director of institute avikon professor komarov v.a ...airframe design process. 4 ewade 2007 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 structural design 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 design paradigme is use very simple, (insufficiently exact) mathematical models on early stage 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 structural design

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 gross weight via “equation of existence”

whereppfsysst

plo mmmm

mm

−−−−=

1

stst

o

mmm

=

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Example of calculation a wing mass fraction via “weight equation”

Typical weight equation (Eger)

( ) 015,05,4311

14

cos10

7

0

32

5,175,000

4

01st ++

+−−∗

++∗=

pkk

cp

mnkm p

ηµ

ηη

χ

ϕλ

0 0,05 0,1

0,15 0,2

0,25

0,3 0,35 0,4 stm

mo = 270 000 kg mo = 685 000 kg

Mel

vill

Lipt

rote

Farre

n

Taye

Den

t

Koz

lovs

ky

Drig

gs

Bad

yagi

n

Ray

mer

Eger

Patte

rsso

n

Tore

nbee

k

Shej

nin

Aver

age

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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

?=stm ??=stm(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 lNG

1

∑=

⋅=n

iii SRG

1

∫=V

eqvdVG σ

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Definition of structural mass via“load-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 and technology perfect)

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

[ ] i

n

iii

n

i

iT lFlV ⋅=⋅= ∑∑

== 11

Nσ

[ ]σρϕρϕ GVm Tst ⋅⋅=⋅⋅=

σϕ Gmst =

σϕ

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2nd idea. Size less criteria of load carrying perfection of structure

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

Sizeless criteria– coefficient of load carrying factor

where P- specific loadL- specific size

whence (aerodynamic analogy : )

LPGCK ⋅

=

PLCG K= qSCY y=

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Example of simple structures

CK = 2,00

α

l

a

c

b

d

aP

l

CK = 3,41aP

b

d

a

c

h

CK = 10,00

l

aP

b a

l

b a aP

CK = 1,00

a) c)

b)

d)

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

Specific size – square of wing in degree ½ -Specific load – lift

whence

Weight equation :

S

SgmnCG oK ⋅⋅⋅⋅=

**

*

SgmnGC

o*K

⋅⋅⋅=

gmnY ⋅⋅= 0

S gn Cm Kwing ⋅⋅⋅=σϕ Sg mn Cm oKwing ⋅⋅⋅⋅=

σϕ

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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

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

Strategy IIStrategy I

Panel structures

Membrane structuresWing

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Example of morphing wingaerodynamic and weight efficiency research

Grant CRDF: REO-1386

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1

4

c tip =

3

c root =

4

2 12

b/2 = 20

Axis of symmetry

6

24

2.19

35

4.38

7

2.38

7

4.77

4

Wing 1a

Wing 1b

Wing 2a

Wing 2b

Wing 3a

Wing 3b

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Scheme of wing parts joints

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Inner wing

Beam Outer wing

Rolls

Fuselage joints1

Rigid connection3

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3rd 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

ieqvi

i

constρσ

σρ σ

=

=

[ ] [ ]E E

σ ρ σρ= ⋅

= ⋅

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Test

3D-model of the wing structurep

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

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

with variable density

22.50 22.34 22.23 22.16 22.1122.7523.1423.8125.05

28.10

19.58

1820

222426

2830

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

C K

s olid (8 layers )

As pec t ratio b /c = 8

w ing box

41.15 40.83 40.61 40.45 40.3541.6342.4143.73

46.1151.74

35.56

34363840424446485052

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

C K

s olid (8 layers )

As pect 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 load dis tribution

tc

C K

dim

ensi

onle

ss e

qviv

alen

t of w

ing

wei

gh

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

MorphTrap

L/D max

tc

max

imum

aer

odyn

amic

effi

cien

cy

geometrical parameter of te les 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 –

VPGCK ⋅

=

23=KC

3=KC

3=KC

3=KC

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ConclusionLoad-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 and perspective designs.

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

KC

director of institute avikon professor komarov v.a ...airframe design process. 4 ewade 2007 komarov...

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