CN104359696A - Method for determining calendar safety service life of airplane structure base body - Google Patents
Method for determining calendar safety service life of airplane structure base body Download PDFInfo
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Abstract
The invention discloses a method for determining the calendar safety service life of an airplane structure base body. The method for determining the calendar safety service life of the airplane structure base body is characterized by comprising the following steps that an research object is selected, and structure base body simulation test articles are designed and manufactured; a structure local base body environment spectrum and a structure load spectrum are compiled; the base body calendar safety service life of a loaded structure (corrosion fatigue key components and stress corrosion key components) is determined; the base body calendar safety service life of an unloaded structure is determined. The method for determining the calendar safety service life of the airplane structure base body has the advantages that the calendar safety service life of the airplane structure base body can be determined by the adoption of the method, accordingly, the safety service life of the structure base body can be determined after an airplane structure protection system loses efficacy, and thus it is of great significance to guaranteeing the serviceability safety of an airplane structure.
Description
Technical field
The present invention relates to a kind of defining method of aircaft configuration matrix calendar safe life, belong to aircaft configuration and determine longevity technical field.
Background technology
The life-span of aircraft refers to aircraft term of life from the retired grounding of coming into operation under normal service state, refer generally to the structural life-time of airframe, there are two leading indicators: one is consider that flight alternate load is to the fatigue lifetime of structure influence, characterizes with pilot time number or the number of times that rises and falls; Two is consider that environmental corrosion is to the calendar life of structure influence, characterizes with tenure of use.When the longevity determined by aircaft configuration, no matter be fatigue lifetime or calendar life, include corresponding head and turn over phase, time between overhaul and entire life, and should provide and repair outline accordingly.In existing life-span management means, when the equivalent pilot time number of aircraft, arbitrary index of rising and falling in number of times and tenure of use three indexs reach the setting when longevity determined by aircraft, all mean that aircaft configuration reaches and use restriction and to the longevity.
Aircaft configuration matrix is the remainder after surfacecti proteon system removed by aircaft configuration, and generally playing a part holding structure shape and load, is the major part that aircaft configuration plays its function, is also the pith affecting aircaft configuration safety.The calendar life of aircaft configuration matrix is the important component part of calendar life of aircraft structure, to ensureing that the safety of aircaft configuration is significant.
Existingly determine that the method for structural matrix calendar life is mainly based on empirical method and test method(s).
(1) empirical method
Mainly according to Long-Time Service experience, carry out analogy with close type, adopt leading flight of part aircraft put into practice and by structure overhaul check, determine calendar entire life and overhaul period.In the deterministic process of aircraft calendar life, include the determination of structural matrix calendar life.Empirical method is adopted to carry out the evaluation of structure structural matrix calendar life, relevant with the experience of estimator own, still there is no complete theory support.
(2) test method(s)
By working out the equivalent accelerated environment spectrum of aircaft configuration and loading spectrum, carrying out structural matrix simulating piece accelerated corrosion test in laboratory conditions or corrosion fatigue test, verifying the injuring rule of matrix under equivalent accelerated environment spectrum and loading spectrum.How the method in the judgement of structural matrix failure criteria, and is generally also provided by experience according in the problems such as the calendar life of test findings determination aircraft practical structures matrix, does not have systematic method to support.
But present stage, to the research of aircaft configuration matrix corrosion problem, does not exist the process of fail-safe analysis, and the calendar life provided by it refers to life-span during structural failure, instead of meet the security restriction value that certain fiduciary level and confidence level require.In fact, the corrosion failure time of identical type structural matrix has dispersiveness, and its calendar life obeys certain probability distribution rule.If the part-structure considered repealed time in a group of planes is shorter than the calendar life determined, then because maintenance causes the damage of aircaft configuration matrix not in time, flight safety may be threatened.Therefore, for the calendar life of aircaft configuration matrix, also reliability design thought should be implemented.
For this reason, the present invention proposes the concept of aircaft configuration matrix calendar safe life, and establish the defining method of aircaft configuration matrix calendar safe life, the longevity of determining of being intended to for aircaft configuration provides technical support.
Summary of the invention
The object of the present invention is to provide a kind of defining method of aircaft configuration matrix calendar safe life, for rationally determining the calendar life of aircaft configuration matrix, using aircaft configuration to provide Theories and methods support safely.
In order to realize above-mentioned target, the present invention adopts following technical scheme:
A defining method for aircaft configuration matrix calendar safe life, is characterized in that, comprise the following steps:
Step 1: choose research object, manufacture and design structural matrix simulation test piece;
Step 2: programming structure local matrix Environmental Spectrum and structural loads spectrum;
Step 3: the matrix calendar safe life determining aircaft configuration
For the corrosion fatigue key component in loaded structure, determine that the step of its matrix calendar safe life is as follows:
(1) the fatigue safety life-span of overall aircraft is determined;
(2) testpieces is divided into some groups, often organizes testpieces under accelerated environment spectrum, experience the different pre-etching cycles;
(3), after pre-etching, under the loading spectrum of establishment, torture test is carried out to fracture;
(4) under selected fiduciary level and confidence level, the safe life often organizing prior-corroded fatigue testpieces is calculated;
(5) the prior-corroded fatigue safe life often organizing testpieces is carried out matching, simulate a pre-etching cycle to the influence curve in fatigue safety life-span;
(6) the Residual Damage degree of computation structure matrix after protection system lost efficacy;
(7) in the pre-etching cycle to the influence curve in fatigue safety life-span being determined the point corresponding with the residue pilot time number of aircraft or the application plan of aircraft, thus determine the year injury tolerance of structural matrix under its corresponding flight rate or under its application plan, namely Residual Damage degree is obtained the calendar safe life of corrosion fatigue key component divided by year injury tolerance;
For the stress corrosion key component in loaded structure, determine that the step of its matrix calendar safe life is as follows:
(1) position and the direction of check that the most easily produce stress corrosion crack in structure is determined;
(2) testpieces is divided into some groups, according to the position and the direction of check that the most easily produce stress corrosion crack, to the initial crack of the preset different length of the testpieces of difference group;
(3) stress corrosion (cracking) test of each group of testpieces is carried out;
(4) propagation law of identified sign corrosion cracking and Critical fracture length;
(5) dispersion coefficient under given fiduciary level and confidence level is tried to achieve;
(6) namely stress corrosion cracking (SCC) expansion time is obtained the calendar safe life of stress corrosion key component divided by dispersion coefficient;
For not loaded structure, determine that the step of its matrix calendar safe life is as follows:
(1) criterion of the disabler of not loaded structure is determined;
(2) carry out the corrosion test of testpieces, at set intervals extraction portion separating tests part measure the maximum corrosion depth of testpieces, obtain meeting under this abrasion cycle the matrix maximum corrosion depth that given fiduciary level and confidence level require;
(3) comprehensively analyze meeting the matrix maximum corrosion depth that given fiduciary level and confidence level require under different abrasion cycle, obtain abrasion cycle when structure reaches failure criteria, the aforementioned abrasion cycle i.e. matrix calendar safe life of not loaded structure.
The defining method of aforesaid aircaft configuration matrix calendar safe life, is characterized in that, in step 1, aforementioned structure matrix simulation test piece carries out design and manufaction according to the corrosion failure form of research object.
The defining method of aforesaid aircaft configuration matrix calendar safe life, is characterized in that, in step 2, the process of programming structure local matrix Environmental Spectrum is as follows:
(2a) the actual Service Environment of aircraft is surveyed, determine the external environment condition feature of aircraft;
(2b) set up want the local environment at research structure place and the relational model of external environment condition;
(2c) according to determined aircaft configuration local environment feature, programming structure local matrix Environmental Spectrum.
The defining method of aforesaid aircaft configuration matrix calendar safe life, is characterized in that, in step 2, according to the flight actual measurement load programming structure loading spectrum of aircaft configuration.
The defining method of aforesaid aircaft configuration matrix calendar safe life, it is characterized in that, in step 4, aforementioned not loaded structure is not loaded structure completely, the criterion of not loaded structure disabler is completely: structure generation penetrability is corroded, or corrosion product peels off and has influence on the performance of other position functions.
The defining method of aforesaid aircaft configuration matrix calendar safe life, it is characterized in that, in step 4, aforementioned not loaded structure is non-fully not loaded structure, and the criterion of non-fully not loaded structure disabler is: non-fully is the maximum corrosion depth that allows of loaded structure not.
Usefulness of the present invention is:
1, the defining method of aircaft configuration matrix calendar safe life that provides of the present invention, may be used for the safe service life determining structural matrix after aircaft configuration protection system lost efficacy, to ensureing that the use safety of aircaft configuration is significant;
2, aircaft configuration matrix calendar safe life is the basis determining the overall calendar safe life of aircaft configuration, the present invention is to determining the overall calendar safe life of aircaft configuration, and and then determine that the calendar safe life of the full machine of aircraft is significant, to promoting, the management level of Aircraft Structural Life are significant.
Accompanying drawing explanation
Fig. 1 is the process flow diagram of determination aircaft configuration matrix calendar safe life of the present invention;
Fig. 2 is the structural representation of aircraft bulkhead matrix simulation test piece.
Embodiment
First, the concept of aircaft configuration matrix calendar safe life is introduced.
The matrix calendar safe life of aircaft configuration; refer under the protective effect not having surfacecti proteon system; can complete the calendar service time of its using function according to the determined aircaft configuration matrix of safe-life design criterion, the aircaft configuration matrix namely obtained by fail-safe analysis has the calendar life restriction of pole low corrosion failure probability.
The calendar safe life of structural matrix, with position, structure loading conditions, the relating to parameters such as fiduciary level and confidence level residing for the environment for use of the material selected by structural matrix and processing technology, version and Anti fatigue Design level, aircraft and military service course, structure.The form that corrosion occurs structural matrix may comprise contact corrosion, spot corrosion, degrades, stress corrosion crack, corrosion fatigue crack etc., and concrete needs is analyzed according to material type, version and structure loading conditions.In order to ensure the safe and reliable of structural matrix, according to the Corrosion Types of structural matrix and structural matrix corrosion damage rule under this form, the structural matrix calendar safe life under given fiduciary level and confidence level to be determined.
Structural matrix material corrodes, and will directly affect the performance of structure allomeric function, threatens flight safety.Therefore, the calendar safe life of structural matrix is relevant to the safety in utilization of structure, must choose a very high fiduciary level, make structural matrix have extremely low corrosion failure probability within its calendar safe life phase, to guarantee the use safety of structure.The distribution pattern that fiduciary level and confidence level will be obeyed according to its corrosion damage life-span is usually determined.Such as, if the corrosion damage life-span obeys logarithm normal distribution of structural matrix, then the fiduciary level of calendar safe life demand fulfillment 99.9% of structural matrix and the confidence level of 90%; If obedience Weibull distribution, then the fiduciary level of demand fulfillment 95% and the confidence level of 95%.Next, the defining method of aircaft configuration matrix calendar safe life of the present invention is introduced by reference to the accompanying drawings with specific embodiment.
With reference to Fig. 1, determine the method for aircaft configuration matrix calendar safe life, specifically comprise the steps:
Step 1: choose research object, manufacture and design structural matrix simulation test piece
Can consider from the angle of relatively safety, the testpieces selected by research structure matrix calendar safe life does not have the protection of any surfacecti proteon system.
First, select the research object of matrix calendar safe life according to the object of research, as the main load-bearing part etc. of corrosion-vulnerable most in aircaft configuration.
Secondly, determine the corrosion failure form of research object according to the material, processing technology, position, loading conditions etc. of research object, as spot corrosion, degrade, corrosion fatigue, stress corrosion crack etc.
Again, according to the corrosion failure form of research object, the design and manufaction of structural simulation testpieces is carried out.
Carry out the design and manufaction of matrix simulation test piece, need to follow following principle:
(1) testpieces uses the matrix material consistent with aircraft practical structures, comprises identical material trademark, identical processing technology, identical condition of heat treatment etc.;
(2) testpieces surface removal protection system;
(3) shape and size designing of simulation test piece is carried out according to practical structures and corrosion failure form thereof: 1. in testpieces, all should consider that those affect the architectural feature of material corrosion, as contact, circular hole etc.; If 2. practical structures not stand under load, then it is relatively simple that corresponding with it testpieces can design, as long as can reflect corrosion regularity; If 3. practical structures stand under load, then corresponding testpieces should be designed to can in the upper convenient shape loaded of fatigue tester (or at stress corrosion loading equipemtn), this type of testpieces also wants the local feature that can reflect practical structures, is distributed in practical structures consistent with local stress when guaranteeing testpieces stand under load;
(4) aircraft of a group of planes is produced by the time longer for experience, therefore, the matrix material that an actual group of planes adopts may not be one batch and produce, and adds the starting material that man-hour should select different batches as far as possible, to reflect the dispersiveness of material and technology at testpieces.
Step 2: programming structure local matrix Environmental Spectrum and structural loads are composed
Carry out the accelerated test study under laboratory condition, must the local environment equivalent damage of the accelerated environment spectrum that adopts of warranty test and aircaft configuration position, this just needs the local accelerated environment spectrum at position, programming structure place.
First, the actual Service Environment of aircraft is surveyed, determine the external environment condition feature of aircraft.Secondly, set up want the local environment at research structure place and the relational model of external environment condition.Again, according to determined aircaft configuration local environment feature, programming structure local environment accelerates spectrum.
Although to the aircaft configuration of stand under load mainly to manage fatigue lifetime, but under the acting in conjunction of corrosion environment and load (cyclic loading, static load or unrelieved stress), may be there is corrosion fatigue or stress corrosion crack in structure, these situations also should bring the research category of matrix calendar safe life into.Therefore, the flight actual measurement load according to aircaft configuration is needed, programming structure loading spectrum.
It should be noted that, reflected the loading conditions of actual measurement aircraft according to the loading spectrum of aircaft configuration actual measurement load establishment, generally can be described as reference load spectrum.But due to the difference of completed aerial mission, under same model, the load order of severity of different aircraft is distinguished to some extent.When benchmark loading spectrum determined matrix calendar safe life carries out aircaft configuration matrix life-span management, the practical flight hourage equivalent damage of aircraft should be converted the reference flight hourage under reference load spectrum.
Step 3: the matrix calendar safe life determining aircaft configuration
Aircaft configuration is divided into loaded structure and non-loaded structure, introduces the defining method of its matrix calendar safe life below respectively.
First, the defining method of the matrix calendar safe life of loaded structure is introduced.
Loaded structure in aircaft configuration, its biggest threat being corroded environmental impact is generally corrosion fatigue or stress corrosion crack.
(1) for corrosion fatigue key component, determine that the concrete steps of its matrix calendar safe life are as follows:
1. according to the design level of aircraft, the fatigue safety life-span of overall aircraft is determined;
2. testpieces is divided into some groups, often organizes testpieces under accelerated environment spectrum, experience the different pre-etching cycles (equivalence corrosion year number);
3., after pre-etching, under the loading spectrum of establishment, torture test is carried out to fracture;
4., under selected fiduciary level and confidence level, the safe life often organizing prior-corroded fatigue testpieces is calculated;
5. the prior-corroded fatigue safe life often organizing testpieces is carried out matching, simulate a pre-etching cycle to the influence curve in fatigue safety life-span;
6. the Residual Damage degree of computation structure matrix after protection system lost efficacy;
If 7. the use target of aircraft is finished in the design fatigue safety life-span of aircaft configuration, then can according to the pre-etching cycle to the corresponding point in the residue pilot time number determination curve of the influence curve in fatigue safety life-span and aircraft, thus determine the year injury tolerance of structural matrix under its corresponding flight rate, consider the Residual Damage degree of structural matrix after protection system lost efficacy, just can in the hope of the calendar safe life of structural matrix;
If 8. aircraft uses according to predetermined flight planning, can according to the pre-etching cycle to the corresponding point in the application plan determination curve of the influence curve in fatigue safety life-span and aircraft, thus determine the year injury tolerance of structural matrix under this application plan, consider the Residual Damage degree of structural matrix after protection system lost efficacy, just can in the hope of the calendar safe life of structural matrix.
Make following supplementary notes to said process: the fatigue safety life-span of overall aircraft is determined by some specific crucial bearing members, fatigue safety life-span of aircraft is inherently provided by torture test and fail-safe analysis by these structural members.If with its matrix calendar safe life of these structural researches, its fatigue safety life-span after excessive erosion cannot reach design fatigue safety life-span of aircraft certainly.That is, for these structures, to by it with to the fatigue safety life-span to the longevity, the calendar safe life of its matrix is 0 year, namely the matrix of these structures can not be corroded impact, their protection system calendar safe life should have very high level of reliability, to ensure that protection system is effective before structure overhaul.For other positions of aircaft configuration, although be also manage according to the airplane design fatigue safety life-span, the fatigue safety life-span of their reality is longer than the design fatigue safety life-span of aircraft.Therefore, the matrix material of these structures, after living through the environmental corrosion of some cycles, is the design fatigue safety life requirements that can reach aircraft.Determine the essence of matrix calendar safe life, determine above-mentioned abrasion cycle exactly.
(2) for stress corrosion key component, determine that the step of its matrix calendar safe life is as follows:
1. stress analysis is carried out to structure, determine the position and the direction of check that the most easily produce stress corrosion crack in structure;
2. testpieces is divided into some groups, according to the position and the direction of check that the most easily produce stress corrosion crack, to the initial crack of the preset different length of the testpieces of difference group (wherein one group of not pre-existing crack, for the identified sign corrosion cracking time);
3. the stress corrosion (cracking) test of each group of testpieces is carried out;
4. each group of test figure is comprehensively analyzed, the propagation law of identified sign corrosion cracking and Critical fracture length;
5. by fail-safe analysis, the dispersion coefficient under given fiduciary level and confidence level is tried to achieve;
6. by stress corrosion cracking (SCC) expansion time divided by dispersion coefficient, obtain the calendar safe life of stress corrosion key component.
In actual applications, integrated structure inspection is answered in the management carrying out matrix calendar safe life, if structural matrix has found when overhaul to be present in corrosion damage, should place under repair to damage location immediately, and the life appraisal of structure after placing under repair, judge that can structure once have enough fiduciary levels to ensure not lose efficacy before overhaul on arriving.
Next, the defining method of the matrix calendar safe life of not loaded structure is introduced.
Determining the matrix calendar safe life of not loaded structure, is first the criterion of the disabler will determining not loaded structure.
For in aircaft configuration completely not by the structure (called after completely not loaded structure) of load, the criterion of its disabler can be taken as the corrosion of structure generation penetrability, or corrosion product peels off and has influence on the performance of other position functions.
But, a class formation is also there is in aircaft configuration, they are not completely not by the impact of load, but loading conditions is less, corrosion fatigue structure can not be divided into, and not be subject to the effect of lasting static load or unrelieved stress, stress corrosion structure can not be divided into, the category that this class formation can be divided into not loaded structure carries out calendar life management, existing by this class formation called after non-fully not loaded structure, in order to distinguish not loaded structure completely above-mentioned.That is, loaded structure does not comprise: not loaded structure and non-fully not loaded structure completely.For non-fully not loaded structure, need the maximum load that may run within the aircraft life. cycle phase according to them as examination condition, by test or stress analysis, judge the non-fully not maximum corrosion depth that allows of loaded structure, and using the maximum corrosion depth allowed as the criterion of aircaft configuration disabler.
Carry out the corrosion test of testpieces, extraction portion separating tests part measure the maximum corrosion depth of testpieces at set intervals, then carry out Study on regularity and the fail-safe analysis of maximum corrosion depth, obtain meeting under this abrasion cycle the matrix maximum corrosion depth that given fiduciary level and confidence level require.
Comprehensively analyzing meeting the matrix maximum corrosion depth that fiduciary level and confidence level require under different abrasion cycle, determining the Changing Pattern of matrix maximum corrosion depth.
According to the Changing Pattern of matrix maximum corrosion depth, abrasion cycle when structure reaches failure criteria can be obtained, i.e. the matrix calendar safe life of not loaded structure.
Below for the loaded structure bulkhead of aircraft, further illustrate method of the present invention.
Step 1: choose research object, manufacture and design structural matrix simulation test piece
With the bulkhead of aircraft for research object, the position that this structure is the weakest is positioned at its thickness thinnest part, and the form that corrosion failure occurs is corrosion fatigue crack.Therefore, the matrix testpieces of design as shown in Figure 2.Testpieces material therefor is consistent with practical structures, is 2A12-T4 aluminium alloy; Testpieces is drawn materials along rolling direction, without surfacecti proteon process, without aluminium coating.In Fig. 2, shadow region is the examination district of testpieces, and when carrying out corrosion test, the exposed corrosive attack accepting accelerated environment spectrum in this region, all the other positions use paraffin sealing.
Step 2: programming structure local matrix Environmental Spectrum and structural loads are composed
Laboratory acceleration environment test is carried out in salt-mist corrosion tester, corrosion temperature is 40 ± 2 DEG C, and corrosive liquid is 5%NaCl aqueous solution, adds a small amount of rare H2SO4, make the pH value of solution reach 4-4.5, the salt fog deposition of salt spray test chamber controls at 1-2mL/ (h80cm
2).Under this corrosion environment, often corrosion is then equivalent to practical structures corrosion 1 year under environment under arms for 65 hours.
Fatigue load spectrum selects constant amplitude load to compose the mode loaded, and maximum stress 190MPa, stress ratio is 0.06.Under this loading environment, namely the load injury of 40 circulations is equivalent to the aircraft practical flight amount of damage of 1 hour.
Step 3: determine that the corrosion time limit is on the impact in matrix fatigue safety life-span
This testpieces is divided into some groups, after each group of testpieces distinguishes pre-etching 0 hour, 325 hours, 650 hours, 1300 hours and 1950 hours (equivalence 0 year, 5 years, 10 years, 20 years and 30 years), carry out torture test respectively, the test findings obtained is as shown in table 1.
Fatigue lifetime due to aircaft configuration general obeys logarithm normal distribution, the fiduciary level of fatigue safety life-span demand fulfillment 99.9% and the confidence level of 90%, the fatigue safety life-span can be tried to achieve by formula (1):
In formula (1), N
99.9(T) be equivalence corrosion T after the fatigue safety life-span;
for the logarithmic mean of test life after equivalence corrosion T; K is the monolateral tolerance factor of satisfied 99.9% fiduciary level and 90% confidence level; S
tfor the logarithm standard deviation of test life after equivalence corrosion T.Wherein:
The logarithmic mean of test life after equivalence corrosion T
can be tried to achieve by formula (2):
The logarithm standard deviation S of test life after equivalence corrosion T
tcan be tried to achieve by formula (3):
In formula (2) and formula (3), n is data amount check, N
i(T) be the fatigue lifetime that rear i-th testpieces of T is corroded in equivalence;
Monolateral tolerance factor k obtains by searching GB/T 4885-2009, because valid data are 4 in this example, so checking in result k value is 7.1293.
Equivalence being corroded the fatigue safety life-span after Different years also lists table 1 in.
Table 1 structural matrix simulating piece prior-corroded fatigue test findings
The fatigue safety life-span of equivalence being corroded the matrix simulating piece of Different years carries out matching, and the fitting formula obtained is as follows:
N
99.9(T)＝5150-715.85T
0.537(4)
Degree of fitting R
2=0.999, meet the accuracy requirement of engineer applied.
Step 4: the matrix calendar safe life determining loaded structure
The design fatigue safety life-span of aircraft was 4500 pilot time.After supposing aircraft utilization 3900 pilot time, the protection system of institute's research structure (aircraft bulkhead) lost efficacy.Because the actual fatigue safety life-span of institute's research structure was 5150 pilot time, then the Residual Damage degree of this structural matrix is 1-3900/5150=0.2427.
According to the actual user demand of aircraft, determine the calendar safe life of structural matrix in two kinds of situation.
Situation 1: the use target of aircraft is finished in the design fatigue safety life-span of aircraft
Calendar etching time corresponding to (4500-3900)/0.2427=2472 pilot time is found on the influence curve in matrix fatigue safety life-span, by N at the corrosion time limit
99.9(T)=2472 substitute into formula (4), obtain T=11.66.This means that structural matrix is under the protective effect not having protection system, corrode 11.66, can use for 2472 pilot time safely; Can use for 212 pilot time every year on average, the year injury tolerance of structure correspondence under this flight rate is 212/2472=0.0858.
Residual Damage degree due to structural matrix is 0.2427, then the calendar safe life of structural matrix is 0.2427/0.0858=2.83.
Be finished at remaining 600 pilot time in 2.83, the annual flight rate of its correspondence was 212 pilot time just.
Situation 2: aircraft uses according to predetermined flight planning
Suppose that the flight application plan of aircraft is annual 150 pilot time.
At the corrosion time limit to the influence curve in matrix fatigue safety life-span being found point corresponding to flight rate 150 pilot time in year.According to formula N
99.9(T)=150T and formula (4), try to achieve T=14.4, N
99.9(T)=2160 pilot time.
This means that structural matrix is under the protective effect not having protection system, annual used for 150 pilot time, 14.4 can be used safely, 2160 pilot time; The year injury tolerance of structure correspondence under this flight rate is 150/2160=0.0694.
Residual Damage degree due to structural matrix is 0.2427, then the calendar safe life of structural matrix is 0.2427/0.0694=3.50.
Under the working strength at annual 150 pilot time, aircaft configuration matrix uses 3.50 will reach calendar safe life, can use for 525 pilot time.
Below for the not loaded structure drag parachute bearing member of aircraft, further illustrate method of the present invention.
Step 1: choose research object, manufacture and design structural matrix simulation test piece
With the drag parachute bearing member of aircraft for research object, because this structure is only stressed when aircraft landing, in life cycle management, stressed number of times is less, and be not subject to again the impact of sustained load, therefore be divided into the research category of not loaded structure, specifically belong to the non-fully not loaded structure in not loaded structure.Testpieces material therefor is consistent with practical structures, and be 2A12-T4 aluminium alloy, material yield strength is 300MPa; Because testpieces only carries out corrosion test, therefore the design form of testpieces is rectangular flat test specimen, and thickness is 5mm; Testpieces without surfacecti proteon process, without aluminium coating.
Step 2: programming structure local matrix Environmental Spectrum
Laboratory acceleration environment test is carried out in salt-mist corrosion tester, and corrosion temperature is 40 ± 2 DEG C, and corrosive liquid is 5%NaCl aqueous solution, adds a small amount of rare H
2sO
4, make the pH value of solution reach 4-4.5, the salt fog deposition of salt spray test chamber controls at 1-2mL/ (h80cm
2).Under this corrosion environment, often corrosion is then equivalent to practical structures corrosion 1 year under environment under arms for 65 hours.
Step 3: determine structural matrix critical point corrosion size
By measuring and calculating, determining that the maximum stress that structure is born in its lifetime is 160MPa, for ensureing the safety by static load structure, generally maximum stress being amplified 1.5 times as calibration load, i.e. 240MPa.
When structural matrix is corroded, cause structural section to amass and diminish, the load of bearing due to structure is constant, and after must making corrosion, the actual stress of structure becomes large.Concerning original thickness 5mm is subject to the structure of 240MPa load, when matrix thickness is reduced to 4mm, the actual stress that structure is subject to is 300MPa, reaches the yield strength of structure.Therefore, 4mm can be selected as the critical point corrosion size of structural matrix.
Step 4: the matrix calendar safe life determining not loaded structure
Testpieces is divided into some batches, often criticize and corrode (equivalence 3 years, 5 years, 7 years and 10 years) after 195 hours, 325 hours, 455 hours and 650 hours respectively, testpieces is taken out, cut into some sections, and measure the least residue thickness in every section of cross section, the testpieces of each corrosion time limit measures 50 data.
Use normal distribution, lognormal distribution, Weibull distribution, Logistic distribution and Gumbel distribution to verify each group of data respectively, find the least residue thickness Normal Distribution of the rear matrix of corrosion.
Therefore, formula (1), formula (2) and formula (3) can be used to determine the matrix least residue life-span of satisfied 99.9% fiduciary level and 90% confidence level.When sample number is 50, the value of monolateral tolerance factor k is 3.60.
Under the different corrosion time limit, the matrix least residue one-tenth-value thickness 1/10 meeting 99.9% fiduciary level and 90% confidence level is as shown in table 2.
Table 2 meets the matrix least residue one-tenth-value thickness 1/10 of 99.9% fiduciary level and 90% confidence level
The matrix least residue one-tenth-value thickness 1/10 meeting 99.9% fiduciary level and 90% confidence level is carried out matching, and the fitting formula obtained is as follows:
t
99.9(T)＝-0.0884T+4.5576 (5)
Formula fitting degree R
2=0.999, meet the accuracy requirement of engineer applied.
In formula (5), t
99.9(T) for corrosion T meets the matrix least residue one-tenth-value thickness 1/10 of 99.9% fiduciary level and 90% confidence level afterwards, T is the corrosion time limit.By t
99.9(T)=4mm substitutes into formula (5), obtains corrosion and is limited to 6.3 years year.That is, there is the assurance of 90% to say, after this structural matrix experienced by the Service Environment corrosion of 6.3 years under the protective effect of unshielded system, have at least its least residue thickness of the region of 99.9% to be greater than 4mm.Therefore, the matrix calendar safe life of this structure can be decided to be 6.3 years.
Be presented above concept and the defining method of aircaft configuration matrix calendar safe life, the calendar life management of aircaft configuration matrix is carried out by reliable method, the safe service life of the rear structural matrix of aircaft configuration protection system inefficacy can be determined, to ensureing that the use safety of aircaft configuration is significant
In addition, the present invention to determining the overall calendar safe life of aircaft configuration, and and then determine that the calendar safe life of the full machine of aircraft is significant, significant to the management level promoting Aircraft Structural Life.
Above-described embodiment does not limit the present invention in any form, the technical scheme that the mode that all employings are equal to replacement or equivalent transformation obtains, and all drops in protection scope of the present invention.
Claims (6)
1. the defining method of aircaft configuration matrix calendar safe life, is characterized in that, comprise the following steps:
Step 1: choose research object, manufacture and design structural matrix simulation test piece;
Step 2: programming structure local matrix Environmental Spectrum and structural loads spectrum;
Step 3: the matrix calendar safe life determining aircaft configuration
For the corrosion fatigue key component in loaded structure, determine that the step of its matrix calendar safe life is as follows:
(1) the fatigue safety life-span of overall aircraft is determined;
(2) testpieces is divided into some groups, often organizes testpieces under accelerated environment spectrum, experience the different pre-etching cycles;
(3), after pre-etching, under the loading spectrum of establishment, torture test is carried out to fracture;
(4) under selected fiduciary level and confidence level, the safe life often organizing prior-corroded fatigue testpieces is calculated;
(5) the prior-corroded fatigue safe life often organizing testpieces is carried out matching, simulate a pre-etching cycle to the influence curve in fatigue safety life-span;
(6) the Residual Damage degree of computation structure matrix after protection system lost efficacy;
(7) in the pre-etching cycle to the influence curve in fatigue safety life-span being determined the point corresponding with the residue pilot time number of aircraft or the application plan of aircraft, thus determine the year injury tolerance of structural matrix under its corresponding flight rate or under its application plan, namely Residual Damage degree is obtained the calendar safe life of corrosion fatigue key component divided by year injury tolerance;
For the stress corrosion key component in loaded structure, determine that the step of its matrix calendar safe life is as follows:
(1) position and the direction of check that the most easily produce stress corrosion crack in structure is determined;
(2) testpieces is divided into some groups, according to the position and the direction of check that the most easily produce stress corrosion crack, to the initial crack of the preset different length of the testpieces of difference group;
(3) stress corrosion (cracking) test of each group of testpieces is carried out;
(4) propagation law of identified sign corrosion cracking and Critical fracture length;
(5) dispersion coefficient under given fiduciary level and confidence level is tried to achieve;
(6) namely stress corrosion cracking (SCC) expansion time is obtained the calendar safe life of stress corrosion key component divided by dispersion coefficient;
For not loaded structure, determine that the step of its matrix calendar safe life is as follows:
(1) criterion of the disabler of not loaded structure is determined;
(2) carry out the corrosion test of testpieces, at set intervals extraction portion separating tests part measure the maximum corrosion depth of testpieces, obtain meeting under this abrasion cycle the matrix maximum corrosion depth that given fiduciary level and confidence level require;
(3) comprehensively analyze meeting the matrix maximum corrosion depth that given fiduciary level and confidence level require under different abrasion cycle, obtain abrasion cycle when structure reaches failure criteria, the described abrasion cycle i.e. matrix calendar safe life of not loaded structure.
2. the defining method of aircaft configuration matrix calendar safe life according to claim 1, is characterized in that, in step 1, described structural matrix simulation test piece carries out design and manufaction according to the corrosion failure form of research object.
3. the defining method of aircaft configuration matrix calendar safe life according to claim 1, is characterized in that, in step 2, the process of programming structure local matrix Environmental Spectrum is as follows:
(2a) the actual Service Environment of aircraft is surveyed, determine the external environment condition feature of aircraft;
(2b) set up want the local environment at research structure place and the relational model of external environment condition;
(2c) according to determined aircaft configuration local environment feature, programming structure local matrix Environmental Spectrum.
4. the defining method of aircaft configuration matrix calendar safe life according to claim 1, is characterized in that, in step 2, according to the flight actual measurement load programming structure loading spectrum of aircaft configuration.
5. the defining method of aircaft configuration matrix calendar safe life according to claim 1, it is characterized in that, in step 3, described not loaded structure is not loaded structure completely, the criterion of not loaded structure disabler is completely: structure generation penetrability is corroded, or corrosion product peels off and has influence on the performance of other position functions.
6. the defining method of aircaft configuration matrix calendar safe life according to claim 1, it is characterized in that, in step 3, described not loaded structure is non-fully not loaded structure, and the criterion of non-fully not loaded structure disabler is: non-fully is the maximum corrosion depth that allows of loaded structure not.
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