CN105334032A - Calculation method of structural lifetime of machine types - Google Patents

Abstract

The invention provides a calculation method of structural lifetime of machine type and relates to the field of airplane fatigue technology. The structural lifetime of a contrast machine type is given out according to existing structural lifetime of an airplane type. According to a key part simulation test piece fatigue comparison test of an original machine type and an improved machine type, quantitative relation of structural lifetime of similar machine types is given, and on the basis of lifetime evaluation results of a full scale fatigue test of the original machine type, lifetime of the advanced machine type is given, so objectives of shortening of type preparation time and reduction of preparation cost on the premise that use safety of an airplane is ensured are achieved. According to the invention, based on the key part simulation test piece fatigue comparison test and the lifetime evaluation results of a full scale fatigue test of the original machine type, quantitative relation of structural lifetime of similar machine types is given; important basis is provided for structural lifetime determining of the improved machine type; the calculation method has great significance for shortening of type preparation time and reduction of preparation cost; and safety guarantee is provided for the improved machine type.

Description

The computing method in a kind of model structure life-span

Technical field

The present invention relates to aircraft fatigue to learn a skill field, in particular to the computing method in a kind of model structure life-span, for providing the structural life-time improving type according to the contrast test of existing aircraft model structural life-time.

Background technology

According to the development and design flow process of aircraft, for determining structure fatigue life, the aircraft on production line need be extracted, carrying out full scale fatigue test.In the middle of modern aircraft design research, be satisfied different user demand, generally by a certain with reference to based on type machine, the type of the model that multiple structure is close, service condition is different can be derived.Relative to reference type machine, be not by with reference to the new architecture developed based on type machine owing to being brand-new aircraft, by developing flow process normally, whole development tasks of corresponding code requirement must be carried out, but for the improvement type of the derive type based on reference type machine, generally take two kinds of development modes:

A) identical with reference to type machine, all develop task by code requirement;

B) by research fund and the restriction of lead time, by contrasting with reference to type machine, only carrying out design analysis and development and design test, and not carrying out full-scale demonstration test.

The first shortcoming of a) planting mode in above-mentioned two kinds of development modes is that research fund is many, the lead time is long, and the second b) although mode is saved research fund, shortened the lead time, in the security of aircraft, make larger sacrifice.

The technical matters needing now solution badly how to reduce reasearch funds and lead time, namely the second b can be used under the prerequisite not using the first a) development mode of mode) mode carries out the development of new architecture, and can improve the security of the aircraft improving type.

Summary of the invention

The object of the invention is to solve above-mentioned deficiency of the prior art, the computing method in a kind of model structure life-span are provided, reduce research fund, shorten the development time and improve the security of new architecture.

Object of the present invention is achieved through the following technical solutions: the computing method in a kind of model structure life-span, is drawn the structural life-time improving type, comprise the steps: by comparative trial of life-span

According to the difference improving type use-pattern, S1, on prototype basis, determines that improving type typical case uses mission profile;

S2, works out the fatigue load spectrum for improvement of type longevity assessment;

S3, determines to improve the structural key position of type, according to geometry, the material characteristics of key position, design and by the type testing part of same process processing and manufacturing for comparative trial of life-span;

S4, is equally divided into two groups by the testpieces of same specification, the torture test under carrying out prototype respectively and improving type loading spectrum, log;

S5, analytical test result, calculates the life span comparison relation of structural key position under two kinds of different loads spectrums improving type;

S6, the comparative trial of life-span analysis result of comprehensive multiple key position, based on prototype longevity assessment conclusion, provides the life-span quantitative relationship improving type.

, in S1, typical case uses mission profile to be improve the typical service condition of type in such scheme preferably, comprise the taking off of aircraft, climb, cruise, maneuvering flight, attack, downslide and landing.

In above-mentioned either a program preferably, in S3, the quantity of the type testing part processing of same specification is 14-20.

In above-mentioned either a program preferably, S5 comprises following calculation procedure:

S _5-1, parameter estimation

According to fatigue statisic principle, fatigue lifetime obeys logarithm normal distribution, note x=logN, then the probability density function of x is $f\left(x\right)=\frac{1}{\sqrt{2\mathrm{\π}\mathrm{\σ}}}\exp \[-\frac{1}{2}{\left(\frac{x-\mathrm{\μ}}{\mathrm{\σ}}\right)}^2\],$ Correlation parameter estimated value is

In formula, for all test findings take the logarithm after mean value,

with the standard deviation that s is testpieces fatigue test results,

N ₅₀for logarithmic mean value;

S _5-2, error analysis

Get degree of confidence γ, corresponding t distribution quantile is t _1-γ, logarithm median life estimated value with the relative error of logarithm median life true value be

$\mathrm{\δ}=\frac{s\·t_{1-r}}{\widehat{\mathrm{\μ}}\sqrt{n}}---\left(2\right)$

In formula, n is testpieces number;

S _5-3, homogeneity test of variance;

Contrast prototype and the ratio of Typical Aircraft testpieces life-span variance under different loads is composed improving type with F _α/2(ν ₂, ν ₁) judge whether two test findings have homogeneity of variance,

In formula, ν ₂=n ₂-1, ν ₁=n ₂-1 is the degree of freedom of two groups of testpieces of respective function, n ₂, n ₁it is the number of two groups of testpieces;

S _5-4, t distribution inspection

Structure t distribution function

$\hat{t}=\frac{{\widehat{\mathrm{\μ}}}_1-{\widehat{\mathrm{\μ}}}_2}{\sqrt{\frac{s_1^2}{n_1}+\frac{s_2^2}{n_2}}}---\left(3\right)$

Its degree of freedom is

$v_t=\frac{{(\frac{s_1^2}{n_1}+\frac{s_2^2}{n_2})}^2}{\frac{1}{n_1-1}{\left(\frac{s_1^2}{n_1}\right)}^2+\frac{1}{n_2-1}{\left(\frac{s_2^2}{n_2}\right)}^2}---\left(4\right)$

In formula, for the t distribution function of corresponding two groups of testpieces,

with be respectively two groups of test findings take the logarithm after mean value,

S ₁and s ₂be respectively the logarithm standard deviation of two groups of test findings,

N ₁and n ₂be respectively the testpieces quantity of two groups of tests,

ν _tfor the degree of freedom of t distribution function,

show that two test findings do not have significant difference, on the contrary, show that two test findings have notable difference;

S _5-5, two comparison of test results

Whether the index of aging judging to improve type by the homogeneity of variance that contrasts two test findings and t assay is identical with prototype, improves type and prototype type testing part life-span ratio

$k=\frac{N_{50,2}}{N_{50,1}}---\left(5\right)$

In formula, N _50,1and N _50,2be respectively the logarithmic mean value of prototype and the test of improvement type.

In above-mentioned either a program preferably, improving type in S6 with prototype type testing part life-span ratio is

$k=\frac{N_{50,2}}{N_{50,1}}---\left(5\right)$

In formula, N _50,1and N _50,2be respectively the logarithmic mean value of prototype and the test of improvement type, calculate the life-span of improving type according to formula (5).

The beneficial effect of the computing method in model structure life-span provided by the present invention is, by on key position imitation specimen Fatigue Comparative and existing type full scale fatigue test longevity assessment result basis, provide and improve model structure life-span quantitative relationship, determine the longevity for improvement model structure and important evidence is provided, to shortening the new machine lead time, save development cost significant, and to improvement type safety guarantee is provided.

Accompanying drawing explanation

Fig. 1 is the schematic flow sheet of the preferred embodiment of computing method according to the model structure life-span of the present invention;

Fig. 2 is the schematic diagram of the type testing part for comparative trial of life-span of preferred embodiment shown in the Fig. 1 according to the computing method in model structure life-span of the present invention;

Fig. 3 is the improvement type overload transcendental number curve of preferred embodiment shown in the Fig. 1 according to the computing method in model structure life-span of the present invention and the curve map that compares with prototype;

Fig. 4 be in the improvement type of preferred embodiment shown in the Fig. 1 according to the computing method in model structure life-span of the present invention outer wing to the schematic diagram of band plate Φ 14 auricle testpieces;

Fig. 5 is the schematic diagram of the central wing lower wall panels titanium alloy welding testpieces of the improvement type of preferred embodiment shown in the Fig. 1 according to the computing method in model structure life-span of the present invention;

Fig. 6 is the schematic diagram of the undercarriage beam test part of the improvement type of preferred embodiment shown in the Fig. 1 according to the computing method in model structure life-span of the present invention.

Embodiment

In order to understand the computing method in the model structure life-span according to the present invention program better, below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is further described in more detail.In the accompanying drawings, same or similar label represents same or similar element or has element that is identical or similar functions from start to finish.Described embodiment is the present invention's part embodiment, instead of whole embodiments.Be exemplary below by the embodiment be described with reference to the drawings, be intended to for explaining the present invention, and can not limitation of the present invention be interpreted as.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.Below in conjunction with accompanying drawing, embodiments of the invention are described in detail.

In describing the invention; it will be appreciated that accompanying drawing is only the present invention for convenience of description and simplified characterization; instead of indicate or imply that the device of indication or element must have specific orientation, with specific azimuth configuration and operation, therefore can not be interpreted as limiting the scope of the invention.

As shown in figs 1 to 6, the computing method in model structure life-span provided by the invention, are drawn the structural life-time improving type, comprise the steps: by comparative trial of life-span

S1, on prototype basis, determine that improving type typical case uses mission profile according to the difference (the homotype schoolaeroplane as developed on prototype basis trains the aerial mission ratio shared by Co-pilot obviously more than prototype compared with prototype) improving type use-pattern;

S2, works out the fatigue load spectrum for improvement of type longevity assessment;

S3, determines to improve the structural key position of type, according to geometry, the material characteristics of key position, design and by the type testing part of same process processing and manufacturing for comparative trial of life-span;

S4, is equally divided into two groups by the testpieces of same specification, the torture test under carrying out prototype respectively and improving type loading spectrum, log;

S5, analytical test result, calculates the life span comparison relation of structural key position under two kinds of different loads spectrums improving type;

S6, the comparative trial of life-span analysis result of comprehensive multiple key position, based on prototype longevity assessment conclusion, provides the life-span quantitative relationship improving type.

In above-mentioned steps S1-S6, the typical case of S1 uses mission profile for improving the typical service condition of type, comprise the taking off of aircraft, climb, cruise, maneuvering flight, attack, downslide and landing.In S3, the quantity of the type testing part processing of same specification is 14-20.

S5 comprises following calculation procedure:

S _5-1, parameter estimation

According to fatigue statisic principle, fatigue lifetime obeys logarithm normal distribution, note x=logN, then the probability density function of x is $f\left(x\right)=\frac{1}{\sqrt{2\mathrm{\π}\mathrm{\σ}}}\exp \[-\frac{1}{2}{\left(\frac{x-\mathrm{\μ}}{\mathrm{\σ}}\right)}^2\],$ Correlation parameter estimated value is

In formula, for all test findings take the logarithm after mean value,

with the standard deviation that s is testpieces fatigue test results,

N ₅₀for logarithmic mean value;

S _5-2, error analysis

Get degree of confidence γ, corresponding t distribution quantile is t _1-γ, logarithm median life estimated value with the relative error of logarithm median life true value be

$\mathrm{\δ}=\frac{s\·t_{1-r}}{\widehat{\mathrm{\μ}}\sqrt{n}}---\left(2\right)$

In formula, n is testpieces number;

S _5-3, homogeneity test of variance;

Contrast prototype and the ratio of Typical Aircraft testpieces life-span variance under different loads is composed improving type with F _α/2(ν ₂, ν ₁) judge whether two test findings have homogeneity of variance,

In formula, ν ₂=n ₂-1, ν ₁=n ₂-1 is the degree of freedom of two groups of testpieces of respective function, n ₂, n ₁it is the number of two groups of testpieces;

S _5-4, t distribution inspection

Structure t distribution function

$\hat{t}=\frac{{\widehat{\mathrm{\μ}}}_1-{\widehat{\mathrm{\μ}}}_2}{\sqrt{\frac{s_1^2}{n_1}+\frac{s_2^2}{n_2}}}---\left(3\right)$

Its degree of freedom is

${\mathrm{\ν}}_t=\frac{{(\frac{s_1^2}{n_1}+\frac{s_2^2}{n_2})}^2}{\frac{1}{n_1-1}{\left(\frac{s_1^2}{n_1}\right)}^2+\frac{1}{n_2-1}{\left(\frac{s_2^2}{n_2}\right)}^2}---\left(4\right)$

In formula, for the t distribution function of corresponding two groups of testpieces,

with be respectively two groups of test findings take the logarithm after mean value,

S ₁and s ₂be respectively the logarithm standard deviation of two groups of test findings,

N ₁and n ₂be respectively the testpieces quantity of two groups of tests,

ν _tfor the degree of freedom of t distribution function,

show that two test findings do not have significant difference, on the contrary, show that two test findings have notable difference;

S _5-5, two comparison of test results

Whether the index of aging judging to improve type by the homogeneity of variance that contrasts two test findings and t assay is identical with prototype.

5, the computing method in model structure life-span as claimed in claim 1, it is characterized in that, improving type in S6 with prototype type testing part life-span ratio is

$k=\frac{N_{50,2}}{N_{50,1}}---\left(5\right)$

In formula, N _50,1and N _50,2be respectively the logarithmic mean value of prototype and the test of improvement type, calculate the life-span of improving type according to formula (5).

In concrete use procedure, calculate according to the structural life-time of step to prototype of the computing method preferred embodiment in model structure life-span provided by the invention.

According to the difference improving type use-pattern, S1: on prototype basis, determines that improving type typical case uses mission profile.One of certain prototype loading spectrum substantially spectrum block rise and fall for totally 90 times form by 15 typical subject (comprising the particular flight of some use mission profiles), represented for 120.833 pilot time, in table 1.

Certain prototype of table 1 typical case uses mission profile

Modified is compared with prototype, subject 2 is divided into subject 2 and subject 2-1, all the other flight subjects are identical, but flight section object ratio is different, in table 2: wherein, the flight ratio of the subject 6,7,8,9 that flight damage is larger is large compared with prototype, and illustrate that the working strength of modified aircraft is comparatively large, its loading spectrum will overweight prototype.

Table 2 improves type typical case and uses mission profile

S2: the typical case according to the modified aircraft of table 2 uses mission profile, establishment loading spectrum, Fig. 3 give modified Developing Aircraft Spectrum Based overload transcendental number curve and with the comparing of prototype, improve the curve of type in figure on prototype, demonstrate the loading spectrum improving type further and overweight prototype.

S3: determine to improve the structural key position of type, according to geometry, the material characteristics of key position, design and by the type testing part of same process processing and manufacturing for comparative trial of life-span.According to structural life-time analysis and the longevity assessment work of prototype, for housing construction, determine outer aileron edge strip, middle outer wing jointing strip plate, central wing lower wall panels, rise and fall set a roof beam in place, the structural key position at the position such as vertical fin 2 beam, stabilizer torque tube.For improvement type, because version is close, therefore above-mentioned position is still structural key position for improvement type.By the design such as geometrical parameters, the material type testing part of above-mentioned key position, testpieces quantity is in table 3, and version is shown in Fig. 2, Fig. 4 ~ Fig. 6.

Table 3 is for the testpieces quantity of comparative trial of life-span

S4: the testpieces of same specification is equally divided into two groups, the torture test under carrying out prototype respectively and improving type loading spectrum, log.

Aileron edge strip testpieces is example in addition, and table 4 sets forth the outer aileron edge strip of prototype and improves the test findings of type.

Table 4 test findings

S5: analytical test result, calculates the life span comparison relation of structural key position under two kinds of different loads spectrums improving type.

S _5-1, parameter estimation

According to formula (1), calculate the intermediate value initiating life of two test findings.

Table 5 liang test crack initiation life estimation of distribution parameters result

S _5-2, error analysis

Get engineering analysis error delta=5%, calculate corresponding t by formula (2) _1-γ, and try to achieve degree of confidence γ (looking into the t function distribution table in mathematical statistics book) further, in table 6.

Table 6 error analysis

Error analysis result shows: have the assurance of more than 99.9% to say and state the error of two kinds of logarithm intermediate value test lifes tested and logarithm median life true value within 5%, the precision of median life estimated value is acceptable in engineering.

S _5-3, homogeneity test of variance

Get significance α=0.05, the ratio of amphitypy Typical Aircraft testpieces life-span variance under different loads spectrum $\frac{s_2^2}{s_1^2}={\left(\frac{0.05599}{0.02212}\right)}^2=6.407>F_{0.025}(8-1,7-1)=5.70,$ (8,7 is two groups of test numbers of packages tested, and 8-1,7-1 are the degree of freedom of F function two variable, is obtained the numerical value of 5.70 by the F function table consulting mathematical statistics) shows that two test findings do not have homogeneity of variance.

S _5-4, t distribution inspection

Get significance α=0.05, by formula (3), have:

$\hat{t}=\frac{{\widehat{\mathrm{\μ}}}_1-{\widehat{\mathrm{\μ}}}_2}{\sqrt{\frac{s_1^2}{n_1}+\frac{s_2^2}{n_2}}}=\frac{4.36712-4.29375}{\sqrt{\frac{{0.05599}^2}{8}+\frac{{0.02212}^2}{7}}}=3.41437$

Show that its degree of freedom is ν by formula (4) _t=9.

show that two test findings have notable difference.

S _5-5, two comparison of test results

According to S _5-3, S _5-4computational analysis, because two test findings do not have homogeneity of variance, t inspection also shows there is notable difference, and therefore, according to formula (5), the life-span ratio of the outer aileron edge strip type testing part of modified and prototype is:

S6: the comparative trial of life-span analysis result of comprehensive multiple key position, provides the life-span quantitative relationship improving type.

According to above-mentioned test and analytical procedure, complete comparative trial of life-span and the computational analysis of total Test part listed by table 3, obtain the life-span ratio of each testpieces as shown in table 7.

The life-span ratio of each key position of table 7 modified and prototype

Sequence number	Position	The life-span of comparative trial of life-span compares k
			1	Outer wing 1 the foot of a wall subordinate edge strip	0.87
2	Middle outer wing is to band plate Φ 14 auricle	0.85
			3	Middle outer wing is to band plate Φ 12.5 auricle	0.82
4	Middle outer wing is to band plate and vertical wall connecting portion	0.80
			5	Central wing lower wall panels titanium alloy welding position	0.80

6	Rise and fall and set a roof beam in place	0.83
			7	Vertical fin 2 beam and wallboard connecting portion	0.88

The test findings of each key position in consolidated statement 7, modified compared about 0.85, lower than the index of aging of prototype with the life-span of prototype, for ensureing the flight use safety improving type, for the purpose of conservative, get the minimum life-span than 0.8, namely improving type is 0.8 with the life-span ratio of prototype.

Computing method specific embodiment more than in conjunction with the model structure life-span of the present invention is described in detail, but be not limitation of the present invention, everyly according to technical spirit of the present invention, technical scope of the present invention is all belonged to any simple modification made for any of the above embodiments, also it should be noted that, comprise the combination in any between each part mentioned above according to the category of the computing method technical scheme in model structure life-span of the present invention.

Claims (5)

1. the computing method in model structure life-span, is characterized in that, drawn the structural life-time improving type, comprise the steps: by comparative trial of life-span

According to the difference improving type use-pattern, S1, on prototype basis, determines that improving type typical case uses mission profile;

S2, works out the fatigue load spectrum for improvement of type longevity assessment;

S3, determines to improve the structural key position of type, according to geometry, the material characteristics of key position, design and by the type testing part of same process processing and manufacturing for comparative trial of life-span;

S4, is equally divided into two groups by the testpieces of same specification, the torture test under carrying out prototype respectively and improving type loading spectrum, log;

S5, analytical test result, calculates the life span comparison relation of structural key position under two kinds of different loads spectrums improving type;

S6, the comparative trial of life-span analysis result of comprehensive multiple key position, based on prototype longevity assessment conclusion, provides the life-span quantitative relationship improving type.

2. the computing method in model structure life-span as claimed in claim 1, is characterized in that: in S1, typical case uses mission profile to be the typical service condition improving type, comprise the taking off of aircraft, climb, cruise, maneuvering flight, attack, downslide and landing.

3. the computing method in model structure life-span as claimed in claim 1, is characterized in that: in S3, the quantity of the type testing part processing of same specification is 14-20.

4. the computing method in model structure life-span as claimed in claim 1, it is characterized in that, S5 comprises following calculation procedure:

S _5-1, parameter estimation

According to fatigue statisic principle, fatigue lifetime obeys logarithm normal distribution, note x=logN, then the probability density function of x is $f\left(x\right)=\frac{1}{\sqrt{2\mathrm{\π}\mathrm{\σ}}}\exp \[-\frac{1}{2}{\left(\frac{x-\mathrm{\μ}}{\mathrm{\σ}}\right)}^2\],$ Correlation parameter estimated value is

$\widehat{\mathrm{\μ}}=\frac{1}{n}\underset{i=1}{\overset{n}{\Σ}}{\mathrm{logN}}_i$

$N_{50}={10}^{\widehat{\mathrm{\μ}}}$

In formula, for all test findings take the logarithm after mean value,

with the standard deviation that s is testpieces fatigue test results,

N ₅₀for logarithmic mean value;

S _5-2, error analysis

Get degree of confidence γ, corresponding t distribution quantile is t _1-γ, logarithm median life estimated value with the relative error of logarithm median life true value be

$\mathrm{\δ}=\frac{s\·t_{1-r}}{\widehat{\mathrm{\μ}}\sqrt{n}}---\left(2\right)$

In formula, n is testpieces number;

S _5-3, homogeneity test of variance;

Contrast prototype and the ratio of Typical Aircraft testpieces life-span variance under different loads is composed improving type with F _α/2(ν ₂, ν ₁) judge whether two test findings have homogeneity of variance,

In formula, ν ₂=n ₂-1, ν ₁=n ₂-1 is the degree of freedom of two groups of testpieces of respective function, n ₂, n ₁it is the number of two groups of testpieces;

S _5-4, t distribution inspection

Structure t distribution function

$\hat{t}=\frac{{\widehat{\mathrm{\μ}}}_1-{\widehat{\mathrm{\μ}}}_2}{\sqrt{\frac{s_1^2}{n_1}+\frac{s_2^2}{n_2}}}---\left(3\right)$

Its degree of freedom is

${\mathrm{\ν}}_t=\frac{{(\frac{s_1^2}{n_1}+\frac{s_2^2}{n_2})}^2}{\frac{1}{n_1-1}{\left(\frac{s_1^2}{n_1}\right)}^2+\frac{1}{n_2-1}{\left(\frac{s_2^2}{n_2}\right)}^2}---\left(4\right)$

In formula, for the t distribution function of corresponding two groups of testpieces,

with be respectively two groups of test findings take the logarithm after mean value,

S ₁and s ₂be respectively the logarithm standard deviation of two groups of test findings,

N ₁and n ₂be respectively the testpieces quantity of two groups of tests,

ν _tfor the degree of freedom of t distribution function,

show that two test findings do not have significant difference, on the contrary, show that two test findings have notable difference;

S _5-5, two comparison of test results

Whether the index of aging judging to improve type by the homogeneity of variance that contrasts two test findings and t assay is identical with prototype.

5. the computing method in model structure life-span as claimed in claim 1, it is characterized in that, improving type in S6 with prototype type testing part life-span ratio is

$k=\frac{N_{50,2}}{N_{50,1}}---\left(5\right)$

The life-span of improving type is calculated according to formula (5), in formula, N _50,1and N _50,2be respectively the logarithmic mean value of prototype and the test of improvement type.