CN104021291A - Method for determining fatigue life extension test period of aging aircraft - Google Patents

Method for determining fatigue life extension test period of aging aircraft Download PDF

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CN104021291A
CN104021291A CN201410250164.XA CN201410250164A CN104021291A CN 104021291 A CN104021291 A CN 104021291A CN 201410250164 A CN201410250164 A CN 201410250164A CN 104021291 A CN104021291 A CN 104021291A
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aircraft
machine
load spectrum
life
fatigue
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CN104021291B (en
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何宇廷
高潮
崔荣洪
伍黎明
安涛
杜金强
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Air Force Engineering University of PLA
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Air Force Engineering University of PLA
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Abstract

The invention discloses a method for determining the fatigue life extension test period of an aging aircraft. The method is characterized by including the following steps: (1) selecting fatigue test load spectra of a life extension testing machine, (2) determining the total equivalent flight hours, (3) determining fatigue dispersion coefficients of the remaining fatigue life of the aging aircraft, and (4) determining the fatigue life extension test period of the aging aircraft. The method has the advantages that the fatigue dispersion coefficients of the remaining fatigue life (durability) can be determined according to different flight states of the aging aircraft, and the test period of whole aircraft fatigues (durability) of the aging aircraft is accordingly calculated according to a life extension target; under the condition that an on-service aircraft is on active service under the new whole aircraft fatigue test load spectra, and the load spectra are increased in the follow-up using process, the load spectra with the injury tolerance which is m' times that of the average load spectra of follow-up flights are selected for serving as whole aircraft fatigue test load spectra of the life extension testing machine, and the test period of the whole aircraft fatigues (durability) of the life extension testing machine can be shortened.

Description

Definite method in tired life extension test cycle of Aircraft
Technical field
The present invention relates to a kind of Aircraft definite method in tired life extension test cycle, belong to aircraft experimental study technical field.
Background technology
At present, the fatigue of aircraft (permanance) safe life generally represents with pilot time number, conventionally according to tired (permanance) pilot fight hourage of full machine, divided by tired dispersion coefficient, obtains.When the pilot time of military service aircraft number reaches initial safe during the life-span, in order further to excavate the life-span potentiality of Aircraft, conventionally need to carry out full machine tired (permanance) test to Aircraft, further extend the military service serviceable life of Aircraft.
The method that existing Aircraft tired (permanance) test adopts is conventionally: from pilot time number has reached the military service group of planes aircraft in initial safe life-span, randomly draw an Aircraft of repairing through permanance and carry out full machine tired (permanance) test.Generally, be not that this Aircraft test to destroying under test load spectrum, but determine Aircraft fatigue (permanance) life extension test cycle according to the fatigue of Aircraft (permanance) the safe life target of lengthening the life.The fatigue of Aircraft (permanance) safe life is lengthened the life target conventionally according to the configuration state of aircraft and the task of follow-up flight are given at present.In order to guarantee the security of the follow-up military service of Aircraft, the lengthen the life product of target of the tired dispersion coefficient that utilizes Aircraft residual fatigue (permanance) life-span and tired (permanance) safe life is determined fatigue (permanance) life extension test cycle of Aircraft.
The tired dispersion coefficient in Aircraft residual fatigue (permanance) life-span is to determine under tired (permanance) test load spectrum of the full machine of new machine, and military service aircraft under arms in process due to the variation of the service conditions such as flight subject, its actual maneuvering load spectrum can be different with tired (permanance) test load spectrum of the full machine of new machine, and even difference is very large for some.When military service aircraft practical flight hourage reaches initial safe during the life-span, military service aircraft practical flight hourage is converted to the pilot time number under tired (permanance) test load spectrum of the full machine of new machine according to equivalent damage principle, think equivalent pilot time number.At this moment the equivalent pilot time number of aircraft of being on active service is generally not equal to the initial safe life-span, need determine according to the equivalent pilot time number of military service aircraft the tired dispersion coefficient in Aircraft residual fatigue (permanance) life-span, thereby calculate fatigue (permanance) the life extension test cycle of Aircraft under current life extension test loading spectrum.
As can be seen here, there is following shortcoming in tired (permanance) life extension test technology of existing Aircraft: Aircraft tired (permanance) target of lengthening the life is given, but under the different service states of Aircraft, the residual fatigue dispersion coefficient in residual fatigue (permanance) life-span can only dependence experience carry out value, not theoretical foundation.
Summary of the invention
For solving the deficiencies in the prior art, the object of the present invention is to provide a kind of definite method in tired life extension test cycle of Aircraft of the service life potentiality of fully excavating Aircraft in the situation that not affecting flight safety.
In order to realize above-mentioned target, the present invention adopts following technical scheme:
Definite method in tired life extension test cycle of Aircraft, is characterized in that, comprises the following steps:
(1), choose the fatigue test load spectrum of life extension test machine:
(1), to start be to be on active service under the new full machine fatigue test load spectrum of machine to military service aircraft, follow-up maneuvering load spectrum is constant or lighten, and chooses the full machine fatigue test load spectrum of new machine or suitable loading spectrum as the full machine fatigue test load spectrum of life extension test machine;
(2), to start be to be on active service under the new full machine fatigue test load spectrum of machine to military service aircraft, follow-up maneuvering load spectrum increases the weight of, and chooses the average load spectrum of follow-up flight as the full machine fatigue test load spectrum of life extension test machine;
(2), determine total yield pilot time number:
Suppose that the pilot time number of military service aircraft under the new full machine fatigue test load spectrum of machine is N 1, the pilot time number of being on active service under follow-up flight load spectrum is N 2, the injury tolerance that follow-up flight load is composed under identical pilot time number is l times of the full machine fatigue test load spectrum of new machine injury tolerance, the total yield pilot time of aircraft under the new full machine fatigue test load spectrum of machine of being on active service counts N and is:
N＝N 1+l·N 2；
(3), determine the tired dispersion coefficient of Aircraft remanent fatigue life:
(1), according to the distribution function of former group of planes aircraft parent fatigue lifetime, produce at random the random array of a group obeys logarithm normal distribution/Two-parameter Weibull Distribution, the sample size of every group of random array is b, wherein, a >=50, b >=50;
(2) each random number, in every group of random array all deducts the total yield pilot time and counts N, obtains the new random array that a group is obeyed new lognormal distribution/Two-parameter Weibull Distribution, and the sample size of every group of new random array is b;
(3), according to a, organize logarithm standard deviation/curve shape parameter of the new random array of every group of new random number group digital simulation, obtain a new logarithm standard deviation/curve shape parameter value, and a new logarithm standard deviation/curve shape parameter value averaged;
(4) calculate the tired dispersion coefficient L under fiduciary level P and confidence level γ f:
1., lognormal distribution:
In formula, σ is the logarithm life standard error of Aircraft remanent fatigue life,
U pfor adding up functional value by the determined standardized normal distribution of fiduciary level P,
U γfor adding up functional value by the determined standardized normal distribution of confidence level γ,
N is sample size;
2., Two-parameter Weibull Distribution:
In formula, S cfor confidence factor,
M is curve shape parameter,
R is fiduciary level;
(4), determine the tired life extension test cycle of Aircraft:
Suppose to use the tired safe life of Aircraft under average load spectrum to lengthen the life target for N at current flight g, current flight is used the tired life extension test cycle N under average load spectrum yfor:
N Y＝L f·N g。
Definite method in tired life extension test cycle of aforesaid Aircraft, it is characterized in that, in the process of fatigue test load spectrum of choosing life extension test machine, under arms aircraft start be under the new full machine fatigue test load spectrum of machine, be on active service, follow-up maneuvering load spectrum is increase the weight of in the situation that, the average load spectrum injury tolerance m' that chooses injury tolerance and be follow-up flight loading spectrum is doubly as the full machine fatigue test load spectrum of life extension test machine.
Definite method in tired life extension test cycle of aforesaid Aircraft, is characterized in that, the tired life extension test cycle N of Aircraft yfor:
N Y = L f · N g m ′ .
Usefulness of the present invention is: can determine according to the different state of flight of Aircraft the tired dispersion coefficient in residual fatigue (permanance) life-span, thereby according to the target of lengthening the life, calculate the test period of the full machine of Aircraft tired (permanance); Under arms aircraft start be under the new full machine fatigue test load spectrum of machine, be on active service, follow-up maneuvering load spectrum is increase the weight of in the situation that, the average load spectrum injury tolerance m' that chooses injury tolerance and be follow-up flight loading spectrum doubly, as the full machine fatigue test load spectrum of life extension test machine, can shorten the test period of the full machine of life extension test machine tired (permanance).
Embodiment
Below in conjunction with specific embodiment, the present invention is done to concrete introduction.
Military service aircraft is under arms in process, and due to the variation of the service conditions such as flight subject, its actual maneuvering load spectrum can be different with tired (permanance) test load spectrum of the full machine of new machine, and even difference is very large for some.So, need to choose tired (permanance) test load spectrum of life extension test machine, conventionally can be divided into three kinds of situations:
1, to start be to be on active service the new full machine fatigue test load spectrum of machine (or suitable loading spectrum) is lower to military service aircraft, follow-up maneuvering load spectrum is constant, be on active service aircraft from start to finish all in the lower military service of new machine tired (permanance) test load spectrum of full machine (or suitable loading spectrum), at this moment choose the full machine fatigue test load spectrum of new machine (or suitable loading spectrum) as the full machine fatigue test load spectrum of life extension test machine;
2, to start be to be on active service the new full machine fatigue test load spectrum of machine (or suitable loading spectrum) is lower to military service aircraft, follow-up maneuvering load spectrum lightens, by the 1st kind of situation, process too conservatively, at this moment choose the full machine fatigue test load spectrum of new machine (or suitable loading spectrum) as the full machine fatigue test load spectrum of life extension test machine;
3, to start be to be on active service the new full machine fatigue test load spectrum of machine (or suitable loading spectrum) is lower to military service aircraft, and a period of time N is on active service 1after, due to increasing the weight of of aerial mission, the working strength of aircraft of making to be on active service strengthens, be that follow-up maneuvering load spectrum increases the weight of, military service aircraft is to be on active service under follow-up flight load spectrum, the injury tolerance of follow-up flight load spectrum is l times of tired (permanance) test load spectrum of the full machine of new machine injury tolerance, at this moment in order more realistically military service aircraft to be verified, chooses the average load spectrum of follow-up flight as tired (permanance) test load spectrum of the full machine of life extension test machine.
The 3rd kind of situation choosing tired (permanance) test load spectrum of life extension test machine of take is below example, and method of the present invention is described in detail.
Embodiment 1
1, choose the fatigue test load spectrum of life extension test machine
It is to be on active service under the new full machine fatigue test load spectrum of machine that military service aircraft starts, and follow-up maneuvering load spectrum increases the weight of, and chooses the average load spectrum of follow-up flight as the full machine fatigue test load spectrum of life extension test machine.
2, determine total yield pilot time number
Suppose that the pilot time number of military service aircraft under tired (permanance) test load spectrum of the full machine of new machine is N 1, the pilot time number of being on active service under follow-up flight load spectrum is N 2under identical pilot time number, the injury tolerance of follow-up flight load spectrum is l times that tired (permanance) test load of the full machine of new machine is composed injury tolerance, and the total yield pilot time of aircraft under tired (permanance) test load spectrum of the full machine of new machine of being on active service counts N and is:
N＝N 1+l·N 2。
3, determine the tired dispersion coefficient of Aircraft remanent fatigue life
According to law of great number, when Sample Size is greater than necessarily when several, just can represent parent population parameter by sample estimated value, practical experience it is generally acknowledged that the increment of Sample Size >=50 is large samples.
(1) according to the distribution function of former group of planes aircraft parent fatigue lifetime (can determine longevity conclusion (of pressure testing) by former new machine obtains), produce at random the random array of a group obeys logarithm normal distribution/Two-parameter Weibull Distribution, obtain a sample, representative has tired (permanance) testing data of life-span of a group group of planes aircraft, the sample size of every group of random array is b, represent every group of fatigue (permanance) testing data of life-span that has b airplane, wherein, a >=50, b >=50.
(2), each random number in every group of random array all deducts the total yield pilot time and counts N, obtain the new random array of a group, obtain a group new samples, represent a group Aircraft residual fatigue (permanance) life-span sample, it obeys new lognormal distribution/Two-parameter Weibull Distribution, the sample size of every group of new random array is b, represents every group of residual fatigue (permanance) lifetime data that has b frame Aircraft.
(3), according to a in step (2), organize logarithm standard deviation/curve shape parameter of every group of new random array of new random number group digital simulation, obtain a new logarithm standard deviation/curve shape parameter value, and a new logarithm standard deviation/curve shape parameter value averaged, can obtain logarithm standard deviation/curve shape parameter of new lognormal distribution/Two-parameter Weibull Distribution function, it represents the parameter value (logarithm standard deviation/curve shape parameter) of Aircraft residual fatigue (permanance) life-span distribution function.
(4) according to logarithm standard deviation/curve shape parameter of Aircraft residual fatigue (permanance) the life-span distribution function of life extension test data sample capacity and above-mentioned gained, can calculate the tired dispersion coefficient L under fiduciary level P and confidence level γ f:
1., lognormal distribution:
In formula, σ is the logarithm life standard error of Aircraft remanent fatigue life,
U pfor adding up functional value by the determined standardized normal distribution of fiduciary level P,
U γfor adding up functional value by the determined standardized normal distribution of confidence level γ,
N is sample size;
2., Two-parameter Weibull Distribution:
In formula, S cfor confidence factor,
M is curve shape parameter,
R is fiduciary level;
When m is known, S ccan obtain by following formula:
∫ 0 S C m · n n Γ ( n ) x mn - 1 · e - n · x m dx = γ
When confidence level is 95%, S ccan approximate expression be:
S c = 3 1 m - 1 m lgn .
4, determine the tired life extension test cycle of Aircraft
Suppose to use the tired safe life of Aircraft under average load spectrum to lengthen the life target for N at current flight g, current flight is used the torture test cycle N under average load spectrum yfor:
N Y＝L f·N g。
The derivation of this formula is specific as follows:
According to equivalent damage principle, the target of lengthening the life N gconversion is to the target N that lengthens the life of Aircraft fatigue (permanance) safe life under tired (permanance) test load spectrum of the full machine of new machine j:
N j＝N g·l
According to step 3, can determine the tired dispersion coefficient L in Aircraft residual fatigue (permanance) life-span f, from full angle analysis content to retain sovereignty over a part of the country, the tired median life of Aircraft remanent fatigue life is:
[N 50]＝L f·N j
(1), for lognormal distribution, when sample size is 1, when choosing an airplane and carrying out full machine tired (permanance) test, the tired median life [N in Aircraft residual fatigue (permanance) life-span 50] be exactly the test period N of life extension test machine under tired (permanance) loading spectrum of the full machine of former new machine s.According to equivalent damage principle, the test period N by life extension test machine under tired (permanance) loading spectrum of the full machine of former new machine sconversion is used fatigue (permanance) the test period N under average load spectrum to current flight y:
N Y = N s l = L f · N g .
(2), for Two-parameter Weibull Distribution, when sample size is 1, when choosing an airplane and carrying out full machine tired (permanance) test, the estimated value of characteristics life parameter for:
At this moment, the estimated value of characteristics life parameter can think to be exactly the test period N of life extension test machine under tired (permanance) loading spectrum of the full machine of former new machine s.According to equivalent damage principle, the test period N by life extension test machine under tired (permanance) loading spectrum of the full machine of former new machine sconversion is used fatigue (permanance) the test period N under average load spectrum to current flight y:
N Y = N s l = L f · N g
Therefore current flight is used the tired safe life of the lower Aircraft of average load spectrum to lengthen the life target for N gtime, current flight is used the torture test cycle N under average load spectrum yfor:
N Y＝L f·N g。
For the 3rd kind of situation (it is the situation that military service under the new full machine fatigue test load spectrum of machine, follow-up maneuvering load spectrum increase the weight of that the aircraft of being on active service starts) of choosing tired (permanance) test load spectrum of life extension test machine, make l=1, can obtain choosing the 1st kind of situation of tired (permanance) test load spectrum of life extension test machine and the 2nd kind of situation (aircraft of being on active service start be under the new full machine fatigue test load spectrum of machine, be on active service, follow-up maneuvering load spectrum is constant or situation about lightening) tired life extension test cycle of lower Aircraft, therefore do not repeat them here.
In order to make object of the present invention, technical scheme and advantage clearer, below in conjunction with concrete data, the present invention is further elaborated.
Tired (permanance) the life-span obeys logarithm normal distribution of the aircraft of herein only take is example analytic explanation, and the situation of obedience Two-parameter Weibull Distribution of tired (permanance) life-span of aircraft similarly, repeats no more.
Tired (permanance) the life-span obeys logarithm normal distribution of postulated mechanism swarming machine, the logarithm standard deviation of life-span parent is 0.1021, logarithm mathematical expectation is 4.1761, corresponding 15000 pilot time.Suppose military service aircraft active time N under tired (permanance) test load spectrum of the full machine of new machine 1be 1000 pilot time, active time N under the loading spectrum of follow-up flight 2be 2500 pilot time, the injury tolerance of the loading spectrum of follow-up flight is 1.6 times of tired (permanance) test load spectrum of the full machine of new machine injury tolerance.The average load spectrum that tired (permanance) test load spectrum of the full machine of Aircraft is used for the follow-up flight of military service aircraft, current flight is used average load spectrum, and it was 500 pilot time that Aircraft is used the target of lengthening the life under average load spectrum at current flight.Examination determines that group of planes aircraft is after completing actual 3500 pilot time, then fatigue (permanance) the life extension test cycle of the 500 pilot time safe lifes of lengthening the life (select one to longevity aircraft after permanance is repaired as life extension test machine).
Step (1): choose tired (permanance) test load spectrum of life extension test machine
The 3rd kind of situation of choosing according to tired (permanance) test load spectrum of life extension test machine, chooses military service aircraft current flight and uses average load spectrum as tired (permanance) test load spectrum of the full machine of life extension test machine.
Step (2): determine that the total yield pilot time counts N
The total yield pilot time of military service aircraft under tired (permanance) test load spectrum of the full machine of new machine counts N and is:
N＝N 1+l·N 2＝5000(h)
Step (3): determine tired dispersion coefficient of Aircraft residual fatigue (permanance) life-span
Take 4.1761 as logarithm mathematical expectation, take 0.1021 as logarithm standard deviation, produce at random the random number of 50 groups of obeys logarithm normal distribution, the sample size of every group of random number is 50.50 groups of random numbers represent fatigue (permanance) life-span of 50 groups of group of planes aircrafts, and 50 random numbers in every group of random number represent every group of fatigue (permanance) life-span that has 50 airplanes.Every group of random number deducted to total yield pilot time number 5000 pilot time of military service aircraft under tired (permanance) test load spectrum of the full machine of new machine simultaneously, represent Aircraft residual fatigue (permanance) life-span, and calculate the logarithm standard deviation in every group of Aircraft group of planes residual fatigue (permanance) life-span, obtain 50 logarithm standard deviations, then averaging and just can obtaining the logarithm standard deviation in Aircraft group of planes residual fatigue (permanance) life-span is 0.1556.
When sample size is 1, choose one to longevity aircraft as life extension test machine, the logarithm standard deviation sigma in Aircraft residual fatigue (permanance) life-span is 0.1556 o'clock, fiduciary level P be 99.9% and confidence level γ be that the tired dispersion coefficient dividing in 90% time Aircraft residual fatigue (permanance) life-span is:
L f = 10 ( u γ n - u p ) σ = 4.7898
For the purpose of conservative, suggestion rounds up the tired disperse system numerical value in Aircraft residual fatigue (permanance) life-span, is taken as 5.0.
Step (4): determine tired (permanance) the life extension test cycle N of Aircraft y
Aircraft is used fatigue (permanance) safe life under the average load spectrum target N that lengthens the life at current flight gbe 500 pilot time, according to equivalent damage principle, 500 pilot time of target of lengthening the life converted to lower Aircraft fatigue (permanance) safe life of tired (permanance) test load spectrum of the full machine of new machine target N that lengthens the life j:
N j＝N g·l＝800(h)
According to step (3), can determine the tired dispersion coefficient L in Aircraft residual fatigue (permanance) life-span fbe 5.0, the tired median life in Aircraft residual fatigue (permanance) life-span is:
[N 50]＝L f·N j＝4000(h)
For lognormal distribution, when sample size is 1, when choosing an airplane and carrying out full machine tired (permanance) test, the tired median life [N in Aircraft residual fatigue (permanance) life-span 50] be exactly the test period N of life extension test machine under tired (permanance) loading spectrum of the full machine of former new machine s.
According to equivalent damage principle by life extension test machine the test period N under tired (permanance) loading spectrum of the full machine of former new machine sconversion is used fatigue (permanance) the test period N under average load spectrum to current flight y:
N Y = N s l = L f · N g = 2500 ( h )
It is 2500 pilot fights hour that Aircraft is used fatigue (permanance) the life extension test cycle under average load spectrum at current flight.
Embodiment 2
Under arms aircraft start be under the new full machine fatigue test load spectrum of machine, be on active service, follow-up maneuvering load spectrum is increase the weight of in the situation that, in the process of fatigue test load spectrum of choosing life extension test machine, conventionally choose the average load spectrum of follow-up flight as the full machine fatigue test load spectrum of life extension test machine, the i.e. situation of embodiment 1.
In order to shorten the test period of the full machine of life extension test machine tired (permanance), as a kind of preferred scheme, the average load spectrum injury tolerance m' that chooses injury tolerance and be follow-up flight loading spectrum is doubly as the full machine fatigue test load spectrum of life extension test machine.
So, definite method in tired life extension test cycle of Aircraft of the present invention, implementation step is as follows:
1, choose the fatigue test load spectrum of life extension test machine
It is to be on active service under the new full machine fatigue test load spectrum of machine that military service aircraft starts, and follow-up maneuvering load spectrum increases the weight of, and the average load spectrum injury tolerance m' that chooses injury tolerance and be follow-up flight loading spectrum is doubly as the full machine fatigue test load spectrum of life extension test machine.
2, determine total yield pilot time number
Suppose that the pilot time number of military service aircraft under tired (permanance) test load spectrum of the full machine of new machine is N 1, the pilot time number of being on active service under follow-up flight load spectrum is N 2under identical pilot time number, the injury tolerance of follow-up flight load spectrum is l times that tired (permanance) test load of the full machine of new machine is composed injury tolerance, and the total yield pilot time of aircraft under tired (permanance) test load spectrum of the full machine of new machine of being on active service counts N and is:
N＝N 1+l·N 2。
3, determine the tired dispersion coefficient of Aircraft remanent fatigue life
According to law of great number, when Sample Size is greater than necessarily when several, just can represent parent population parameter by sample estimated value, practical experience it is generally acknowledged that the increment of Sample Size >=50 is large samples.
(1) according to the distribution function of former group of planes aircraft parent fatigue lifetime (can determine longevity conclusion (of pressure testing) by former new machine obtains), produce at random the random array of a group obeys logarithm normal distribution/Two-parameter Weibull Distribution, obtain a sample, representative has tired (permanance) testing data of life-span of a group group of planes aircraft, the sample size of every group of random array is b, represent every group of fatigue (permanance) testing data of life-span that has b airplane, wherein, a >=50, b >=50.
(2), each random number in every group of random array all deducts the total yield pilot time and counts N, obtain the new random array of a group, obtain a group new samples, represent a group Aircraft residual fatigue (permanance) life-span sample, it obeys new lognormal distribution/Two-parameter Weibull Distribution, the sample size of every group of new random array is b, represents every group of residual fatigue (permanance) lifetime data that has b frame Aircraft.
(3), according to a in step (2), organize logarithm standard deviation/curve shape parameter of every group of new random array of new random number group digital simulation, obtain a new logarithm standard deviation/curve shape parameter value, and a new logarithm standard deviation/curve shape parameter value averaged, can obtain logarithm standard deviation/curve shape parameter of new lognormal distribution/Two-parameter Weibull Distribution function, it represents the parameter value (logarithm standard deviation/curve shape parameter) of Aircraft residual fatigue (permanance) life-span distribution function.
(4) according to logarithm standard deviation/curve shape parameter of Aircraft residual fatigue (permanance) the life-span distribution function of life extension test data sample capacity and above-mentioned gained, can calculate the tired dispersion coefficient L under fiduciary level P and confidence level γ f:
1., lognormal distribution:
In formula, σ is the logarithm life standard error of Aircraft remanent fatigue life,
U pfor adding up functional value by the determined standardized normal distribution of fiduciary level P,
U γfor adding up functional value by the determined standardized normal distribution of confidence level γ,
N is sample size;
2., Two-parameter Weibull Distribution:
In formula, S cfor confidence factor,
M is curve shape parameter,
R is fiduciary level;
When m is known, S ccan obtain by following formula:
∫ 0 S C m · n n Γ ( n ) x mn - 1 · e - n · x m dx = γ
When confidence level is 95%, S ccan approximate expression be:
S c = 3 1 m - 1 m lgn .
4, determine the tired life extension test cycle of Aircraft
Suppose to use the tired safe life of Aircraft under average load spectrum to lengthen the life target for N at current flight g, current flight is used the torture test cycle N under average load spectrum yfor:
N Y = L f · N g m ′ .
The derivation of this formula is specific as follows:
According to equivalent damage principle, the target of lengthening the life N gconversion is to the target N that lengthens the life of Aircraft fatigue (permanance) safe life under tired (permanance) test load spectrum of the full machine of new machine j:
N j＝N g·l
According to step 3, can determine the tired dispersion coefficient L in Aircraft residual fatigue (permanance) life-span f, from full angle analysis content to retain sovereignty over a part of the country, the tired median life of Aircraft remanent fatigue life is:
[N 50]＝L f·N j
(1), for lognormal distribution, when sample size is 1, when choosing an airplane and carrying out full machine tired (permanance) test, the tired median life [N in Aircraft residual fatigue (permanance) life-span 50] be exactly the test period N of life extension test machine under tired (permanance) loading spectrum of the full machine of former new machine s.
According to equivalent damage principle, the test period N by life extension test machine under tired (permanance) loading spectrum of the full machine of former new machine sconversion is used fatigue (permanance) the test period N under average load spectrum to current flight y:
N Y = N s l = L f · N g
If the average load spectrum injury tolerance m' that chooses injury tolerance and be follow-up flight loading spectrum is doubly as the full machine fatigue test load spectrum of life extension test machine, tired (permanance) life extension test cycle of Aircraft be basis on shorten again m' doubly, N yfor:
N Y = 1 m ′ · N s l = L f · N g m ′
(2), for Two-parameter Weibull Distribution, when sample size is 1, when choosing an airplane and carrying out full machine tired (permanance) test, the estimated value of characteristics life parameter for:
At this moment, the estimated value of characteristics life parameter can think to be exactly the test period N of life extension test machine under tired (permanance) loading spectrum of the full machine of former new machine s.
According to equivalent damage principle, the test period N by life extension test machine under tired (permanance) loading spectrum of the full machine of former new machine sconversion is used fatigue (permanance) the test period N under average load spectrum to current flight y:
N Y = N s l = L f · N g
If the average load spectrum injury tolerance m' that chooses injury tolerance and be follow-up flight loading spectrum is doubly as the full machine fatigue test load spectrum of life extension test machine, tired (permanance) life extension test cycle of Aircraft be basis on shorten again m' doubly, N yfor:
N Y = 1 m ′ · N s l = L f · N g m ′
As can be seen here, definite method in tired life extension test cycle of Aircraft of the present invention is further perfect can not determine the deficiency of tired dispersion coefficient of Aircraft residual fatigue (permanance) life-span under different conditions in tired (permanance) life extension test technology of existing Aircraft, for extending tired (permanance) service life of Aircraft, provide powerful, technical support reliably.
It should be noted that, above-described embodiment does not limit the present invention in any form, and all employings are equal to replaces or technical scheme that the mode of equivalent transformation obtains, all drops in protection scope of the present invention.

Claims (3)

1. definite method in tired life extension test cycle of Aircraft, is characterized in that, comprises the following steps:
(1), choose the fatigue test load spectrum of life extension test machine:
(1), to start be to be on active service under the new full machine fatigue test load spectrum of machine to military service aircraft, follow-up maneuvering load spectrum is constant or lighten, and chooses the full machine fatigue test load spectrum of new machine or suitable loading spectrum as the full machine fatigue test load spectrum of life extension test machine;
(2), to start be to be on active service under the new full machine fatigue test load spectrum of machine to military service aircraft, follow-up maneuvering load spectrum increases the weight of, and chooses the average load spectrum of follow-up flight as the full machine fatigue test load spectrum of life extension test machine;
(2), determine total yield pilot time number:
Suppose that the pilot time number of military service aircraft under the new full machine fatigue test load spectrum of machine is N 1, the pilot time number of being on active service under follow-up flight load spectrum is N 2, the injury tolerance that follow-up flight load is composed under identical pilot time number is l times of the full machine fatigue test load spectrum of new machine injury tolerance, the total yield pilot time of aircraft under the new full machine fatigue test load spectrum of machine of being on active service counts N and is:
N＝N 1+l·N 2；
(3), determine the tired dispersion coefficient of Aircraft remanent fatigue life:
(1), according to the distribution function of former group of planes aircraft parent fatigue lifetime, produce at random the random array of a group obeys logarithm normal distribution/Two-parameter Weibull Distribution, the sample size of every group of random array is b, wherein, a >=50, b >=50;
(2) each random number, in every group of random array all deducts the total yield pilot time and counts N, obtains the new random array that a group is obeyed new lognormal distribution/Two-parameter Weibull Distribution, and the sample size of every group of new random array is b;
(3), according to a, organize logarithm standard deviation/curve shape parameter of the new random array of every group of new random number group digital simulation, obtain a new logarithm standard deviation/curve shape parameter value, and a new logarithm standard deviation/curve shape parameter value averaged;
(4) calculate the tired dispersion coefficient L under fiduciary level P and confidence level γ f:
1., lognormal distribution:
In formula, σ is the logarithm life standard error of Aircraft remanent fatigue life,
U pfor adding up functional value by the determined standardized normal distribution of fiduciary level P,
U γfor adding up functional value by the determined standardized normal distribution of confidence level γ,
N is sample size;
2., Two-parameter Weibull Distribution:
In formula, S cfor confidence factor,
M is curve shape parameter,
R is fiduciary level;
(4), determine the tired life extension test cycle of Aircraft:
Suppose to use the tired safe life of Aircraft under average load spectrum to lengthen the life target for N at current flight g, current flight is used the tired life extension test cycle N under average load spectrum yfor:
N Y＝L f·N g。
2. definite method in tired life extension test cycle of Aircraft according to claim 1, it is characterized in that, in the process of fatigue test load spectrum of choosing life extension test machine, under arms aircraft start be under the new full machine fatigue test load spectrum of machine, be on active service, follow-up maneuvering load spectrum is increase the weight of in the situation that, the average load spectrum injury tolerance m' that chooses injury tolerance and be follow-up flight loading spectrum is doubly as the full machine fatigue test load spectrum of life extension test machine.
3. definite method in tired life extension test cycle of Aircraft according to claim 2, is characterized in that, the tired life extension test cycle N of Aircraft yfor:
N Y = L f · N g m ′ .
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