A severe ground spectrum compilation method based on severe fleet damage

Abstract

The application discloses a severe ground spectrum compiling method based on severe fleet damage, which comprises the following steps: inputting the use requirements of an airplane, and outputting the composition and proportion of a mission profile; pre-processing measured load data, wherein the pre-processing comprises filtering and overload standardization; statistically processing the load data to obtain a measured ground overload cumulative overrun number curve family of a taxiing mission section and an overload cyclic peak-valley value of a landing impact mission section; statistically analyzing the damage of a load sequence of each mission profile, taking the damage of each mission profile whose reliability reaches a first preset value as severe damage of each mission profile, and inversely calculating severe ground overload cumulative overrun number curves of the taxiing mission section and each level load of the landing impact mission section corresponding to the severe damage; and compiling a severe ground overload spectrum. The severe spectrum compiled by the method can significantly reduce the test time and can fully expose the use cracks.

Description

Technical Field

[0001] This invention relates to the field of severe ground spectrum technology, and in particular to a method for compiling severe ground spectrum based on severe cluster damage. Background Technology

[0002] Flight-ground load spectrum refers to the spectrum compiled from the load time history experienced by an aircraft during flight and ground missions. It is compiled through specialized testing modifications and flight tests to determine and verify the aircraft's design service life, and is a prerequisite for determining and extending the lifespan of aircraft structures due to fatigue. Ground loads account for a significant proportion of damage during aircraft ground-to-air-to-ground operations; therefore, compiling the measured ground load spectrum is of great importance for extending the lifespan of civil aircraft.

[0003] Even for aircraft used under the same operating requirements, the load-time histories of different aircraft within a fleet vary significantly, corresponding to the dispersion of load spectra. Durability analysis and testing must be conducted under a definite (unique) load spectrum. Therefore, how to select and compile a reasonable load spectrum has become the key to structural durability analysis and assessment. To this end, the "critical spectrum" has been proposed. The critical spectrum has the advantages of being able to expose the failure characteristics of the aircraft itself and reducing test time. As a result, the critical spectrum is increasingly used in the compilation of measured spectra today.

[0004] The concepts, compilation methods, and lifetime analysis methods for average spectra are relatively mature, but there are still several key technologies to be solved in the study of severe spectra.

[0005] Regarding specific spectrum compilation methods, the US military standard MIL-A-8866 mentions that for ground mission segments, it is advisable to use equivalent first-order spectra for load spectrum compilation, but the severity is unknown. Currently, there is no relevant information in China on the method of compiling severe ground spectrum for aircraft.

[0006] Therefore, it is necessary to propose a method for compiling the severe ground-based measured spectrum of aircraft while ensuring safety and economy, and fully considering the dispersion and characteristics of ground loads. Summary of the Invention

[0007] In view of the above problems, the present invention proposes a method for compiling a severe ground spectrum based on severe cluster damage that at least solves some of the above technical problems. The severe spectrum compiled by this method can reduce the fatigue test time, and the dispersion factor used in life determination only needs to consider the dispersion factor of the structure.

[0008] This invention provides a method for compiling a severe ground spectrum based on severe cluster damage, comprising:

[0009] Input the aircraft's usage requirements, and output the composition and scale of the mission profile; for each mission profile, output the composition, order, scale, and parameters of the mission segments that make up the mission profile.

[0010] The measured load data is preprocessed, including filtering and overload normalization.

[0011] Statistical processing of the load data yields the family of measured ground overload cumulative exceedance curves for the taxiing mission segment and the overload cycle peak and valley values ​​for the landing and impact mission segment.

[0012] Based on the flight time and standard time of the mission segment corresponding to the measured data, the cumulative overload overload overload data of the mission segment in the measured taxiing mission segment overload cumulative overload overload curve family is converted into the cumulative overload overload overload data of the standard time.

[0013] Statistical analysis was performed on the damage of the measured takeoff and landing load sequences under each mission profile. Damage that reached the first preset value in the reliability of each mission profile of the aircraft group was taken as severe damage. The severe ground overload cumulative exceedance number curve of the taxiing mission segment and the load levels of the landing impact mission segment corresponding to the severe damage were inverted. The load levels include: the peak and valley values ​​of the landing impact load and the number of load cycles.

[0014] Based on the cumulative exceedance number curve of severe ground overload in the taxiing mission segment and the load levels in the landing and impact mission segment, a severe ground overload spectrum is compiled.

[0015] Furthermore, the measured load data undergoes preprocessing, including:

[0016] Subtract the second preset value from the measured center of gravity overload to obtain the incremental overload at that moment;

[0017] Based on the Y-axis overload data of the aircraft's center of gravity and wings, the ratio of its corresponding actual mass to the standard aircraft mass of the corresponding mission segment in the flight profile diagram is corrected.

[0018] Furthermore, statistical processing is performed on the load data to obtain a family of measured ground overload cumulative exceedance number curves for the taxiing mission segment, including:

[0019] By limiting the peak value across the average and adding preset constraints, positive peak values ​​and negative valley values ​​can be obtained.

[0020] Select several load levels, and record the positive ground overload cumulative exceedance number and the negative ground overload cumulative exceedance number for the positive peak value and the negative valley value respectively;

[0021] The mean of the cumulative exceedance number corresponding to a symmetrical ground overload is obtained by geometric mean, thus obtaining a family of measured ground overload cumulative exceedance number curves.

[0022] Furthermore, before the damage to the reliability of each mission profile of the aircraft group reaches a first preset value is considered severe damage, the following steps are also included:

[0023] The Odin transform method is used to analyze the ground load damage of the aircraft.

[0024] Damage calculations were performed on the time series of measured ground overload peak and valley values ​​after collecting peak and valley values ​​for each task segment under all profiles.

[0025] Calculate the equivalent damage for a single cycle and accumulate the load spectrum damage for the mission segment.

[0026] The total damage of this takeoff and landing is obtained by summing the damage of the load spectrum of the mission segment.

[0027] Furthermore, damage where the reliability of each mission profile of the aircraft group reaches a first preset value is considered severe damage, including:

[0028] The severity spectrum should reflect the severe usage status of 90% of the aircraft in the fleet, and the corresponding severe damage is the fleet damage corresponding to 90% reliability.

[0029] Severe damage is cluster damage with 90% reliability D 90 :

[0030] D 90 =10^(μ) lgD +u 90 σ lgD )

[0031] In the formula, μ is the logarithmic mean of the damage, σ is the logarithmic standard deviation of the damage, and u 90 This represents the quantile corresponding to the 90th percentile of the standard normal distribution.

[0032] Furthermore, the compilation of the severe ground overload spectrum includes:

[0033] Based on the typical task segments in the aforementioned task profile, a spectrum of critical task segments is compiled.

[0034] The typical task segments constitute the severity spectrum of the task profile;

[0035] A severe ground overload spectrum is compiled by randomly sorting the severe spectrum of the mission profile in proportion.

[0036] Furthermore, based on the typical task segments in the aforementioned task profile, a spectrum of critical task segments is compiled, including:

[0037] By keeping the total number of payload pairs in each mission segment equal to the total number of cycles in each flight, a severe mission segment spectrum is compiled.

[0038] Furthermore, the compilation of the severe ground overload spectrum includes the following:

[0039] Determination of ground overload cumulative exceedance curve and landing impact load for the severe skidding mission segment:

[0040] Inversion D 90 The reliability of the overload cumulative exceedance number curve corresponding to the taxiing mission segment and the reliability P corresponding to the peak and valley values ​​of the impact mission segment. b The reliability of the exceedance number for overload during the coasting mission segment under block spectrum conditions should be P. b Discrete (Δn) incremental overload exceedance curve y (N) i (i = 1, ..., n) Data pairs and reliability P of the landing and impact mission segment b The total damage of the three corresponding overload cycles should be equal to D. 90 .

[0041] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0042] This invention provides a method for compiling a severe ground spectrum based on severe aircraft group damage, comprising: inputting aircraft usage requirements and outputting the composition and proportion of mission profiles; preprocessing measured load data, including filtering and overload normalization; statistically processing the load data to obtain a family of measured ground overload cumulative exceedance number curves for the taxiing mission segment and overload cyclic peak-valley values ​​for the landing impact mission segment; statistically analyzing the damage of the load sequence for each mission profile, taking the damage where the reliability of each mission profile reaches a first preset value as the severe damage of each mission profile, inverting the severe ground overload cumulative exceedance number curve for the taxiing mission segment and the load levels for the landing impact mission segment corresponding to the severe damage; and compiling a severe ground overload spectrum. The severe spectrum compiled by this method can significantly reduce fatigue testing time, and the dispersion factor used during life determination only needs to consider the dispersion factor of the structure.

[0043] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0044] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0045] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0046] Figure 1A flowchart of a method for compiling a severe ground spectrum based on severe damage in a fleet mission profile, provided in an embodiment of the present invention;

[0047] Figure 2 The μ fitting result diagram provided in the embodiment of the present invention;

[0048] Figure 3 The σ fitting result diagram provided in the embodiment of the present invention;

[0049] Figure 4 A severe cumulative exceedance number curve provided for embodiments of the present invention;

[0050] Figure 5 The C-type random spectrum provided in the embodiments of the present invention. Detailed Implementation

[0051] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0052] This invention provides a method for compiling a severe ground spectrum based on severe cluster damage, referring to... Figure 1 As shown, it includes:

[0053] S1. Input the aircraft's usage requirements and output the composition and scale of the mission profile; for each mission profile, output the composition, order, scale, and parameters of the mission segments that make up the mission profile.

[0054] S2. Preprocess the measured load data, including filtering and overload standardization.

[0055] S3. Perform statistical processing on the load data to obtain the family of measured ground overload cumulative exceedance number curves for the taxiing mission segment and the overload cycle peak and valley values ​​for the landing and impact mission segment.

[0056] S4. Based on the flight time and standard time of the mission segment corresponding to the measured data, convert the cumulative overload overload overload data of the mission segment in the family of measured ground overload cumulative overload overload curves of the taxiing mission segment into the cumulative overload overload overload data of the standard time.

[0057] S5. Statistical analysis of the damage of the measured take-off and landing load sequences under each mission profile is performed. Damage that reaches the first preset value in the reliability of each mission profile of the aircraft group is taken as severe damage. The severe ground overload cumulative exceedance number curve of the taxiing mission segment and the loads at all levels of the landing impact mission segment corresponding to the severe damage are inverted. The loads at all levels include: the peak and valley values ​​of the landing impact load and the number of load cycles.

[0058] S6. Based on the cumulative exceedance number curve of severe ground overload in the taxiing mission segment and the loads at each level in the landing and impact mission segment, compile a severe ground overload spectrum.

[0059] The severity spectrum prepared by this method can significantly reduce the fatigue test time, and the dispersion factor used for life determination only needs to consider the dispersion factor of the structure.

[0060] The compilation of ground spectrum for severe durability mainly consists of four steps:

[0061] (1) Define the aircraft mission profile. Based on the aircraft's operational requirements, define the composition and proportion of the mission profile; for each mission profile, define the composition, order, proportion, and parameters of the mission segments that constitute the mission profile;

[0062] (2) Load data preparation. Preprocess the measured load data, including filtering and overload normalization;

[0063] (3) Statistical processing of load data to obtain a family of measured ground overload cumulative exceedance number curves based on the mission segment;

[0064] (4) Determination of the cumulative exceedance number curve for severe ground overload. The severity spectrum should meet the requirements of GJB 67.6A-2008 "Strength Specifications for Military Aircraft: Repeated Loads, Durability and Damage Tolerance" regarding the durability severity spectrum. According to this standard, the durability severity spectrum should reflect 90% of the aircraft fleet's usage. In this embodiment, the Monte Carlo method is used to simulate the damage distribution of the aircraft fleet, and damage with a reliability of 90% (first preset value) is taken as severe damage. Then, the cumulative exceedance number curve for severe overload is obtained based on damage inversion.

[0065] (5) Compile a severe ground overload spectrum. Determine the five load levels based on the load spectrum equivalent criterion and compile a 5×5 spectrum based on the mission segment: First, compile a severe mission segment spectrum for typical mission segments in the mission profile; then, construct a severe spectrum (takeoff and landing spectrum) for the mission profile based on the mission segments; finally, compile a severe ground overload flight-continued flight spectrum with a cycle of 1000 flights based on the mission profile severe spectrum in a proportionally randomized manner.

[0066] The core of compiling a severe ground overload spectrum for durability lies in how to determine the cumulative exceedance number curve for severe ground overload based on the mission segment.

[0067] Ground spectral compilation method:

[0068] Define the mission profile:

[0069] Determine the aircraft's mission profile, mission profile scale, and mission profile composition, and provide mission profile parameters such as: mission segments, mission segment altitude, speed, weight, flight distance, and flight time. The division of mission segments based on measured data follows these principles:

[0070] 1) The takeoff taxiing start point is determined by the speed being greater than 0 after the engine test is completed;

[0071] 2) The takeoff taxiing end point is determined by the complete departure of all three landing gears from the ground;

[0072] 3) The landing impact initiation point is determined by the change in Y-axis load;

[0073] 4) The landing impact termination point is determined by the return of the main launcher's Y-axis load to a stable ground state;

[0074] 5) The landing taxiing start point is determined by the main landing gear contacting the ground;

[0075] 6. The landing taxiing end point is determined by a yaw angle greater than 10°.

[0076] The overload spectrum for the taxiing mission segment in section 1 is compiled using a "5×5" spectrum, which means: first, the overload spectrum is discretized into a five-level spectrum, and then the discrete spectrum is compiled into load spectra for five typical flight types with different degrees of severity. There are a total of five typical flight types.

[0077] Preprocessing of measured load data:

[0078] The measured center of gravity overload n y Subtracting 1 (the second preset value) yields the incremental overload Δn at that moment. y .

[0079] Overload data n y Standardization process:

[0080] According to the specifications of aircraft cross-sectional diagrams, the Y-axis overload data of the aircraft's center of gravity and wings are represented by their corresponding actual mass "G". i The ratio of the standard aircraft mass "G0" for this mission segment to the flight profile diagram is corrected. That is:

[0081] △n y0 =△n yi *Gi / G0 (1)

[0082] In the formula, △n y0 The overload value is the corrected value according to the standard task section specifications; △n yi These are measured overload values. The actual load mass data is given by subtracting fuel consumption from the aircraft weight. Fuel consumption is calculated as an overall average (the average fuel consumption is calculated from the start of takeoff taxiing to the end of landing impact).

[0083] Peak and valley value collection:

[0084] Peak-valley detection involves identifying all peak and valley values ​​during the counting process, filtering out the data between peak and valley values, and retaining the corresponding sampling point number.

[0085] If satisfied

[0086]

[0087] Then the peak value (or valley value) is taken once.

[0088] Statistical analysis of the family of curves for cumulative overload during coasting missions:

[0089] Overload time history counting (limited peak-to-average counting method):

[0090] The restricted peak value counting method is a counting method formed by adding certain restrictions to the peak value method. Its specific processing requirements are as follows: Using the "1g" load state of each task segment as a baseline, if the valley value between two peaks (or the peak value between two valleys) does not exceed the upper deviation (lower deviation in the case of negative overload) of the "1g" baseline for that task segment, only the maximum peak value (valley value in the case of negative overload) is recorded, and the upper and lower deviations are 20% of the maximum peak value. This deviation is the restriction condition.

[0091] The cumulative exceedance number of each load level is obtained as follows:

[0092] The peak value obtained by the above-mentioned peak-to-average-peak counting method is greater than 0, and the valley value is less than 0. Several load levels are selected, and for both positive peak values ​​and negative valley values, the cumulative exceedance counts of positive and negative ground overloads are recorded, denoted as N(+Δn). y ) and N(-Δn y ).

[0093] For ground taxiing missions, ground disturbances of the same intensity (i.e., the same amplitude) have equal probabilities of occurrence in the positive (upward) and negative (downward) directions. Therefore, theoretically, the measured cumulative exceedance number curves for positive and negative ground overloads should be symmetrical. However, in practice, the cumulative exceedance number curves for positive and negative ground overloads often differ. In engineering, a geometric mean is used to obtain the average of the cumulative exceedance numbers corresponding to a symmetrical ground overload. This yields ±Δn. y The family of cumulative transcendental number curves is shown in equation (3).

[0094]

[0095] Standardization of the cumulative G-force exceedance number considering flight duration:

[0096] Because the measured load spectrum data differs between the mission segment flight time and the standard time of the mission segment in the mission profile, it is necessary to convert the measured cumulative overload exceedance data of the mission segment into cumulative exceedance data of the standard time. Let the flight time corresponding to the measured data be t. M The standard time for the task segment is t. S The cumulative exceedance number N of the i-th level load obtained from the measured time. ib Then the cumulative exceedance number of the i-th level load in standard time should be:

[0097]

[0098] By substituting the cumulative overload exceedance counts for each load level according to the above formula, the cumulative overload exceedance count data for the task segment at standard time can be obtained.

[0099] Fitting the overload cumulative exceedance number curve:

[0100] The cumulative overload exceedance data for the taxiing mission segment (Δn) y ,N) i The fitting equation is as follows:

[0101] Δn y =a*lgN+b (5)

[0102] The overload cumulative exceedance curve for each task segment was calculated.

[0103] Overload-cumulative exceedance curve hierarchical discretization:

[0104] Discretize the overload-cumulative exceedance curve. Discretize it into (Δn) y (N) i For data pairs (i = 1, ..., n), the transcendental number ΔN is calculated. i =N i -N i-1 Obtain exceedance number data pairs (Δn) corresponding to different ground overloads. y ,ΔN) i (i = 1, ..., n).

[0105] Transcendental number distribution property test:

[0106] A random variable model is typically used, assuming a specified Δn. y The corresponding transcendental number ΔN follows a log-normal distribution.

[0107] Distribution parameter estimation:

[0108] For a specific task segment, when the measured sample size is large, it is recommended to use the maximum likelihood estimation method to estimate the distribution parameters. The likelihood function is shown in the following equation.

[0109]

[0110] In the formula x i =lgΔN i The objective parameters (μ, σ) are solved by finding that the derivatives of the likelihood functions with respect to μ and σ are zero.

[0111]

[0112]

[0113] Processing of distributed parameters for the landing impact mission segment:

[0114] The landing impact mission load cycle typically consists of one landing impact load cycle with a large amplitude and two rotation load cycles with smaller amplitudes. For the statistical distribution of the landing impact mission load, the peak and trough values ​​(Δn) of its three load cycles are considered to be... yp ,Δn yv ) i (i = 1, 2, 3) are random variables. Statistical analysis is performed on the peak and trough values ​​of each of the three cycles (a total of 6 random variables), assuming they follow a normal distribution. The likelihood function is shown in the following equation.

[0115]

[0116] In the formula x i =Δn y The objective parameters (μ, σ) are solved by finding that the derivatives of the likelihood functions with respect to μ and σ are zero.

[0117]

[0118]

[0119] Group damage statistical analysis:

[0120] Group damage calculation method:

[0121] The damage calculation model uses the Odin transform method to analyze the damage caused by aircraft ground loads. It also uses the measured time series of ground overload peak and valley values ​​(n) collected from peak and valley values ​​under each mission segment in all profiles. y,max n y,min ) i Damage calculation is performed, and the equivalent damage of a single cycle is calculated using equation (9). The cumulative damage D of the load spectrum of the mission segment is then obtained. eq .

[0122]

[0123] In the formula, m is the damage index, which is the slope of the material / structure fatigue SN curve when R=0. k is a dimensionless coefficient of the standard weight of the aircraft mission segment.

[0124] The total damage D for this takeoff and landing is obtained by summing the damage of each segment of the mission.

[0125] Damage distribution parameters of the aircraft group:

[0126] A method for estimating fleet damage simulates severe fleet damage. Assume the fleet damage sample set is {D1, D2, D3, D4, ..., D...}. m}

[0127] Assuming that the ground spectral damage of the aircraft group follows a log-normal distribution, calculate the distribution parameters. For specific steps, refer to the distribution parameter estimation.

[0128] Severe injury confirmed

[0129] The severity spectrum should reflect the severe usage status of 90% (first preset value) of the fleet, and the corresponding severe damage is the fleet damage corresponding to 90% (first preset value) of reliability.

[0130] Severe damage is defined as cluster damage D with a reliability of 90% (first preset value). 90 :

[0131] D 90 =10^(μ) lgD +u 90 σ lgD )

[0132] In the formula, μ is the logarithmic mean of the damage, σ is the logarithmic standard deviation of the damage, and u 90 This represents the quantile corresponding to the 90th percentile of the standard normal distribution.

[0133] Severe ground spectrum compilation:

[0134] Determination of ground overload cumulative exceedance curve and landing impact load for the severe skidding mission segment:

[0135] Inversion D 90 The reliability of the overload cumulative exceedance number curve corresponding to the taxiing mission segment and the reliability P corresponding to the peak and valley values ​​of the impact mission segment. b For block spectrum conditions, the reliability of the exceedance number of the coasting mission segment overload should be P. b Discrete (Δn) incremental overload exceedance curve y (N) i (i = 1, ..., n) Data pairs and reliability P of the landing and impact mission segment b The total damage of the three corresponding overload cycles should be equal to D. 90 .

[0136] Determination of each load level in the coasting overload spectrum

[0137] (1) Determination of load levels based on mission profile

[0138] In Profile 1, each mission segment of the flight is discretized into 5 levels. The number of loads after discretization is an integer in a program block, and each mission segment is flown at least once. The representative value of each load level (i.e., equivalent load) is determined by adjusting for damage equal to that of the discrete segment.

[0139] (2) Determination of load parameters for each stage of the 5×5 spectrum

[0140] Based on the cumulative exceedance number curve of severe ground overload in the mission segment, the load spectrum equivalent is calculated using the method described in the "Manual of Durability and Damage Tolerance Design for Civil Aircraft Structures, Volume 1". Equivalent load calculation: Assume that the equivalent load for a discrete segment requiring equivalent calculation is Δn. yd The equivalent load cycle number is N eq If we replace the discrete segment of the curve with m straight lines, the linear equation of the i-th segment is:

[0141] Δg=a i lg N+b i (10)

[0142] In the formula, a i b i is a constant of the i-th segment of the load spectrum curve.

[0143] The equivalent load is:

[0144]

[0145] In the formula:

[0146]

[0147] S is the slope parameter of the SN curve for the material; for aluminum alloy, S = 2.0.

[0148] Equivalent load cycle count:

[0149]

[0150] Determining the flight type:

[0151] The load spectra of the flight mission profiles in Profile 1 are compiled according to five different flight types. The principle for determining the typical flight types in Profile 1 is: based on the ground spectrum of the flight (glide path) with the highest load, and assuming that the highest load in each flight (glide path) follows a normal logarithmic extreme distribution, the frequency of each flight type is determined (y is determined). i Based on the assumption that the ground spectrum shapes of various flight types are similar, ground incremental overload spectra for various flight types are compiled for 1000 flights (determining B). ij ).

[0152] Compile 5×5 spectra for all task segments under all profiles using the method described above. Furthermore, y1, y2, y3, y4, and y5 are identical for the 5×5 spectra of each task segment under each task profile.

[0153] Severe ground overload spectrum compilation:

[0154] (1) Compile the task segment spectrum

[0155] ① Compilation of severe ground skidding spectrum

[0156] Based on the data in the 5×5 spectrum compiled in 4.4.2, the load levels and their corresponding frequencies under the k-th flight type of the i-th mission segment of the j-th profile are linked together. Peak and trough values ​​are randomly selected and paired randomly to form the load spectrum for the specific flight type of the mission segment, denoted as (Δn). ydn ,-Δn ydm ) h The task segment spectrum (j×i×k segments in total) is represented as a sequence of load pairs in the following form:

[0157] f i,j,k =(Δn) ydn ,-ΔΔn ydm ) h (14)

[0158] In the formula, Δn ydn This represents the nth (n = 1, 2, 3, 4, 5) level load of this task segment, indicating the peak load; -Δn ydm This represents the m-th (m = 1, 2, 3, 4, 5) level load of the mission segment, indicating the valley load. The total number of load pairs for each flight type mission segment should be equal to the total number of cycles for each flight in the table above. Following this method, compile the spectra (load pair sequences) for all flight types under all mission segments.

[0159] ② Compilation of severe ground impact spectrum

[0160] The landing impact mission load cycle consists of three load cycles (Δn) yp ,-Δn yv ) i (i = 1, 2, 3). The reliability corresponding to each peak and trough value is P. b .

[0161] (2) Compile task profile spectrum

[0162] Let F be the load spectrum of the k-th flight type on the j-th profile. j,k F j,k This can be represented as a load pair sequence f i,j,kSort the tasks according to the order i (i = 1, 2, 3... m) under this profile, i.e., f 1,j,k ,f 2,j,k ,f 3,j,k ,f 4,j, k ......f m,j,k This yields the mission profile spectrum for a complete flight. The same method is used to compile mission profile spectra for all flight types under all mission profiles. All mission profile spectra are then represented in vector form.

[0163] B = [F] 1,1 … F 1,K F 2,1 … F 2,K F 3,1 … F 3,K ... F L,1 … F L,K (15)

[0164] For example, Profile 1 contains three mission segments, each with five flight types. Therefore, five mission profile spectra need to be compiled for Profile 1, representing the five flight types respectively. These are denoted as A1, B1, C1, D1, and E1. When compiling the A1 spectra, the spectra of flight type A under each mission segment are arranged, i.e., f... 1,j,k ,f 2,j,k ,f 3,j,k The A1 spectrum can then be obtained, and the same applies to other types of task profile spectra.

[0165] (3) Compile flight-continued flight spectrum

[0166] The flight-continued-flight spectrum is randomly arranged according to the frequency of occurrence of each flight type under the block spectrum (1000 flights) to form a severe flight-continued-flight spectrum.

[0167] The following is a detailed explanation of the severe ground spectrum compilation method based on severe cluster damage provided in this embodiment, using a practical application example:

[0168] Task profile:

[0169] A certain type of aircraft has one mission profile, designated as Profile 1 flight. The mission is organized in units of 1000 flights.

[0170] Measured load spectrum data:

[0171] A total of 10 flight data points for the X aircraft were measured. The flight data provided include time, flight altitude, Y-axis overload at the center of gravity, remaining fuel in the left / right engines, flap deflection, and elevator deflection.

[0172] Preprocessing of measured load data:

[0173] Overload data n y Standardization process:

[0174] The standard aircraft mass data for the mission segment is shown in the table below. The actual payload mass data is calculated by subtracting fuel consumption from the aircraft weight. Fuel consumption is calculated as an overall average (the average fuel consumption is calculated from the start of takeoff taxiing to the end of landing impact). The aircraft center of gravity y-axis overload data is standardized using the method described above.

[0175] Table 1 Standard Quality for Each Task Segment

[0176]

[0177]

[0178] Peak and valley value collection:

[0179] Before performing the counting statistics, the peak and valley values ​​of the statistical parameters were detected according to the aforementioned method to obtain the ground overload peak and valley value data pairs (Δn). y峰 ,Δn y谷 ) i .

[0180] Statistical analysis of the family of curves for cumulative overload during coasting missions:

[0181] Overload time history count:

[0182] With Δn y =Starting at 0.05g, with intervals of 0.05g. Using the aforementioned method, overload time histories of the standardized overload time history were counted, resulting in ground overload peak-valley data pairs (Δn). y峰 ,Δn y谷 ) i The peak values ​​here are all positive overloads, and the valley values ​​are all negative overloads.

[0183] Consideration of time-based overload exceedance standardization:

[0184] The aforementioned method was used to count the cumulative overload exceedances for both positive peak overload and negative trough overload. Flight duration was considered, and the cumulative overload exceedances for each level were standardized.

[0185] Overload exceedance statistics for each task segment:

[0186] Using the aforementioned method, the distribution parameters of the overload exceedance numbers at each level were estimated. Starting with lgN=1, fitting was performed at intervals of 0.5. The fitting results for mid-altitude flight landing taxiing are as follows: Figure 2 and Figure 3 As shown.

[0187] Group damage analysis:

[0188] The distribution parameters of the aircraft group damage profile extracted using the aforementioned method were calculated.

[0189] In this case, the severe injury D90 is 5838.

[0190] Severe ground spectrum compilation:

[0191] Determination of the cumulative exceedance curve for severe ground overload:

[0192] Severe damage value D 90 The value is 5838. After inversion, the reliability of the exceedance number under the specified overload in the taxiing mission segment and the reliability of the peak-valley value in the landing and impact mission segment are 94%. The cumulative exceedance number curve of severe ground overload in Profile 1 is as follows. Figure 4 As shown.

[0193] The severe load cycles during the landing impact mission phase were (0.65g, -0.3g), (0.31g, -0.13g), and (0.18g, -0.07g).

[0194] High-load cutoff and low-load cutoff:

[0195] (1) High load interception

[0196] The high load interception values ​​for each task segment are shown in Table 2 below.

[0197] Table 2 High-load interception values ​​for each task segment

[0198] Task segment High load cutoff value / g Section 1 Takeoff taxiing 0.67 Section 1 Landing and taxiing 0.71

[0199] (2) Low-load cutoff

[0200] The low-load deletion values ​​for each task segment are shown in Table 3 below.

[0201] Table 3 Low-load deletion values ​​for each task segment

[0202] Task segment Low load delete value / g Section 1 Takeoff taxiing 0.18 Section 1 Landing and taxiing 0.23

[0203] Load spectrum compilation:

[0204] 5×5 Spectral Compilation:

[0205] Based on the compilation principles, the number of flight types for the severe ground spectrum profile 1 flight profile is given separately. The number of flight types for the severe ground spectrum is shown in Table 4.

[0206] Table 4. Number of flight types in a typical flight profile (1000 flights)

[0207] Serial Number Typical flight profile A B C D E 1 Section 1 1 7 54 278 660

[0208] Random arrangement of fatigue load spectrum:

[0209] For Profile 1, profile spectra for five flight types were compiled. Based on the frequency of occurrence of each flight type in 1000 takeoffs and landings, the profile spectra for each flight type were randomly arranged in the 1000 takeoffs and landings to form a severe-continuation-flight spectrum. The random spectra for the climb and landing impact phases of Flight Type C are shown below. Figure 5 .

[0210] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for compiling a severe ground spectrum based on severe cluster damage, characterized in that, include: Input the aircraft's usage requirements, and output the composition and scale of the mission profile; For each task profile, output the task segments that make up the task profile, their order, proportions, and parameters; The measured load data is preprocessed, including filtering and overload normalization. Statistical processing of the load data yields the family of measured ground overload cumulative exceedance curves for the taxiing mission segment and the overload cycle peak and valley values ​​for the landing and impact mission segment. Based on the flight time and standard time of the mission segment corresponding to the measured data, the cumulative overload overload overload data of the mission segment in the family of measured cumulative overload overload overload curves of the taxiing mission segment are converted into cumulative overload overload overload data of the standard time. Statistical analysis was performed on the damage of the measured takeoff and landing load sequences under each mission profile. Damage that reached the first preset value in the reliability of each mission profile of the aircraft group was taken as severe damage. The severe ground overload cumulative exceedance number curve of the taxiing mission segment and the load levels of the landing impact mission segment corresponding to the severe damage were inverted. The load levels include: the peak and valley values ​​of the landing impact load and the number of load cycles. Based on the cumulative exceedance number curve of severe ground overload in the taxiing mission segment and the load levels in the landing and impact mission segment, a severe ground overload spectrum is compiled.

2. The method for compiling a severe ground spectrum based on severe cluster damage as described in claim 1, characterized in that, Preprocessing of the measured load data includes: Subtract the second preset value from the measured center of gravity overload to obtain the incremental overload at that moment; Based on the Y-axis overload data of the aircraft's center of gravity and wings, the ratio of its corresponding actual mass to the standard aircraft mass of the corresponding mission segment in the flight profile diagram is corrected.

3. The method for compiling a severe ground spectrum based on severe cluster damage as described in claim 1, characterized in that, Statistical processing of the load data yields a family of measured ground overload cumulative exceedance number curves for the taxiing mission segment, including: By limiting the peak value across the mean and adding preset constraints, positive peak values ​​and positive valley values ​​can be obtained. Select several load levels, and record the positive ground overload cumulative exceedance number and the negative ground overload cumulative exceedance number for the positive peak value and the negative valley value respectively; The mean of the cumulative exceedance number corresponding to a symmetrical ground overload is obtained by geometric mean, thus obtaining a family of measured ground overload cumulative exceedance number curves.

4. The method for compiling a severe ground spectrum based on severe cluster damage as described in claim 3, characterized in that, Before damage that causes the reliability of each mission profile of the aircraft group to reach a first preset value is considered severe damage, the following are also included: The Odin transform method is used to analyze the ground load damage of the aircraft. Damage calculations were performed on the time series of measured ground overload peak and valley values ​​after collecting peak and valley values ​​for each task segment under all profiles. Calculate the equivalent damage for a single cycle and accumulate the load spectrum damage for the mission segment. The total damage of this takeoff and landing is obtained by summing the damage of the load spectrum of the mission segment.

5. The method for compiling a severe ground spectrum based on severe cluster damage as described in claim 4, characterized in that, Damage that reaches a first preset reliability value in each mission profile of the aircraft group is considered severe damage, including: The severity spectrum should reflect the severe usage status of 90% of the aircraft in the fleet, and the corresponding severe damage is the fleet damage corresponding to 90% reliability. Severe damage is cluster damage with 90% reliability D 90 : D 90 =10^(μ lgD +u 90 s lgD ) In the formula, μ is the logarithmic mean of the damage, σ is the logarithmic standard deviation of the damage, and u 90 This represents the quantile corresponding to the 90th percentile of the standard normal distribution.

6. The method for compiling a severe ground spectrum based on severe cluster damage as described in claim 1, characterized in that, The compilation of the severe ground overload spectrum includes: Based on the typical task segments in the aforementioned task profile, a spectrum of critical task segments is compiled. The typical task segments constitute the severity spectrum of the task profile; A severe ground overload spectrum is compiled by randomly sorting the severe spectrum of the mission profile in proportion.

7. The method for compiling a severe ground spectrum based on severe cluster damage as described in claim 6, characterized in that, Based on the typical task segments in the aforementioned task profile, a spectrum of critical task segments is compiled, including: By keeping the total number of payload pairs in each mission segment equal to the total number of cycles in each flight, a severe mission segment spectrum is compiled.

8. The method for compiling a severe ground spectrum based on severe cluster damage as described in claim 6, characterized in that, The severe ground overload spectrum compilation includes the following: Determination of ground overload cumulative exceedance curve and landing impact load for the severe skidding mission segment: Inversion D 90 The reliability of the overload cumulative exceedance number curve corresponding to the taxiing mission segment and the reliability P corresponding to the peak and valley values ​​of the impact mission segment. b The reliability of the exceedance number for overload during the coasting mission segment under block spectrum conditions should be P. b Discrete (Δn) incremental overload exceedance curve y (N) i (i = 1, ..., n) Data pairs and reliability P of the landing and impact mission segment b The total damage of the three corresponding overload cycles should be equal to D. 90 .

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