An anti-slip ability evaluation method for the connection of a combined rotor bolt group

Abstract

The present invention is directed to a connection structure of a combined rotor bolt group, and discloses a method for evaluating the anti-slip ability of the connection of the combined rotor bolt group. Starting from ultrasonic detection technology, based on the measured pre-tightening force distribution of the rotor bolts, according to Coulomb's friction law, the local friction force under the action of the pre-tightening force is solved, and according to the phases of the bolts, the obtained local friction forces are vectorially summed to establish a calculation method for evaluating the anti-slip ability of the connection of the combined rotor bolt group. This method can be used to evaluate whether the bolt group after tightening meets the anti-slip performance requirements of the connection structure, and at the same time, the positions where slip and dislocation are likely to occur in the bolt group connection can also be determined by this method, which has important guiding significance for further improving the stability of the combined rotor bolted structure.

Description

Technical Field

[0001] The present invention relates to a method for evaluating the anti-slip ability of a combined rotor bolt group connection, in particular to a method for evaluating the anti-slip ability of a bolt group connection of a high-pressure turbine rotor of an aero-engine. Background Art

[0002] Bolt group connection is a typical connection form in rotating machinery such as aero-engines and wind power equipment. Due to the existence of assembly eccentricity unbalance and usually being in a high-temperature and high-pressure environment during the service stage, it is inevitable to cause slip and misalignment at the connection interface. If the anti-slip ability of the rotor bolt group connection is not considered, it will lead to interface slip wear, vibration exceeding the standard, etc. of the assembled rotor during the service stage, affecting the stable operation of the equipment. Therefore, in the process of analyzing the assembly of a combined rotor, it is particularly important to effectively evaluate the anti-slip ability of the bolt group connection.

[0003] The distribution of bolt pre-tightening force is an important factor affecting the slip of the rotor connection interface. For a long time, scholars at home and abroad have carried out a large number of studies on the process methods to improve the consistency of bolt pre-tightening force distribution, such as controlling bolt tightening methods (torque-angle method, elongation control method, etc.), bolt tightening sequences (cross method, star tightening method, etc.), and the number of tightening passes. With the improvement of testing technology, it is currently possible to accurately test the bolt pre-tightening force through ultrasonic testing equipment. However, few people have studied the anti-slip ability of the bolt group connection after tightening, and the anti-slip ability is crucial for the stability of rotor assembly performance. Therefore, in order to effectively improve the anti-slip ability of the rotor bolt group connection, there is an urgent need for a method for evaluating the anti-slip ability of the rotor bolt group connection based on accurate pre-tightening force testing.

[0004] To solve the above problems, starting from ultrasonic testing technology, based on the measured pre-tightening force distribution of the rotor bolts, according to Coulomb's friction law, the local friction force under the action of the pre-tightening force is solved, and the obtained local friction forces are vectorially summed according to the phases of each bolt, and a calculation model for evaluating the anti-slip ability of the combined rotor bolt group connection is established. Summary of the Invention[[ID=!7]]

[0005] The main object of the present invention is to provide a calculation model for evaluating the anti-slip ability of a rotor bolt group connection, so as to realize the evaluation of the anti-slip ability of the bolt group connection.

[0006] A method for evaluating the anti-slip ability of a combined rotor bolt group connection comprises the following steps:

[0007] 1) Stack and assemble the combined rotor according to the assembly drawing, determine the 0 phase of the combined rotor, with the counterclockwise direction as the positive direction. And number the ultrasonic intelligent bolts in sequence as 1, 2,... i,... n-1, n.

[0008] 2) Place the ultrasonic smart bolt into the bolt hole of the combined rotor, with the bolt at phase 0 numbered 1. The bolt numbers increase in counterclockwise order. Tighten the ultrasonic smart bolt using the specified tightening process.

[0009] 3) After the bolts are tightened, let them stand for 15 minutes until the self-relaxation process of the bolts is basically completed. Then, use the ultrasonic bolt preload intelligent detection system to detect the preload force of each bolt. The detection process is as follows:

[0010] Place the ultrasonic probe on the head of the ultrasonic smart bolt and make the probe contact the piezoelectric ceramic piece on the top of the ultrasonic smart bolt. At this time, the waveform is displayed on the oscilloscope and transmitted to the computer through the data transmission line. After being processed by the bolt preload detection software, the preload of the numbered bolt is obtained and recorded. Repeat the above steps to complete the preload detection of all bolts.

[0011] 4) Based on the preload force of each numbered bolt obtained in step 3), calculate the radial friction force f at each numbered bolt i .

[0012] The calculation method is as follows:

[0013] By consulting relevant data, we can obtain the friction coefficient of the combined rotor mating surface as μ. According to Coulomb's friction law, the radial friction force at each numbered bolt is:

[0014] f i =μ×N i i=1、2…n-1、n

[0015] 5) Based on the radial friction force at each numbered bolt obtained in step 4), vector summation is performed according to the phase relationship between the bolts to obtain the weighted radial friction force at each numbered bolt.

[0016] The calculation method is as follows:

[0017] For the combined rotor bolt group, the phase angle of each numbered bolt is:

[0018] θ i =(i-1)*2π / ni=1, 2…n-1, n

[0019] The friction force at each numbered bolt is weighted and summed according to the phase angle. The friction force at each numbered bolt after weighted summation is:

[0020]

[0021] 6) Based on the weighted friction force values at each numbered bolt obtained in step 5), find the bolt number with the smallest friction force value after weighted summation. The position of the bolt with this number is the weak part prone to slip dislocation. Subtract the smallest friction force value from the largest one, and use the difference ΔF between the two as an evaluation index for the anti-slip ability of the combined rotor bolt group connection, that is:

[0022] ΔF = max(F i ) - min(F i ) i = 1, 2…n - 1, n

[0023] 7) According to the ΔF obtained in step 6), compare it with the rated ΔF ed obtained through the bolt group process experiment, and then judge whether the anti-slip ability of the bolt group connection after tightening meets the standard.

[0024] The judgment basis is:

[0025] If ΔF < ΔF ed , the anti-slip ability of the bolt group connection after tightening meets the standard; if ΔF > ΔF ed , the anti-slip ability of the bolt group connection after tightening does not meet the standard.

[0026] 8) It is also possible to evaluate the quality of different bolt pre-tightening force distributions obtained under the same combined rotor connection structure and tightening process by comparing the magnitudes of the ΔF values.

[0027] The analysis method is:

[0028] Execute steps 4), 5), and 6) to obtain the ΔF values of different bolt pre-tightening force distributions. The smaller the ΔF value, the stronger the anti-slip ability of the bolt group connection under this pre-tightening force distribution; conversely, the weaker the anti-slip ability of the bolt group connection under this pre-tightening force distribution.

[0029] Advantages of the present invention: The present invention proposes an evaluation method for the anti-slip ability of the connection interface considering the characteristics of the pre-tightening force distribution for the combined rotor bolt group connection structure. This method can be used to evaluate whether the bolt group after tightening meets the anti-slip performance requirements of the connection structure. At the same time, it can also determine the positions prone to slip dislocation in the bolt group connection through this method, which has important guiding significance for further improving the stability of the combined rotor bolted structure. Description of the Drawings

[0030] Figure 1 is a simulated rotor assembly drawing.

[0031] Figure 2 is a schematic diagram of an ultrasonic intelligent bolt.

[0032] Figure 3 is a schematic diagram of the bolt number sequence.

[0033] Figure 4 is the radial frictional force at each numbered bolt.

[0034] Figure 5 is the weighted radial frictional force at each numbered bolt.

[0035] Figure 6 are 8 groups of bolt pre-tightening forces generated by the Gaussian method; a - example 1; b - example 2; c - example 3; d - example 4; e - example 5; f - example 6; g - example 7; h - example 8.

[0036] Figure 7 are the corresponding calculated weighted frictional forces; a - example 1; b - example 2; c - example 3; d - example 4; e - example 5; f - example 6; g - example 7; h - example 8.

[0037] In the figure: 1 - front axle disc; 2 - intermediate rotor disc; 3 - ultrasonic intelligent bolt; 4 - nut; 5 - rear axle disc; 6 - top electrode; 7 - piezoelectric ceramic sheet; 8 - bottom electrode; 9 - top slotted bolt; 10 - adhesive. Specific implementation manners

[0038] To describe the purpose, technical solutions and advantages of the present invention more clearly, taking an aviation engine simulated combined rotor as an example below, in combination with the attached drawings in the examples of the present invention, the technical solutions in the present invention will be described completely.

[0039] The assembly drawing of the aviation engine simulated rotor is as Figure 1 shown. First, fix the rear axle disc of the rotor on the vertical assembly platform, then place the intermediate disc on the top of the rear axle disc and align the bolt holes, and finally place the front axle disc of the rotor on the top of the intermediate disc and align the bolt holes.

[0040] The bolts used in the assembly of the simulated combined rotor are piezoelectric ceramic intelligent bolts, as Figure 2 shown. Number all 36 M8 intelligent bolts, and put the numbered intelligent bolts into the bolt holes in sequence. Let the No. 1 bolt be at the initial 0-phase position, and the counterclockwise direction be the positive direction, as Figure 3 shown.

[0041] Use the torque-rotation angle method to tighten the intelligent bolts at the connection part of the high-pressure turbine rotor of the aviation engine. After all are tightened, let it stand for 15 minutes.

[0042] After the short-term relaxation process of the bolts ends, place the ultrasonic probes on the piezoelectric ceramic intelligent bolts in sequence according to the numbers, measure and record the bolt pre-tightening forces.

[0043] Refer to the friction coefficient of the mating surface of the combined rotor according to the material, heat treatment method, and surface roughness of the rotor. It is known that the friction coefficient μ at the mating interface of the combined rotor is 0.1. Based on the pre-tightening forces of the bolts with various numbers obtained, use the method in Step 4 to calculate the radial frictional forces at the bolts with various numbers. The calculation results are as Figure 4 shown.

[0044] Use the method in Step 5 to perform weighted averaging on the radial frictional forces at the bolts with various numbers, and use Matlab software to plot the weighted radial frictional force curves at the bolts with various numbers, as Figure 5 shown.

[0045] Use the method in Step 6 to obtain the bolt number 8 that is prone to slip and dislocation after the combined rotor is tightened. The phase angle at this bolt number is 70°. And through calculation, obtain the weighted frictional force difference ΔF = 340.9 N, and use the magnitude of ΔF to evaluate the anti-slip ability of the bolt connection system.

[0046] In addition to obtaining the pre-tightening forces of the bolt group through testing, the pre-tightening forces of multiple groups of bolts can also be randomly generated by means of computer numerical simulation. Relevant data shows that the pre-tightening forces of the bolt group have a Gaussian distribution characteristic. In order to compare the advantages and disadvantages of the anti-slip abilities of different pre-tightening force distributions, use computer simulation to obtain the pre-tightening forces of 8 groups of 48-bolt groups with Gaussian distribution characteristics. The randomly generated pre-tightening forces are as Figure 6 shown, and the weighted frictional forces are as Figure 7 shown. Determine the weak bolt numbers, phase angles, and frictional force differences ΔF of different bolt groups according to Steps 2, 3, and 4, as shown in Table 1:

[0047] Bolt group serial number Weak bolt number Phase angle (°) Friction force difference ΔF (N) A 8 70 173.4 B 29 280 201.4 C 33 320 418.8 D 13 120 287.3 E 24 230 155.8 F 10 90 875.3 G 4 30 458.8 H 10 90 415.5

[0048] According to the description in Step 5, through the data in Table 1, it can be clearly seen that the pre-tightening force distribution of Group E bolts has better anti-slip ability.

Claims

1. A method for evaluating the anti-slip ability of a combined rotor bolt group connection, characterized in that, The steps are as follows: 1) Stack and assemble the combined rotor according to the assembly drawing, determine the 0-phase of the combined rotor, with the counterclockwise direction as the positive direction, and number the ultrasonic intelligent bolts as 1, 2, … i, … n-1, n in sequence; 2) Place the ultrasonic intelligent bolts into the bolt holes of the combined rotor, with the bolt number at the 0-phase being 1, and the bolt numbers increasing in sequence according to the counterclockwise order; tighten the ultrasonic intelligent bolts using the specified tightening process; 3) After the bolts are tightened, let it stand for 15 minutes until the self-relaxation process of the ultrasonic intelligent bolts ends, and then use the ultrasonic bolt pre-tightening force intelligent detection system to detect the pre-tightening force of each ultrasonic intelligent bolt. The detection process is as follows: Place the ultrasonic probe on the head of the ultrasonic intelligent bolt, make the ultrasonic probe contact the piezoelectric ceramic chip at the top of the ultrasonic intelligent bolt. At this time, a waveform is displayed on the oscilloscope and transmitted to the computer through the data transmission line. After being processed by the bolt pre-tightening force detection software, the pre-tightening force of the ultrasonic intelligent bolt with this number is obtained and recorded. Repeat the above actions to complete the pre-tightening force detection work of all ultrasonic intelligent bolts; 4) Calculate the radial friction force f at each numbered ultrasonic intelligent bolt according to the pre-tightening force of each numbered ultrasonic intelligent bolt obtained in step 3). i ; The calculation method is as follows: Obtain the friction coefficient μ at the mating surface of the combined rotor by referring to relevant materials. According to Coulomb's friction law, the radial friction force at each numbered ultrasonic intelligent bolt is: f i = μ × N i , i = 1, 2… n-1, n 5) Based on the radial friction forces at each numbered ultrasonic intelligent bolt obtained in step 4), perform vector summation according to the phase relationship between the ultrasonic intelligent bolts to obtain the weighted radial friction forces at each numbered ultrasonic intelligent bolt; The calculation method is as follows: For the bolt group of the combined rotor, the phase angles of each numbered ultrasonic intelligent bolt are: θ i = (i - 1) * 2π / n, where i = 1, 2, …, n - 1, n Perform weighted summation of the friction forces at each numbered ultrasonic intelligent bolt according to the phase angle. The friction forces at each numbered ultrasonic intelligent bolt after weighted summation are: 6) Based on the weighted friction force values at each numbered ultrasonic intelligent bolt obtained in step 5), find the number of the ultrasonic intelligent bolt with the smallest friction force value after weighted summation. The position of this numbered ultrasonic intelligent bolt is the weak part prone to slip dislocation; and subtract the smallest friction force value from the largest friction force value, and use the difference ΔF between the two as the evaluation index for evaluating the anti-slip ability of the bolt group connection of the combined rotor, that is: ΔF = max(F i ) - min(F i ), i = 1, 2... n - 1, n 7) Based on the ΔF obtained in step 6), compare it with the rated ΔF ed to further determine whether the anti-slip capacity of the bolt group connection after tightening meets the standard; The judgment basis is: If ΔF < ΔF ed , the anti-slip capacity of the bolt group connection meets the standard after tightening. If ΔF > ΔF ed , the anti-slip capacity of the bolt group connection does not meet the standard after tightening; 8) Or evaluate the quality of the pre-tightening force distribution under the same combined rotor connection structure and bolt tightening process by comparing the magnitudes of the ΔF values; The analysis method is: Execute steps 4), 5), and 6) to obtain the ΔF values of different bolt pre-tightening force distributions. The smaller the ΔF value, the stronger the anti-slip ability of the bolt group connection under this pre-tightening force distribution, and vice versa, the weaker the anti-slip ability of the bolt group connection under this pre-tightening force distribution.

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