A method and device for non-destructively evaluating the effectiveness of electromagnetic reinforcement of a bearing

Abstract

A method and device for nondestructive evaluation of the effectiveness of electromagnetic reinforcement of bearings, belonging to the field of electromagnetic reinforcement of bearings. The independent components of the bearing, the outer bearing ring and the inner bearing ring, are placed coaxially outside and inside the detection coil, respectively, and a sinusoidal current is passed through, and the real and imaginary parts of the impedance of the detection coil are detected; at the same time, the real and imaginary parts of the impedance of the bearing components that have not been subjected to electromagnetic reinforcement and the real and imaginary parts of the impedance of the bearing components that have been subjected to electromagnetic reinforcement are compared. By detecting the change in the impedance of the detection coil, it can be determined whether the bearing components have been subjected to electromagnetic reinforcement, and all bearing components of the same batch can be detected. The method has the advantages of non-contact, high efficiency, easy implementation and low cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of bearing electromagnetic strengthening, and particularly relates to a method and device for nondestructively evaluating the effectiveness of bearing electromagnetic strengthening. BACKGROUND

[0002] Bearings are indispensable parts in aero-engines. With the increase of the thrust-to-weight ratio of aero-engines, the service environment of bearings becomes more severe, and the service performance requirements of bearings are also higher and higher. Electromagnetic strengthening treatment technology has been proved to be able to improve the wear resistance and fatigue life of bearings, but at present, the effectiveness of strengthening is mainly evaluated through material-level mechanical property tests and random sampling simulation working condition bench tests, both of which are destructive and low in efficiency, and there is a lack of nondestructive and efficient evaluation means for aero-engine bearings.

[0003] There are mainly two ways to evaluate the effectiveness of bearing electromagnetic strengthening, one is microstructure characterization represented by electron backscatter diffraction, and the other is mechanical property test represented by friction and wear test. Both of the above two methods are destructive, and therefore are only suitable for the material level, and there is a lack of efficient and nondestructive evaluation means for aero-engine bearings with strict reliability requirements.

[0004] Electromagnetic strengthening technology regulates the microstructure of bearing materials through "magnetic phase transition" and "magnetic plasticity", and then improves the mechanical properties of the materials. The electrical conductivity of metal materials is extremely sensitive to the changes of the composition and microstructure of the materials, and therefore the changes of the electrical conductivity of the materials can be used to analyze the changes of the internal structure of the materials, and to infer the changes of the mechanical properties of the materials.

[0005] There are mainly two ways to test the electrical conductivity of metal materials:

[0006] (1) Direct current four-probe method

[0007] The direct current four-probe method mainly consists of metal probes, a current source and a potential difference meter. When measuring, the four probes can be arranged in a row at unequal distances, the outer side is the current probe, and the inner side is the voltage probe. A small current is input by the current source to make the sample inside produce a voltage drop, and at the same time, the voltage between the voltage probes is measured by a high-impedance electrometer, an electronic millivoltmeter or a digital voltmeter. The resistivity of the material is calculated according to the voltage, current and probe spacing.

[0008] (2) Ultrasonic detection method

[0009] The material resistivity measuring device based on the ultrasonic detection technology mainly comprises a low-frequency signal generator, an oscilloscope, an ultrasonic transducer and a material fixing device. The transmitting end of the ultrasonic transducer converts the sine wave signal of the low-frequency signal generator into an ultrasonic signal, and the receiving end converts the ultrasonic signal into an electric signal and inputs the electric signal into the oscilloscope to display a Lissajous figure of the material, and the change amount of the conductive performance of the material is calculated according to the periodic change of the Lissajous figure.

[0010] The prior art has defects and problems:

[0011] 1. The probe of the direct current four-probe method needs to be in contact with the surface of the sample, and is greatly affected by the contact force and the diameter of the probe needle tip, and the measurement repeatability is poor.

[0012] 2. The measurement of high-resistance materials requires a large current, which is easy to cause the sample to heat and introduce measurement errors.

[0013] 3. The ultrasonic detection system is relatively complex and expensive, and is inconvenient to operate and low in efficiency.

[0014] The application provides a method and device for determining whether an aero-engine bearing has been subjected to qualified electromagnetic strengthening treatment by detecting the change of the impedance of a detection coil.

[0015] When an alternating current is input into the detection coil, an alternating primary magnetic field is generated around the detection coil; since the strength of the magnetic field changes over time, according to Faraday's law of electromagnetic induction, an induced eddy current is generated in the bearing component in the primary magnetic field, and a secondary magnetic field with a direction opposite to that of the primary magnetic field is generated around the bearing component. When the conductive performance of the material of the bearing changes, the distribution and strength of the eddy current also change, and the strength of the secondary magnetic field also changes. The change of the secondary magnetic field affects the primary magnetic field, and then causes the current or induced voltage in the detection coil to change, which is manifested as the change of the impedance of the detection coil. The change of the impedance of the detection coil is accurately measured by an instrument, and then the measurement data is analyzed to determine whether the surface or near-surface of the bearing component has been subjected to electromagnetic strengthening treatment. SUMMARY

[0016] According to the above principle, the application provides a method for nondestructively evaluating the effectiveness of electromagnetic strengthening treatment of an aero-engine bearing, and the specific steps are as follows:

[0017] (1) selecting a detection coil with a suitable size according to the structure and geometric size of the bearing component to be measured;

[0018] (2) cleaning the bearing component to be measured to ensure that the surface is free of other conductive substances;

[0019] (3) using 4-terminal Kelvin clip to connect the 2 pins of the detection coil with the 4 interfaces of the digital bridge tester, 2 high potential interfaces correspond to 1 pin, and 2 low potential interfaces are connected to the other pin;

[0020] (4) placing the bearing part to be tested into the detection coil, keeping coaxial with the detection coil, and making the lower end surface of the bearing part to be tested in contact with the upper end surface of the detection coil framework boss;

[0021] (5) inputting the current with the frequency of 1Hz-200kHz, the amplitude of 0.01mA-1A, and the waveform of sine wave according to the detection requirement; recording the real part and the imaginary part of the impedance of the detection coil measured in the digital bridge tester when the current is input into the detection coil;

[0022] (6) repeating the steps (4)-(5) to obtain the real part 1 and the imaginary part 1 of the impedance of the detection coil after electromagnetic strengthening treatment of the same bearing part to be tested; repeating the steps (4)-(5) to obtain the real part 2 and the imaginary part 2 of the impedance of the detection coil without electromagnetic strengthening treatment of the same bearing part to be tested;

[0023] (7) comparing the real part and the imaginary part of the impedance of the bearing part to be tested obtained in the step (5) with the real part 1 and the imaginary part 1, the real part 2 and the imaginary part 2, and determining the electromagnetic strengthening or non-electromagnetic strengthening according to the closest one;

[0024] The electromagnetic parameters of the real part 1 and the imaginary part 1 of the coil impedance corresponding to the electromagnetic strengthening can be set to multiple different values to obtain different real part 1 and imaginary part 1, and the closest one is determined according to the real part and the imaginary part obtained in the step (5).

[0025] To realize the above method, the device comprises a signal transmitter (1), a power amplifier (2), a multi-channel system (3), a detection coil (4), a bearing outer ring (5), a bearing inner ring (6), a signal receiver (7), and a computer system (8); the signal transmitter (1) is electrically connected with the power amplifier (2) and the multi-channel system (3), the multi-channel system (3) is electrically connected with the detection coil (4) and the signal receiver (7), and the signal receiver (7) is electrically connected with the computer system (8); the functions of the signal transmitter (1), the power amplifier (2), the multi-channel system (3), and the signal receiver (7) are realized by using the digital bridge tester.

[0026] The detection coil (4) is an independent wound spring structure coil, and the inner and outer sides of the detection coil (4) are wrapped with insulating hard materials; the inner and outer insulating hard wraps are the inner and outer skeletons of the coil, and a circle of protrusions is arranged on the inner skeleton of the inner side of the detection coil (4) and is marked as an inner protrusion, and a circle of protrusions is arranged on the outer skeleton of the outer side of the detection coil (4) and is marked as an outer protrusion;

[0027] The bearing outer sleeve (5) and the bearing inner sleeve (6) are independent components of the bearing, and during testing, the bearing outer sleeve (5) is coaxially located outside the detection coil (4), the lower end surface of the bearing outer sleeve (5) is supported by the outer protrusion, the bearing inner sleeve (6) is coaxially located inside the detection coil (4), and the lower end surface of the bearing inner sleeve (6) is supported by the inner protrusion, so that the bearing outer sleeve (5) and the bearing inner sleeve (6) are correspondingly arranged inside and outside.

[0028] The implementation of the detection method is realized by a digital bridge tester and a detection coil, wherein the detection coil needs to be designed according to the actual size of the bearing component to be detected. By detecting the change of the impedance of the detection coil, it can be determined whether the bearing component has been subjected to electromagnetic strengthening treatment, and all bearing components in the same batch can be detected. The method has the advantages of non-contact, high efficiency, easy implementation and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a schematic diagram of the detection device of the present application.

[0030] Wherein 1 is a signal transmitter; 2 is a power amplifier; 3 is a multi-channel system; 4 is a ring copper coil (axial section); 5 is a signal receiver; 6 is a computer system.

[0031] Figure 2 It is a structural schematic diagram of the position relationship of the bearing outer sleeve, the bearing inner sleeve and the detection coil.

[0032] Figure 3 It is an actual detection device diagram.

[0033] Figure 4 It is an actual diagram of the cooperation of the bearing outer sleeve, the bearing inner sleeve and the detection coil. DETAILED DESCRIPTION

[0034] The present application will be further described below in conjunction with examples, but the present application is not limited to the following examples.

[0035] Example 1:

[0036] A detection coil with a height of 40 mm and an inner diameter of 11 mm is selected, a sinusoidal wave current with a frequency of 10 kHz and an amplitude of 1 mA is input, and the same batch of Φ10 mm*35 mm GCr15 bearing steel cylindrical rollers are detected. When the cylindrical rollers without electromagnetic strengthening treatment are placed in the detection coil, the impedance real part of the detection coil is 29.3285±0.0718Ω, and the impedance imaginary part is 47.3223±0.1236Ω. When the cylindrical rollers treated by electromagnetic strengthening treatment with a magnetic field strength of 0.8T, a frequency of 1 Hz and a waveform of half-sine wave are placed in the detection coil, the impedance real part of the detection coil is 29.0547±0.0411Ω, and the impedance imaginary part is 46.4467±0.0664Ω. If an unknown cylindrical sample is placed, the impedance measurement result of the detection coil is closer to the impedance real part and imaginary part of the detection coil when the cylindrical rollers without electromagnetic strengthening treatment are placed, which indicates that the cylindrical rollers have not been treated by electromagnetic strengthening treatment or the effect of electromagnetic strengthening treatment is poor; otherwise, it indicates that the cylindrical rollers have been treated by qualified electromagnetic strengthening treatment.

[0037] Example 2:

[0038] A detection coil with a height of 65 mm and a coil cross-section center radius of 20.5 mm is selected, a sinusoidal wave current with a frequency of 200 kHz and an amplitude of 0.05 mA is input, and the same batch of NU1006 bearing inner and outer rings made of M50 bearing steel are detected. When the NU1006 bearing inner and outer rings without electromagnetic strengthening treatment are placed in the detection coil, the impedance real part of the detection coil is 142.5824±0.2632Ω and 135.593±0.3123Ω respectively. When the NU1006 bearing inner and outer rings treated by electromagnetic strengthening treatment with a magnetic field strength of 0.8T, a frequency of 1 Hz and a waveform of half-sine wave are placed in the detection coil, the impedance real part of the detection coil is 139.6243±0.137Ω and 132.9299±0.2567Ω respectively. If an unknown NU1006 bearing inner and outer ring is placed, the impedance real part of the detection coil is closer to the impedance real part of the detection coil when the NU1006 bearing inner and outer ring without electromagnetic strengthening treatment is placed, which indicates that the cylindrical roller has not been treated by electromagnetic strengthening treatment or the effect of electromagnetic strengthening treatment is poor; otherwise, it indicates that the NU1006 bearing inner and outer ring has been treated by qualified electromagnetic strengthening treatment.

Claims

1. A method of non-destructively evaluating the effectiveness of an electromagnetic strengthening treatment of an aircraft bearing, characterized in that, The specific steps are as follows: (1) Select a detection coil of appropriate size according to the structure and geometry of the bearing component to be tested; (2) Clean the bearing components to be tested to ensure that there are no other conductive substances on their surface; (3) Use a 4-terminal Kelvin clip to connect the two pins of the detection coil to the four interfaces of the digital bridge tester. The two high-potential interfaces correspond to one pin, and the two low-potential interfaces are connected to the other pin. (4) Place the bearing component to be tested into the detection coil, keeping it coaxial with the detection coil, and make sure that the lower end face of the bearing component is in contact with the upper end face of the detection coil skeleton boss. (5) Input a current with a frequency of 1Hz to 200kHz, an amplitude of 0.01mA to 1A, and a sine wave waveform according to the detection requirements; after the current is applied to the detection coil, record the real and imaginary parts of the detection coil impedance measured in the digital bridge tester; (6) After electromagnetic strengthening treatment of the same bearing component to be tested, repeat the above steps (4)-(5) to obtain the real part 1 and imaginary part 1 of the electromagnetically strengthened detection coil impedance; repeat the above steps (4)-(5) of the same bearing component that has not undergone any electromagnetic strengthening to obtain the real part 2 and imaginary part 2 of the non-electromagnetically strengthened detection coil impedance. (7) Compare the real and imaginary parts of the impedance corresponding to the bearing component to be tested obtained in step (5) with the real and imaginary parts 1 and 2 respectively. The component that is closest to the real part is either electromagnetically strengthened or not electromagnetically strengthened.

2. The method of claim 1, wherein, The electromagnetic parameters for electromagnetic enhancement of the coil impedance real part 1 and imaginary part 1 can be set to multiple different values ​​as needed, thus obtaining different impedance real parts 1 and imaginary parts 1. Find the closest corresponding real and imaginary parts of the impedance obtained in step (5).

3. The method of claim 1, wherein, The device used includes a signal transmitter (1), a power amplifier (2), a multi-channel system (3), a detection coil (4), a bearing outer ring (5), a bearing inner ring (6), a signal receiver (7), and a computer system (8). The signal transmitter (1) is electrically connected to the multi-channel system (3) via the power amplifier (2), the multi-channel system (3) is electrically connected to the detection coil (4), the multi-channel system (3) is also electrically connected to the signal receiver (7), and the signal receiver (7) is electrically connected to the computer system (8). The functions of the signal transmitter (1), the power amplifier (2), the multi-channel system (3), and the signal receiver (7) are realized using a digital bridge tester.

4. The method of claim 3, wherein, The detection coil (4) is an independent wound spring structure coil. The inner and outer sides of the detection coil (4) are encased in insulating hard material. The inner and outer insulating hard encasing is the inner and outer skeleton of the coil. The inner skeleton of the detection coil (4) has a ring of protrusion, which is called the inner protrusion. The outer skeleton of the detection coil (4) has a ring of protrusion, which is called the outer protrusion. The outer ring (5) and inner ring (6) of the bearing are independent components of the bearing. During the test, the outer ring (5) of the bearing is coaxially located outside the detection coil (4), and the lower end face of the outer ring (5) is supported by an outward protrusion. The inner ring (6) of the bearing is coaxially located inside the detection coil (4), and the lower end face of the inner ring (6) is supported by an inward protrusion, so that the outer ring (5) and inner ring (6) of the bearing correspond to each other inside and out.

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