Pre-tightening force distribution uniformity quantitative evaluation method for bolt group connection rotor

Abstract

The invention provides a pre-tightening force distribution uniformity quantitative evaluation method for a bolt group connection rotor, and the method comprises the steps: S1, determining the number of bolts, carrying out the initial numbering, obtaining the pre-tightening force data of the bolts after the initial numbering, and calculating the mean value of the pre-tightening force of the bolts; the number of the bolts is increased, the bolts are renumbered, and the pre-tightening force values of the renumbered bolts are calculated; s2, constructing a generalized pixel value based on the bolt pre-tightening force value according to the renumbering of the bolt and the renumbered bolt pre-tightening force value; s3, constructing a generalized gray level co-occurrence matrix based on the generalized pixel values; and S4, standardizing the generalized gray-level co-occurrence matrix, calculating contrast texture features, and quantitatively evaluating the uniformity of pre-tightening force distribution of the bolt group according to the contrast texture features. The method not only considers the pre-tightening force value of the bolt, but also considers the spatial position of the bolt on the rotor connection interface, and can quantitatively and accurately evaluate the distribution uniformity of the pre-tightening force.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical engineering / measurement technology, and particularly relates to a method for quantitatively evaluating the uniformity of pre-tightening force distribution. Background Art

[0002] The connection of bolt groups is a typical connection form in rotor equipment such as aero-engines and large-scale wind power. Since the uniformity of pre-tightening force distribution is an important indicator for evaluating the connection quality of bolt groups. If the uniformity of bolt pre-tightening force distribution is ignored during the assembly process of bolt groups, it will lead to a rapid degradation of the interface bearing performance of mechanical equipment in a strong service environment, thereby affecting the stability of equipment operation. Therefore, in the process of assembling the rotor with bolt group connection, it is extremely important to effectively characterize the uniformity of pre-tightening force distribution of bolt groups.

[0003] The pre-tightening force distribution is an important factor for evaluating the interface bearing performance of bolt group connection structures. For a long time, domestic and foreign scholars have carried out a large number of studies on the tightening process methods of bolt groups to improve the uniformity of pre-tightening force distribution. And with the improvement of pre-tightening force testing technology, the accurate value of bolt pre-tightening force can be obtained through various methods (such as piezoelectric intelligent bolts, fiber optic intelligent bolts, etc.). However, in terms of the quantitative evaluation of the uniformity of bolt group pre-tightening force distribution, in actual assembly sites, it is still mainly characterized by mathematical statistical features such as mean, variance, and standard deviation. However, the above statistical features do not consider the spatial position distribution of each bolt in the actual rotor, often making different pre-tightening force distribution data have the same mathematical statistical features, thus unable to effectively evaluate the uniformity of pre-tightening force distribution of different bolt groups. Therefore, it is impossible to directly carry out quantitative evaluation of the uniformity of pre-tightening force distribution for the interface bearing performance of bolt group connection rotors.

[0004] The invention patent with the publication number of CN117408100A, a method for predicting the pre-tightening force distribution of group bolts based on BP neural network, uses the neural network after successful testing to predict the pre-tightening force distribution of group bolts under a given tightening sequence. At the same time, calculate the standard deviation value of the pre-tightening force after the group bolts are tightened, use it to evaluate the quality of the pre-tightening force distribution, and compare it with the design requirements to judge whether it meets the design requirements and determine whether to perform secondary tightening or replacement. The evaluation method of pre-tightening force distribution adopted in this invention is unable to effectively evaluate the uniformity of pre-tightening force distribution of different bolt groups in the face of complex bolt pre-tightening force data. Summary of the Invention

[0005] Aiming at the technical problem that the existing methods do not consider the spatial position distribution of each bolt in the actual rotor, resulting in different pre-tightening force distribution data having the same mathematical statistical features, thus unable to effectively evaluate the uniformity of pre-tightening force distribution of different bolt groups, the present invention proposes a method for quantitatively evaluating the uniformity of pre-tightening force distribution for bolt group connection rotors, which can quantitatively and accurately evaluate the uniformity of pre-tightening force distribution.

[0006] To achieve the above object, the technical solution of the present invention is implemented as follows:

[0007] A method for quantitatively evaluating the uniformity of pre-tightening force distribution for a bolt group-connected rotor, comprising the steps:

[0008] S1: Determine the number of bolts and perform an initial numbering, obtain the pre-tightening force data of the bolts after the initial numbering and calculate the average pre-tightening force N of the bolts mean ; Expand the number of bolts and re-number them, and calculate the pre-tightening force values of the bolts after re-numbering;

[0009] S2: Construct a generalized pixel value based on the pre-tightening force value of the bolt according to the re-numbering of the bolt and the pre-tightening force value of the bolt after re-numbering;

[0010] S3: Construct a generalized gray-level co-occurrence matrix based on the generalized pixel value;

[0011] S4: Standardize the generalized gray-level co-occurrence matrix and calculate the contrast texture feature, and quantitatively evaluate the uniformity of the pre-tightening force distribution of the bolt group according to the contrast texture feature.

[0012] Furthermore, the calculation formula for the pre-tightening force value of the bolt after re-numbering is:

[0013]

[0014] where j is the re-numbering of the bolt, and the value of j is {1, 2,..., m - 1, m}, m is the total number of bolts after expansion, and P j is the pre-tightening force value of the bolt numbered j after re-numbering, and N (j / 2) is the pre-tightening force value of the bolt numbered j / 2 at the time of initial numbering.

[0015] Furthermore, the method for constructing the generalized pixel value is:

[0016]

[0017] where round() represents the rounding function, and GP j is the jth generalized pixel value.

[0018] Furthermore, the method for constructing the generalized gray-level co-occurrence matrix based on the generalized pixel value is: construct generalized pixel pairs according to the generalized pixel value, calculate the order of the generalized gray-level co-occurrence matrix according to the generalized pixel value, and calculate the element G in the generalized gray-level co-occurrence matrix G according to the generalized pixel pair and the order of the generalized gray-level co-occurrence matrix x,y , j traverses from 1 to m to obtain the generalized gray-level co-occurrence matrix G.

[0019] Further, the method for constructing a generalized pixel pair based on the generalized pixel value is as follows: Define the j-th generalized pixel pair GP2 j containing the generalized pixel value GP j and the generalized pixel value GP J , where the subscript J of the generalized pixel value GP J ranges from 1 to m, and |j - J| = n, where n is the total number of bolts during the initial numbering.

[0020] Further, the method for calculating the order of the generalized gray-level co-occurrence matrix based on the generalized pixel value is as follows:

[0021]

[0022] where max() represents the maximum value function, and min() represents the minimum value function; the pixel interval the generalized pixel value set GP = {GP1, GP2, …, GP j , …, GP m}, and L is the order of the generalized gray-level co-occurrence matrix.

[0023] Further, the method for calculating the element G x,y in the generalized gray-level co-occurrence matrix G is as follows:

[0024]

[0025] where G x,y represents the element in the x-th row and y-th column of the generalized gray-level co-occurrence matrix G, and [x, y] is the element value.

[0026] The method for normalizing the generalized gray-level co-occurrence matrix is as follows:

[0027]

[0028] where represents the normalized generalized gray-level co-occurrence matrix.

[0029] Further, the method for calculating the contrast texture feature based on the generalized gray-level co-occurrence matrix is as follows:

[0030]

[0031] where CON is the contrast texture feature, is the element in the x-th row and y-th column of the normalized generalized gray-level co-occurrence matrix.

[0032] Furthermore, the method for quantitatively evaluating the uniformity of the pre-tightening force distribution of the bolt group based on the contrast texture feature is as follows: the smaller the value of the contrast texture feature CON, the better the uniformity of the pre-tightening force distribution of the bolt group; the larger the value of the contrast texture feature CON, the worse the uniformity of the pre-tightening force distribution of the bolt group.

[0033] The beneficial effects of the present invention are as follows:

[0034] The method for quantitatively evaluating the uniformity of the pre-tightening force distribution of the bolt group connecting the rotor proposed by the present invention overcomes the adverse factor that subsequent generalized pixel pair construction cannot be carried out when the number of bolt groups is odd by doubling the original number of bolt groups and re-numbering them, and defining the pre-tightening force data of the newly numbered bolts.

[0035] Through the construction of the generalized gray-level co-occurrence matrix and the calculation of the contrast texture feature, the pre-tightening force distribution data can be processed by image analysis methods, which not only considers the pre-tightening force values of the bolts, but also considers the spatial positions of the bolts on the rotor connection interface, overcoming the problem that traditional mathematical statistical features such as mean and variance cannot effectively evaluate the uniformity of the pre-tightening force distribution of multiple bolt groups with the same pre-tightening force value but different spatial distribution orders.

[0036] By constructing a generalized gray-level co-occurrence matrix based on the pre-tightening force data, extracting the contrast texture feature of the generalized gray-level co-occurrence matrix, and using this value to measure the uniformity of the pre-tightening force distribution, the accurate quantitative evaluation of the uniformity of the pre-tightening force distribution of the bolt group connecting the rotor is realized.

[0037] The method proposed by the present invention is mainly used for the quantitative evaluation of the pre-tightening force distribution of the bolt group connecting the rotor after tightening, and has important guiding significance for further improving the uniformity of the pre-tightening force distribution of the bolt group connecting the rotor structure. Description of the Drawings

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0039] Figure 1 is the overall flowchart of the present invention.

[0040] Figure 2 is the three-dimensional assembly schematic diagram of the simulated bolt group connecting the rotor in Embodiment 2 of the present invention.

[0041] Figure 3 is the schematic diagram of the numbering of 18 bolts in Embodiment 2 of the present invention.

[0042] Figure 4 It is the pre-tightening force distribution of the bolt group connecting the rotor in Embodiment 2 of the present invention.

[0043] Figure 5 It is the pre-tightening force distribution of 36 re-numbered bolts in Embodiment 2 of the present invention.

[0044] Figure 6 It is 36 generalized pixel values in Embodiment 2 of the present invention.

[0045] Figure 7 It is the standardized generalized gray-level co-occurrence matrix in Embodiment 2 of the present invention of the three-dimensional histogram.

[0046] Figure 8 They are 8 groups of pre-tightening force distributions of bolt groups simulated in the present invention; (A) - Example 1; (B) - Example 2; (C) - Example 3; (D) - Example 4; (E) Example 5; (F) - Example 6; (G) - Example 7; (H) - Example 8.

[0047] In the figure: 1 - upper rotor part; 2 - middle rotor part; 3 - lower rotor part; 4 - nut; 5 - bolt. Specific implementation manners

[0048] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] Embodiment 1

[0050] A method for quantitatively evaluating the uniformity of pre-tightening force distribution of a bolt group connecting a rotor, as Figure 1 shown, includes the steps:

[0051] S1: Determine the number of bolts and perform an initial numbering, obtain the pre-tightening force data of the bolts after the initial numbering and calculate the average pre-tightening force N of the bolts mean ; Expand the number of bolts and re-number them, and calculate the pre-tightening force values of the bolts after re-numbering;

[0052] The method is:

[0053] Determine the number of bolts and perform an initial numbering: In the counterclockwise order, perform an initial numbering on each bolt in the bolt group, and the initial numbers are 1, 2,... i,... n - 1, n in sequence. Among them, the phase of the bolt with the initial number i is:

[0054]

[0055] where n is the number of bolts, and α i is the phase of the i-th bolt.

[0056] Furthermore, obtain the pre-tightening force data of the bolts after the initial numbering and calculate the mean pre-tightening force N of the bolts mean : Denote the pre-tightening force values of each bolt as N (i) , and at the same time define N (0) = N (n) , and then calculate the mean pre-tightening force N of the bolts mean .

[0057] Furthermore, expand the number of bolts and re-number them: Double the determined number of bolts and re-number them in counterclockwise order. The new numbers are 1, 2, …, j, …, m - 1, m, where m is the total number of bolts after expansion, and m = 2n. The phase of the bolt numbered j is:

[0058]

[0059] where β j is the phase of the j-th bolt.

[0060] Furthermore, calculate the pre-tightening force values of the bolts after re-numbering: Calculate the pre-tightening force value of the bolt numbered j:

[0061]

[0062] where P j is the pre-tightening force value of the bolt numbered j after re-numbering, and N (j / 2) is the pre-tightening force value of the bolt numbered j / 2 among the corresponding n pre-tightening force values during the initial numbering.

[0063] Use the new numbers and the pre-tightening force values of the bolts corresponding to the new numbers for the calculations in the subsequent steps.

[0064] S2: Construct a generalized pixel value based on the bolt pre-tightening force value according to the re-numbering of the bolts and the pre-tightening force values of the bolts after re-numbering.

[0065] The construction method of the generalized pixel value is:

[0066]

[0067] where round() represents the rounding function, and GP j is the j-th generalized pixel value.

[0068] Finally, obtain the generalized pixel value set GP = {GP1, GP2, …, GP j , …, GP m}。

[0069] S3: Construct a generalized gray-level co-occurrence matrix based on the generalized pixel values.

[0070] The method is as follows:

[0071] Construct generalized pixel pairs according to the generalized pixel values: Define the j-th generalized pixel pair GP2 j which contains two generalized pixel values GP j and GP J where the subscript J of the generalized pixel value GP J ranges from 1 to m, and |j - J| = n;

[0072] Furthermore, calculate the order of the generalized gray-level co-occurrence matrix according to the generalized pixel values: Let the pixel interval Calculate the order L of the generalized gray-level co-occurrence matrix. The formula is:

[0073]

[0074] where max() represents the maximum value function and min() represents the minimum value function.

[0075] Furthermore, calculate the element G x,y in the generalized gray-level co-occurrence matrix G according to the generalized pixel pairs and the order of the generalized gray-level co-occurrence matrix:

[0076]

[0077] where G x,y represents the element in the x-th row and y-th column of the generalized gray-level co-occurrence matrix G, and [x, y] is the element value.

[0078] j traverses from 1 to m, |j - J| = n, and finally the generalized gray-level co-occurrence matrix G is obtained.

[0079] S4: Standardize the generalized gray-level co-occurrence matrix and calculate the contrast texture feature, and quantitatively evaluate the uniformity of the pre-tightening force distribution of the bolt group according to the contrast texture feature.

[0080] The method for standardizing the generalized gray-level co-occurrence matrix is as follows:

[0081]

[0082] where represents the standardized generalized gray-level co-occurrence matrix.

[0083] Furthermore, calculate the contrast texture feature according to the generalized gray-level co-occurrence matrix:

[0084]

[0085] Among them, CON is the contrast texture feature, which is the element in the x-th row and y-th column of the standardized generalized gray-level co-occurrence matrix.

[0086] Furthermore, according to the contrast texture feature CON, the uniformity of the pre-tightening force distribution of the bolt group is quantitatively evaluated. The smaller the value of the contrast texture feature CON, the better the uniformity of the pre-tightening force distribution of the bolt group; the larger the value of the contrast texture feature CON, the worse the uniformity of the pre-tightening force distribution of the bolt group.

[0087] Example 2

[0088] A method for quantitatively evaluating the uniformity of pre-tightening force distribution for a rotor connected by a bolt group. Taking a simulated rotor connected by a bolt group as an example, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the present invention are described completely.

[0089] As Figure 2 shown, it is a three-dimensional assembly schematic diagram of the simulated rotor connected by a bolt group in this embodiment, where 1 - upper rotor part; 2 - middle rotor part; 3 - lower rotor part; 4 - nut; 5 - bolt.

[0090] According to step S1, Figure 2 There are a total of 18 bolts in the rotor connected by the bolt group shown, that is, n = 18. The 18 bolts are numbered, with the counterclockwise direction as the positive direction, as Figure 3 shown. The phase of the i-th bolt is:

[0091] The ultrasonic pre-tightening force test method is used to Figure 2 carry out the pre-tightening force test on the rotor connected by the bolt group after assembly, obtain the pre-tightening force data of 18 bolts, upload the pre-tightening force data to the computer, and the pre-tightening force distribution of the rotor connected by the bolt group drawn by using Matlab software is as Figure 4 shown.

[0092] According to step S1, the 18 bolts are expanded to 36 bolts and the phase allocation and numbering are carried out again, the pre-tightening force of the 36 bolts with the re-numbered is calculated, and the pre-tightening force distribution of the 36 re-numbered bolts is drawn by using Matlab software, as Figure 5 shown.

[0093] According to step S2, the generalized pixel values are calculated by using the construction method of the generalized pixel values described above, a total of 36 generalized pixel values, and the 36 generalized pixel values drawn by using Matlab software are as Figure 6 shown.

[0094] According to step S3, the generalized pixel pairs are constructed by using the method of constructing generalized pixel pairs based on the generalized pixel values. Taking the generalized pixel value GP j as the abscissa and the generalized pixel value GPJ Taking the coordinates of 36 generalized pixels as the ordinate.

[0095] According to step S3, the calculated pixel interval ΔL = 400, and then the order L of the generalized gray-level co-occurrence matrix G is calculated as L = 15.

[0096] According to the elements G in the generalized gray-level co-occurrence matrix G in step S3 x,y Calculate the elements G in the generalized gray-level co-occurrence matrix according to the calculation method of x,y .

[0097] According to step S4, the generalized gray-level co-occurrence matrix G is standardized by using the method of the standardized generalized gray-level co-occurrence matrix, and the standardized generalized gray-level co-occurrence matrix is obtained. The standardized generalized gray-level co-occurrence matrix is represented by a three-dimensional histogram , as Figure 7 shown.

[0098] The calculated contrast value CON = 67.78 is obtained, and the CON value is used to quantitatively evaluate the uniformity of the pre-tightening force distribution of the simulated bolt group connecting the rotor.

[0099] In addition to obtaining the pre-tightening force of the bolt group through testing, multiple groups of bolt pre-tightening forces can also be randomly generated by computer numerical simulation. The pre-tightening force of the bolt group after actual tightening follows a Gaussian distribution. To compare the differences in the uniformity of different pre-tightening force distributions, assuming that there are 18 bolt pre-tightening forces in the bolt group, 8 groups of bolt pre-tightening forces with Gaussian distribution characteristics are obtained by computer simulation, and the randomly generated pre-tightening forces are as Figure 8 shown. According to steps S1 to S4, the contrast values of different bolt group pre-tightening force distributions are calculated as shown in the following table:

[0100] Table 1

[0101] Bolt group serial number CON value Bolt group serial number CON value A 13.00 E 51.17 B 2.50 F 6.39 C 101.00 G 32.44 D 27.33 H 10.50

[0102] Combined with the data in Table 1, it can be clearly seen that the pre-tightening force distribution of bolt group B has the best uniformity, and the pre-tightening force distribution of bolt group C has the worst uniformity.

[0103] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A quantitative evaluation method for the uniformity of pre-tightening force distribution of a bolt group-connected rotor, characterized in that, Including the steps: S1: Determine the number of bolts and conduct initial numbering, obtain the pre-tightening force data of the bolts after initial numbering, and calculate the average pre-tightening force N of the bolts mean ; Expand the number of bolts and re-number them, and calculate the pre-tightening force values of the bolts after re-numbering; S2: Construct a generalized pixel value based on the bolt pre-tightening force value according to the re-numbering of the bolts and the pre-tightening force value of the re-numbered bolts; S3: Construct a generalized gray-level co-occurrence matrix based on the generalized pixel value; S4: Standardize the generalized gray-level co-occurrence matrix and calculate the contrast texture feature, and quantitatively evaluate the uniformity of the pre-tightening force distribution of the bolt group according to the contrast texture feature.

2. The quantitative evaluation method for the pre-tightening force distribution uniformity of the bolt group-connected rotor according to claim 1, characterized in that The calculation formula for the pre-tightening force value of the re-numbered bolts is: Among them, j is the re-numbering of the bolts, and the value range of j is {1, 2, …, m-1, m}, where m is the total number of bolts after expansion, P j is the pre-tightening force value of the bolt numbered j after re-numbering, N (j / 2) is the pre-tightening force value of the bolt numbered j / 2 during the initial numbering.

3. The quantitative evaluation method for the uniformity of pre-tightening force distribution of a rotor connected by a bolt group according to claim 2, characterized in that The construction method of the generalized pixel value is: Among them, round() represents the rounding function, and GP j is the j-th generalized pixel value.

4. The method for quantitatively evaluating the uniformity of pre-tightening force distribution for connecting a rotor facing a bolt group according to any one of claims 1 to 3, characterized in that The method for constructing a generalized gray-level co-occurrence matrix based on generalized pixel values is as follows: construct generalized pixel pairs according to the generalized pixel values, calculate the order of the generalized gray-level co-occurrence matrix according to the generalized pixel values, and calculate the elements G in the generalized gray-level co-occurrence matrix G according to the generalized pixel pairs and the order of the generalized gray-level co-occurrence matrix x,y , where j traverses from 1 to m to obtain the generalized gray-level co-occurrence matrix G.

5. The quantitative evaluation method for the uniformity of pre-tightening force distribution of a rotor connected to a bolt group according to claim 4, characterized in that The method for constructing a generalized pixel pair according to the generalized pixel value is as follows: Define the j-th generalized pixel pair GP2 j including the generalized pixel value GP j and the generalized pixel value GP J , where the subscript J of the generalized pixel value GP J ranges from 1 to m, and |j - J| = n, where n is the total number of bolts during the initial numbering.

6. The quantitative evaluation method for the pre-tightening force distribution uniformity of a bolt group-connected rotor according to claim 5, characterized in that The method for calculating the order of the generalized gray-level co-occurrence matrix according to the generalized pixel value is: Among them, max() represents the maximum value function, and min() represents the minimum value function; pixel interval The generalized pixel value set GP = {GP1, GP2, …, GP j , …, GP m}, where L is the order of the generalized gray-level co-occurrence matrix.

7. The quantitative evaluation method for the pre-tightening force distribution uniformity of the bolt group-connected rotor according to claim 6, characterized in that The method for calculating the element G in the generalized gray-level co-occurrence matrix G x,y is as follows: Among them, G x,y represents the element in the x-th row and y-th column of the generalized gray-level co-occurrence matrix G, and [x, y] is the element value.

8. The quantitative evaluation method for the uniformity of pre-tightening force distribution of a bolt group-connected rotor according to claim 7, characterized in that The method for standardizing the generalized gray-level co-occurrence matrix is: Among them, represents the standardized generalized gray-level co-occurrence matrix.

9. The quantitative evaluation method for the uniformity of pre-tightening force distribution of a rotor connected to a bolt group according to claim 8, characterized in that The method for calculating the contrast texture feature according to the generalized gray-level co-occurrence matrix is: Among them, CON is the contrast texture feature, is the element in the x-th row and y-th column of the normalized generalized gray-level co-occurrence matrix.

10. The quantitative evaluation method for the uniformity of pre-tightening force distribution of a rotor connected by a bolt group according to claim 9, characterized in that The method for quantitatively evaluating the uniformity of the pre-tightening force distribution of the bolt group according to the contrast texture feature is: The smaller the value of the contrast texture feature CON, the better the uniformity of the pre-tightening force distribution of the bolt group; the larger the value of the contrast texture feature CON, the worse the uniformity of the pre-tightening force distribution of the bolt group.

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