analysis of natural frequency for an aircraft … · the spar carries the whole weight of the wings...

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 8, August 2017, pp. 1118–1123, Article ID: IJMET_08_08_111

Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=8

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

ANALYSIS OF NATURAL FREQUENCY FOR AN

AIRCRAFT WING STRUCTURE UNDER

PRE-STRESS CONDITION

V. Saran*, V. Jayakumar, G. Bharathiraja

Department of Mechanical Engineering, Saveetha School of Engineering,

Saveetha University, Chennai, Tamilnadu, India

K. S. Jaseem

Technical Support Engineer, CAD Solutions, Coimbatore, Tamil Nadu, India

G. Ragul

Department of Mechanical Engineering, Budge Budge Institute of Technology,

Kolkata, India

ABSTRACT

The content of this paper is all about the analysis of natural frequency for

avoiding resonance on the material to prevent failure and to simulate according to the

boundary conditions. The Vibrations of an aircraft wing structure is analyzed using

CATIA and ANSYS software. The natural frequency of the component is analyzed by

the frequency at which a system vibrates about an altitude and a time period, when not

subjected to a continuous or repeated external force. A wing structure is the main

machine component of the aircraft which is connected to the fuselage and it is acts

like a cantilever beam in which the one end of the wing is fixed and other end remains

free at the end. The wing structure consists of spars, stingers, rear ribs, mid ribs and

skin. In pre-stress condition, the pressure force is acting on the wing structure while

flying in the sky, the overall deformation of the wing structure is calculated using a

ANSYS workbench. By analyzing the frequency of the wing structure its helps to

calculate resonance that should not be equal to or more than the natural frequency.

The material used for aircraft wing is aluminum alloy which is less in weight and

having density, one third of the steel that does not affects its strength.

Keywords: Wing structure, Natural frequency, Resonance, Failure, Ansys Workbench,

Deformation.

Cite this Article: V. Saran, V. Jayakumar, K. S. Jaseem, G. Bharathiraja, G. Ragul,

Analysis of Natural Frequency for an Aircraft Wing Structure Under Pre-Stress

Condition, International Journal of Mechanical Engineering and Technology 8(8),

2017, pp. 1118–1123.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=8

Analysis of Natural Frequency for an Aircraft Wing Structure Under Pre-Stress Condition


1. INTRODUCTION

1.1 Wing Structure

A wing structure of an aircraft which is capable to fly with help of airfoil profile that

generates lift by the vehicle's forward airspeed and the shape of the wings as shown in Figure

1. Fixed-wing aircraft follows the cantilever beam structure in which the one end is fixed to

the fuselage and another is set to be the free end. The aircraft wing model is created according

to the data available and value found from the geometry and trigonometric relation.

Figure 1 Aero foil diagram of an aircraft wing structure

1.1.1 Components of Wing Structure

Rib is one of the elements in the wing structure, especially in conventional construction [1]

.

Ribs are made out of wood, metal, plastic, composites, foam. Ribs are classified into three

main parts. They are front-rib, middle-rib and rear-rib. The rib construction of an aircraft wing

is shown in Figure 2.

Figure 2 Wing Structure

V. Saran, V. Jayakumar, K. S. Jaseem, G. Bharathiraja, G. Ragul


Spar is the main structural member of the wing structure, constructed at span-wise at right

angle to the fuselage as shown in Figure 2. The spar carries the whole weight of the wings

while on the ground. Apart from that other structural and forming members such as ribs may be

attached to the spar. Skin is as of the minimum thickness for resisting the pressure applied on

it while flying on the sky from 0.015 to 0.025 inches [2]

. The strength requirements are should

be relatively low; the skin needs moderately high yield strength and hardness to minimize

ground damage from stones, debris, mechanic’s tools, and general handling.

The objective of this work is to calculate the resonance of the machine component

(aircraft wing) to prevent the critical vibrations which causes deformation. Resonance is a

phenomenon that occurs when a vibrating system or external force drives another system to

oscillate with greater amplitude at a specific preferential frequency [4]

. Natural frequency is the

frequency at which a system tends to oscillate in the absence of any driving or damping force.

2. MODAL ANALYSIS

The purpose of modal analysis in design mechanics is to determine the natural mode shapes

and frequencies of an object or structure during free vibration. It is generally to use the finite

element analysis (FEA) to perform this analysis. Modal analysis of the wing structure is

analyzed with and without pre-stress conditions. Pre-stress means of permanent stresses in a

structure for the purpose of improving its performance under various service conditions. In

pre-stress condition, the wing is subjected to pre-stress modal to static structural and modal

analysis to analyze the natural frequency in all nodal displacements using Ansys software [5-9]

.

3. TOTAL DEFORMATION

3.1. Deformation 1

Figure 3 represents the total deformation of the wing structure at the first nodal displacement,

in which at one end the deformation is maximum highlighted in red color and the blue color

denotes the minimum deformation occurs due to frequency of the aircraft wing while flying in

sky.

Figure 3 Deformation 1

3.2. Deformation 2

Figure 4 represents the total deformation of the wing structure at the second nodal

displacement, in which at one end the deformation is maximum highlighted in red color and

the blue color denotes the minimum deformation occurs due to frequency of the aircraft wing

while flying in sky.




3.3. Deformation 3

Figure 5 represents the total deformation of the wing structure at the third nodal displacement,



sky.


3.4. Deformation 4

Figure 6 represents the total deformation of the wing structure at the fourth nodal

displacement, in which at one end the deformation is maximum highlighted in red color and

the blue color denotes the minimum deformation occurs due to frequency of the aircraft wing

while flying in sky.


3.5. Deformation 5

Figure 7 represents the total deformation of the wing structure at the fifth nodal displacement,



sky.

V. Saran, V. Jayakumar, K. S. Jaseem, G. Bharathiraja, G. Ragul



3.6. Deformation 6

Figure 8 represents the total deformation of the wing structure at the sixth nodal displacement,



sky.


Total deformation of the wing structure according to its nodal displacement as shown in

the Table 1

Total

Deformation

Max.

Deformation, m

Min.

Deformation, m Frequency, Hz

1 0.12 0.0 73.93

2 0.14 0.0 412.05

3 0.122 0.0 439.37

4 0.187 0.0 518.1

5 0.14 0.0 1003.1

6 0.174 0.0 1359.8

Table 1 Modal analysis of wing structure with pre-stress

4. CONCLUSIONS

The Natural frequency of the wing structure is analyzed within the pre-stress with the help of

Ansys Workbench 16.2 software. According to the resonance factor it tends to failure of the

wing. The overall deformation of the wing structure is determined under pre-stress while

flying using the modal analysis in the Ansys. By knowing the natural frequency of the aircraft

wing, it helps to calculate the resonance of the wing structure. The resonance of the wing

structure is determined to prevent the failure of the component in the aircraft.



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analysis of natural frequency for an aircraft … · the spar carries the whole weight of the wings...

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