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Design Optimization of Aircraft Fuselage Under Dynamic Response by Using Finite Element Analysis
1K. Vamssi Venugopal, 2I. R. K. Raju
1,2Department of Mechanical Engineering, Chaitanya Engineering College, Visakhapatnam Email: [email protected]
Abstract : The fuselage is the primary structural component that supports the airframe structure. The Fuselage is a semi – monologue structure where the skin carries the external loads, the internal fuselage pressurization and is strengthen using stringers, frames and bulkheads. Now-a-days the weight of the structure has become an important factor due to increase of production cost. The fuselage structures are made up of conventional metals alloys and efforts are being made to reduce the weight and consequently increase the life of the structure.
The use of composites material improves the performance and offers a significant amount of material savings. The payload performance / speed / operating range depends upon the weight. The lower the weight the better the performance, one way of reducing the weight is by reducing the weight of the structure.
This paper presents some of the important aspects in the design and analysis of aircraft structures. These important aspects are related to material selection, structural configuration, loads evaluation, static strength and deflection, static stability evaluation and influence of dynamic loadings. The key aspects in specific areas are combined to provide an overall perspective of aircraft structural design and analysis. Simulation of fuselage structure is done for dynamic deformation and dynamic response of optimized material. The fuselage structure was modeled in CATIA and Finite Element Analysis (FEA) is carried out using ANSYS software.
Keywords: Center Fuselage Structure, Finite Element Analysis, Optimization, Aluminum, Carbon Fiber
I. INTRODUCTION
The fuselage is the main structure, or body, of the aircraft. The fuselage is the main body section that holds crew and passengers. The power plant, wings, stabilizers, and landing gear are attached to it. Fuselage must provide the necessary strength and rigidity to sustain the loads and environment that it will be subjected during the operational life of the airplane.
The fuselage of a modern aircraft is commonly referred to as semi- monocoque construction. The semi- monocoque fuselage is constructed primarily of aluminum alloy, although steel and titanium are found in high-temperature areas. A pure monocoque shell is unstiffened tube of thin skins, and as it is inefficient since unsupported thin sheets are unstable in shear and
compression. In order to support the skin, we need to provide bulkheads, frames, stiffening members, stringers and longerons. The fuselage as a beam contains longerons and stringers, frames and bulkhead.
II. LITERATURE REVIEW
Marco et al performed a buckling analysis for the composite fuselage. Finite element analysis was done on composite fuselage structure. The reduction of weight between the carbon/epoxy composite and the aluminum material is also high, thus encouraging the suitability of carbon/epoxy for fuselage applications [1].
Prem Chand et al performed an optimization for the airplane fuselage structure based on weight and strength criteria using different materials which are aluminum and Eglass/epoxy. They performed a structural static analysis on the finite element model of the airplane fuselage under static loads to determine the deflections and stresses. Also, Harmonic analysis was performed at critical frequencies obtained from the modal analysis for operating conditions. Since the selection criteria was weight and strength, the Eglass/epoxy was proved as the best suited material from their analysis between the two materials [2].
Edwin L. Fasanella et al. has performed an analytical /experimental correlation by conducting a vertical drop test of a fuselage section of a Boeing 737 aircraft. The effect on the impact response of the airframe structure and the occupants and the structural integrity of a conformable auxiliary fuel tank mounted beneath the floor was evaluated. The experimental data was compared with the simulation results. The degree of analytical and experimental correlation obtained for this simulation illustrates the potential of transient dynamic finite element modeling as a design tool for aircraft crashworthiness [3].
Marampalli Shipla et al. conducted modal analysis, linear buckling and fatigue analysis on the fuselage structure for A320 NEO aircraft by using Solidworks as CAD software and Ansys as finite element software [4].
Khairi Yusuf et al. performed a finite element analysis on fuselage structure. For the nonlinear analysis, load
increments and convergence tolerance for the analysis are continually adjusted to ensure an accurate and successful solution. Stress analysis was performed under concentrated force and pressure and the results show that the design structure is rigid and safe. A different stress analysis with internal pressure as the loading conditions also produced safer stress distribution of the fuselage skin with the stringers [5].
Han-Gi Son et al. performed an analysis for the loading conditions of internal pressure, Shear load, Bending moment, torsional load and axial compressive buckling.
Safer loading conditions for the proposed stacking sequence of composite layers are evaluated. The skin and frame stacking sequences which are considered are
45/90/ 45/0/ 45/0/ 4 and 90/ 45/ 5 5
s 4
2sRespectively. The failure theories which they have considered are maximum stress failure theory and Tsai – Wu failure theory. Based on the above theories, failure load for the proposed composite material is evaluated [6].
B. Karthick et al. performed a static analysis for the lattice structure of the fuselage structure rather than the stiffened shell structure. Analysis was performed on finite element program Ansys with model generated in CAD program Catia. The proposed design seems to be safe under the first loading condition, both end of the structure is fixed and internal pressure load is applied inside the fuselage stringers alone. The material used was aluminum alloy [7].
III. METHODOLOGY
The model of fuselage is imported to ANSYS to perform finite element analysis. Static analysis is performed on fuselage for aluminum material and carbon fiber for static loads to determine deflections and stresses. Modal analysis is performed to calculate natural analysis to see the structure behavior of fuselage. Transient analysis is performed to determine the dynamic response of a structure under the action of any general time-dependent loads for operating loads and deflections, stresses are tabulated. From the analysis, results of both materials are tabulated. From these results, better material is selected based on weight and strength.
IV. DESIGN PARAMETERS
Table 1: Design Parameters Parameter Value
Length 15m
Width Height Fuselage Dimensions 5.77 m 5.94 m Door Dimensions 0.75 m 1.5 m Window Dimensions 0.27 m 0.47 m
Cabin 5.49
V. DESIGN OF FUSELAGE STRUCTURE USING CATIA
Geometric configuration of the fuselage: A segment of the fuselage is considered in the current study. The structural components of the fuselage are skin, bulkhead and Stiffeners. Geometric modeling is carried out by using CATIA software.
Figure 1 Final Structure of Fuselage (Skin – Stringers – Bulk Heads – Cabin Floor)
VI. FINITE ELEMENT METHOD
The basic idea in the Finite Element Method is to find the solution of complicated problems with relatively easy way. The Finite Element Method has been a powerful tool for the numerical solution of a wide range of engineering problems.
The Finite Element Method is used to solve physical problems in engineering analysis and design. The physical problems typically involve an actual structure component subjected to certain loads. The idealization of the physical problem to a mathematical model
differential equations governing the mathematical model.
The Finite Element Analysis solves the mathematical model, which describes the physical problem. The FEM (Finite Element Method) is a numerical procedure; it is necessary to assess the solution accuracy, it is clear that the Finite Element solution will solve selected mathematical model with all the assumptions, which reflects on the predicted response.
There are three basic steps involved in finite element method.
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2. Solution (Applying loads and solving) 3. Post Processor (Reviewing the results)
Role of fem in structural analysis is probably the most common application of the finite element method.
Figure 2 Basic Model Approach
VII. STATIC ANALYSIS
Static analysis is used to determine the displacement, stresses strains and forces in structural components caused by loads that do not include significant inertia and damping effects. Steady loading and response conditions are assumed i.e. the loads and the structures response are assumed to vary slowly with respect to time.
Figure 3 STATIC ANALYSIS OF FUSELAGE STRUCTURE FOR ALUMINIUM
Figure 4 STATIC ANALYSIS OF FUSELAGE STRUCTURE FOR COMPOSITE
VIII. MODAL ANALYSIS
Modal analysis is technique used to determine the vibration characteristics (natural frequencies and mode shapes) of a structure or a machine component while it is being designed. It also can be a starting point for another, more detailed, dynamic analysis, such as a transient dynamic analysis, a harmonic response analysis, or a spectrum analysis.
Figure 5 MODAL ANALYSIS OF FUSELAGE STRUCTURE FOR ALUMINIUM
Figure 6 MODAL ANALYSIS OF FUSELAGE STRUCTURE FOR COMPOSITE
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IX. BUCKLING ANALYSIS
Buckling analysis is a technique used to determine buckling loads. Critical loads at which the structure becomes unstable and buckled. Buckling analysis is a technique used to determine buckling analysis and element type, material properties; boundary conditions are same as for static analysis except the pre-stress effects are to be included.
Figure 7 ALUMINIUM
Figure 8 COMPOSITE
X. TRANSIENT DYNAMIC ANALYSIS
Transient dynamic analysis (sometimes called time- history analysis) is a technique used to determine the dynamic response of a structure under the action of any general time-dependent loads.
Figure 9 DYNAMIC RESPONSE OF FUSELAGE STRUCTURE FOR ALUMINIUM
Figure 10 DYNAMIC RESPONSE OF FUSELAGE STRUCTURE FOR COMPOSITE
XI. RESULTS AND DISCUSSION
STATIC MATERIALS
MAXIMUM VALUES ALUMINUM CARBON FIBER EQUIVALENT
STRESS (Mpa) 38.59 36.245
TOTAL
DEFORMATION (mm)
2.493 2.1975
Table 1COMPARISON OF MATERIAL UNDER STATIC ANALYSIS
FREQUENCIES (Hz) MODES
SHAPES ALUMINUM CARBON FIBER
1 27.245 28.118
2 30.029 31.821
3 30.122 31.852
4 30.607 38.293
5 30.768 41.719
6 31.242 41.767
Table 2 COMPARISON OF MATERIAL UNDER MODAL ANALYSIS
MATERIAL LOAD MULTIPLIER ALUMINUM 16.155
CARBON FIBER 17.021
Table 3 COMPARISON OF MATERIAL UNDER BUCKLING ANALYSIS
DYNAMIC
RESPONSE MATERIALS
MAXIMUM VALUES ALUMINUM CARBON FIBER EQUIVALENT
STRESS (Mpa) 183.98 37.666
TOTAL
DEFORMATION (mm) 91.196 2.3042
Table 4 COMPARISON OF MATERIALS UNDER DYNAMIC RESPONSE
Case 1:
The analysis has been carried out to find the material that has minimum weight considering the boundary conditions. It is observed that the composite material carbon fiber has less weight when compared to remaining material i.e. Aluminum
Case 2:
1. From table it is observed that for carbon fiber equivalent stress is 36.245Mpa under static condition which is less when compared to the other material aluminum i.e. 38.59 Mpa. And the buckling factor by numerical for carbon fiber is 17.021mm greater than the aluminum i.e. 16.155 mm.
2. From table it is observed that frequencies for carbon fiber which is higher when compared to the other material aluminum.
3. From table it is observed that for carbon fiber equivalent stress is 37.666 Mpa under dynamic response which is less when compared to the other material aluminum i.e. 183.98 Mpa.
XII. CONCLUSION AND FUTURE SCOPE
The main aim of this project is to minimize weight and increase performance. To reduce weight material optimization is done. The analysis of model was done
with two different material properties using finite element analysis. The study finite element analysis of stresses of dissimilar materials was performed with the software ANSYS. The finite element method is an efficient technique in analyzing stresses. After material optimization the structure is substituted to both static and dynamic load conditions by comparing results, the modified design Carbon fiber has given best results compared to other material. Furthermore, the analysis can be carried studying for failures criteria of composite material.
REFERENCES
[1] Marco Aurelio Rossi, Sergio Frascino Muller de Almeida. Design and Analysis of a Composite Fuselage, Brazilian Symposium on Aerospace Engineering and Applications, 2009.
[2] Y Prem Chand, K Krishna Veni. Weight and Strength Optimization of Airplane Fuselage Structure for different Materials, International Journal of Mechanical Engineering Research and Technology, Vol. 1, No. 2, November 2015.
[3] Edwin L. Fasanella and Karen E. Jackson, Yvonne T. Jones, Gary Frings and Tong Vu.
Crash Simulation of a Boeing 737 Fuselage Section Vertical Drop Test.
[4] Marampalli Shilpa, M. Venkateshwar Reddy, Dr.
A. Siva Kumar. Design and Analysis of Fuselage Structure using Solidworks and Ansys, International Journal of Engineering Sciences and Research Technology, 3(9): September, 2014.
[5] Khairi Yusuf, Nukman Y., S. Z. Dawal, Devi Chandra, N. Sofia. Conceptual Design of Fuselage Structure of Very Jet Aircraft, Latest Trends on Theoretical and Applied Mechancis, Fluid Mechancis and Heat & Mass Transfer.
[6] Han – Gi Son, Deepak Kumar, Yong-Bin Park, Jin-Hwe Kweon and Jin-Ho Choi. Structural Design and Analysis of Composite Aircraft Fuselage Used to Developo AFP Technology, Aerospace and Informatics Engineering, Japan, February21-23, 2013.
[7] B. Karthick, S. Balaji, P. Maniiarasan. Structural Analysis of Fuselage with Lattice Structure, International Journal of Engineering Research &
Technology, Vol. 2 Issue 6, June – 2013.
