Modal Analysis of a Typical Landing Gear Oleo Strut

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1 Modal Analysis of a Typical Landing Gear Oleo Strut Dr. N. Sreenivasa Babu Engineering Department- Mechanical, Shinas college of Technology Abstract: Landing gear is a critical component of an air craft during landing and take-off. In this analysis, a typical oleo strut of a landing gear is investigated for its structural analysis to investigate the deformation and von mises stress levels, and vibration analysis to evaluate the frequency levels under different conditions. In this contrast, different materials are investigated for take-off and landing conditions and compared the levels of frequencies at various loading conditions. Keywords: Oleo strut, Ferrium S53, Al 2040, Ti 10V-2Fe-3Al, Frequencies, Von mises stress, Block Lanczos method. I.INTRODUCTION Air craft is an important commodity in the field of civil aviation industry. Day to day, the demand for such an air craft is increasing and top priority is to be adopted for the risk free aviation transportation. An oleo strut [2] is a hydraulic device used in landing gear mechanism as shown in figure: 1, comprising spring damper system and other pneumatic system also. Figure: 1 Typical Oleo strut diagram with dimensions For this purpose different materials are chosen individually and their properties [1] are given below in table:1. DOI: /IJRTER WKSGC 1

2 S.No. Material International Journal of Recent Trends in Engineering & Research (IJRTER) Table: 1 Material properties Tensile Strength (N/mm 2 ) Density, (kg /m 3 ) Poission s Ratio Young s Modulus (N/mm 2 ) 1 Ferrium S53 Steel Ferrium M54 Steel Aermet 100 Alloy Ti-10V-2Fe-3Al Alloy Ti 6Al - 4V Alloy Al II.LITERATURE SURVEY An aircraft major component that is needed to be designed is landing gear (undercarriage). The structure of the landing gear supports an aircraft on the ground and allows it to take-off and landing. AyanDutta et al., carried out Linear static analysis in the Design and Analysis of Nose landing gear, to evaluate the stresses and deformations by using different materials to get the characteristics and selection of materials [1]. It is essential that the modal analysis is also need to be carried out to evaluate the natural and forced frequencies to check the material feasibility under loading conditions. M. Alex et al., designed a shock absorber system to smooth out or damp shock impulse, and dissipate kinetic energy for understanding to improve the performance characteristics of modified oleo strut shock absorber for lighter aircraft application. In this work, the author evaluated the deflection and von mises stress for solid spring and oleo strut [3].The failure criterion is also to be evaluated for its fatigue failure and natural frequencies of the system. Rajesh A et al., Design and Analysis Aircraft Nose and Nose Landing Gear, carried out Static structural and Impact test for designed geometry [6]. Stress distribution and deformation was evaluated for two distinct materials such as steel and aluminum alloy and primary results of acoustics. The structure need to be designed based on its fatigue performance also, by choosing the satisfactory results from modal analysis. III. MODEL DEVELOPMENT & STRATEGY A typical oleo strut is modeled using a 3D design engineering software solid works developed by Dassault systems SOLIDWORKS Corporation and imported in the analysis software Ansys[4] used to simulate engineering models of structures, electronics, or machine components to simulate strength, toughness, elasticity, temperature distribution, electromagnetism, fluid flow, and other All Rights Reserved 2

3 Figure: 2 - A typical model of Oleo Strut A solid brick element has chosen for its meshing element, block Lanczos mode extraction method is adopted for the modal analysis during the extraction of 5 modes. In this investigation, different loads were considered during take-off and landing for airbus A380. Maximum take-off weight (MTOW): 560,000 kg and maximum landing weight (MLW): 386,000 kg [7] has been chosen for airbus A380 technical specifications. Based on the area of loading, the Oleo strut adopted for full loading conditions and these weights are converted in to MPa pressure for Take-off and MPa pressure for landing. IV. RESULTS AND DISCUSSIONS The Oleo strut is examined for its deformation, stress and frequency levels during take-off and landing with different materials. The results are tabulated and compared its dynamic stability. Table: 2 Oleo Strut displacements and Von mises stresses - Take-off condition S.No: Material Name Displacement in mm Stress in y-direction in MPa Von mises stress in MPa 1 Ferrium S53 Steel Ferrium M54 Steel Aermet 100 Alloy Ti-10V-2Fe-3Al Alloy Ti 6Al - 4V Alloy Al All Rights Reserved 3

4 Table: 3 Oleo Strut displacements and Von mises stresses Landing condition S.No: Material Name Displacement in Stress in y-direction in Von mises stress in MPa mm MPa 1 Ferrium S53 Steel Ferrium M54 Steel Aermet 100 Alloy Ti-10V-2Fe-3Al Alloy Ti 6Al - 4V Alloy Al Table: 4 Oleo Strut natural Frequencies in Hz during Take-off condition S.No: Material Name Mode 1 Mode 2 Mode 3 Mode 4 Mode 5 1 Ferrium S53 Steel Ferrium M54 Steel Aermet 100 Alloy Ti-10V-2Fe-3Al Alloy Ti 6Al - 4V Alloy Al Table: 5 Oleo Strut natural Frequencies in Hz during Landing condition S.No: Material Name Mode 1 Mode 2 Mode 3 Mode 4 Mode 5 1 Ferrium S53 Steel Ferrium M54 Steel Aermet 100 Alloy Ti-10V-2Fe-3Al Alloy Ti 6Al - 4V Alloy Al Based on the modal analysis, the Ti 6Al-4V Alloy material is proven stable during take-off and landing in mode5. However, Ferrium S53 is the best suitable sustainable material with respect to displacement and stress, in comparison with other All Rights Reserved 4

5 Figure: 2 - Ferrium S53 Oleo strut displacement in mm during take off condition Figure: 3 - Ferrium S53 Oleo strut von mises stress in MPa during take All Rights Reserved 5

6 Figure: 4 - Ti 6Al-4V Alloy material Oleo strut Mode 5 - frequency in Hz during Landing V. CONCLUSIONS The frequencies are evaluated in modal analysis for different materials. For Ti 6Al-4V material oleo strut, the frequency is Hz and difference is not evident during Take-Off and Landing. From the static analysis, the results for displacement is 0.36 mm and Von mises Stress is for Ferrium S53 material and it is best suitable and sustainable for both landing and Take-off. REFERENCES I. AyanDutta, Design and Aanlysis of Nose Landing Gear, InternationResearch Journal of Engineering and Technology, vol. 03, issue 10, Oct II. III. M. Alex, Design and Analysis of Modified Oleo Strut ShockAbsorber System in Aircraft Landing Gear, nternational Journal of TechnoChem Research, Vol.02, No.02, pp , IV. V. MechanicsandEquipment/Lectures Aircraft/ForuthGrade /AircraftDesign2.pdf VI. Rajesh A and Abhay B T, Design and Analysis Aircraft Nose and Nose Landing Gear, The International Journal Of Engineering And Science, Vol.4, Issues.10, pp 74-80, VII. All Rights Reserved 6