COMPARISION STUDY OF STRUCTURAL ANALYSIS OF UCAV WING

International Journal of Innovative Research in Advanced Engineering (IJIRAE) ISSN: 2349-2163
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COMPARISION STUDY OF STRUCTURAL ANALYSIS OF
UCAV WING
Sri Ramachari Mukund1*
, Varun K C1
, Shivaramu H T2
,Umashankar K S3
1*, 1
UG Students, Department of Mechanical engineering, KVGCE, Sullia, DK, Karnataka.
2
Assistant Professor, Department of Mechanical engineering, KVGCE, Sullia, DK, Karnataka.
3
Professor, Department of Mechanical engineering, KVGCE, Sullia, DK, Karnataka.
Abstract: The wing of Unmanned Combat Aerial Vehicle (UCAV) structural analysis is investigated considering loading
condition of the munitions. The wing is modeled using ‘I’ section and Warren trusses on the tailless UCAV. Stress, strain
and deformation are obtained for comparisons. The wing section connecting the fuselage was made the fixed end and
overall 3 hard points were platformed for loading condition. The Aluminium alloy (Al-7075 T-6) is used as material. The
structural analysis of wing comparison is made on the basis of stress and strain, concluded that Warren Truss with
vertical chord is a better choice for Designed UCAV.
Keywords: Warren Trusses, ‘I’ Section, Unmanned Combat Aerial Vehicle (UCAV)
I. INTRODUCTION
The Unmanned Combat Air Vehicle (UCAV) vision is an affordable weapon system that expands tactical mission options for
revolutionary new air power as an integrated part of a system of systems solution. The UCAV weapon system will exploit the
design and operational freedoms of relocating the pilot outside of the vehicle to enable a new paradigm in aircraft
affordability while maintaining the rationale, judgment and moral qualities of the human operator. In analysis vision is
weapon system will require minimal maintenance, can be stored for extended periods of time and is capable of dynamic
mission control while engaging multiple targets in a single mission under minimal human supervision. The UCAV will
conduct missions from ordinary airfields as part of an integrated force package complementary to manned tactical and
support assets. UCAV controllers will observe rules of engagement and make the critical decisions to use or refrain from
using force. The initial design of UCAV consists of Delta Wing. The tailed Delta configuration is used to take advantage of
both high angle of attack flying capability and high speeds. It was used in the MiG-21 ("Fishbed") and Sukhoi Su-9/Su-11/15
fighters, built by the tens of thousands. The tailless Delta became a favoured design for high speed aircraft, and was used
almost to the exclusion of other designs by Convair and by Dassault Aviation, notably with the Dassault Mirage III [1]. Delta
wings can be differentiated into 6 types, among which the designed UCAV uses ogee Delta type [2]. The ogee delta (or
ogival delta) used on the Anglo-French Concorde Mach 2 airliner is similar. But with a smooth ogee curve joining the two
parts rather than an angle. Various different types of delta wings are are shown in Fig. 1.
Fig.1: Types of Delta Wings
The general characteristics of delta wing have. The long root chord and short span of the delta wing make it structurally
efficient. It can be built stronger, stiffer and at the same time lighter than a swept wing of equivalent lifting capability. Its
long root chord also allows a deeper structure for a given aerofoil section, providing more internal volume for fuel and other
storage. Because of its light, robust structure it is easy and relatively inexpensive to build – a substantial factor in the success
of the MiG-21 and Mirage aircraft [3].

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The disadvantages, especially marked in the older tailless delta designs, are a loss of total available lift caused by turning up
the wing trailing edge or the control surfaces (as required to achieve a sufficient stability) and the high induced drag of this
low aspect ratio type of wing. This causes delta winged aircraft to ‘bleed off' energy very rapidly in turns, a disadvantage in
aerial manoeuvre combat and dog fighting [4].
II. CATIA 3D MODEL OF UCAV
Fig 2:- 3-D models of UCAV, leading edges are shown as followed.
The modelling of the UCAV is done by using CATIAV5. Some of sketch commands used in this particular aircraft
modelling are CATIA generative shape design, sketcher, part design, assembly design, drafting etc. The
III. UCAV WING MODEL
3.1. INTRODUCTION TO ‘I’ SECTION.
An I-beam, also known as H-beam, W-beam (for "wide flange"), Universal Beam (UB), Rolled Steel Joist (RSJ), or double-T
(especially in Polish, Bulgarian, Spanish, Italian and German), is a beam with an I or H-shaped cross-section. The horizontal
elements of the "I" are known as flanges, while the vertical element is termed the web. When a beam is subjected to stresses,
the outer layer is compressed, with the inner one undergo tension. The middle layer is a neutral layer, which do not
experience either tension or compression. Now, as we move away from Neutral Axis, the stress due to bending moment
increases proportionally, according to bending moment equation (i).
----------- Equation (i)
Where, y= distance from neutral axis
I=Moment of Inertia.
M=Bending Moment.
Fig. 3: The largest stresses in a beam under bending are in the locations farthest from the neutral axis.
In the case of I section, the web resists shear forces, while the flanges resist most of the bending moment experienced by the
beam. Beam theory shows that the I-shaped section is a very efficient form for carrying both bending and shears loads in the
plane of the web. On the other hand, the cross-section has a reduced capacity in the transverse direction, and is also
inefficient in carrying torsion, for which hollow structural sections are often preferred. But it is more complicated and
expensive to manufacture hollow beam, so for this reason it is not used practically. The Fig. 4 shows how the web resists
most of the shear force [3].
Fig.4: ‘I’ Section
3.2. WARREN TRUSS SECTION

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The Warren Truss is a very common design for both real and model bridges. The Warren Truss uses equilateral triangles to
spread out the loads on the bridge. This is opposed to the Neville Truss which used isosceles triangles. The equilateral
triangles minimize the forces to only compression and tension. Interestingly, as a load (such as a car or train) move across the
bridge sometimes the forces for a member switch from compression to tension. When the span length increases and the height
of the truss necessarily increase, the long compression members in the top chord need bracing to minimize buckling in the
vertical direction. In this case, verticals are placed from the lower chord panel points up to the midpoint of the chord member
directly above. In addition, the deck structure stringers get longer requiring either heavier members or the addition of
verticals from the top chord panel points dropping down to shorten panel lengths.
(a)
(b)
Fig.5: a and b Warren Trusses
The Fig. 5a shown Warren Trusses with vertical support top chord Usage of Warren Truss with vertical support is also
analysed so that the study of truss is Judged properly[2]. Warren Truss without Vertical Support is shown in Fig. 5b.
Dimension of the Wing is shown in Fig. 6, the Wing Length is 9889.64mm, width=2627.15mm and distance between ribs are
520mm.only the weapons loading area of wing section is considered.
Fig. 6: Wing Dimension (mm)
The ‘I’ section of the wing is given below .The wing has 16 Ribs and 3 spars making it highly structured part and strong. This
can be visulised in the analysis result at the end.
Fig. 7: I section wing with 3 hard points and Spar
The Fig. 7 is ‘I’ section Ribs and Spar section of the UCAV which is designed as ‘I’ beam.

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Fig. 8: Dimensions of the ‘I’ section (mm)
Mean while in Warren truss section first, sixth and eleventh ribs were designed interms of Warren Truss also Holes were
created just to ensure the connection lines were not hindered is shown in Fig. 9 and 10.
Fig.9: Warren Truss Section of wing along with Holed sections.
Fig.10: Warren truss design with Vertical Chord.
IV. ANALYSIS PROCESS OF UCAV WING
The Designed wing part was optimized and imported to the analysis platform. The engineering data was specified having the
aluminium alloy (Aluminium 7075 T-6). Meshing was carried out with the skin surface on the bottom part of the wing.
Meshing is an important criterion in the analysis part; the elements were created through nodes and all the properties as well
as the calculation are defined at the nodes. The mesh shape is Hexa-Dominant for better accuracy in the result is shown in
Fig. 11. The mesh size is 20mm. Then the boundary conditions were given such as the wing and the fuselage contact point
was the fixed end and the loading condition were at the 3 designed hard points as 1000kg, 250kg and150kg keeping in mind
the actual mass of the munitions. The solutions were then calculated for deformation and the stress produced for different
types of wing sections.
Fig.11: Hexa-Dominant Type Mesh
4.1. MATERIAL PROPERTIES

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Designing a component is only good as it is displayed, but when it comes to analysis part there is cloud of material to be
selected. It gets even more complicated when dealing with aircraft structures. The material in this experiment is an aluminium
alloy, to be more specific it is aluminium 7075 T-6.
The aluminium 7075 T-6 Composition is shown in Table 1.
TABLE 1: COMPOSITION OF AL 7075 T-6
copper Magnesium zinc Chromium
1.6% 2.5% 5.6% 0.3%.
The mechanical properties of Al 7075 T-6 is as follows
The Density of the metal =2770 kg/m3
Tensile Compressive yield strength= 280MPa.
Tensile Ultimate Strength =310MPa.
V. ANALYSIS AND RESULTS
The results were interpreted for deformation and stress produced for the defined loading conditions. The experiment is based
on the analysis of wing of an UCAV when loaded with munitions. The importance of this study is used to compare between
the ‘I’ section and Warren truss, both being important from mechanical properties point of view.
5.1. ANALYSIS OF ‘I’ SECTION
The ‘I’ section usually strong in general engineering terms. When the loading conditions were given, the deformation, stress
and the elastic strain were obtained in order to study the characteristics of the wing section.
Fig.11: Deformation produced.
The total deformation is 1.6463 mm is noticed in Fig. 11.
Fig.12: Equivalent elastic strain
The equivalent elastic strain 0.0003231 is observed in Fig. 12.
Fig.13: von Mises Stress
Stresses are localised near and around the edges which makes it very suspicious for failure at the leading edges. The stress
produced (max) is found to be around 21.83 MPa is shown in Fig. 13.
5.2. ANALYSIS OF WARREN TRUSSES (WITHOUT VERTICAL SUPPORT CHORD)
Warren Truss is usually employed in bridges and aircraft frames. The designed Warren truss includes circular cross section
for even stress distribution in terms of mechanics and also importantly the connection of avionics of the flight systems.

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Fig.14:Total Deformation.
Fig.15: von Mises Stress
Fig.16: Equivalent elastic strain
The total deformation is 1.8404mm found in Fig. 14. The stress produced (max) is found to be around 26.905 MPa is shown
in Fig. 15. The equivalent elastic strain 0.0003813 observed in Fig. 16. Stresses are localised near the circular section which
is better than the stress localised near the edges. This takes out the possibilities of getting failure, which is more prone in
edges.
5.3. WARREN TRUSS (WITH VERTICAL SUPPORT CHORD)
The analysis of Warren Truss with
Fig. 17: Total deformation
Fig. 18: von Mises Stress

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Fig. 19: Equivalent elastic strain
The total deformation is 1.8393, Max stress at inner section of wing is 25.30 MPa and equivalent elastic strain 0.0003569 is
shown in Fig. 17, 18 and 19 respectively.
VI. CONCLUSION
The comparison of wings are concluding as follows
 The deformation being lesser in ‘I’ Section making it susceptible to be chosen. But that only can’t make the critical
criteria to confront on. Even though the stress acting on the ‘I’ section is pretty much lesser than Warren Truss
section. The weight carried by the ‘I’ section is more than the Truss members. The Warren Truss having much
hallow design making it more efficient and also ease with laying the avionics of the flight system.
 The truss with vertical chord gave very soothing results with even stress distribution comparatively without vertical
chord.
 The stress distribution was evenly formed on the Warren Truss and the stress was concentrated on the inner
chamber of the ribs i.e. around the circular section rather than near the edges making it less prone to failure.
 Keeping aside other factors Warren Truss can be opted for the designing into prototype model of UCAV.
REFERENCES
[1]. Bradley, Robert ,"The Birth of the Delta Wing". J. Am. Aviation Hist. Soc, page no. (5489-5498), 2003
[2]. Mason W.H.; "Configuration Aerodynamics", AOE 4124, Virginia Tech, page no.(203-208), 19 january 2013.
[3]. Sritharan, S. S , "Nonlinear Aerodynamics of Supersonic Conical Delta wings",1982.
[4]. Avnish Kumar "Investigation of Airfoil Design", Thesis
[5]. Numerical Analysis of Overall Stability of Unbraced Stainless Steel Simply-supported Beams with Fabricated I-section,
page no.(6059-6062), 7 november 2011.
[6]. Stability Analysis on Large-span Steel Tubular Truss Based on Finite Element Simulation Jianjun Bi (Liaoning Jianzhu
Vocational College; Liaoyang 111000, China), page no. (237-240), 2016.
[7]. G .Mathiyazhagan, N .Vasiraja, “Finite Element Analysis on Curved Beams of Various Section”, page no.(168-
173),2013
[8]. Mostafa Abdalla, Roeland , “Aircraft Stress Analysis and Structural Design Reader AE2-521N”
[9]. Modeling and structural analysis of wing structure Kakumani Sureka1 and R Satya , vol no. 4 , April 2015.
[10]. AircraftStructures Aircraft Structures Session MrRamjanPathan M.S. Ramaiah School of Advanced Studies, Bengaluru

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