical surface defects of rails and wheels, caused by the repeated transverse and longitudinal traction of the rail and wheel. The rolling contact fatigue crack usually extends to the inside of the rail at an angle (vertical angle) of 10-30 degrees with the horizontal direction (figure 1), and when the crack extends to the fatigue limit, the crack rapidly extends to the inside of the rail at a larger vertical angle to cause the fracture of the rail, thus easily causing the derailment accident of the train. From the standpoint of rail maintenance, it is necessary to periodically grind the rail to remove cracks before they reach a critical depth. The precondition of rail grinding is that the vertical propagation depth of cracks in the rail needs to be known, and the corresponding grinding depth and maintenance period can be scientifically and quantitatively set. In actual rail grinding applications, the vertical depth of the crack is often calculated based on an assumed known vertical angle or compared to a standard crack signal. Because the rolling contact fatigue crack shapes have random irregularity and are mostly arranged in crack clusters, the algorithm for measuring the crack size needs to be corrected empirically, the maintenance cost is high, and the grinding depth of the steel rail is inaccurate. If the grinding degree is relatively low, the cracks cannot be completely eliminated, so that the cracks continue to expand into the steel rail, and the steel rail is broken; if the grinding degree is larger, the loss of the steel rail material is more, the service cycle of the steel rail is shortened, and the railway operation cost is increased.
The alternating current electromagnetic field measurement method is an electromagnetic nondestructive detection technology based on an alternating current skin effect, and is one of electromagnetic nondestructive detection technologies widely applied to surface defect detection of metal components such as deep sea drilling platforms, petroleum pipelines, steel rails and the like in a global range. Compared with other nondestructive testing technologies, the alternating current electromagnetic field measuring method has the characteristics of non-contact type, high temperature resistance, corrosion resistance, high efficiency, high speed, small equipment, economy, practicability and the like. Generally, an alternating current magnetic field measuring probe scans along the surface length of a crack, so that a uniform alternating current electric field perpendicular to the length direction of the crack is introduced to the metal surface, the existence of crack defects disturbs the uniform distribution of the electric field, current is forced to flow to two ends of the crack and the crack surface, and the probe detects the change of a magnetic field caused by the electric field to judge the existence and the size of the crack. Because current flows along the crack surface, the magnetic field intensity passing through the crack is reduced, and a wave trough appears in a Bx signal of the alternating current electromagnetic field measuring method; the propagation depth of the crack, i.e. the pocket depth, can be measured by the change of the magnetic field in the x-direction (Bx signal), see fig. 1 and fig. 2. Current flows through two ends of the crack clockwise and anticlockwise to cause the fluctuation of the magnetic field in the z direction, and positive-negative magnetic field distribution is formed, so that the wave crest and the wave trough appear on the Bz signal of the alternating current electromagnetic field measurement method; the surface length of the crack can be measured by the distance between the peak and the trough of the Bz signal, figure 2.
The existing alternating current electromagnetic field measuring method can only detect the surface length of cracks and the pocket depth, for railway maintenance, a steel rail needs to be periodically polished to eliminate rolling contact fatigue cracks, and the measuring parameter which needs to be known urgently is the vertical expansion depth, which is shown in figure 1. The invention provides a method for measuring the vertical angle of the crack based on the existing alternating current electromagnetic field measurement technology and combined with finite element simulation, thereby calculating the vertical depth of the crack by combining the pocket depth of the crack, providing quantitative analysis for rail grinding, improving the rail maintenance system, prolonging the life cycle of the rail and improving the use safety of the rail.
Disclosure of Invention
The invention aims to nondestructively detect the size of the rolling contact fatigue crack of the steel rail by using an alternating current electromagnetic field measurement method, calculate the vertical depth of the crack expanding to the inside of the steel rail by using the signal analysis method disclosed by the patent, provide a quantitative analysis basis for the regular maintenance (steel rail grinding) of the railway, guarantee the use safety of the railway and prolong the life cycle of the steel rail. And scanning the crack by using an alternating current electromagnetic field measuring probe in a direction forming an included angle of 45 degrees with the surface length of the crack to obtain a Bz signal of an alternating current electromagnetic field measuring method. Because the vertical angle of the crack can cause the deviation of the magnetic field distribution relative to the crack position, the trough and the wave peak value of the Bz signal are asymmetric, so that a measuring parameter of the trough-wave peak ratio of the Bz signal is provided, and the vertical angle relation between the parameter and the actual crack is researched, wherein the attached figure 2 is shown in the specification; establishing a simulation finite element model for measuring rolling contact fatigue cracks by using an alternating current magnetic field, and verifying the correctness of the model through an actual measurement result; and establishing a wave trough peak ratio-crack vertical angle of the Bz signal under different crack lengths by using a finite element model, and establishing a database. According to the actual crack measurement result, the vertical angle of the crack is determined through the database, the vertical depth of crack propagation is calculated and determined by combining the depth of the crack pocket, and the flow of the method is shown in the attached figure 3.
The method comprises the following specific real-time steps:
1. and scanning the alternating current electromagnetic field measuring probe along the length of the surface of the crack to obtain Bx and Bz signals and determine the pocket depth and the surface length of the crack.
2. And scanning the crack by the alternating current electromagnetic field measuring probe in a direction forming an included angle of 45 degrees with the surface length of the crack, passing through the center point of the surface length of the crack to obtain a Bz signal, and calculating to obtain a Bz wave trough peak ratio.
3. According to the actual measurement principle, an alternating current electromagnetic field measurement rolling contact fatigue crack simulation finite element model is established, a simulation signal is obtained through solving, and the accuracy of the model is determined through verifying by using an actual measurement result.
4. And solving by using a finite element model to obtain the relation between the sag squareness (0-90 degrees) and the Bz wave trough peak ratio of the cracks with different surface lengths (3-40mm), and establishing a database for analyzing actual measurement results.
5. And inputting the crack surface length and the Bz trough-to-peak ratio obtained by actual measurement in a database, and outputting the vertical depth of the crack.
6. Combining the pocket depth of the crack and the output vertical angle of the crack, and calculating by utilizing a trigonometric function to obtain the vertical depth of the crack
Has the advantages that: the invention aims to provide a method for nondestructively detecting the vertical depth of the rolling contact fatigue crack propagation of a steel rail, which is based on the existing alternating current electromagnetic field measurement technology, is simple, efficient and convenient to operate, and provides a wave trough and wave crest ratio concept of a Bz signal through an improved measurement method to accurately calculate the vertical propagation depth of the crack. The finite element model and the database established by the method are visual and simple, the operation is simple, the finite element model and the database can be updated and expanded according to the actual crack condition, and the finite element model and the database can be repeatedly and quickly used once being established. The crack propagation vertical depth calculated by the method provides theoretical quantitative analysis for maintenance of the steel rail of the railway system, the target quantity of the periodic polishing depth of the steel rail is determined, the aim is achieved, the existing empirical judgment is replaced, the service life of the steel rail is greatly prolonged, the railway operation maintenance cost is reduced, the railway transportation safety is better guaranteed, and the preventive protection effect on the property safety of people is achieved. The method is not limited to the detection of the steel rolling contact fatigue crack, and is also suitable for the characterization of the non-vertical propagation crack on the surface of the metal material, such as stress corrosion crack, gear root crack and the like.
Drawings
FIG. 1 is a schematic view showing the rolling contact fatigue crack propagating into a rail.
FIG. 2 is a schematic diagram of the current around the crack, the magnetic field distribution and the probe measurement path.
FIG. 3 is a flow chart of rolling contact fatigue crack vertical depth determination.
FIG. 4 is a comparison of finite element simulations of a single crack and the actually measured Bz trough-to-peak ratio.
Detailed Description
Example 1
Under the laboratory condition, single cracks with different vertical depths are manufactured on the steel rail by utilizing electric spark machining, alternating current electromagnetic field measurement is carried out on the cracks according to the steps 1 and 2 to obtain Bx and Bz signals, and the depth, the surface length and the Bz wave trough and peak ratio are calculated. And (4) inputting the depth of the crack pocket, the surface length and the ratio of the Bz wave trough and the wave crest to obtain the vertical angle of the crack in the finite element database established in the steps (3) and (4), and calculating by utilizing a trigonometric function to obtain the vertical depth of the crack. The finite element simulation and the actually measured Bz trough-peak ratio are compared and shown in the attached figure 4.
Example 2
The difference between the present application example and example 1 is that the detection object is a rolling contact fatigue crack cluster (generally composed of a plurality of cracks, with a pitch of about 1-20 mm) in an actual steel rail. And similarly, establishing a crack cluster information database by using a finite element model, and measuring and judging the longest vertical depth of cracks in the crack cluster so as to completely remove the cracks. And scanning the alternating current electromagnetic field measuring probe across the central point of the crack in a direction of 45 degrees with the length of the surface of the crack to obtain a Bz wave trough and wave crest ratio, inputting data into a database to calculate to obtain the vertical angle of the crack, and calculating the maximum vertical depth of the crack by combining the depth of the pocket. The calculated results are compared with the actual results as shown in the following table:
TABLE 1 comparison of crack vertical depth calculated by the method of the present invention with actual value
Claims (1)
1. A method for nondestructively detecting the vertical depth of the rolling contact fatigue crack propagation of a steel rail is characterized by comprising the following steps:
(1) scanning the alternating current electromagnetic field measuring probe along the length of the surface of the crack to obtain Bx and Bz signals and determine the pocket depth and the surface length of the crack;
(2) scanning the crack by the alternating current electromagnetic field measuring probe in a direction forming an included angle of 45 degrees with the surface length of the crack, passing through the center point of the surface length of the crack to obtain a Bz signal, and calculating to obtain a Bz wave trough peak ratio;
(3) establishing an alternating current magnetic field measurement rolling contact fatigue crack simulation finite element model according to an actual measurement principle, solving to obtain a simulation signal, verifying by using an actual measurement result, and determining the correctness of the model;
(4) solving by using a finite element model to obtain the relation between the different surface lengths of the cracks, the vertical sag angles of 0-90 degrees and the wave crest ratio of the Bz wave trough, and establishing a database for analyzing actual measurement results;
(5) inputting the crack surface length obtained by actual measurement, the Bz wave trough peak ratio and the vertical depth of the crack in a database;
(6) and (4) calculating the vertical depth of the crack by utilizing a trigonometric function according to the pocket depth of the crack and the output vertical angle of the crack.
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| CN110926942B (en) * | 2019-11-19 | 2022-01-07 | 西安理工大学 | Numerical analysis method for rolling contact fatigue cracks of rails in ABAQUS |
| CN111855448B (en) * | 2020-07-31 | 2022-06-24 | 东风商用车有限公司 | Metal material rolling contact fatigue test crack detection method |
| CN113030187A (en) * | 2021-03-05 | 2021-06-25 | 桂林理工大学 | Method for representing three-dimensional size of steel rail rolling contact fatigue crack cluster in electromagnetic nondestructive mode |
| CN112857197B (en) * | 2021-04-09 | 2022-04-19 | 中国石油大学(华东) | Rotating electromagnetic field non-ferromagnetic material crack size measurement method |
| CN113433060A (en) * | 2021-06-23 | 2021-09-24 | 马鞍山钢铁股份有限公司 | Method for evaluating rolling contact fatigue performance of railway locomotive wheel surface |
| CN113390955B (en) * | 2021-07-08 | 2022-04-19 | 中国石油大学(华东) | Visual monitoring and evaluation method for cracks of alternating current magnetic field |
| AU2022308214A1 (en) * | 2021-07-08 | 2024-02-29 | China University Of Petroleum | Underwater structure crack propagation visual monitoring system based on alternating-current electromagnetic field, and alternating-current electromagnetic field crack visual monitoring and evaluation method |
| CN114543656B (en) * | 2022-03-07 | 2024-02-06 | 桂林理工大学 | Rail asymmetric crack growth shape reconstruction method based on alternating current electromagnetic field |
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| US5055783A (en) * | 1989-09-05 | 1991-10-08 | Westinghouse Electric Corp. | Magnetic field strength indicator for use prior to a magnetic particle inspection procedure |
| JP3816071B2 (en) * | 2003-10-17 | 2006-08-30 | 神鋼検査サービス株式会社 | Eddy current flaw detector |
| CN100573132C (en) * | 2007-08-17 | 2009-12-23 | 中国人民解放军装甲兵工程学院 | Utilize the method for variated magnetic signal monitoring ferromagnetic material fatigue crack expansion |
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| CN109060944A (en) * | 2018-08-31 | 2018-12-21 | 南京航空航天大学 | Steel rail defect depth detection method based on leakage magnetic detection device and neural network |
| CN109060942A (en) * | 2018-08-31 | 2018-12-21 | 南京航空航天大学 | Steel rail defect depth detection method based on leakage magnetic detection device |
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