Modern Trends in Airframe Structural Design Komarov

7/31/2019 Modern Trends in Airframe Structural Design Komarov

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EWADE 2007 Komarov V.A.

Modern Trends in AirframeStructural Design

Professor Komarov V.A.Director of Institute AVIKON

Of Samara State Aerospace University


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Plan of the presentation

1. General view on the modern structuraldesign problems.

2. New ideas for improving design process.3. The example of using a new ideas for research aerodynamic and weight

efficiency of morphing wing.


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Airframe design process


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Time and resource expediture

The main reason of greater charges of time and resources in sequential designparadigme is use very simple, (insufficiently exact) mathematical models on earlystage of design.

For reduction of designing time it is suitable use of highly accuracy mathematical modelson early stage design.


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New paradigm for Airframe Structure Design


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The problem of weight estimation in structuraldesign

1. Choice of structure topology (skeleton design).2. Estimation of structural mass fraction.3. Weight estimation of the wing, fuselage, etc.4. Weight check.


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Choice of structure topology


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Estimation of structural mass fraction

Definition of flight vehicles takeoff grossweight via equation of existence

where

pp f sys st

pl o mmmm

mm = 1

st st

o

mm

m=


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Example of calculation a wing mass fractionvia weight equation

Typical weight equation (Eger)

( )015,0

5,431

114

cos10

7

0

32

5,175,000

4

01st ++

+

++

= p

k k

c p

mnk m p

0

0,05

0,1

0,15

0,2

0,25

0,30,35

0,4 st mm o = 270 000 kgm o = 685 000 kg

M

e l v i l l

L i p t r o t e

F a r r e n

T a y e

D e n t

K o z l o v s k y

D r i g g s

B a d y a g i n

R a y m e r

E g e r

P a t t e r s s o n

T o r e n b e e k

S h e j n i n

A v e r a g e


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Weight Check

1. Definition of the weight limits for different part of structure before design.

2. Analyses of weight penalty after design (if necessary).Looking for decrease of structural mass.


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Unconventional flight vehiclesMorphing Wing from TUDelft

?= st m ??= st m(http://www.lr.tudelft.nl/live/pagina.jsp?id=fd5540a7-0cfe-44e5-b1bc-c806fa0410b8&lang=en )


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New ideas for improving design process

1st

idea. Load-carrying factor Frame

Thin-wall structure

3D-structure

=

=n

iii l N G

1

=

=n

iii S RG

1

=V

eqv dV G


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Definition of structural mass viaload-carrying factor

Theoretical structural material volume

Real mass of structure

or

G take into account topology, geometry and external loads specific durability of material

coefficient of full-mass structure, (it depends on design andtechnology perfect)

G-criteria allows to calculate absolutely mass of unconventionalstructure with high accuracy

[ ] in

iii

n

i

iT l F l V ==

== 11

N

[ ] G

V m T st == G

m st =


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2nd idea. Size less criteria of load carryingperfection of structure

Load-carrying factor is proportional to the linear sizes (coordinates of nodals) of structure andvalue of nodal forces (at retaining of the law of distribution of external loading) dimensional quantity

Sizeless criteria coefficient of load carryingfactor

where P- specific load L- specific size

whence ( aerodynamic analogy : )

P GC K

=

PLC G K = qS C Y y=


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Example of simple structures

C K = 2,00

l

a

c

b

d

a P

l

C K = 3,41a P

b

d

a

c

h

C K = 10,00

l

a P

b a

l

b a a P

C K = 1,00

a) c)

b )

d )


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New weight equation for definition of full wingmass and wing mass fraction

Specific size square of wing in degree -Specific load lift

whence

Weight equation :

S

S g mnC G o K =

**

*

S g mn

GC

o* K

=

g mnY = 0

S g nC m K wing = S g mnC m o K wing =


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Example of structural topology choice

3,563,032,682,832,752,692,553

1,981,891,831,811,781,761,682

2,071,941,841,711,701,681,621

= 0,4 = 0,5 = 0,6 = 0,4 = 0,5 = 0,6

Strategy IIStrategy I

Panel structures

Membranestructures

Wing


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Example of morphing wingaerodynamic and weight efficiency research

Grant CRDF: REO-1386

2 4

1

4

c t i p = 3

c

r o o

t

= 4

2 12

b /2 = 20

Axis of symmetry

6

2 4

2 . 1

9 3 5

4 . 3

8 7

2 . 3

8 7

4 . 7

7 4

Wing 1a

Wing 1b

Wing 2a

Wing 2b

Wing 3a

Wing 3b


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Scheme of wing parts joints

2

Inner wing

Beam Outer wing

Rolls

Fuselage joints1

Rigid connection3


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3 rd idea. Using 3D-model with variable density

Model

Traditional material


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.Hypothetic material with variable density

Algorithm of density distribution optimization

[ ]

0

01

1.

2.

3.

i

i

eqvi

i

const

=

=

[ ] [ ] E E

=

=


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Test

3D-model of the wing structure p

8-layers of 3D-solid finite elementsBoundary conditionsof console


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Comparison of load-carrying factor coefficientcalculations for thin-wall structure and 3D-solid model

with variable density

22.50 22.34 22.23 22.16 22.1122.7523.1423.81

25.05

28.10

19.58

18

20

22

24

26

28

30

1 2 3 4 5 6 7 8 9 10 11Iteration n

C K

solid (8 layers)

Aspe ct ra tio b /c = 8

w ing box

41.15 40.83 40.61 40.45 40.3541.6342.41

43.7346.11

51.74

35.56

3436384042444648

5052

1 2 3 4 5 6 7 8 9 10 11Iteration n

C K

s olid (8 laye rs )

Aspec t ratio b /c = 12

w ing box


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Wind tunnel model 1


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Wind tunnel model 2with pressure of orifices


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Spanwise load distributions


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3D-model with variable density of material

X

Y

Z


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External loads


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Comparison of weight perfection

0,000

5,000

10,000

15,000

20,000

25,000

30,000

35,000

0 0,25 0,5 0,75 1

Morph

Trap

Morph for uniform loa d dis tribution

t c

C K

d i m e n s

i o n

l e s s e q v

i v a l e n

t o

f w

i n g w e i g

h

ge om e trica l pa ra m e te r of te le s cope wing


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Comparison maximum aerodynamic efficiency

0.000

5.000

10.000

15.000

20.000

25.000

30.000

35.000

40.000

0 0.25 0.5 0.75 1

Morph

Trap

L/D max

t c

m a x

i m u m

a e r o

d y n a m

i c e

f f i c i e n c

geome trica l parame ter of teles cope wing


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Pressurized cabin, pressure vesselSpecific volume volume - VSpecific load pressure P

Some results for reservoirs:

Spherical

Cylindrical

Spherical from CM

Cylindrical from CM

V P G

C K

=

23=

K C

3= K C

3= K C

3= K C


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Conclusion

Load-carrying factor allows :

1. To put in according to load-carrying scheme(topology of structure) the certain dimensionlessvalue which defines weight perfection of a design.

2. To build "weight" formulas for any designs.3. To accumulate the knowledge in convenient form(dimensionless!) for analysis of existing andperspective designs.

There are 3 new ideas in the lecture, which can be usefulto increase efficiency of early stage design.

K C

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Modern Trends in Airframe Structural Design Komarov