Design method for clearance of rivet runway holes in annular U-shaped high-temperature thin-walled casing reinforcement ring

Abstract

The present invention provides a method for designing the clearance of rivet runway holes in an annular U-shaped high-temperature thin-walled casing reinforcement ring, comprising: step one, determining the theoretical value of the clearance of the rivet runway holes; step two, determining the design test load spectrum of the clearance of the rivet runway holes; step three, determining the probability distribution of the clearance of the rivet runway holes; step four, determining the probability distribution of the clearance of the failed runway holes; step five, determining the optimized value of the clearance of the rivet runway holes according to step three and step four. In order to reduce the probability of rivet failure, the present invention introduces a rivet runway hole clearance-rivet failure interference model, which fully considers the dispersion of manufacturing, assembly, and thermal load, greatly improves the working reliability of the rivet structure, and greatly reduces a large amount of testing and labor costs.

Description

Technical Field

[0001] The invention relates to the technical field of aeroengines, and in particular to a method for designing a runway hole clearance of an annular U-shaped high-temperature thin-wall casing reinforcement ring rivet. Background Art

[0002] Due to the need for weight reduction design and release of thermal deformation, a U-shaped high-temperature thin-walled casing is often used in aircraft engines. At the same time, in order to avoid excessive deformation of the entire casing and cause loss of aerodynamic performance, a reinforcement ring is riveted at the local flexible position of the casing for positioning. The structural diagram is shown in Figure 5 . However, the high-temperature thin-walled casing is subject to a large circumferential temperature difference and strong randomness in the thermal load, which can easily lead to thermal deformation inconsistency between the high-temperature thin-walled casing and the low-temperature reinforcement ring at the riveted position, followed by cracks on the edges of the riveted holes or failure and falling of the rivets, posing a major hidden danger to flight safety. Designing a runway hole with a reserved gap at the reinforcement ring is a simple and efficient solution, but the gap of the runway hole is affected by the dispersion of manufacturing, assembly, and thermal loads. There is a large difference between the design value and the measured value, and multiple tests are required to determine a more appropriate gap value, which results in a large waste of tests and manpower. Summary of the invention

[0003] In view of this, the present invention provides a method for designing the runway hole clearance of an annular U-shaped high-temperature thin-walled casing reinforcement ring rivet, so as to fully consider the dispersion of manufacturing, assembly, and thermal load, quickly obtain a reasonable clearance value, greatly improve the working reliability of the rivet structure, and greatly reduce the number of test repetitions.

[0004] The present invention provides the following technical solution: a method for designing the clearance of the rivet runway holes of an annular U-shaped high-temperature thin-walled casing reinforcement ring, comprising:

[0005] Step 1: Determine the theoretical value of the rivet runway hole clearance;

[0006] Step 2: Determine the rivet runway hole clearance and design the test load spectrum;

[0007] Step 3, determine the probability distribution of the rivet runway hole gap;

[0008] Step 4: Determine the probability distribution of the gap between the failed runway holes;

[0009] Step 5: According to step 3 and step 4, determine the optimal value of the rivet runway hole gap.

[0010] Furthermore, step one includes: by formula Determine the theoretical value of the rivet runway hole gap Δ0, δ1 is the deformation difference between the high-temperature thin-walled casing and the reinforcement ring rivet connection under the highest temperature and maximum temperature difference conditions; δ2 is the radius increase deformation of the rivet during the assembly stamping process; k is a real number, and k≥1.3.

[0011] Furthermore, step two includes determining the rivet runway hole clearance design test load spectrum through a functional verification test, a durability test, and a performance retention test.

[0012] Furthermore, step three includes:

[0013] After the actual test, all the rivet runway hole clearance values ​​of the thin-walled casing reinforcement ring were determined and the first sample X1 was determined;

[0014] The distribution law of the first sample X1 is statistically analyzed, and the sample distribution law is fitted and verified to determine the probability distribution of the rivet runway hole gap.

[0015] Furthermore, step four includes:

[0016] Collect the gap value of the rivet track hole where the rivet is sheared off by overload or cracked by the rivet hole after the test and determine the second sample X2;

[0017] The distribution law of the second sample X2 is statistically analyzed, and the sample distribution law is fitted and verified to determine the probability distribution of the gap between the failed runway holes.

[0018] Furthermore, step five includes:

[0019] According to the second sample X2 and by the formula The gap threshold Δsx is determined, where μ2 is the mean of the second sample X2 and σ2 is the standard deviation of the second sample X2.

[0020] Furthermore, step five also includes:

[0021] The first sample X1 is translated to obtain an optimized rivet runway hole gap sample X3;

[0022] By formula The statistical minimum value Δmin of the optimized rivet runway hole gap sample X3 is obtained, wherein μ3 is the mean of the optimized rivet runway hole gap sample X3, and σ3 is the standard deviation of the optimized rivet runway hole gap sample X3.

[0023] Furthermore, step five also includes: making the statistical minimum value Δmin and the gap threshold value Δsx of the optimized rivet runway hole gap sample X3 satisfy the following formula: .

[0024] Furthermore, step five also includes: the translation amount of the first sample X1 to the optimized rivet runway hole gap sample X3 is Δpy, where: , μ1 is the mean of sample X1; σ1 is the standard deviation of sample X1.

[0025] Furthermore, step five also includes: according to the formula Determine the optimal value of the rivet runway hole gap Δ yh .

[0026] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above-mentioned technical solutions adopted by the present invention include at least the following: in order to reduce the probability of rivet failure, the present invention introduces a rivet runway hole gap-rivet failure interference model, which fully considers the dispersion of manufacturing, assembly, and thermal loads, greatly improves the working reliability of the rivet structure, and greatly reduces a large amount of testing and labor costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 is a schematic diagram of a flow chart of an embodiment of the present invention;

[0029] Figure 2 It is a schematic diagram of the gap between all rivet runway holes after the normal distribution fitting test;

[0030] Figure 3 It is a schematic diagram of the runway hole gap of the rivet work failure after the normal distribution fitting test;

[0031] Figure 4 It is a schematic diagram of the rivet runway hole gap-rivet failure interference model;

[0032] Figure 5 It is a schematic diagram of the U-shaped high-temperature thin-walled casing reinforcement ring and its runway hole structure. DETAILED DESCRIPTION

[0033] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0034] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0035] like Figure 1 As shown, an embodiment of the present invention provides a method for designing a runway hole clearance of an annular U-shaped high-temperature thin-walled casing reinforcement ring rivet, comprising:

[0036] Step 1: Determine the theoretical value of the rivet runway hole gap. By means of calculation and analysis, the deformation difference between the high-temperature thin-walled casing and the reinforcement ring rivet connection under the highest temperature and maximum temperature difference working conditions is obtained, which is recorded as δ1; by means of process tests, the radius increase deformation of the rivet during the assembly and stamping process is obtained, which is recorded as δ2.

[0037] The theoretical value of the rivet runway hole gap Δ0 can be determined by the following formula:

[0038] (1)

[0039] In the above formula, k≥1.3 is determined based on engineering experience such as the accuracy of simulation calculation and the maturity of assembly process. In theory, this value can fully alleviate the problem of thermal deformation incompatibility, so it is determined as the theoretical value of the rivet runway hole clearance.

[0040] Step 2, determine the design test load spectrum of the rivet runway hole gap. The rationality of the rivet gap value design needs to be verified by testing. The test load spectrum is divided into three stages: function verification, endurance test, and performance maintenance. The cumulative test time is not less than 70 hours. The function verification test includes test procedures related to component functional parameters such as maximum state reliability, slow to maximum acceleration and deceleration characteristics, aerodynamic characteristics, and temperature distribution characteristics. The endurance test includes several step tests to verify long-term working reliability, long-term cruising and other test procedures. Performance maintenance includes test procedures such as verification of work efficiency and typical working conditions of temperature rise.

[0041] Step 3, determine the probability distribution of the rivet runway hole gap. The gap values ​​of all rivet runway holes of the thin-walled casing reinforcement ring after the actual test are recorded as X1. Since the rivet runway hole gap is affected by multiple factors such as thermal load, assembly process, and assembly error, the first sample X1 has a certain dispersion. Therefore, the distribution law of the first sample X1 is further statistically analyzed. According to the number of samples and the specific distribution law, the sample distribution law can be fitted empirically using appropriate statistical distribution laws, but the KS test of the empirical normal distribution is required. The KS test is based on the cumulative distribution function and is used to test whether an empirical distribution conforms to a certain theoretical distribution or to compare whether there is a significant difference between two empirical distributions. According to the difference between the cumulative distribution of the empirical distribution function and the expected distribution function, a statistic that obeys the Kolmogorov distribution can be constructed and then tested. If it meets the significance level requirements of the test, it indicates that the empirical distribution is consistent with the expected distribution law. Otherwise, other statistical distribution laws are sought for testing, such as normal distribution, t distribution, Weibull distribution, etc. Figure 2 provides a schematic diagram of the gaps between all rivet runway holes after the normal distribution fitting test. The sample number is greater than 30, and the normal distribution law can be used empirically to fit the sample distribution law. Table 1 gives the normal distribution test results of the sample case, and the results show that the sample case conforms to the normal distribution law.

[0042] Table 1 Normal distribution test of all rivet track hole gaps after the test

[0043]

[0044] Step 4, determine the probability distribution of the gap between the failed runway holes. Through the assessment test and trial run method, the gap values ​​of the rivet runway holes at the places where the rivet is overloaded and sheared or the rivet hole is cracked after the test are collected. The second sample data is recorded as X2, and the sample is a subsample of the first sample X1. According to the number of samples and the specific distribution law, the distribution law of the second sample X2 can be fitted empirically using appropriate statistical distribution laws, and the empirical distribution still needs to be tested by KS. Figure 3 provides a schematic diagram of the runway hole gap of the failed rivet fitting with a normal distribution. The number of case samples is close to 30, and the normal distribution law can be used empirically to fit the sample distribution law. Table 2 gives the normal distribution test results of the sample case, and the results show that the sample case conforms to the normal distribution law.

[0045] Table 2 Normal distribution test of runway hole gaps with working failure

[0046]

[0047] Step 5: Determine the optimized value of the rivet runway hole gap. According to the distribution law of the first sample X1 and the second sample X2, a [-3σ, +3σ] rivet runway hole gap-rivet failure interference model is constructed, and the optimized gap value is obtained using the interference model.

[0048] Figure 4 provides a schematic diagram of the rivet runway hole gap-rivet failure interference model. According to the distribution law of the second sample X2 of the rivet failure gap, the [+3σ] interference model is used to predict the rivet failure gap threshold Δ sx , that is, when the value is greater than this, the probability of rivet failure will be very low. Therefore, the gap threshold Δ sx Determine as follows:

[0049] (2)

[0050] In the above formula:

[0051] μ2——mean of the second sample X2;

[0052] σ2——Standard deviation of the second sample X2.

[0053] refer to Figure 4 , let the optimized rivet runway hole gap sample be the third sample X3, adopt [-3σ] interference model, the statistical minimum value Δ of the optimized gap third sample X3 min , that is, the probability of a rivet gap value smaller than this value will be very low. Therefore, Δ min Calculated as follows:

[0054] (3)

[0055] In the above formula:

[0056] μ3——mean of the third sample X3;

[0057] σ3——Standard deviation of the third sample X3.

[0058] Referring to FIG4 , in order to minimize the probability of failure of the optimized rivet, the statistical minimum value Δ of the third sample X3 of the optimized gap is min It should be greater than or equal to the gap value Δsx where the probability of rivet failure is extremely small, that is, the following formula needs to be satisfied:

[0059] (4)

[0060] Referring to Figure 4, when the working conditions and rivet assembly process have not changed significantly, it can be assumed that the distribution law of the gap third sample X3 after the rivet runway hole optimization is the same as the distribution characteristics of the gap first sample X1 before optimization. The distribution law of the gap third sample X3 can be optimized by translating the distribution law of the first sample X1. At this time, the standard deviation of the third sample X3 is equal to that of the first sample X1. In order to satisfy formula (4), substitute formula (2) and formula (3), and the translation amount Δ py The following formula must be satisfied:

[0061] (5)

[0062] In the above formula:

[0063] μ1——mean of the first sample X1;

[0064] σ1——Standard deviation of the first sample X1.

[0065] To achieve the translation amount Δ py , while maintaining the rigidity requirement and not designing too large a gap, take the translation amount Δ py The optimal design is performed based on the minimum value of the rivet runway hole gap Δ yh for:

[0066] (6)

[0067] In the above formula:

[0068] ——Translation Δ py The minimum value of .

[0069] Table 3 shows that the present invention can effectively and significantly improve the working reliability of the rivet structure. Compared with the gap value proposed by engineering experience, the rivet failure percentage is greatly reduced from 10% to 2% under the optimized gap value proposed by the present invention, which greatly improves the working reliability of the rivet structure. At the same time, the number of tests is reduced from 5 to 2, saving a lot of test and labor costs.

[0070] Table 3 Comparison of rivet working reliability between the optimized value of the present invention and the engineering experience value

[0071]

[0072] The following is described with reference to a specific embodiment:

[0073] Step 1: Determine the theoretical value of the rivet runway hole gap.

[0074] Through calculation and analysis, the deformation difference at the connection between the thin-walled casing and the reinforcement ring rivet under the condition of the highest temperature and the largest temperature difference was obtained, which was recorded as δ1=0.06mm; through process tests, the deformation of the rivet radius during the assembly and stamping process was obtained, which was recorded as δ2=0.13mm.

[0075] In this case, the value of k in formula (1) is as follows. When there is actual measured data of the highest temperature and the largest temperature difference working condition and the rivet assembly process is mature, the theoretical value of the rivet runway hole gap Δ0 can be determined by the following formula:

[0076] (7)

[0077] In other cases, the theoretical value of the rivet runway hole gap Δ0 can be determined by the following formula:

[0078] (8)

[0079] Since the maturity of the rivet assembly process in this case has not been repeatedly verified by process tests, it is difficult to obtain a relatively objective and accurate radius increase deformation of the rivet during the assembly stamping process. Therefore, formula (2) is used to determine the theoretical value Δ0 as 0.35 mm.

[0080] Step 2: Determine the rivet runway hole clearance and design test load spectrum.

[0081] The rationality of the rivet gap value design needs to be evaluated through experiments. In this case, the evaluation procedure is determined according to the evaluation test procedure, which covers three stages: function verification, durability test, and performance maintenance. The function verification test includes test procedures related to component functional parameters such as maximum state reliability, acceleration and deceleration characteristics from slow to maximum, aerodynamic characteristics, and temperature distribution characteristics. The durability test includes several step tests to verify long-term working reliability, long-term cruising and other test procedures. Performance maintenance includes test procedures such as verification of work efficiency and various typical working conditions of temperature rise.

[0082] Step 3: Determine the probability distribution of all rivet track hole gaps after the test.

[0083] Through the assessment test and trial run, the gap values ​​of all rivet runway holes of the thin-walled casing reinforcement ring after the actual test are measured, and the sample data is recorded as X1. Since the gap of the rivet runway hole is affected by multiple factors such as thermal load, assembly process, and assembly error, the first sample X1 has a certain dispersion. Therefore, the distribution law of the first sample X1 is further statistically analyzed. According to the number of samples and the specific distribution law, the sample distribution law can be fitted empirically using appropriate statistical distribution laws, but the empirical normal distribution needs to be tested by KS. Figure 2 provides a schematic diagram of the gap of all rivet runway holes after the normal distribution fitting test. The normal distribution law can be used empirically to fit the sample distribution law. Table 1 gives the normal distribution test results of the sample case. The results show that the sample case conforms to the normal distribution law.

[0084] Step 4: Determine the probability distribution of the gap between the failed runway holes after the test.

[0085] Through the assessment test and trial run, the rivet runway hole gap value at the rivet overload shearing or rivet hole cracking after the test is collected. The sample data is recorded as X2, and the sample is a subsample of the first sample X1. According to the number of samples and the specific distribution law, the distribution law of the second sample X2 can be fitted empirically using appropriate statistical distribution laws, and the empirical distribution still needs to be tested by KS. Figure 3 provides a schematic diagram of the runway hole gap of the failed rivet work in the normal distribution fitting of this implementation case. The normal distribution law can be used to fit the sample distribution law empirically. Table 2 gives the normal distribution test results of the sample case, and the results show that the sample case conforms to the normal distribution law.

[0086] Step 5: Determine the optimal value of the rivet runway hole gap.

[0087] FIG4 provides a schematic diagram of the rivet runway hole gap-rivet failure interference model of this embodiment. According to the distribution law of the second sample X2 of the rivet failure gap, it can be seen that the mean and variance of the second sample X2 are 0.189 mm and 0.086 mm respectively. The gap threshold Δ is determined according to formula (2): sx It is 0.397mm.

[0088] When the working conditions and rivet assembly process have not changed significantly, it can be assumed that the distribution law of the gap third sample X3 after the rivet runway hole optimization is the same as the distribution characteristics of the gap first sample X1 before optimization. The distribution law of the gap third sample X3 can be optimized by translating the distribution law of the first sample X1. The mean and variance of the first sample X1 are 0.264mm and 0.072mm respectively. In order to minimize the probability of failure of the optimized rivet, the statistical minimum value Δ min Should be greater than or equal to the rivet failure gap threshold Δ sxAccording to formula (5), the minimum translation amount is determined to be 0.345 mm.

[0089] The initial gap value is 0.35 mm corresponding to the first sample X1. The third sample X3 is obtained by translating the distribution law of the first sample X1 by 0.345 mm. At this time, the gap optimization value determined by the third sample X3 can be determined as 0.70 mm according to formula (6).

[0090] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for designing the clearance of rivet runway holes in an annular U-shaped high-temperature thin-walled casing reinforcement ring, characterized in that: include: Step 1: Determine the theoretical value of the rivet runway hole clearance; Step 2: Determine the rivet runway hole clearance and design the test load spectrum; Step 3: After testing, all the rivet runway hole clearance values ​​of the thin-walled casing reinforcement ring are obtained and the first sample X1 is determined; statistical analysis is performed on the distribution law of the first sample X1, and the sample distribution law is fitted and verified to determine the probability distribution of the rivet runway hole clearance; Step 4: Collect the rivet runway hole gap values ​​at the rivet overload shearing or rivet hole cracking after the test and determine the second sample X2; perform statistical analysis on the distribution law of the second sample X2, and perform fitting verification on the sample distribution law to determine the probability distribution of the failed runway hole gap; Step 5: According to the second sample X2 and by the formula Determine the gap threshold Δsx, where μ2 is the mean of the second sample X2; σ2 is the standard deviation of the second sample X2; The first sample X1 is translated to obtain an optimized rivet runway hole gap sample X3; By formula Obtain the statistical minimum value Δmin of the optimized rivet runway hole gap sample X3, where μ3 is the mean of the optimized rivet runway hole gap sample X3, and σ3 is the standard deviation of the optimized rivet runway hole gap sample X3; The statistical minimum value Δmin and the gap threshold Δsx of the optimized rivet runway hole gap sample X3 satisfy the following formula: ; The translation amount of the first sample X1 to the optimized rivet runway hole gap sample X3 is Δpy, where: , μ1 is the mean of sample X1; σ1 is the standard deviation of sample X1; According to the formula Determine the optimal value of the rivet runway hole gap Δ yh .

2. The method for designing the clearance of the rivet runway holes of the annular U-shaped high-temperature thin-walled casing reinforcement ring according to claim 1 is characterized in that: The step 1 comprises: Determine the theoretical value of the rivet runway hole gap Δ0, δ1 is the deformation difference between the high-temperature thin-walled casing and the reinforcement ring rivet connection under the highest temperature and maximum temperature difference conditions; δ2 is the radius increase deformation of the rivet during the assembly stamping process; k is a real number, and k≥1.

3.

3. The method for designing the clearance of the rivet runway holes of the annular U-shaped high-temperature thin-walled casing reinforcement ring according to claim 2 is characterized in that: The step 2 includes determining the rivet runway hole clearance design test load spectrum through a function verification test, a durability test, and a performance retention test.

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