A device and method for laser ultrasonic detection of the fit between connecting rod bushing and bottom hole

Abstract

The present 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. The device includes a workbench, a piezoelectric probe is provided on the workbench, a laser transmitter is provided on the workbench, an ultrasonic amplifier is connected to the piezoelectric probe, and a filter is connected to the ultrasonic amplifier. The method includes the following steps: emitting a laser to different detection points on the outer wall of the connecting rod head; receiving ultrasonic waves at different detection points, calculating the guided wave power of the current connecting rod head and the bushing, and further calculating the fit between the current connecting rod bushing and the connecting rod head. The present invention can conveniently detect the fit of the bushing in the connecting rod head and visualize the detection results.

Description

Technical Field

[0001] The present 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 engine's operating efficiency and service life, so there are extremely strict requirements on assembly accuracy.

[0003] To ensure smooth and efficient engine operation, the contact stress between the connecting rod's small end bore and the bushing must be sufficiently high and maintain excellent contact quality. This requirement prevents the connecting rod from vibrating violently during reciprocating motion, which can lead to problems such as abnormal engine noise and performance degradation. Therefore, the fit between the bushing and the bore has become a key indicator of connecting rod performance.

[0004] In the past, bushing fit testing primarily relied on destructive spot checks. However, this method inevitably damages connecting rods during testing, so it only allows for sampling and cannot cover all products. This can lead to the possibility that some untested connecting rods may not meet assembly accuracy standards, thus creating quality risks.

[0005] In addition, although ultrasonic detection technology has also been used in detection in this field, this method requires the use of coupling agent during implementation. The application of 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, resulting in 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 laser ultrasonic detection of the fit between a connecting rod bushing and a bottom hole, which adopts the following technical solutions:

[0008] 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 the connecting rod small head, the laser emitter is arranged outside the connecting rod small head, the emitting end of the laser emitter faces the outer wall of the connecting rod small head, the piezoelectric probe is connected to an ultrasonic amplifier, and the ultrasonic amplifier is connected to a filter.

[0009] In a specific implementation scheme, the laser emitter is connected to a laser control module.

[0010] 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:

[0011] A method for detecting the fit between a connecting rod bushing and a bottom hole by laser ultrasonic detection comprises the following steps:

[0012] Laser is emitted to different detection points on the outer wall of the connecting rod small end to stimulate ultrasonic waves inside the connecting rod small end;

[0013] Receive ultrasonic waves from multiple directions in the bottom hole of the connecting rod small end;

[0014] The received ultrasonic sound wave signal is amplified, filtered and converted into analog to digital, and 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.

[0015] In a specific possible 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 the fit of 85% is used as the fit threshold;

[0016] 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.

[0017] In a specific embodiment,

[0018] The method for calculating the current connecting rod fit includes the following steps:

[0019] Perform Fourier transform on the ultrasonic signal:

[0020]

[0021] In the above formula, is the ultrasonic signal, is a complex function, is the frequency variable, For time, is an imaginary unit;

[0022] Calculate the power spectrum of an ultrasonic signal:

[0023]

[0024] Normalize the power spectrum to obtain unit power spectral density:

[0025]

[0026] In the above formula, is the normalization factor;

[0027] Through the equation: , the unit power spectral density is converted into Welch power spectral density through the equation;

[0028] The guided wave power is obtained by frequency-integrating the Welch power spectral density:

[0029]

[0030] Further calculate the average guided wave power:

[0031]

[0032] In the above formula, Indicates the number of the connecting rod to be tested. The guided wave power at each detection point, express The sum of the guided wave powers of the detection points with a fit of 0, express The first of the detection points A detection point.

[0033] In a specific embodiment, the degree of fit is calculated based on the waveguide power, and the degree of fit calculation formula is:

[0034]

[0035] In the above formula, Indicates the degree of fit, Indicates the average guided wave power at the test point where the fit is 100%.

[0036] In a specific feasible implementation scheme, after calculating the waveguide power of the current connecting rod, the fitting condition of the bushing and the connecting rod is converted into an image for visualization output.

[0037] In a specific embodiment, the method of converting the fitting condition of the bushing and the connecting rod into an image includes the following steps:

[0038] Calculate scanning direction and the thickness direction of the connecting rod small end Different positions on exist Absolute guided wave power at time: ;

[0039] Construct the two-dimensional wave equation:

[0040]

[0041] In the above formula, is the speed of sound in the medium;

[0042] Scanning direction , thickness direction and time Perform a Fourier transform:

[0043]

[0044] Scanning direction and time Perform a Fourier transform:

[0045]

[0046] Only consider In the case of , the dispersion equation is constructed:

[0047]

[0048] 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 velocity;

[0049] Generate an imaging matrix based on the dispersion equation;

[0050] An image is generated by an imaging matrix.

[0051] In a specific embodiment, the calculation formula of the imaging matrix is:

[0052]

[0053] In the above formula, Represents the complex exponential function.

[0054] In a specific 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:

[0055]

[0056] 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.

[0057] In summary, the present invention has the following beneficial effects:

[0058] 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 facilitates the fit testing without causing damage to the connecting rod and the bushing.

[0059] 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.

[0060] 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.

[0061] 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

[0062] Figure 1 It is a structural diagram of the connecting rod.

[0063] Figure 2 It is a structural schematic diagram of a device for detecting the fit between a connecting rod bushing and a bottom hole using laser ultrasonic testing.

[0064] 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.

[0065] Explanation of the accompanying symbols: 1. Laser control module; 2. Laser emitter; 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

[0066] The following combination Figure 1-Figure 3 The present invention is described in further detail.

[0067] Reference Figure 1 and Figure 2 The device for laser ultrasonic testing the fit between the connecting rod bushing and the bottom hole includes a workbench 5, on which are mounted a piezoelectric probe 3 and a laser emitter 1. A connecting rod 4 is placed on the workbench 5, and the piezoelectric probe 3 is placed in the bottom hole of the connecting rod head 41, with the detection end of the piezoelectric probe 3 in close contact with the inner wall of the bushing 10. The laser emitter 2 is disposed outside the connecting rod 4, with the emitting end of the laser emitter 2 facing the outer wall of the connecting rod 4, emitting laser light into the connecting rod 4.

[0068] 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 is irradiated onto the surface of the material. The material will absorb a large amount of laser energy in an extremely short period of 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 shear waves, longitudinal waves and surface waves. The stress waves propagate inside the material and are eventually converted into ultrasonic waves.

[0069] That is, after the laser emitter 2 emits a laser toward the outer wall of the connecting rod head 41, ultrasonic waves are generated within the connecting rod head 41, which are then detected and received by the piezoelectric probe 3. When ultrasonic waves encounter different media, they are reflected, refracted, and their waveforms converted. Because the interference fit between the connecting rod 4 and the bushing 10 varies in quality, the ultrasonic waves experience varying degrees of reflection and attenuation when passing through the surfaces where the bushing 10 and the connecting rod 4 meet. This allows the fit between the bushing 10 and the connecting rod 4 to be detected based on the energy transmitted by the ultrasonic waves.

[0070] A controller 6 is mounted on the workbench 5, capable of controlling its height and other parameters. A laser control module 1 is connected to the laser emitter 2, which communicates with a pre-installed computer 9. Laser control module 1 receives control commands from computer 9, sends start and stop signals to laser emitter 2, and adjusts parameters such as the intensity of the laser emitted by laser emitter 1.

[0071] Piezoelectric probe 3 is communicatively connected to ultrasonic amplifier 7, which is communicatively connected to filter 8, which is communicatively connected to computer 9. After acquiring ultrasonic waves, piezoelectric probe 3 transmits the acoustic wave signal to ultrasonic amplifier 7, which amplifies the acoustic wave signal. Filter 8, which has analog-to-digital (A / D) conversion capabilities, filters and converts the acoustic wave signal. The filtered acoustic wave signal is converted into a digital signal and output to computer 9. Computer 9 acquires the digital signal from filter 8 and stores it for subsequent calculations.

[0072] Reference Figure 3 The present invention further 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:

[0073] S100, data acquisition, calibration data and fit threshold calculation.

[0074] By varying the position of the laser emitter, the laser is fired at different test points on the connecting rod, with a single pulse output energy of 2 MJ. The connecting rods are identical to the connecting rod being tested, with fit levels of 0%, 85%, and 100%. By varying the position of the piezoelectric probe, ultrasonic waves are generated at different locations within the connecting rod and transmitted to an acoustic amplifier. The acoustic signals are amplified, filtered, and converted to analog-to-digital before being stored in a computer.

[0075] Calculate the average guided wave power , and Since the calculation method for average guided wave power is the same, only the calculation method is explained below. The calculation of 0%, 85%, and 100% fit is just a parameter replacement and will not be repeated here.

[0076] Perform Fourier transform on the ultrasonic signal:

[0077] In the above formula, is the ultrasonic signal, is a complex function, is the frequency variable, For time, Is an imaginary unit.

[0078] According to the Fourier transform results, the power spectrum of the ultrasonic signal is calculated:

[0079]

[0080] Normalize the power spectrum to obtain unit power spectral density:

[0081]

[0082] In the above formula, is the normalization factor.

[0083] Through the equation: , convert the unit power spectral density into Welch power spectral density.

[0084] The guided wave power is obtained by frequency-integrating the Welch power spectral density:

[0085] Further calculate the average guided wave power:

[0086]

[0087] 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 The guided wave power at each detection point, .

[0088] The above method can be used to calculate the average guided wave power when the fit is 0%, 85% and 100%. , , .

[0089] Since the fit is greater than or equal to 85% to be qualified, the average guided wave power when the fit is equal to 85% is calculated. as the fit threshold.

[0090] S200, calculating the degree of fit of the connecting rod to be tested, and determining the degree of fit.

[0091] The calculation formula for ultrasonic transmittance is:

[0092]

[0093] 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.

[0094] According to the ultrasonic transmittance calculation formula, 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.

[0095] The calculation formula for the average guided wave power of the connecting rod to be tested is:

[0096]

[0097] In the above formula, Indicates the number of the connecting rod to be tested. The guided wave power at each detection point, express The sum of the guided wave powers of the detection points with a fit of 0, express The first of the detection points A detection point.

[0098] The degree of 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:

[0099]

[0100] In the above formula, Indicates the degree of fit, Indicates the average guided wave power at the test point where the fit is 100%.

[0101] The fit determination function can be further generated:

[0102]

[0103] When , it means the fit is qualified. , it means the fit is unqualified.

[0104] S300: Generate an image based on the fit between the bushing 10 and the connecting rod.

[0105] Specifically, the steps include:

[0106] S310, scanning direction and thickness direction Different positions on exist Absolute guided wave power at , from which we can further construct the following two-dimensional wave equation:

[0107]

[0108] In the above formula, is the speed of sound in the medium. , , The Fourier transform of is:

[0109]

[0110] For the two-dimensional wave equation , The Fourier transform of is:

[0111]

[0112] In the above formula, For the The wave number of the direction, For the The wave number in the direction.

[0113] S320, when only considering the extraordinary solution, i.e. In the case of , the following dispersion equation can be further constructed:

[0114]

[0115]

[0116] We can further obtain:

[0117]

[0118] 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, Using equivalent wave velocity Instead. The above formula can be rewritten as the following formula:

[0119]

[0120] Equivalent wave speed The calculation formula is as follows:

[0121]

[0122] 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 .

[0123] S330, further according to the formula:

[0124]

[0125] Calculation Point Imaging matrix at , in the above formula, is a complex exponential function, which means the wave Directional propagation.

[0126] S340, according to the pre-determined scanning step and point Variation in thickness direction ,make , and loop steps S220-S230 until a focused imaging matrix within the entire imaging range is obtained.

[0127] S350, generating an image through an imaging matrix.

[0128] The above are all preferred embodiments of the present invention, and are not intended to limit the scope of protection 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 scope of protection of the present invention.

Claims

1. A device for detecting the fit between a connecting rod bushing and a bottom hole using laser ultrasonic technology, 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 the bottom hole of the connecting rod head (41), and the detection end of the piezoelectric probe (3) is in close contact with the inner wall of the bushing (10), and the laser emitter (2) is arranged outside the connecting rod head (41), and the emission end of the laser emitter (2) faces the outer wall of the connecting rod 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 using laser ultrasonic testing, characterized in that: The method is used in conjunction with the device for detecting the fit between the connecting rod bushing and the bottom hole of any one of claims 1 to 2 using laser ultrasonic technology, comprising the following steps: Laser is emitted to different detection points on the outer wall of the connecting rod small end to stimulate ultrasonic waves inside 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, and 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, characterized in that: Before calculating the average guided wave power of the current connecting rod, calculate 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%, 0%, and 100% for calibration. The average guided wave power of the 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, 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 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 connecting rod to be tested. The guided wave power at each detection point, express The sum of the guided wave powers of the detection points with a fit 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 is calculated based on the waveguide power. The fit 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 current connecting rod's guided wave power, 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 for converting the fitting condition of the bushing and the connecting rod into an image includes 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 Perform a Fourier transform: Scanning direction and time Perform a 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 velocity; 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.

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