Device and method for laser ultrasonic detection of fitting degree of connecting rod bushing and bottom hole

Abstract

The invention relates to the field of connecting rod bushing fitting degree detection, in particular to a device and method for laser ultrasonic detection of the fitting degree of a connecting rod bushing and a bottom hole, the device comprises a workbench, a piezoelectric probe is arranged on the workbench, a laser transmitter is arranged on the workbench, an ultrasonic amplifier is connected to the piezoelectric probe, and a filter is connected to the ultrasonic amplifier. The method comprises the following steps: emitting laser to different detection points on the outer wall of the small end of the connecting rod; and receiving ultrasonic waves of different detection points, calculating the guided wave power of the current connecting rod small end and the bushing, and further calculating the fitting degree of the current connecting rod bushing and the connecting rod small end. According to the invention, the fitting degree of the bushing in the small end of the connecting rod can be conveniently detected, and the detection result can be visually displayed.

Description

Technical Field

[0001] The invention relates to the field of connecting rod bushing fit detection, and in particular to a device and method for laser ultrasonic detection of the fit between a connecting rod bushing and a bottom hole. Background Art

[0002] The connecting rod is a key component that connects the piston and crankshaft in the engine. The quality of its assembly accuracy is directly related to the operating efficiency and service life of the engine, so there are extremely strict requirements on the assembly accuracy.

[0003] To ensure that the engine can maintain a stable and efficient operation, the contact stress between the bottom hole of the connecting rod and the bushing must reach a sufficiently high level, and the contact quality must be maintained. This requirement is to prevent the connecting rod from vibrating violently during reciprocating motion, which in turn causes a series of problems such as abnormal engine noise and performance degradation. Therefore, the fit between the bushing and the bottom hole has become an important indicator for measuring the performance of the connecting rod.

[0004] In the past, the main method for testing the bushing fit was a destructive sampling method. However, this method can only achieve sampling testing and cannot cover all products because it will inevitably damage the connecting rod during the testing process. This may result in the assembly accuracy of some untested connecting rods not meeting the standards, thus burying quality risks.

[0005] In addition, although ultrasonic detection technology has also been used in detection in this field, this method requires the use of a coupling agent during implementation. The application of the coupling agent is not only time-consuming, but if the coupling agent fails to fully cover the entire area, it may cause the contact probe to be unable to perform effective detection, leading to missed detection. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a device and method for laser ultrasonic detection of the fit between a connecting rod bushing and a bottom hole.

[0007] The present invention provides a device for detecting the fit between a connecting rod bushing and a bottom hole by laser ultrasonic, which adopts the following technical scheme: A device for laser ultrasonic detection of the fit between a connecting rod bushing and a bottom hole comprises a workbench, a piezoelectric probe is provided on the workbench, a laser emitter is provided on the workbench, the piezoelectric probe is arranged in the bottom hole of a connecting rod small end, the laser emitter is arranged outside the connecting rod small end, the emitting end of the laser emitter faces the outer wall of the connecting rod small end, the piezoelectric probe is connected to an ultrasonic amplifier, and the ultrasonic amplifier is connected to a filter.

[0008] In a specific implementation manner, the laser transmitter is connected to a laser control module.

[0009] The present invention also provides a method for detecting the fit between a connecting rod bushing and a bottom hole by laser ultrasonic detection, which adopts the following technical solution: A method for detecting the fit between a connecting rod bushing and a bottom hole by laser ultrasonic detection comprises the following steps: Laser is emitted to different detection points on the outer wall of the connecting rod small end to stimulate ultrasonic waves in the connecting rod small end; Receive ultrasonic waves from multiple directions in the bottom hole of the connecting rod small end; The received ultrasonic sound wave signal is amplified, filtered and converted into analog to digital, the guided wave power of the current connecting rod is calculated, and the average guided wave power of the current connecting rod is further calculated.

[0010] In a specific feasible implementation scheme, before calculating the average guided wave power of the current connecting rod, the average guided wave power of the connecting rod and bushing of the same model as the current connecting rod with a fit of 85%, a fit of 0%, and a fit of 100% is calculated for calibration, and the average guided wave power of a fit of 85% is the fit threshold; If the average guided wave power of the current connecting rod is greater than or equal to the fit threshold, it indicates that the fit between the bushing and the connecting rod is qualified; otherwise, it indicates that the fit between the bushing and the connecting rod is unqualified.

[0011] In a specific embodiment, The method for calculating the current connecting rod fit includes the following steps: Perform Fourier transform on the ultrasonic signal:

[0012] In the above formula, is the ultrasonic signal, is a complex function, is the frequency variable, For time, is an imaginary unit; Calculate the power spectrum of an ultrasonic signal:

[0013] Normalize the power spectrum to obtain unit power spectral density:

[0014] In the above formula, is the normalization factor; Through the equation: , the unit power spectral density is converted into the Welch power spectral density through the equation; The guided wave power is obtained by frequency-integrating the Welch power spectral density:

[0015] Further calculate the average guided wave power:

[0016] In the above formula, Indicates the number of The guided wave power at each detection point, express The sum of the guided wave powers of the detection points with a fit degree of 0, express The first of the detection points A detection point.

[0017] In a specific implementation scheme, the degree of fit is calculated based on the waveguide power, and the degree of fit calculation formula is:

[0018] In the above formula, Indicates the degree of fit, Indicates the average guided wave power at the test point where the fit is 100%.

[0019] In a specific feasible implementation scheme, after calculating the waveguide power of the current connecting rod, the fit between the bushing and the connecting rod is converted into an image for visualization output.

[0020] In a specific embodiment, the method of converting the fitting condition of the bushing and the connecting rod into an image comprises the following steps: Calculate scanning direction and the thickness direction of the connecting rod small end Different positions on exist Absolute guided wave power at time: ; Construct the two-dimensional wave equation:

[0021] In the above formula, is the speed of sound in the medium; Scanning direction , thickness direction and time Take the Fourier transform:

[0022] Scanning direction and time Take the Fourier transform:

[0023] Only consider In the case of , the dispersion equation is constructed:

[0024] In the above formula, is the two-dimensional spectrum of the detection plane; In the thickness direction The two-dimensional spectrum of the plane, represents the equivalent wave speed; Generate an imaging matrix based on the dispersion equation; An image is generated by an imaging matrix.

[0025] In a specific implementation scheme, the calculation formula of the imaging matrix is:

[0026] In the above formula, Represents the complex exponential function.

[0027] In a specific feasible implementation method, before generating the imaging matrix according to the dispersion equation, the equivalent wave velocity is calculated by a numerical calculation method. The calculation formula of the equivalent wave velocity is:

[0028] In the above formula, is the speed of sound in the connecting rod, is the connecting rod thickness, is the speed of sound in the bushing, is the thickness of the bushing.

[0029] In summary, the present invention has the following beneficial effects: 1. The ultrasonic wave generated by the laser shooting into the connecting rod is used to detect the fit between the connecting rod and the bushing, thereby realizing non-destructive testing of the fit between the bushing and the connecting rod. This makes it convenient to detect the fit without causing damage to the connecting rod and the bushing.

[0030] 2. By converting the acoustic wave signal, the fit test results can be visualized, making it convenient and intuitive to conduct a comprehensive assessment of the fit between the bushing and the connecting rod.

[0031] 3. Test the fit between the connecting rod small end and the bushing from multiple test points to improve the comprehensiveness and accuracy of the fit test.

[0032] 4. Different types of connecting rods are calibrated separately, so that different types of connecting rods have different testing standards, which improves the accuracy of connecting rod fit testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the connecting rod structure.

[0034] Figure 2 It is a structural schematic diagram of a device for detecting the fit between a connecting rod bushing and a bottom hole by laser ultrasonic testing.

[0035] Figure 3 It is a flow chart of a method for laser ultrasonic testing the fit between a connecting rod bushing and a bottom hole.

[0036] Explanation of the accompanying drawings: 1. Laser control module; 2. Laser transmitter; 3. Piezoelectric probe; 4. Connecting rod; 41. Small end of connecting rod; 5. Workbench; 6. Controller; 7. Ultrasonic amplifier; 8. Filter; 9. Computer; 10. Bushing. DETAILED DESCRIPTION

[0037] The following combination Figure 1-Figure 3 The present invention is described in further detail.

[0038] Reference Figure 1 and Figure 2 The device for laser ultrasonic detection of the fit between the connecting rod bushing and the bottom hole comprises a workbench 5, on which a piezoelectric probe 3 and a laser emitter 1 are arranged. The connecting rod 4 is placed on the workbench 5, the piezoelectric probe 3 is placed in the bottom hole of the connecting rod head 41, and the detection end of the piezoelectric probe 3 is close to the inner wall of the bushing 10. The laser emitter 2 is arranged outside the connecting rod 4, and the emission end of the laser emitter 2 faces the outer wall of the connecting rod 4, and emits laser into the connecting rod 4.

[0039] According to the thermoelastic excitation mechanism, when the energy of the incident pulse laser is low and does not reach the damage threshold of the material, a short pulse laser irradiates the surface of the material, and the material absorbs a large amount of laser energy in a very short time (nanosecond or picosecond level). This instantaneous energy deposition will cause rapid local heating and rapid expansion of the material surface, thereby generating instantaneous thermal stress waves, such as transverse waves, longitudinal waves and surface waves. The stress waves propagate inside the material and are eventually converted into ultrasonic waves.

[0040] That is to say, after the laser transmitter 2 emits the laser to the outer wall of the connecting rod head 41, ultrasonic waves are generated in the connecting rod head 41, which are then detected and received by the piezoelectric probe 3. When ultrasonic waves encounter different media, they will produce reflection, refraction and waveform conversion. Since the quality of the interference fit between the connecting rod 4 and the bushing 10 is different, when the ultrasonic waves pass through the surfaces where the bushing 10 and the connecting rod 4 are in contact, there are different degrees of reflection and attenuation, so that the contact degree between the bushing 10 and the connecting rod 4 can be detected according to the energy transmitted by the ultrasonic waves.

[0041] A controller 6 is installed on the workbench 5, which can control the height of the workbench 5, etc. A laser control module 1 is connected to the laser emitter 2, and the laser control module 1 is connected to the pre-prepared computer 9. The laser control module 1 obtains the control command issued by the computer 9, sends the start and stop signal to the laser emitter 2, and adjusts the parameters such as the intensity of the laser emitted by the laser emitter 1.

[0042] The piezoelectric probe 3 is communicatively connected to an ultrasonic amplifier 7, and the ultrasonic amplifier 7 is communicatively connected to a filter 8, which is communicatively connected to a computer 9. After the piezoelectric probe 3 acquires the ultrasonic wave, the acoustic wave signal is transmitted to the ultrasonic amplifier 7, and the ultrasonic amplifier 7 amplifies the acoustic wave signal, and the filter 8 with an analog-to-digital (A / D) conversion function filters and converts the acoustic wave signal into a digital signal, and outputs the filtered acoustic wave signal to the computer 9. After the computer 9 acquires the digital signal sent by the filter 8, it stores it for subsequent calculations.

[0043] Reference Figure 3 The present invention also discloses a method for detecting the fit between a connecting rod bushing and a bottom hole by using laser ultrasonic technology, which is used in conjunction with the above-mentioned device for detecting the fit between a connecting rod bushing and a bottom hole by using laser ultrasonic technology, and comprises the following steps: S100, data acquisition, calibration data and fit threshold calculation.

[0044] By changing the position of the laser transmitter, the laser is emitted to different detection points on the connecting rod, and the single pulse output energy of the laser is 2MJ. The connecting rod is the same model as the connecting rod to be tested, and the fit is 0%, 85% and 100%. The position of the piezoelectric probe is changed to receive the ultrasonic wave generated from different positions in the connecting rod, and the acoustic wave signal is transmitted to the acoustic wave amplifier. After amplification, filtering and analog-to-digital conversion, the acoustic wave signal is stored in the computer.

[0045] Calculate the average guided wave power , and Since the calculation method of the average guided wave power is the same, only the calculation method is described below. The calculation of the fit degree 0%, 85% and 100% is just a replacement of parameters and will not be repeated.

[0046] Perform Fourier transform on the ultrasonic signal: In the above formula, is the ultrasonic signal, is a complex function, is the frequency variable, For time, Is an imaginary unit.

[0047] According to the Fourier transform results, the power spectrum of the ultrasonic signal is calculated:

[0048] Normalize the power spectrum to obtain unit power spectral density:

[0049] In the above formula, is the normalization factor.

[0050] Through the equation: , convert the unit power spectral density into Welch power spectral density.

[0051] The guided wave power is obtained by frequency-integrating the Welch power spectral density: The average guided wave power is further calculated:

[0052] In the above formula, is the total number of detection points on the connecting rod, that is, the total number of lasers directed to the connecting rod, Indicates The guided wave power at each detection point, .

[0053] The above method can be used to calculate the average waveguide power when the fit is 0%, 85% and 100%. , , .

[0054] Since the fit degree is greater than or equal to 85%, the average waveguide power when the fit degree is equal to 85% is calculated. as the fit threshold.

[0055] S200, calculation of the degree of fit of the connecting rod to be tested, and determination of the degree of fit.

[0056] The calculation formula of ultrasonic transmittance is:

[0057] In the above formula, represents ultrasonic transmittance; , represents the ultrasonic angular frequency,; represents the acoustic impedance of the connecting rod material, represents the acoustic impedance of the bushing 10 material; represents the interface stiffness.

[0058] It can be seen from the ultrasonic transmittance calculation formula that when the contact stress increases, the gap decreases, the interface stiffness increases, the actual contact area increases, and the ultrasonic transmittance also increases. The connecting rod and the bushing 10 are fitted with an interference fit. Therefore, when the incident energy remains constant, the ultrasonic guided wave power received by the piezoelectric probe is will also increase.

[0059] The calculation formula for the average guided wave power of the connecting rod to be tested is:

[0060] In the above formula, Indicates the number of The guided wave power at each detection point, express The sum of the guided wave powers of the detection points with a fit degree of 0, express The first of the detection points A detection point.

[0061] The fit between the connecting rod to be tested and the bushing 10 can be further calculated based on the guided wave power of the connecting rod to be tested:

[0062] In the above formula, Indicates the degree of fit, Indicates the average guided wave power at the test point where the fit is 100%.

[0063] The fit determination function can be further generated:

[0064] When , it means the fit is acceptable. , it means the fit is unqualified.

[0065] S300: Generate an image based on the fit between the bushing 10 and the connecting rod.

[0066] Specifically, the steps include: S310, scanning direction and thickness direction Different positions on exist The absolute guided wave power at , from which we can further construct the following two-dimensional wave equation:

[0067] In the above formula, is the speed of sound in the medium. , , The Fourier transform of is:

[0068] For the two-dimensional wave equation , The Fourier transform of is:

[0069] In the above formula, For along The wave number of the direction, For along Direction of the wave number.

[0070] S320, when only considering the extraordinary solution, that is, In the case of , the following dispersion equation can be further constructed:

[0071]

[0072] We can further get:

[0073] In the above formula, is the two-dimensional spectrum of the detection plane, that is, the two-dimensional spectrum of the outer wall surface of the connecting rod small end 41; In the thickness direction The two-dimensional spectrum of the plane is the two-dimensional spectrum of the inner wall of the liner 10. The above formula represents the wave field extrapolated from the detection plane to the depth In the actual detection process, since the fit between the bushing 10 and the inner wall of the connecting rod is difficult to ensure, there is a gap between the bushing 10 and the inner wall of the connecting rod that causes the fit to be unqualified. Therefore, there is a situation where the propagation path changes from the excitation point-receiving point to the excitation point-defect-receiving point. In order to ensure the consistency of time during the detection process, Equivalent wave speed Instead. The above formula can be rewritten as follows:

[0074] Equivalent wave speed The calculation formula is as follows:

[0075] In the above formula, is the speed of sound in the connecting rod small end 41, is the thickness of the connecting rod small end 41, is the speed of sound in the bushing 10, is the thickness of the bushing 10 .

[0076] S330, further according to the formula:

[0077] Calculation Point Imaging matrix at , in the above formula, is a complex exponential function, which means that the wave Direction of propagation.

[0078] S340, according to the predetermined scanning step and Point The change in thickness direction ,make , and loop steps S220-S230 until a focused imaging matrix within the entire imaging range is obtained.

[0079] S350, generating an image through an imaging matrix.

[0080] The above are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for detecting the fit between a connecting rod bushing and a bottom hole by laser ultrasonic detection, characterized in that: The invention comprises a workbench (5), wherein a piezoelectric probe (3) is provided on the workbench (5), and a laser emitter (2) is provided on the workbench (5), wherein the piezoelectric probe (3) is arranged in a bottom hole of a connecting rod small head (41), and the laser emitter (2) is arranged outside the connecting rod small head (41), and the emission end of the laser emitter (2) faces the outer wall of the connecting rod small head (41), and the piezoelectric probe (3) is connected to an ultrasonic amplifier (7), and the ultrasonic amplifier (7) is connected to a filter (8).

2. The device for detecting the fit between the connecting rod bushing and the bottom hole by laser ultrasonic detection according to claim 1, characterized in that: The laser emitter (2) is connected to a laser control module (1).

3. A method for detecting the fit between a connecting rod bushing and a bottom hole by laser ultrasonic detection, characterized in that: The steps include: Laser is emitted to different detection points on the outer wall of the connecting rod small end to stimulate ultrasonic waves in the connecting rod small end; Receive ultrasonic waves from multiple directions in the bottom hole of the connecting rod small end; The received ultrasonic sound wave signal is amplified, filtered and converted into analog to digital, the guided wave power of the current connecting rod is calculated, and the average guided wave power of the current connecting rod is further calculated.

4. The method for detecting the fit between the connecting rod bushing and the bottom hole by laser ultrasonic detection according to claim 3 is characterized in that: Before calculating the average guided wave power of the current connecting rod, the average guided wave power of the connecting rod and bushing of the same model as the current connecting rod with a fit of 85%, a fit of 0%, and a fit of 100% is calculated for calibration, and the average guided wave power of a fit of 85% is the fit threshold; If the average guided wave power of the current connecting rod is greater than or equal to the fit threshold, it indicates that the fit between the bushing and the connecting rod is qualified; otherwise, it indicates that the fit between the bushing and the connecting rod is unqualified.

5. The method for detecting the fit between the connecting rod bushing and the bottom hole by laser ultrasonic detection according to claim 3 is characterized in that: The method for calculating the average guided wave power of the current connecting rod includes the following steps: Perform Fourier transform on the ultrasonic signal: In the above formula, is the ultrasonic signal, is a complex function, is the frequency variable, For time, is an imaginary unit; Calculate the power spectrum of an ultrasonic signal: Normalize the power spectrum to obtain unit power spectral density: In the above formula, is the normalization factor; Through the equation: , the unit power spectral density is converted into the Welch power spectral density through the equation; The guided wave power is obtained by frequency-integrating the Welch power spectral density: Further calculate the average guided wave power: In the above formula, Indicates the number of The guided wave power at each detection point, express The sum of the guided wave powers of the detection points with a fit degree of 0, express The first of the detection points A detection point.

6. The method for detecting the fit between the connecting rod bushing and the bottom hole by laser ultrasonic detection according to claim 5, characterized in that: The fit degree is calculated based on the waveguide power. The fit degree calculation formula is: In the above formula, Indicates the degree of fit, Indicates the average guided wave power at the test point where the fit is 100%.

7. The method for detecting the fit between the connecting rod bushing and the bottom hole by laser ultrasonic detection according to claim 3, characterized in that: After calculating the guided wave power of the current connecting rod, the fit between the bushing and the connecting rod is converted into an image for visualization output.

8. The method for detecting the fit between the connecting rod bushing and the bottom hole by laser ultrasonic detection according to claim 7, characterized in that: The method of converting the fitting condition of the bushing and the connecting rod into an image comprises the following steps: Calculate scanning direction and the thickness direction of the connecting rod small end Different positions on exist Absolute guided wave power at time: ； Construct the two-dimensional wave equation: In the above formula, is the speed of sound in the medium; Scanning direction , thickness direction and time Take the Fourier transform: Scanning direction and time Take the Fourier transform: Only consider In the case of , the dispersion equation is constructed: In the above formula, is the two-dimensional spectrum of the detection plane; In the thickness direction The two-dimensional spectrum of the plane, represents the equivalent wave speed; Generate an imaging matrix based on the dispersion equation; An image is generated by an imaging matrix.

9. The method for detecting the fit between the connecting rod bushing and the bottom hole by laser ultrasonic detection according to claim 8, characterized in that: The calculation formula of the imaging matrix is: In the above formula, Represents the complex exponential function.

10. The method for detecting the fit between the connecting rod bushing and the bottom hole by laser ultrasonic detection according to claim 8, characterized in that: Before generating the imaging matrix according to the dispersion equation, the equivalent wave velocity is calculated by numerical calculation method. The calculation formula of the equivalent wave velocity is: In the above formula, is the speed of sound in the connecting rod, is the connecting rod thickness, is the speed of sound in the bushing, is the thickness of the bushing.

Images