A bolt preload test method based on electromagnetic ultrasonic preload measurement system

Abstract

The invention discloses a bolt preload test method based on an electromagnetic ultrasonic preload measurement system. The waveform data of the transverse and longitudinal waves generated by the electromagnetic ultrasonic probe is collected, and through a data averaging algorithm, only the current frame echo data and the historical accumulated data need to be processed each time, so that the storage space only needs to store the historical accumulated data received by the electromagnetic ultrasonic probe once, thereby improving the data processing speed and signal-to-noise ratio; then the peak value algorithm is used to automatically identify and calculate the wave peak sound time of the transverse and longitudinal wave echo envelope of the bolt, and the bolt preload corresponding to the time period is obtained by fitting the transverse and longitudinal wave sound time ratio, and the calibration curve corresponding to the bolt of this model and specification is obtained, and the calibration curve is used to realize the preload measurement of other bolts of the same model and specification. The invention is easy to operate, can simultaneously excite effective transverse waves and longitudinal waves, and has high measurement precision and accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic ultrasonic preload measurement, and in particular to a bolt preload test method based on an electromagnetic ultrasonic preload measurement system. Background Art

[0002] Bolts are widely used in various mechanical structures. The most important parameter of bolts in use is their preload, which directly reflects the degree of tightness between the bolts and the connecting parts. However, the preload cannot be measured directly and can only be measured indirectly. Currently, the commonly used methods for measuring bolt preload include torque wrench method, strain gauge method, piezoelectric ultrasonic method, etc.

[0003] Torque wrenches are currently used but are prone to large errors due to different skills and techniques of operators. The strain gauge method requires strain gauges to be installed on the bolts, which need to be removed after measurement. The process is cumbersome and not suitable for rapid on-site measurement. The piezoelectric ultrasonic method requires grinding the end face of the bolt, and the operation process is also cumbersome. It is not only time-consuming, but may also damage the bolt surface.

[0004] Therefore, there is an urgent need for a bolt preload measurement method based on an electromagnetic ultrasonic preload measurement system to solve the above-mentioned problems of errors caused by human operation, the need for additional processing of the bolts (such as grinding, sticking strain gauges, etc.), and difficulty in operation. Summary of the invention

[0005] The problem to be solved by the present invention is to provide a bolt preload test method based on an electromagnetic ultrasonic preload measurement system. The bolt preload test method based on the electromagnetic ultrasonic preload measurement system is easy to operate, can simultaneously excite effective transverse waves and longitudinal waves, and has high measurement precision and accuracy.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A bolt preload test method based on an electromagnetic ultrasonic preload measurement system, characterized in that it comprises the following steps:

[0008] (1) An electromagnetic ultrasonic probe (i) is placed on the end face of a bolt, and the electromagnetic ultrasonic probe (i) is used to excite the transverse and longitudinal waves of the bolt. The electromagnetic ultrasonic preload force measurement system receives the transverse and longitudinal wave data of the bolt transmitted multiple times, and stores the transverse and longitudinal wave data of the bolt in a storage space (a). In the storage space (a), a data averaging algorithm is used to calculate and average the transverse and longitudinal wave data of the bolt received multiple times, and a waveform diagram of the transverse and longitudinal waves of the bolt received each time is drawn in real time. The calculation steps of the above data averaging algorithm are as follows:

[0009] (1-1) The Nth frame echo data received by the electromagnetic ultrasonic probe (i) is converted into digital signal data D through an amplifier and an analog-to-digital converter (d). The digital signal data D is expressed as , k represents the number of data points received by the probe per frame, and then Decompose into effective echo data and random noise , get digital signal data ;

[0010] (1-2) Storage space (a) The historical accumulated data A stored is divided into two data paths:

[0011] The first data path is to read the historical accumulated data A from the storage space (a), and then pass the historical accumulated data A through the divider (b) through the Nth input to obtain the intermediate data ;

[0012] The second data path is to directly read the historical accumulated data A from the storage space (a);

[0013] (1-3) The historical accumulated data A obtained from the second data channel and the intermediate data B obtained from the first data channel are calculated by the subtractor (c) to obtain the historical data ;

[0014] (1-4) Through the Nth input, the digital signal data D in step (1-1) is calculated by the divider (k) to obtain the new data ;

[0015] (1-5) The historical data C in step (1-3) and the new data K in step (1-4) are calculated by adder (e) to obtain the average data ;

[0016] (1-6) The average data E is output as the measurement result; at the same time, the average data E is saved again to the storage space (a), the original historical accumulated data A is overwritten, and the storage space (a) stores the new historical accumulated data A, and the new historical accumulated data A is used to recalculate the average with the next frame echo data according to steps (1-1) to (1-5);

[0017] (2) When the bolt is in a state without pre-tightening force, and according to the transverse and longitudinal wave waveforms of the bolt drawn in real time in step (1), the transverse and longitudinal wave echo envelopes are searched respectively from the trailing edge of the starting wave by the electromagnetic ultrasonic pre-tightening force measurement system, and the transverse and longitudinal wave echo envelopes are automatically identified by the peak value algorithm, and one of the wave peak sound times is selected as the ultrasonic sound time to be monitored, and the transverse wave peak sound time and the longitudinal wave peak sound time in the transverse and longitudinal wave echo envelopes of the bolt without pre-tightening force time period are calculated; and the transverse wave ultrasonic sound time of the bolt without pre-tightening force time period is stored as , longitudinal ultrasonic sound is stored as ;

[0018] (3) Apply different preload forces to the bolts in sequence through a material stretching machine , and according to the transverse and longitudinal wave waveforms of the bolt drawn in real time in step (1), the transverse and longitudinal wave echo envelopes are searched respectively from the trailing edge of the starting wave through the electromagnetic ultrasonic preload measurement system, the transverse and longitudinal wave echo envelopes are automatically identified through the peak algorithm, and one of the wave peak sound times is selected as the ultrasonic sound time to be monitored, and the transverse wave peak sound time and the longitudinal wave peak sound time in the transverse and longitudinal wave echo envelopes of the bolt preload time period are calculated; the transverse wave ultrasonic sound time of the bolt preload time period is stored as , longitudinal ultrasonic sound is stored as ;

[0019] (4) The electromagnetic ultrasonic preload measurement system is used to calculate and record the transverse and longitudinal wave acoustic time ratios of the bolts in different preload time periods. The electromagnetic ultrasonic preload measurement system is used to fit the calibration curve of the relationship between the preload and the transverse and longitudinal wave acoustic time ratios of the bolts of this model and specification. The calibration curve is used to obtain the mathematical function relationship between the preload and the transverse and longitudinal wave acoustic time ratios: , where F is the bolt preload, k is the calibration factor (curve slope), is the acoustic time ratio of transverse and longitudinal waves in the bolt, b is the intercept of the calibration curve (constant);

[0020] (5) Use the electromagnetic ultrasonic preload measurement system to measure the transverse and longitudinal wave acoustic time ratios of other bolts of the same model and specification. According to the formula It is possible to measure the preload force of other bolts of the same model and specification.

[0021] The above steps (1-2) perform a division operation through the divider (b) to calculate the intermediate data B, thereby reducing the complexity of subsequent calculations.

[0022] The above steps (1-3) perform subtraction operations through a subtractor (c), which reduces the amount of data that needs to be processed each time and improves the calculation speed.

[0023] The above steps (1-4) perform a division operation through a divider (k) to ensure the accuracy of the new data K.

[0024] The above steps (1-5) are added by the adder (e) to update the average data in real time, ensuring that the average data E output each time is real-time and accurate.

[0025] In the above steps (1-2), when the system is initialized, the historical accumulated data A in the storage space (a) is 0, that is, A = 0. This is because the system has no historical data when it is initialized, so the data in the storage space (a) is empty or initialized to 0, which can ensure that there is no interference from any historical data when the system starts working.

[0026] The data averaging algorithm in the above step (1) only needs to process the current frame echo data and historical accumulated data each time, and the storage space only needs to save the historical accumulated data received by the electromagnetic ultrasonic probe once, and each time after receiving new frame echo data, the average data of the electromagnetic ultrasonic measurement can be output, which greatly reduces the amount of calculation, significantly improves the data processing speed, reduces the repetition frequency of data output, has a higher signal-to-noise ratio, and is conducive to preload measurement. In addition, due to the reduced storage space requirements, this data averaging algorithm can use a smaller capacity storage device to reduce storage costs.

[0027] In the preferred embodiment, in step (2), the steps of automatically identifying the shear wave peak sound time and the longitudinal wave peak sound time in the shear and longitudinal wave echo envelopes in the bolt without pre-tightening force time period are as follows:

[0028] (2-1) The peak algorithm is used to automatically identify the highest continuous j-cycle transverse and longitudinal wave echo envelopes during the bolt no pre-tightening period;

[0029] (2-2) Record the shear wave peak sound time and the longitudinal wave peak sound time of the j-period shear wave and longitudinal wave echo envelopes identified in step (2-1), sort them in chronological order, and store the shear wave peak sound time of the j-period shear wave and longitudinal wave echo envelopes as , the longitudinal wave peak sound time of the j-cycle transverse and longitudinal wave echo envelope is stored as ;

[0030] (2-3) Selecting the Nth peak sound time from the shear wave peak sound time and the longitudinal wave peak sound time of the j-period shear and longitudinal wave echo envelopes in step (2-2) as the designated ultrasonic sound time to be monitored, N≧1;

[0031] In the step (3), the steps of automatically identifying the shear wave peak sound time and the longitudinal wave peak sound time in the shear and longitudinal wave echo envelopes during the bolt pre-tightening time period are as follows:

[0032] (3-1) The peak algorithm is used to identify the highest continuous j-cycle transverse and longitudinal wave echo envelopes during the bolt preload period;

[0033] (3-2) Record the shear wave peak sound time and the longitudinal wave peak sound time of the j-period shear and longitudinal wave echo envelopes identified in step (3-1), and sort them in chronological order, and store the shear wave peak sound time of the j-period shear and longitudinal wave echo envelopes as , the longitudinal wave peak sound time of the j-cycle transverse and longitudinal wave echo envelope is stored as ;

[0034] (3-3) Select the Nth peak sound time from the shear wave peak sound time and the longitudinal wave peak sound time of the j-period shear and longitudinal wave echo envelopes in step (3-2) as the designated ultrasonic sound time to be monitored, N≧1.

[0035] In the preferred embodiment, the electromagnetic ultrasonic probe (i) comprises a shell and an upper cover, as well as a wear-resistant layer, a coil, a sound insulation layer, a magnet and a circular magnetic conductive block arranged in the shell; the upper part of the shell is provided with an upper end opening, the lower part of the shell is provided with a lower end detection port, and the upper cover is closed in the upper end opening; a wire clamp is provided on the outer surface of the shell, and a probe wire is provided in the wire clamp; the magnet is an annular magnet whose magnetic lines of force radiate uniformly from the inner diameter to the outer diameter; the wear-resistant layer, the coil, the sound insulation layer, the annular magnet, and the circular magnetic conductive block are arranged in the shell from bottom to top in sequence, the wear-resistant layer, the coil, the sound insulation layer, and the circular magnetic conductive block are all arranged coaxially with the annular magnet, the wear-resistant layer is in the lower end detection port, and the lower surface of the circular magnetic conductive block is on the upper surface of the annular magnet; there is a gap between the inner wall of the shell and the outer wall of the annular magnet, a lead wire is provided in the gap, and the probe wire is electrically connected to the coil through the lead wire. The gap between the inner wall of the shell and the outer wall of the annular magnet is used to place the lead wire, and the lead wire connects the coil to an external signal processing device to realize signal transmission. When the electromagnetic ultrasonic probe is used to measure the preload force near the bolt, the coil generates an alternating magnetic field after being energized. The alternating magnetic field interacts with the static magnetic field generated by the annular magnet to generate the Lorentz force, which in turn excites ultrasonic waves on the bolt surface. Since the magnetic lines of force of the annular magnet are uniformly radiated from the inner diameter to the outer diameter, the radial magnetic field generated by the annular magnet is relatively strong and can effectively excite longitudinal waves in the bolt, while the axial magnetic field generated by the annular magnet is relatively weak, which helps to reduce the interference of transverse waves and improve the excitation effect of longitudinal waves. This design is particularly suitable for bolts with hollow end faces, such as hexagon socket bolts, because the radial magnetic field can produce a stronger excitation effect on a smaller contact surface.

[0036] When the probe directly contacts the end face of the bolt, the wear-resistant layer is used to protect the internal structure of the electromagnetic ultrasonic probe from being damaged.

[0037] The circular magnetic conductive block is located on the upper surface of the annular magnet, which can concentrate and optimize the distribution of the magnetic field, making the interaction between the alternating magnetic field generated by the coil and the static magnetic field more efficient, which not only enhances the excitation effect of the longitudinal wave, but also improves the excitation effect of the transverse wave, thereby improving the utilization rate of the magnetic field.

[0038] The coil is an electromagnetic coil.

[0039] In a further preferred embodiment, a magnetic column is provided at the center of the lower surface of the circular magnetic block, and the magnetic column is perpendicular to the lower surface of the circular magnetic block. A through hole is provided at the center of the annular magnet, and the magnetic column is in the through hole and is arranged coaxially with the annular magnet. The magnetic column can concentrate and guide the magnetic field, so that the distribution of the magnetic field on the end face of the bolt is more concentrated, and the excitation effect of the transverse wave and the longitudinal wave is improved. The length of the magnetic column can be adjusted to achieve the best conversion efficiency of the transverse wave and the longitudinal wave of the end faces of different hexagon socket bolts. When the length of the magnetic column is increased, the magnetic column can be made to penetrate deeper into the through hole of the annular magnet, the concentration of the magnetic field is enhanced, and the excitation effect of the longitudinal wave is improved, which is suitable for bolts with smaller end faces, such as hexagon socket bolts. When the length of the magnetic column is reduced, the distance between the magnetic column and the annular magnet can be increased, the concentration of the magnetic field is weakened, the strength of the axial magnetic field is increased, and the excitation effect of the transverse wave is improved, which is suitable for bolts with larger end faces.

[0040] In a further preferred embodiment, the outer diameter of the sound insulation layer is greater than or equal to the outer diameter of the annular magnet. The outer diameter of the sound insulation layer is greater than or equal to the outer diameter of the annular magnet, which can ensure that the sound insulation layer completely covers the annular magnet, reduce the interference of the annular magnet on the alternating magnetic field generated by the coil, improve the signal quality and signal-to-noise ratio, and thus improve the precision and accuracy of the measurement.

[0041] In a further preferred embodiment, the sound insulation layer is made of a metal conductive material, which may be copper, aluminum alloy or iron.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] (1) Compared with the traditional ultrasonic measurement method, the present invention has the advantages of being non-contact, not requiring grinding of the bolt end face, and not requiring coupling agent between the probe and the bolt contact surface.

[0044] (2) The electromagnetic ultrasonic probe of the present invention can improve the conversion efficiency of electromagnetic ultrasound to excite transverse waves and longitudinal waves at the bolt end face at the same time, and improve the stability and accuracy of measuring the bolt preload. In particular, it can excite effective transverse waves and longitudinal waves at the same time in hexagon socket bolts, and has high measurement precision and accuracy. Moreover, this dual-wave method of transverse and longitudinal waves of bolts can measure in-service bolts without knowing the length of the bolts.

[0045] (3) The present invention collects the waveform data of the transverse and longitudinal waves generated by the electromagnetic ultrasonic probe, and uses a data averaging algorithm to process only the current frame echo data and the historical accumulated data each time, so that the storage space only needs to save the historical accumulated data received by the electromagnetic ultrasonic probe once, thereby improving the data processing speed and signal-to-noise ratio; then the peak algorithm is used to automatically identify and calculate the peak sound time of the transverse and longitudinal wave echo envelope of the bolt, and the bolt preload force corresponding to the time period is obtained by fitting the calibration curve corresponding to the bolt of this model and specification through the transverse and longitudinal wave sound time ratio, and the calibration curve is used to realize the preload force measurement of other bolts of the same model and specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a schematic diagram of an algorithm flow of Embodiment 1 of the present invention;

[0047] Figure 2 The time period of whether the bolt has pre-tightening force in Example 1 of the present invention Schematic diagram of

[0048] Figure 3 is a preload force calibration curve diagram of Example 1 of the present invention;

[0049] Figure 4 is a schematic structural diagram of the electromagnetic ultrasonic probe (i) in Example 1 of the present invention;

[0050] Figure 5 The time period of whether the bolt has pre-tightening force in Example 2 of the present invention Schematic diagram of

[0051] Figure 6 is a schematic diagram of the structure of Embodiment 3 of the present invention;

[0052] Figure 7 It is a structural schematic diagram of the circular magnetic conductive block and the magnetic conductive column in Example 3 of the present invention. DETAILED DESCRIPTION

[0053] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] like Figure 1-2 As shown, the bolt preload force testing method based on the electromagnetic ultrasonic preload force measurement system in this embodiment includes the following steps:

[0055] (1) An electromagnetic ultrasonic probe (i) is placed on the end face of a bolt, and the electromagnetic ultrasonic probe (i) is used to excite the transverse and longitudinal waves of the bolt. The electromagnetic ultrasonic preload force measurement system receives the transverse and longitudinal wave data of the bolt transmitted multiple times, and stores the transverse and longitudinal wave data of the bolt in a storage space (a). In the storage space (a), a data averaging algorithm is used to calculate and average the transverse and longitudinal wave data of the bolt received multiple times, and a waveform diagram of the transverse and longitudinal waves of the bolt received each time is drawn in real time. The calculation steps of the above data averaging algorithm are as follows:

[0056] (1-1) The Nth frame echo data received by the electromagnetic ultrasonic probe (i) is converted into digital signal data D through an amplifier and an analog-to-digital converter (d). The digital signal data D is expressed as , k represents the number of data points received by the probe per frame, and then Decompose into valid echo data and random noise , get digital signal data ;

[0057] (1-2) Storage space (a) The historical accumulated data A stored is divided into two data paths:

[0058] The first data path is to read the historical accumulated data A from the storage space (a), and then pass the historical accumulated data A through the divider (b) through the Nth input to obtain the intermediate data ;

[0059] The second data path is to directly read the historical accumulated data A from the storage space (a);

[0060] (1-3) The historical accumulated data A obtained from the second data channel and the intermediate data B obtained from the first data channel are calculated by the subtractor (c) to obtain the historical data ;

[0061] (1-4) Through the Nth input, the digital signal data D in step (1-1) is calculated by the divider (k) to obtain the new data ;

[0062] (1-5) The historical data C in step (1-3) and the new data K in step (1-4) are calculated by adder (e) to obtain the average data ;

[0063] (1-6) The average data E is output as the measurement result; at the same time, the average data E is saved again to the storage space (a), the original historical accumulated data A is overwritten, and the storage space (a) stores the new historical accumulated data A, and the new historical accumulated data A is used to recalculate the average with the next frame echo data according to steps (1-1) to (1-5);

[0064] (2) When the bolt is in a state without pre-tightening force, and according to the transverse and longitudinal wave waveforms of the bolt drawn in real time in step (1), the transverse and longitudinal wave echo envelopes are searched respectively from the trailing edge of the starting wave by the electromagnetic ultrasonic pre-tightening force measurement system, and the transverse and longitudinal wave echo envelopes are automatically identified by the peak value algorithm, and one of the wave peak sound times is selected as the ultrasonic sound time to be monitored, and the transverse wave peak sound time and the longitudinal wave peak sound time in the transverse and longitudinal wave echo envelopes of the bolt without pre-tightening force time period are calculated; and the transverse wave ultrasonic sound time of the bolt without pre-tightening force time period is stored as , longitudinal ultrasonic sound is stored as ;

[0065] (3) Apply different preload forces to the bolts in sequence through a material stretching machine , and according to the transverse and longitudinal wave waveforms of the bolt drawn in real time in step (1), the transverse and longitudinal wave echo envelopes are searched respectively from the trailing edge of the starting wave through the electromagnetic ultrasonic preload measurement system, the transverse and longitudinal wave echo envelopes are automatically identified through the peak algorithm, and one of the wave peak sound times is selected as the ultrasonic sound time to be monitored, and the transverse wave peak sound time and the longitudinal wave peak sound time in the transverse and longitudinal wave echo envelopes of the bolt preload time period are calculated; the transverse wave ultrasonic sound time of the bolt preload time period is stored as , longitudinal ultrasonic sound is stored as ;

[0066] (4) The electromagnetic ultrasonic preload force measurement system is used to calculate and record the transverse and longitudinal wave acoustic time ratios of the bolts at different preload time periods. The calibration curve of the relationship between the preload force and the transverse and longitudinal wave acoustic time ratio of this type of bolt is obtained by fitting the electromagnetic ultrasonic preload force measurement system (such as Figure 3 As shown in Figure 2), the mathematical function relationship between the preload force and the transverse and longitudinal wave sound time ratio is obtained using the calibration curve: , where F is the bolt preload, k is the calibration factor (curve slope), is the acoustic time ratio of transverse and longitudinal waves in the bolt, b is the intercept of the calibration curve (constant);

[0067] (5) Use the electromagnetic ultrasonic preload force measurement system to measure the transverse and longitudinal wave acoustic time ratios of other bolts of the same model and specification. , according to the formula It is possible to measure the preload force of other bolts of the same model and specification.

[0068] The above steps (1-2) perform a division operation through the divider (b) to calculate the intermediate data B, thereby reducing the complexity of subsequent calculations.

[0069] The above steps (1-3) perform subtraction operations through a subtractor (c), which reduces the amount of data that needs to be processed each time and improves the calculation speed.

[0070] The above steps (1-4) perform a division operation through a divider (k) to ensure the accuracy of the new data K.

[0071] The above steps (1-5) are added by the adder (e) to update the average data in real time, ensuring that the average data E output each time is real-time and accurate.

[0072] In the above steps (1-2), when the system is initialized, the historical accumulated data A in the storage space (a) is 0, that is, A = 0. This is because the system has no historical data when it is initialized, so the data in the storage space (a) is empty or initialized to 0, which can ensure that there is no interference from any historical data when the system starts working.

[0073] In step (1-3), after the system is initialized, the first frame echo data received by the electromagnetic ultrasonic probe (i) for the first time is converted into digital signal data D through the amplifier and analog-to-digital converter (d) to obtain digital signal data After the system is initialized, when the historical accumulated data A in the storage space (a) is 0 and N=1, the average data in the steps (1-6) Therefore, after the first input, that is, when N=1, the valid echo data in the first frame echo data is , and its random noise is .

[0074] In step (1-3), when the electromagnetic ultrasonic probe (i) receives the second frame echo data for the second time, it is converted into digital signal data D through the amplifier and analog-to-digital converter (d) to obtain digital signal data At this time, the historical accumulated data A in the storage space (a) is the average data stored in the process of receiving the first frame echo data for the first time, that is, , when N=2, the average data in steps (1-6) is Since the valid echo data in the frame echo data is , the echo data of each frame is close to the same, and in general, the effective echo data are basically the same, that is, , the formula for the above average data is simplified to Therefore, after the second input, that is, when N=2, the valid echo data in the second frame echo data is still , and its random noise is .

[0075] In step (1-3), when the third frame echo data received by the electromagnetic ultrasonic probe (i) for the third time is converted into digital signal data D through the amplifier and analog-to-digital converter (d), the digital signal data D is obtained. At this time, the historical accumulated data A in the storage space (a) is the average data stored in the process of receiving the second frame echo data for the second time, that is, , when N=3, the average data in steps (1-6) is Since the valid echo data in the frame echo data is , the echo data of each frame is close to the same, and in general, the effective echo data are basically the same, that is, , the formula for average data is simplified to Therefore, after the third input, that is, when N=3, the valid echo data in the third frame echo data is still , and its random noise is .

[0076] Of course, N can be 4, 5, ..., 100, ..., and the valid echo data in the Nth frame echo data is still , and its random noise will not be listed and calculated here one by one.

[0077] Assume that the random noise in each frame echo data are independent and identically distributed, with a mean of 0 and a variance of We can calculate the variance of these random noises to compare their magnitudes.

[0078] When N=1, the variance of random noise is .

[0079] When N=2, the variance of random noise is .

[0080] When N=3, the variance of random noise is .

[0081] By comparing these variances, we can see that ,It can be seen that with the increase of N inputs, the variance of random noise gradually decreases, which indicates that the influence of random noise also gradually decreases, which means that with the increase of N, the proportion of effective signals in the average data increases, while the proportion of random noise decreases, thereby improving the signal-to-noise ratio of the data.

[0082] In step (2), the steps of automatically identifying the shear wave peak sound time and the longitudinal wave peak sound time in the shear and longitudinal wave echo envelopes during the bolt no pre-tightening time period are as follows:

[0083] (2-1) The peak algorithm is used to automatically identify the two most continuous cycles of transverse and longitudinal wave echo envelopes during the bolt preload-free period;

[0084] (2-2) Record the shear wave peak sound time and the longitudinal wave peak sound time of the two-cycle transverse and longitudinal wave echo envelopes identified in step (2-1), sort them in chronological order, and store the shear wave peak sound time of the two-cycle transverse and longitudinal wave echo envelopes as , the longitudinal wave peak sound time of the two-cycle transverse and longitudinal wave echo envelope is stored as ;

[0085] (2-3) Select the first peak sound time from the shear wave peak sound time and the longitudinal wave peak sound time of the two-cycle shear and longitudinal wave echo envelope in step (2-2) respectively. When used as the designated monitoring ultrasonic sound;

[0086] In the step (3), the steps of automatically identifying the shear wave peak sound time and the longitudinal wave peak sound time in the shear and longitudinal wave echo envelopes during the bolt pre-tightening time period are as follows:

[0087] (3-1) The peak algorithm is used to identify the two consecutive cycles of transverse and longitudinal wave echo envelopes during the bolt preload period;

[0088] (3-2) Record the shear wave peak sound time and the longitudinal wave peak sound time of the two-cycle transverse and longitudinal wave echo envelopes identified in step (3-1), sort them in chronological order, and store the shear wave peak sound time of the two-cycle transverse and longitudinal wave echo envelopes as , the longitudinal wave peak sound time of the two-cycle transverse and longitudinal wave echo envelope is stored as ;

[0089] (3-3) Select the first peak sound time from the shear wave peak sound time and the longitudinal wave peak sound time of the two-cycle shear and longitudinal wave echo envelope in step (3-2) respectively. When used as the designated monitored ultrasonic sound.

[0090] like Figure 4As shown, the electromagnetic ultrasonic probe (i) comprises a shell 1 and an upper cover 2, as well as a wear-resistant layer 3, a coil 4, a sound insulation layer 9, a magnet 5 and a circular magnetic conductive block 6 arranged in the shell 1. The upper part of the shell 1 is provided with an upper end opening, the lower part of the shell 1 is provided with a lower end detection port, and the upper cover 2 is closed in the upper end opening; a wire clamp 7 is provided on the outer surface of the shell 1, and a probe wire 8 is provided in the wire clamp 7; the magnet 5 is an annular magnet 5 whose magnetic lines of force are uniformly radiated from the inner diameter to the outer diameter; the wear-resistant layer 3, the coil 4, the sound insulation layer 9, the magnet 5 and the circular magnetic conductive block 6 are arranged in the shell 1; the upper part of the shell 1 is provided with an upper end opening, the lower part of the shell 1 is provided with a lower end detection port, and the upper cover 2 is covered in the upper end opening; a wire clamp 7 is provided on the outer surface of the shell 1, and a probe wire 8 is provided in the wire clamp 7; the magnet 5 is an annular magnet 5 whose magnetic lines of force are uniformly radiated from the inner diameter to the outer diameter; the wear-resistant layer 3, the coil 4, the sound insulation layer 9, the magnet 5 and the circular magnetic conductive block 6 are arranged in the shell 1 ... magnetic conductive block 6, the magnetic conductive block 6, the magnetic conductive block 6, the magnetic conductive block 6, the magnetic conductive block 6, the magnetic conductive block 6, the magnetic conductive 9. The annular magnet 5 and the circular magnetic conductive block 6 are sequentially arranged in the shell 1 from bottom to top. The wear-resistant layer 3, the coil 4, the sound insulation layer 9 and the circular magnetic conductive block 6 are all arranged coaxially with the annular magnet 5. The wear-resistant layer 3 is in the lower end detection port, and the lower surface of the circular magnetic conductive block 6 is on the upper surface of the annular magnet 5. There is a gap 11 between the inner wall of the shell 1 and the outer wall of the annular magnet 5. A lead 12 is arranged in the gap 11, and the probe line 8 is electrically connected to the coil 4 through the lead 12. The gap 11 between the inner wall of the shell 1 and the outer wall of the annular magnet 5 is used to place the lead 12, and the lead 12 connects the coil 4 to an external signal processing device to achieve signal transmission. When the electromagnetic ultrasonic transverse and longitudinal wave probe is used to measure the preload force close to the bolt, the coil 4 generates an alternating magnetic field after being energized. The alternating magnetic field interacts with the static magnetic field generated by the annular magnet 5 to generate a Lorentz force, thereby exciting ultrasonic waves in the bolt surface. Since the magnetic force lines of the annular magnet 5 are uniformly radiated from the inner diameter to the outer diameter, the radial magnetic field generated by the annular magnet 5 is relatively strong, which can effectively excite the longitudinal wave in the bolt, while the axial magnetic field generated by the annular magnet 5 is relatively weak, which helps to reduce the interference of the transverse wave and improve the excitation effect of the longitudinal wave. This design is particularly suitable for bolts with a hollow end center, such as hexagon socket bolts, because the radial magnetic field can produce a stronger excitation effect on a smaller contact surface.

[0091] When the probe directly contacts the end face of the bolt, the wear-resistant layer is used to protect the internal structure of the electromagnetic ultrasonic transverse and longitudinal wave probe from being damaged.

[0092] The circular magnetic conductive block 6 is located on the upper surface of the annular magnet 5, which can concentrate and optimize the distribution of the magnetic field, making the interaction between the alternating magnetic field generated by the coil 4 and the static magnetic field more efficient, which not only enhances the excitation effect of the longitudinal wave, but also improves the excitation effect of the transverse wave, thereby improving the utilization rate of the magnetic field.

[0093] The outer diameter of the sound insulation layer 9 is greater than or equal to the outer diameter of the annular magnet 5. The outer diameter of the sound insulation layer 9 is greater than or equal to the outer diameter of the annular magnet 5, which can ensure that the sound insulation layer 9 completely covers the annular magnet 5, reduce the interference of the annular magnet 5 on the alternating magnetic field generated by the coil 4, improve the stability of the magnetic field, and also reduce the interference of external noise on the signal, improve the quality of the signal and the signal-to-noise ratio, thereby improving the precision and accuracy of the measurement.

[0094] The sound insulation layer 9 is made of a metallic conductive material.

[0095] Embodiment 2, as Figure 5 As shown, the difference between this embodiment and embodiment 1 is that: in step (2), the steps of automatically identifying the shear wave peak sound time and the longitudinal wave peak sound time in the shear and longitudinal wave echo envelopes in the bolt without pre-tightening force time period are as follows:

[0096] (2-1) The peak algorithm is used to automatically identify the highest continuous three-cycle transverse and longitudinal wave echo envelopes during the bolt no pre-tightening period;

[0097] (2-2) Record the shear wave peak sound time and the longitudinal wave peak sound time of the three-cycle transverse and longitudinal wave echo envelopes identified in step (2-1), sort them in chronological order, and store the shear wave peak sound time of the three-cycle transverse and longitudinal wave echo envelopes as , the longitudinal wave peak sound time of the three-cycle transverse and longitudinal wave echo envelope is stored as ;

[0098] (2-3) Select the second peak sound time from the shear wave peak sound time and the longitudinal wave peak sound time of the three-cycle shear and longitudinal wave echo envelope in step (2-2) respectively. When used as the designated monitoring ultrasonic sound;

[0099] In the step (3), the steps of automatically identifying the shear wave peak sound time and the longitudinal wave peak sound time in the shear and longitudinal wave echo envelopes during the bolt pre-tightening time period are as follows:

[0100] (3-1) The peak algorithm is used to identify the highest three consecutive cycles of transverse and longitudinal wave echo envelopes during the bolt preload period;

[0101] (3-2) Record the shear wave peak sound time and the longitudinal wave peak sound time of the three-cycle transverse and longitudinal wave echo envelopes identified in step (3-1), sort them in chronological order, and store the shear wave peak sound time of the three-cycle transverse and longitudinal wave echo envelopes as , the longitudinal wave peak sound time of the three-cycle transverse and longitudinal wave echo envelope is stored as ;

[0102] (3-3) Select the second peak sound time from the shear wave peak sound time and the longitudinal wave peak sound time of the three-cycle shear and longitudinal wave echo envelope in step (3-2) respectively. When used as the designated monitored ultrasonic sound.

[0103] The identified j period echo envelopes can be expanded to 3 or more, and the data of multiple period echo envelopes can be cross-validated to more accurately capture the characteristics of the echo envelope and reduce measurement errors.

[0104] Embodiment 3, as Figure 6-7As shown, the difference between this embodiment and embodiment 1 is that: a magnetic column 61 is provided at the center of the lower surface of the circular magnetic block 6, and the magnetic column 61 is perpendicular to the lower surface of the circular magnetic block 6. A through hole 51 is provided at the center of the annular magnet 5, which passes through from top to bottom. The magnetic column 61 is in the through hole 51 and is arranged coaxially with the annular magnet 5. The magnetic column 61 can concentrate and guide the magnetic field, so that the distribution of the magnetic field on the end face of the bolt is more concentrated, and the excitation effect of the transverse wave and the longitudinal wave is improved. The length of the magnetic column 61 can be adjusted to achieve the best conversion efficiency of the transverse wave and the longitudinal wave of the end faces of different hexagon socket bolts. When the length of the magnetic column 61 is increased, the magnetic column 61 can be made to penetrate deeper into the through hole 51 of the annular magnet 5, thereby enhancing the concentration of the magnetic field and improving the excitation effect of the longitudinal wave. It is suitable for bolts with hollow end faces, such as hexagon socket bolts. When the length of the magnetic pole 61 is reduced, the distance between the magnetic pole 61 and the annular magnet 5 can be increased, the concentration of the magnetic field is weakened, the strength of the axial magnetic field is increased, and the excitation effect of the transverse wave is improved, which is suitable for bolts with larger end faces.

[0105] In addition, it should be noted that the names of the various parts of the specific embodiments described in this specification may be different, and any equivalent or simple changes made based on the structure, features and principles described in the patent concept of the present invention are included in the protection scope of the patent of the present invention. The technicians in the technical field of the present invention can make various modifications or supplements to the specific embodiments described or replace them in a similar manner, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A bolt preload test method based on an electromagnetic ultrasonic preload measurement system, characterized in that The steps include: (1) An electromagnetic ultrasonic probe (i) is placed on the end face of a bolt, and the electromagnetic ultrasonic probe (i) is used to excite the transverse and longitudinal waves of the bolt. The electromagnetic ultrasonic preload force measurement system receives the transverse and longitudinal wave data of the bolt transmitted multiple times, and stores the transverse and longitudinal wave data of the bolt in a storage space (a). In the storage space (a), a data averaging algorithm is used to calculate and average the transverse and longitudinal wave data of the bolt received multiple times, and a waveform diagram of the transverse and longitudinal waves of the bolt received each time is drawn in real time. The calculation steps of the above data averaging algorithm are as follows: (1-1) The Nth frame echo data received by the electromagnetic ultrasonic probe (i) is converted into digital signal data D through an amplifier and an analog-to-digital converter (d). The digital signal data D is expressed as , k represents the number of data points received by the probe per frame, and then Decompose into valid echo data and random noise , get digital signal data ; (1-2) Storage space (a) The historical accumulated data A stored is divided into two data paths: The first data path is to read the historical accumulated data A from the storage space (a), and then pass the historical accumulated data A through the divider (b) through the Nth input to obtain the intermediate data ; The second data path is to directly read the historical accumulated data A from the storage space (a); (1-3) The historical accumulated data A obtained from the second data channel and the intermediate data B obtained from the first data channel are calculated by the subtractor (c) to obtain the historical data ; (1-4) Through the Nth input, the digital signal data D in step (1-1) is calculated by the divider (k) to obtain the new data ; (1-5) The historical data C in step (1-3) and the new data K in step (1-4) are calculated by adder (e) to obtain the average data ; (1-6) The average data E is output as the measurement result; at the same time, the average data E is saved again to the storage space (a), the original historical accumulated data A is overwritten, and the storage space (a) stores the new historical accumulated data A, and the new historical accumulated data A is used to recalculate the average with the next frame echo data according to steps (1-1) to (1-5); (2) When the bolt is in a state without pre-tightening force, and according to the transverse and longitudinal wave waveforms of the bolt drawn in real time in step (1), the transverse and longitudinal wave echo envelopes are searched respectively from the trailing edge of the starting wave by the electromagnetic ultrasonic pre-tightening force measurement system, and the transverse and longitudinal wave echo envelopes are automatically identified by the peak value algorithm, and one of the wave peak sound times is selected as the ultrasonic sound time to be monitored, and the transverse wave peak sound time and the longitudinal wave peak sound time in the transverse and longitudinal wave echo envelopes of the bolt without pre-tightening force time period are calculated; and the transverse wave ultrasonic sound time of the bolt without pre-tightening force time period is stored as , longitudinal ultrasonic sound is stored as ; (3) Apply different preload forces to the bolts in sequence through a material stretching machine , and according to the transverse and longitudinal wave waveforms of the bolt drawn in real time in step (1), the transverse and longitudinal wave echo envelopes are searched respectively from the trailing edge of the starting wave through the electromagnetic ultrasonic preload measurement system, the transverse and longitudinal wave echo envelopes are automatically identified through the peak algorithm, and one of the wave peak sound times is selected as the ultrasonic sound time to be monitored, and the transverse wave peak sound time and the longitudinal wave peak sound time in the transverse and longitudinal wave echo envelopes of the bolt preload time period are calculated; the transverse wave ultrasonic sound time of the bolt preload time period is stored as , longitudinal ultrasonic sound is stored as ; (4) The electromagnetic ultrasonic preload force measurement system is used to calculate and record the transverse and longitudinal wave acoustic time ratios of the bolts at different preload time periods. The calibration curve of the relationship between the preload force and the transverse and longitudinal wave sound time ratio applied by the bolt of this model specification is fitted by the electromagnetic ultrasonic preload force measurement system. The mathematical function relationship between the preload force and the transverse and longitudinal wave sound time ratio is obtained by using the calibration curve: , where F is the bolt preload, k is the calibration coefficient, is the acoustic time ratio of the transverse and longitudinal waves in the bolt, and b is the intercept of the calibration curve; (5) Use the electromagnetic ultrasonic preload force measurement system to measure the transverse and longitudinal wave acoustic time ratios of other bolts of the same model and specification. , according to the formula It is possible to measure the preload force of other bolts of the same model and specification.

2. The bolt preload force testing method based on the electromagnetic ultrasonic preload force measurement system according to claim 1, characterized in that: In the step (2), the steps of automatically identifying the shear wave peak sound time and the longitudinal wave peak sound time in the shear and longitudinal wave echo envelopes during the bolt no pre-tightening time period are as follows: (2-1) The peak algorithm is used to automatically identify the highest continuous j-cycle transverse and longitudinal wave echo envelopes during the bolt no pre-tightening period; (2-2) Record the shear wave peak sound time and the longitudinal wave peak sound time of the j-period shear and longitudinal wave echo envelopes identified in step (2-1), sort them in chronological order, and store the shear wave peak sound time of the j-period shear and longitudinal wave echo envelopes as , the longitudinal wave peak sound time of the j-cycle transverse and longitudinal wave echo envelope is stored as ; (2-3) Selecting the Nth peak sound time from the shear wave peak sound time and the longitudinal wave peak sound time of the j-period shear and longitudinal wave echo envelopes in step (2-2) as the designated ultrasonic sound time to be monitored, N≧1; In the step (3), the steps of automatically identifying the shear wave peak sound time and the longitudinal wave peak sound time in the shear and longitudinal wave echo envelopes during the bolt pre-tightening time period are as follows: (3-1) The peak algorithm is used to identify the highest continuous j-cycle transverse and longitudinal wave echo envelopes during the bolt preload period; (3-2) Record the shear wave peak sound time and the longitudinal wave peak sound time of the j-period transverse and longitudinal wave echo envelopes identified in step (3-1), sort them in chronological order, and store the shear wave peak sound time of the j-period transverse and longitudinal wave echo envelopes as , the longitudinal wave peak sound time of the j-cycle transverse and longitudinal wave echo envelope is stored as ; (3-3) Select the Nth peak sound time from the shear wave peak sound time and the longitudinal wave peak sound time of the j-period shear and longitudinal wave echo envelopes in step (3-2) as the designated ultrasonic sound time to be monitored, N≧1.

3. The bolt preload force testing method based on the electromagnetic ultrasonic preload force measurement system according to claim 1, characterized in that: The electromagnetic ultrasonic probe (i) comprises a shell and an upper cover, as well as a wear-resistant layer, a coil, a sound insulation layer, a magnet and a circular magnetic conductive block arranged in the shell; the upper part of the shell is provided with an upper end opening, the lower part of the shell is provided with a lower end detection port, and the upper cover is closed in the upper end opening; a wire clamp is provided on the outer surface of the shell, and a probe wire is provided in the wire clamp; the magnet is an annular magnet whose magnetic lines of force radiate uniformly from the inner diameter to the outer diameter; the wear-resistant layer, the coil, the sound insulation layer, the annular magnet and the circular magnetic conductive block are arranged in the shell from bottom to top in sequence, the wear-resistant layer, the coil, the sound insulation layer and the circular magnetic conductive block are all arranged coaxially with the annular magnet, the wear-resistant layer is in the lower end detection port, and the lower surface of the circular magnetic conductive block is on the upper surface of the annular magnet; there is a gap between the inner wall of the shell and the outer wall of the annular magnet, a lead wire is provided in the gap, and the probe wire is electrically connected to the coil through the lead wire.

4. The bolt preload force testing method based on the electromagnetic ultrasonic preload force measurement system as claimed in claim 3, characterized in that: A magnetic column is provided at the center of the lower surface of the circular magnetic block, which is perpendicular to the lower surface of the circular magnetic block. A through hole is provided at the center of the annular magnet, which passes through the through hole. The magnetic column is located in the through hole and is coaxially arranged with the annular magnet.

5. The bolt preload force testing method based on the electromagnetic ultrasonic preload force measurement system as claimed in claim 3, characterized in that: The outer diameter of the sound insulation layer is greater than or equal to the outer diameter of the annular magnet.

6. The bolt preload force testing method based on the electromagnetic ultrasonic preload force measurement system as claimed in claim 5, characterized in that: The sound insulation layer is made of conductive metal material.

7. The bolt preload force testing method based on the electromagnetic ultrasonic preload force measurement system as claimed in claim 6, characterized in that: The metal conductive material is copper, aluminum alloy or iron.

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