CN112417582B - Method for compiling serious gust spectrum based on durability of discrete gust exceeding number curve - Google Patents
Method for compiling serious gust spectrum based on durability of discrete gust exceeding number curve Download PDFInfo
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Abstract
The invention relates to the technical field of severe gust spectrum programming, in particular to a method for programming severe gust spectrum based on durability of a discrete gust exceeding number curve. According to the method, a gust speed curve corresponding to 90% of airplane service conditions is obtained through statistical analysis of a gust speed exceeding number curve family by extrapolation, a Twist spectrum compiling method is adopted to compile a serious gust spectrum, then an overload spectrum is obtained through calculation, further a flight-continuous-flight overload spectrum is compiled, the overload amplitude of the serious spectrum is improved compared with an average spectrum, and the total cycle number is obviously increased. In the design and shaping stage of the aircraft structure, the method ensures the use safety of the structure under the use condition, comprehensively considers factors influencing the dispersion of service life, and carries out durability analysis, test and full-size fatigue test to evaluate the safety service life of the cluster structure. At present, a severe spectrum is adopted in the durability analysis and test of the aircraft structure to reflect the serious use condition of the aircraft in the design use distribution, so that 90% of the aircraft in the fleet are expected to meet the design service life.
Description
Technical Field
The invention relates to the technical field of severe gust spectrum programming, in particular to a method for programming severe gust spectrum based on durability of a discrete gust exceeding number curve.
Background
At present, a method for programming a severe gust spectrum of a durability design mainly comprises the following steps: (1) discrete gust model. The discrete gust model considers that the wind speed of the atmosphere deviates from the average state because discrete and uncorrelated turbulent flow groups exist in the atmosphere, and the wind speeds of different areas inside the turbulent flow groups are different and are overlapped with the average wind speed of the atmosphere, so that gusts are formed. The one-dimensional simplification is carried out, and the gust structure is simplified into a 1-COS pulse. To be used forFor example, a vertical gust is considered that along the flight path, the vertical gust speed from edge to center to edge of a turbulent mass shows a change of 1-COS, the wind speed at the center of the turbulent mass deviates most from the average wind speed of the atmosphere, and the wind speed is recorded as a discrete gust speed U de . The one-dimensional gust does not take into account variations in the gust along the spanwise direction of the aircraft, as shown in fig. 1. And (2) gust overrunning number curve. The discrete gust overrun number curve is a representation of the magnitude and number of gust loads that occur during use of the aircraft. The wind speed is generally represented by a curve with the real value of the discrete gust speed as the abscissa and the logarithmic value of the overrun as the ordinate. In the use process of the aircraft, the discrete gust speed corresponding to the gust load can be obtained every time the aircraft experiences the gust load, and then the overrun number corresponding to the discrete gust speed value is recorded to be increased once. And counting the discrete gust speed overrun number for the service time of the airplane, so as to obtain a gust overrun number curve. And counting the total discrete gust speed overrun numbers of enough airplanes to obtain an average gust speed overrun number curve reflecting the average condition of the fleet. However, both methods cannot fully consider factors affecting the life of the cluster under the condition of ensuring the use safety, so as to evaluate the safety life of the cluster structure.
Disclosure of Invention
First, the technical problem to be solved
The object of the present invention is to provide a method for compiling a severe gust spectrum based on the durability of a discrete gust overrun curve to solve the above mentioned problems.
(II) technical scheme
In order to solve the technical problems, the invention provides a method for compiling a severe gust spectrum based on durability of a discrete gust overrun number curve, which comprises the following steps:
actual measurement U for similar aircraft de The overrunning number curve data are standardized, and standardized overrunning number curve families with different heights are obtained;
the exceeding number delta N at the specified gust speed is subjected to lognormal distribution, and the standardized exceeding number curve families with different heights are processed to obtain fitting results of distribution parameters of the lognormal distribution;
according to the fitting result, calculating U dei Δn corresponding to lower preset coverage p i.p After sequencing, the accumulated overrun number N is obtained i,p Is composed of (U) de ，N p ) i Obtaining U corresponding to the preset coverage rate p de Overrun number curve (U) de ，N p ) i Namely (U) dei ,N i.p )；
Using section task segment parameters of profile in combination with aircraft design, the section segment parameters being defined by the U of the severe-matrix wind spectrum de Obtaining a single flight overload spectrum of the using section through the overrun curve;
and further randomly sequencing the single flight overload spectrums of different using sections according to the length and the composition mode of the flight-continuation-flight block spectrums to obtain a complete flight-continuation-flight test block spectrum.
In some embodiments, it is preferable that the calculating U based on the fitting result dei Δn corresponding to lower preset coverage p i.p After sequencing, the accumulated overrun number N is obtained i,p Is composed of (U) de ，N p ) i Obtaining U corresponding to the preset coverage rate p de The overrunning number curve includes:
by delta N i.p ＝μ i +u p＝p σ i Calculate each U dei Δn corresponding to lower preset coverage p i.p ，u p Corresponding to the preset coverage rate;
according to U dei Sequentially for delta N from big to small i,p Accumulating the counts to obtain accumulated overrun numbers;
consists of (U) de ，N p ) i Obtaining U corresponding to the preset coverage rate p de Transcendental numerical curves.
In some embodiments, preferably, the preset coverage comprises 90% and/or 50%;
when the preset coverage p=90%, u p＝90％ = 1.282, corresponding U de The overrun number curve is a severe overrun number curve;
when the preset coverage p=50%, u p＝50％ =0, corresponding U de The overrun curve is a median overrun curve.
In some embodiments, the normalizing measured overrun profile data for the same class of aircraft preferably includes:
obtaining actual measurement U of same class of aircraft de Surpassing the numerical curve data, the aircraft of the same type has the same aircraft configuration, weight and mission profile;
actual measurement U of similar aircraft according to uniform flight distance and altitude interval de Merging the surpassing number curve data to obtain standardized U with different heights de Transcendental family of curves.
In some embodiments, preferably, the overrule Δn at the specified gust speed obeys a lognormal distribution, and the processing the normalized overrule curve family with different heights to obtain the fitting result of the distribution parameters of the lognormal distribution includes:
setting the overrun delta N under the gust speed to follow the lognormal distribution according toThe logarithmic median μ, logarithmic standard deviation σ, is obtained.
In some embodiments, the determining method of the length and the composition of the "fly-continue-fly" block spectrum preferably includes: determining the life index of the airplane, the use section, the proportion of different use sections and the parameters of each use section; the parameters of each usage profile include: task segment, height, speed, weight, flight distance, and/or flight time of the task segment; according to the life index of the airplane, the using section and/or the proportion of different using sections, the 'flying-continuing-flying' block spectrum is determined, the length of the single block spectrum is 10% of the life index, and the total flight times of the block spectrum and/or the proportion of each section of the block spectrum are determined.
In some embodiments, it is preferred that the mission section parameters of the profile be used in conjunction with the aircraft design, defined by the U of the severe-gust spectrum de The single flight overload spectrum for the usage profile obtained over the number curve includes: according to a TWIST spectrum programming method, a 5*5 task section array wind spectrum is programmed; said according to any of saidAnd converting the task section wind spectrum of 5*5 into a task section overload spectrum according to the task section parameters, and sequentially sequencing and connecting to obtain a single flight overload spectrum of the using section.
In some embodiments, preferably, the compiling a task segment array spectrum of "5*5" according to the method for compiling a spectrum of "TWIST" includes: from U according to mission section flying height and/or distance de Obtaining U with different corresponding heights by exceeding the number curve de Multiplying the overrun number of the task section by the flight distance of the task section to obtain the overrun number of the gust speed of the task section; carrying out maximum gust speed interception and minimum gust speed interception on the gust speed overrun number under a first preset condition; discretizing the processed gust speed override number, and compiling to obtain a '5*5' gust speed distribution matrix of a second preset condition.
In some embodiments, it is preferable that the first flight type is most severely damaged in the "5*5" gust speed distribution matrix of the second preset condition, and the first flight type contains 5-level gust speeds and only occurs once; the fifth flight type has the least damage, only contains the 1-level gust speed and has the largest occurrence frequency; and/or, the first preset condition includes: taking the principle that the maximum gust speed is intercepted only once in a single spectrum; given the damage level, a minimum gust speed cut is performed.
In some embodiments, preferably, the converting the task segment wind spectrum of "5*5" into the task segment overload spectrum according to the task segment parameters, and sequentially sequencing the connections, to obtain the single flight overload spectrum of the usage profile includes:
according to aircraft aerodynamic, weight and flight parameter data, and according to
Overload;
wherein: delta n is delta overload; k (K) g A gust mitigation factor to account for aircraft heave motion and lift growth lag; c (C) La Is the slope (1/rad) of the lift curve of the aircraft; s is the reference wing area; w is the weight of the aircraft; mu (mu) g The quality parameter is marked;the average geometrical chord length of the wing; g is gravity acceleration; ρ 0 For air density, subscript 0 denotes sea level;
converting the wind gust overload into overload required by a fatigue test, wherein the task section weight is required to be converted into a nominal weight, and a conversion formula is as follows: k (1- Δn,1+Δn); k is the ratio of the mission section weight to the nominal weight of the aircraft;
randomly sequencing overload spectrums of the task segments;
sequentially sequencing the task section overload spectrums according to the sequence in the use section to form a single flight overload spectrum; in the single flight overload spectrum, the severity of the task section overload spectrum is the same, and the total number of times of the single flight spectrum is equal to the number of times of flight of the using section in the block spectrum.
(III) beneficial effects
According to the method for compiling the severe gust spectrum based on the durability design of the gust overrun curve, the gust speed curve corresponding to 90% of airplane service conditions is obtained through extrapolation through statistical analysis of gust speed overrun curve families, the severe gust spectrum is compiled by adopting a Twist spectrum compiling method, then an overload spectrum is calculated, further a flight-continuous-flight overload spectrum is compiled, the overload amplitude of the severe spectrum is improved compared with the average spectrum, and the total circulation number is also obviously increased. The durability design severity spectrum compiling technology ensures the use safety of the structure under the use condition in the design and shaping stage of the aircraft structure, comprehensively considers factors influencing the dispersion of service life, and carries out durability analysis, test and full-size fatigue test to evaluate the safety service life of the cluster structure. At present, a severe spectrum is adopted in the durability analysis and test of the aircraft structure, so that the severe use condition of the aircraft in the design use distribution can be reflected, and 90% of the aircraft of the fleet can be expected to meet the design service life.
Drawings
FIG. 1 is a simplified "1-COS" shaped wind gust structure;
FIG. 2 is a schematic diagram illustrating steps in one embodiment of the present invention;
FIG. 3 (a) is 0-1500 feet U de Transcendental family of curves;
FIG. 3 (b) is 1500-4500 feet U de Transcendental family of curves;
FIG. 3 (c) is 4500-9500 feet U de Transcendental family of curves;
FIG. 3 (d) is 9500-19500 feet U de Transcendental family of curves;
FIG. 3 (e) is 19500-29500 feet U de Transcendental family of curves;
FIG. 3 (f) is 29500-39500 feet U de Transcendental family of curves;
FIG. 4 (a) is a fitting result of the logarithmic median μ;
fig. 4 (b) shows the fitting result of the logarithmic standard deviation σ;
FIG. 5 is a family of average overrun curves for 50% coverage and a family of severe overrun curves for 90% coverage;
FIG. 6 is a graph of 5*5 gust velocity distribution matrix;
FIG. 7 (a) is a gust normal extremum distribution criterion;
FIG. 7 (b) is a gust similarity criterion;
FIG. 8 is a family of S-N curves;
FIG. 9 (a) is a log-normal distribution criterion test result of gust extremum;
FIG. 9 (b) is a gust similarity criteria test result;
FIG. 10 (a) is a single-flight average spectrum;
FIG. 10 (b) is a single flight severity spectrum;
FIG. 11 (a) is an average spectrum of the "fly-continue-fly" test block spectrum;
FIG. 11 (b) is an overload spectrum of the "fly-continue-fly" test block spectrum.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
The following describes in further detail the embodiments of the present invention with reference to the drawings and examples. The following examples are illustrative of the invention and are not intended to limit the scope of the invention.
The present invention provides a method for compiling a severe gust spectrum based on durability of a discrete gust overrun curve, as shown in fig. 2 (a), comprising:
actual measurement U for similar aircraft de The overrunning number curve data are standardized, and standardized overrunning number curve families with different heights are obtained;
the exceeding number delta N at the specified gust speed is subjected to lognormal distribution, and standardized exceeding number curve families with different heights are processed to obtain fitting results of distribution parameters of the lognormal distribution;
according to the fitting result, calculate U dei Δn corresponding to lower preset coverage p i.p After sequencing, the accumulated overrun number N is obtained i,p Is composed of (U) de ，N p ) i U for obtaining corresponding preset coverage rate p de An overrunning number curve;
task section parameters of a profile used in conjunction with aircraft design, consisting of U of a severe gust de Obtaining a single flight overload spectrum of the using section through the overrun curve;
and further randomly sequencing the single flight overload spectrums of different using sections according to the length and the composition mode of the flight-continuation-flight block spectrums to obtain a complete flight-continuation-flight test block spectrum.
According to the method for compiling the severe gust spectrum based on the durability design of the gust overrun curve, the gust speed curve corresponding to 90% of airplane service conditions is obtained through extrapolation through statistical analysis of gust speed overrun curve families, the severe gust spectrum is compiled by adopting a Twist spectrum compiling method, then an overload spectrum is calculated, further a flight-continuous-flight overload spectrum is compiled, the overload amplitude of the severe spectrum is improved compared with the average spectrum, and the total circulation number is also obviously increased. The durability design severity spectrum compiling technology ensures the use safety of the structure under the use condition in the design and shaping stage of the aircraft structure, comprehensively considers factors influencing the dispersion of service life, and carries out durability analysis, test and full-size fatigue test to evaluate the safety service life of the cluster structure. At present, a severe spectrum is adopted in the durability analysis and test of the aircraft structure, so that the severe use condition of the aircraft in the design use distribution can be reflected, and 90% of the aircraft of the fleet can be expected to meet the design service life.
The method for generating a severe gust spectrum based on the durability of the discrete gust overrun curve is described in detail below with reference to a specific embodiment, as shown in fig. 2 (b):
a first part: obtaining a severe gust speed overrun curve
Step 101, classifying the use of the aircraft according to the configuration, weight, mission profile and the like of the newly designed aircraft. Collecting the measured overrun curve data of the same type of aircraft, and merging according to the uniform flight distance and the uniform altitude interval to obtain standardized overrun curve families with different altitudes;
u obtained by collection de The super-measured item information is shown in table 1, and the detailed data can be referred to corresponding documents.
Table 1U de Actual measurement project information of overrun number
The number of overruns for class 8 aircraft in table 1 was calculated for 6 altitude intervals: the curves are divided from 0 to 1500 feet, 1500 to 4500 feet, 4500 to 9500 feet, 9500 to 19500 feet, 19500 to 29500 feet, and 29500 to 39500 feet, and are converted into units of overstep curves in sea uniformly, as shown in fig. 3 (a) to (f).
Step 102, elucidate U de Dispersibility beyond the family of numerical curves, assuming a specified U de The lower exceeding number delta N is a random variable, and the distribution characteristic and the estimated distribution parameter of the lower exceeding number delta N are clarified;
assuming that the overrun number Δn at the specified gust speed follows the lognormal distribution, the distribution parameter estimation of the lognormal distribution is performed according to expression (1), μ is the logarithmic median, and σ is the logarithmic standard deviation.
The fitting results are shown in fig. 4 (a) - (b):
step 103, extrapolated to obtain a U of the severe gust spectrum de Transcendental numerical curves. Based on a random variable model of overrun (i.e. dispersion of the family of gust velocity overrun curvesSex model), a severe gust speed U of preset coverage P (e.g. p=90%) for all altitude intervals is obtained de An overrunning number curve;
taking coverage rate P=90% as an example, according to the statistical analysis result of the gust speed overrun curve, firstly calculating each U dei Δn corresponding to lower coverage p=90% i.90 The formula is:
ΔN i.90 ＝μ i +u p＝90％ σ i (2)
wherein u is p＝90％ ＝1.282。
Then press U dei Sequentially for delta N from big to small i,90 Accumulating the count to obtain an accumulated overrun count, which is calculated by (U de ，N 90 ) i Obtain U corresponding to 90% use cases de Overrunning number curve, namely 90% -U de -an N curve. In other embodiments, coverage may be replaced with other values, such as 85%,92%,95%, etc.
Calculated 50% -U as shown in figure 5 de -N curve and 90% -U de -an N curve.
The second part is used for compiling a severe gust spectrum
Step 104, determining the length and the composition of a 'flying-continuing-flying' block spectrum according to the life index of the airplane, the use section and the proportion thereof;
one or more of an aircraft life index, a usage profile, a ratio of different usage profiles, and a composition of each usage profile are determined based on design usage requirements of the aircraft. Each usage profile parameter is determined, such as a mission segment, typical parameters of the mission segment, such as altitude, speed, weight, flight distance, time of flight, etc.
The 'flying-continuing-flying' block spectrum is compiled, the length of the single block spectrum is 10% of the life index, and then the total flying times of the block spectrum and the times proportion of each section are determined.
Step 105, combining task section parameters of a section of the aircraft design use, and compiling a task section array wind spectrum of 5*5 according to a TWIST spectrum compiling method;
according to the flying height and distance of the mission section, from U de Obtaining an overrun number curveTo obtain corresponding U with different heights de Multiplying the overrun number of the task section by the flight distance of the task section to obtain the overrun number of the gust speed of the task section;
total flight distance = distance of the mission segment of the profile x number of flights of the profile;
the flight distance of the profile = total number of flights of the block spectrum x the proportion of the profile.
Taking the principle that the maximum gust speed is intercepted only once in a single spectrum;
giving the damage level, and cutting off the minimum gust speed;
discretizing the gust speed override number to obtain a '5*5' gust speed distribution matrix, as shown in fig. 6; "5*5" represents 5 flight types and 5-level gust speeds, respectively; the first flight type is most severely damaged, contains 5-level gust speed and only appears once; the fifth flight type has the least damage, only contains the 1-level gust speed and has the largest occurrence frequency; the first to fifth types of damage are sequentially alleviated, and the included gust speed level is gradually changed from 5 levels to 1 level.
The "5*5" gust speed distribution matrix requires that the gust normal extremum distribution criteria and gust similarity criteria be met, the gust normal extremum distribution criteria requiring that the 5-level speeds be taken from the same log-log normal distributed matrix, as shown in fig. 7 (a); the gust similarity criterion requires that the gust spectra of the 5 flight types are similar in shape, as shown in fig. 7 (b).
In other embodiments, 5 x 6,5 x 7,5 x 8, etc., and "5*6" means 5 flight types, 6-stage gust speeds, the first flight type comprising 6-stage gust speeds, the second flight type comprising 5-stage gust speeds, and so on, the 5 th flight type comprising 2-stage gust speeds. 5*7,5*8, etc., each flight type increases the gust speed by a corresponding number of steps.
Step 106, converting the task section array wind spectrum into a task section overload spectrum according to the task section parameters, and sequentially sequencing and connecting to obtain a single flight overload spectrum of the using section;
1) Converting the gust speed into gust overload according to the aerodynamic, weight and flight parameter data of the aircraft and the formula (3);
wherein: delta n is delta overload; u (U) de For dispersing gust speed, p 0 For air density, subscript 0 denotes sea level, K g A gust mitigation factor to account for aircraft heave motion and lift growth lag; c (C) La Is the slope (1/rad) of the lift curve of the aircraft; v e For equivalent space velocity, C La Is the slope of the lift line; s is the reference wing area; w is the weight of the aircraft; mu (mu) g The quality parameter is marked;the average geometrical chord length of the wing; g is gravitational acceleration.
2) Converting the wind gust overload into overload, wherein the conversion formula is as follows: k (1- Δn,1+Δn),
3) Scaling the overload data to a nominal weight: k is the ratio of the mission section weight to the nominal weight of the aircraft (typically taken as the design weight).
Step 107, further randomly sequencing the single flight spectrums of different usage profiles to obtain a complete 'flight-continuous-flight' test block spectrum.
1) Randomly sequencing overload of task segments;
2) Sequentially sequencing task section spectrums according to the sequence in the use section to form a single flight spectrum; the severity of the task section spectrum is the same in the same single flight spectrum; the total number of times of the single flight spectrum is equal to the number of flights of the using section in the block spectrum;
3) The single flight spectrums of different using sections are randomly ordered to form a complete 'flight-continuous-flight' block spectrum; to avoid the influence of high-load hysteresis, several single-flight spectrums which are most serious should be uniformly and randomly arranged in the block spectrums, and the rest single-flight spectrums are completely and randomly arranged.
Examples: the P-3C aircraft is used as a subject for carrying out severe gust spectrum compiling, and meanwhile, average gust spectrums are compiled for comparison.
(1) Step 104, determining the length and the composition of a 'flying-continuing-flying' block spectrum according to the life index of the airplane, the use section and the proportion thereof;
the present example considers only one profile of use, and therefore does not need to consider the effect of the proportion of profile use. The basic parameters of the P-3C aircraft are shown in Table 2, the profile parameters are shown in Table 3, and the stress level of 1g overload at a given nominal weight is sigma 1g ＝80MPa。
The design life is 18000 flight hours, the section length is 10.1 flight hours, and therefore the expected number of flights is 1782, and the expected number of flights is 1780, and the block spectrum contains 178 flights.
TABLE 2 P3-C aircraft basic parameters
Table 3P 3c task segment typical parameter values
Step 105, combining task section parameters of a section of the aircraft design use, and compiling a task section array wind spectrum of 5*5 according to a TWIST spectrum compiling method;
a) And obtaining the discrete gust speed overrun number of each task section according to the flight times of the block spectrum and the flight distance of the task section, and intercepting the maximum gust speed on the principle that the discrete gust speed overrun number only appears once in a single block spectrum, wherein the intercepted value is shown in a table 4.
TABLE 4 maximum gust speed cut-out
Minimum gust speed cut-off: the stress cycle corresponding to the test overload k.cndot. (1- Δn,1+Δn) is calculated from formula (4):
calculating fatigue life corresponding to stress cycle from formula (4), and unifying N SN The gust velocity of > 2 x 10 x 11cyc is truncated, the cut-off value is shown in Table 5, and the average spectrum is identical to the cut-off value of the severe spectrum.
S m N SN ＝C (5)
Wherein the values of m and C are based on the parameter fitting of the S-N curve family shown in FIG. 8, and the fitting formula is formula (6).
TABLE 5 minimum gust speed cut-off value
Compiling a 65 x 5' gust speed distribution matrix: taking task segment 1 as an example, as shown in table 6, the test results of the "two criteria" are shown in fig. 9 (a) and 9 (b).
Table 6 task section 1 gust speed distribution matrix
(a) Average spectrum
(b) Stringent spectrum
Step 106, converting the task section array wind spectrum into a task section overload spectrum according to the task section parameters, and sequentially sequencing and connecting to obtain a single flight overload spectrum of the using section;
according to the task section parameters, converting the task section array wind spectrum into a task section overload spectrum according to the following formula (7), and sequentially sequencing and connecting to obtain a single flight overload spectrum of the using section, wherein the task sections are sequentially sequenced according to the sequence in the task section, and the cycle in the task section is randomly sequenced.
Wherein: delta n is delta overload; u (U) de For dispersing gust speed, p 0 For air density, subscript 0 denotes sea level, K g A gust mitigation factor to account for aircraft heave motion and lift growth lag; c (C) La Is the slope (1/rad) of the lift curve of the aircraft; v e S is the reference wing area for equivalent airspeed; w is the weight of the aircraft; mu (mu) g The quality parameter is marked;the average geometrical chord length of the wing; g is gravitational acceleration.
The overload spectrum for each task segment is shown in table 7 after conversion. Taking the single flight spectrum corresponding to the first flight type, i.e. the most serious single flight spectrum as an example, the sequencing result is shown in fig. 10 (a) -10 (b).
TABLE 7 task segment overload spectrum
(a) Average spectrum
(b) Stringent spectrum
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Step 107, further randomly sequencing the single flight spectrums of different usage profiles to obtain a complete 'flight-continuous-flight' test block spectrum.
In the example, only one profile is used, so that all single flight spectrums of the profiles need only be randomly ordered to obtain a complete 'fly-continue-fly' test block spectrum, as shown in fig. 11 (a) -11 (b).
It was found by comparative analysis that in this example, the overload amplitude of the severe spectrum was increased compared to the average spectrum, the total number of cycles was also significantly increased, and the total number of cycles of the severe spectrum was 1.89 times the average spectrum.
The invention provides a method for compiling a severe gust spectrum based on durability design of gust overrun number curves. Through statistical analysis of an array wind speed exceeding number curve family, an array wind speed curve corresponding to 90% of airplane service conditions is obtained through extrapolation, a Twist spectrum editing method is adopted to compile a serious array wind spectrum, then an overload spectrum is obtained through calculation, and then a flight-continuous-flight overload spectrum is compiled. And the preferred gust speed override may be described by a log-log normal distribution. The typical use section of the P-3C aircraft is combined, an example of a severe gust spectrum of durability design is given, and the feasibility of the method is verified; the comparison analysis shows that the overload amplitude of the severe spectrum is improved compared with the average spectrum, the total cycle number is also obviously increased, and the total cycle number of the severe spectrum is 1.89 times of the average spectrum.
In addition, it will be understood by those skilled in the art that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.
In the description of the embodiments of the invention, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description. Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the invention, one or more aspects of the invention are disclosed and described in order to simplify the present embodiment.
However, the disclosed method should not be construed as reflecting the intention that: i.e., an embodiment of the invention that is claimed, requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (8)
1. A method for compiling a severe gust spectrum based on durability of a discrete gust overrun curve, comprising:
actual measurement U for similar aircraft de The overrunning number curve data are standardized, and standardized overrunning number curve families with different heights are obtained;
the exceeding number delta N under the specified gust speed is subjected to lognormal distribution, the standardized exceeding number curve families with different heights are processed to obtain the fitting result of the distribution parameters of the lognormal distribution, the exceeding number delta N under the gust speed is set to be subjected to the lognormal distribution, and the method comprises the following steps ofObtaining a logarithmic median mu and a logarithmic standard deviation sigma；
Based on the fitting result, ΔN is used i.p ＝μ i +u p＝w σ i Calculate each U dei ΔN corresponding to lower preset coverage rate w i.p ，u p Corresponding to the preset coverage rate; according to U dei Sequentially for delta N from big to small i.p Accumulating the count to obtain an accumulated overrun number N i.p The method comprises the steps of carrying out a first treatment on the surface of the Consists of (U) dei ,N i.p ) Obtaining U corresponding to the preset coverage rate w de An overrunning number curve;
using section task segment parameters of profile in combination with aircraft design, the section segment parameters being defined by the U of the severe-matrix wind spectrum de Obtaining a single flight overload spectrum of the using section through the overrun curve;
and further randomly sequencing the single flight overload spectrums of different using sections according to the length and the composition mode of the flight-continuation-flight block spectrums to obtain a complete flight-continuation-flight test block spectrum.
2. The method of programming a severe gust spectrum based on the durability of a discrete gust overrun profile of claim 1, wherein the preset coverage comprises 90% and/or 50%;
when the preset coverage rate w=90%, u p＝90％ = 1.282, corresponding U de The overrun number curve is a severe overrun number curve;
when the preset coverage ratio w=50%, u p＝50％ =0, corresponding U de The overrun curve is a median overrun curve.
3. The method for generating a severe gust spectrum based on durability of a discrete gust overrun profile of claim 1, wherein normalizing measured overrun profile data for a like aircraft comprises:
obtaining actual measurement U of same class of aircraft de Surpassing the numerical curve data, the aircraft of the same type has the same aircraft configuration, weight and mission profile;
actual measurement U of similar aircraft according to uniform flight distance and altitude interval de Overrun countMerging curve data to obtain standardized U with different heights de Transcendental family of curves.
4. A method for generating a severe gust spectrum based on the durability of a discrete gust overrun curve according to any one of claims 1-3, wherein the determination of the length and configuration of the "fly-continue-fly" block spectrum comprises:
determining the life index of the airplane, the use section, the proportion of different use sections and the parameters of each use section; the parameters of each usage profile include: task segment, height, speed, weight, flight distance and flight time of task segment;
according to the life index of the airplane, the using sections and the proportions of the different using sections, the 'flying-continuing-flying' block spectrum is determined, the length of the single block spectrum is 10% of the life index, and the total flight times of the block spectrum and the proportions of the sections of the block spectrum are determined.
5. A method of generating a severe gust spectrum based on the durability of a discrete gust overrun curve according to any one of claims 1 to 3, characterized by the fact that the mission section parameters of the profile are used in connection with the aircraft design, the U of the severe gust spectrum de The single flight overload spectrum for the usage profile obtained over the number curve includes:
according to a TWIST spectrum programming method, a 5*5 task section array wind spectrum is programmed;
and converting the '5*5' task section array wind spectrum into a task section overload spectrum according to the task section parameters, and sequentially sequencing and connecting to obtain a single flight overload spectrum of the using section.
6. The method for generating a severe gust spectrum based on durability of a discrete gust overrun curve according to claim 5, wherein the method for generating a TWIST spectrum is based on
The system '5*5' task section array wind spectrum comprises:
from U according to mission section flying height and/or distance de Obtaining U with different corresponding heights by exceeding the number curve de Multiplying the overrun number of the task section by the flight distance of the task section to obtain the overrun number of the gust speed of the task section;
carrying out maximum gust speed interception and minimum gust speed interception on the gust speed overrun number under a first preset condition;
discretizing the processed gust speed override number, and compiling to obtain a '5*5' gust speed distribution matrix of a second preset condition.
7. The method for generating a severe gust spectrum based on the durability of a discrete gust overrun curve according to claim 6, wherein the first flight type is most severely damaged and comprises a 5-level gust speed which occurs only once in the "5*5" gust speed distribution matrix of the second preset condition; the fifth flight type has the least damage, only contains the 1-level gust speed and has the largest occurrence frequency;
and/or the number of the groups of groups,
the first preset condition includes: taking the principle that the maximum gust speed is intercepted only once in a single spectrum; given the damage level, a minimum gust speed cut is performed.
8. The method for generating a severe wind gust spectrum based on durability of a discrete wind gust overrun curve according to claim 5, wherein the converting the task segment wind gust spectrum of "5*5" to a task segment overload spectrum according to the task segment parameters, and sequentially sequencing the task segment overload spectrum, the obtaining a single flight overload spectrum using a profile comprises:
according to aircraft aerodynamic, weight and flight parameter data, and according to
Overload;
wherein: delta n is delta overload; u (U) de Is the discrete gust speed ρ 0 For air density, subscript 0 denotes sea level, K g Gust mitigation to account for aircraft heave motion and lift growth lagA factor; c (C) La Is the slope (1/rad) of the lift curve of the aircraft; v e S is the reference wing area for equivalent airspeed; w is the weight of the aircraft; mu (mu) g The quality parameter is marked;the average geometrical chord length of the wing; g is gravity acceleration;
converting the wind gust overload into overload required by a fatigue test, wherein the task section weight is required to be converted into a nominal weight, and a conversion formula is as follows: k (1- Δn,1+Δn); k is the ratio of the mission section weight to the nominal weight of the aircraft;
randomly sequencing overload spectrums of the task segments;
sequentially sequencing the task section overload spectrums according to the sequence in the use section to form a single flight overload spectrum; in the single flight overload spectrum, the severity of the task section overload spectrum is the same, and the total number of times of the single flight spectrum is equal to the number of times of flight of the using section in the block spectrum.
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