International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 10 Issue: 07 | July 2023
p-ISSN: 2395-0072
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Fail Safe Design of Skin and Bulkhead of an Aircraft Stiffened Panel by Residual Strength Evaluation Method Shivanandappa N D1, Srinivasa Murthy M K2, Guru Kiran E3 1Assistant Professor, Dept. of Mechanical Engineering, J N N College of Engineering, Shivamogga, Karnataka, India. 2Assistant Professor, Dept. of Mechanical Engineering, J N N College of Engineering, Shivamogga, Karnataka, India. 3PG Student, Dept. of Mechanical Engineering, J N N College of Engineering, Shivamogga, Karnataka, India.
------------------------------------------------------------------------***----------------------------------------------------------------------Abstract - The failsafe design of aircraft structural components is a critical aspect of modern aviation engineering, ensuring the safety and reliability of aircraft in the face of potential failures. With the ever-increasing demands for air travel and the continuous push towards technological advancements, the design of aircraft structural components must adhere to rigorous standards to withstand unforeseen challenges. Stiffened panel is one such component part which is prone to crack initiation and houses many smaller components. All these subcomponents must withstand the applied load in the presence of crack and fluctuating loads for the safety of stiffened panel. Residual strength determination is performed for evaluating the design of the skin and bulkheads. The method involves the finite element analysis of the panel with crack to determine the stress intensity factor by modified virtual crack closure integral method and the maximum stress developed in the components. The residual strength of skin and bulkhead for three different skin thicknesses and varying crack lengths are determined and analysed to estimate the safety of the panel. The results show that the skin offers more resistance to crack propagation as the thickness increases. Also, the result shows that the residual strength of the components increases as the thickness of skin is increased.
built to meet specific static and dynamic loading conditions, deformation requirements, and functioning requirements. Service loads during an aircraft's operation are crucial for both design and durability and damage tolerance testing. A significant difficulty in aircraft design is fatigue and the ensuing fracture growth. Fatigue and damage tolerance design, analysis, testing, and service experience correlation are crucial for maintaining an aircraft's airworthiness during its entire economic service life. A plane's design takes into account determining the ideal ratios between payload and vehicle weight. It must be rigid and powerful enough to fly in unusual situations. Additionally, the aircraft must fly even if a component malfunctions while it is in flight. In contemporary aircraft, the skin serves as a loadbearing element. Unlike flat sheets, which can only support tension, folded sheet metals may support compressive stresses. Stiffeners, when paired with a piece of skin, are analysed as stringers, which are thin-walled structures. In the present scenario, a portion of the fuselage segment's stiffened panel is taken into consideration for the analysis and then put through tensile loading that is equal to the hoop stress created in the fuselage. Fuselage damage must not go beyond the design limit and must not cause the structure to fail catastrophically, which would destroy the aircraft's structural integrity. Therefore, damage tolerance should be included in the design of the structure to prevent structural failure. By thickening the skin of the stiffened panel, the damage to the skin in this situation can be endured.
Keywords —Fail-safe Design, Fracture Toughness, MVCCI method, Stiffened Panel, Residual Strength.
1 INTRODUCTION The damage tolerance and airworthiness requirements must be met for the aircraft to fly safely. A structure is said to be damage tolerant if it continues to function even after an initial damage is discovered. The analysis of fatigue crack propagation is the primary focus while evaluating the damage tolerance. It entails figuring out how fractures spread throughout the service life.
The geometric model of the stiffened panel with fuselage segment has been created in CATIA modeling software and then imported into MSC.PATRAN for finite element modeling. The finite element model is solved using MSC.NASTRAN for solving stiffened panel subjected to the tensile loading with a center crack.
Modern aircraft operate in a complicated environment with varying loading circumstances, resource constraints, and economic demands. The primary aeroplane parts are
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