FATIGUE LIFE ESTIMATION OF LANDING GEARS OF FIGHTER AIRCRAFT USING FINITE ELEMENT ANALYSIS

Abstract

The Total Technical Life (TTL) of fighter aircraft “Article 29L” is 1800 flying hrs. However the TTL of Main Landing Gear (MLG) and Nose Landing Gear (NLG) is only 2000 landing. Considering average sortie duration of 45 minutes, the life of LGs should have been ideally 2400 landings. So there is need to increase the life of LGs. In older days the stress analysis and life extension study was carried out considering the experimental stress analysis approach and testing, which is time consuming and require huge testing setup. In order to bridge this gap and to reduce the effort, it is proposed to estimate the life of the under carriage by Integrated Approach of Finite Element (FE) Analysis. The determination of the fatigue life of an engineering structure is based on two precepts. These are knowledge of the structure itself and knowledge of how that structure is loaded. The information required for fully understanding these two singularly complicated items is significant hence utmost care is taken to estimation of life of LGs. In this work Finite Element (FE) Analysis 3-D geometric modeling developed using CATIA software. The assembly model was imported in PATRAN software and 3-D mesh was generated using HYPERMESH. Connectivity between the components is provided using the surface to surface contact element. Contact elements are capable of transferring the displacement as per contact status and stiffness of contacting body. The FE model was solved using NASTRAN software for stress and displacement, as per fatigue test load data available. Further fatigue analysis has been carried out using MSC Fatigue software for fatigue life estimation. To validate FE stress analysis, results were compared with classical calculations and Rejuvenation zones of MLG. Thus determine cumulative fatigue damage hot spots can be rejuvenated locally and more no of landing (life of LGs) can be extended accordingly and avoid the experimental stress analysis approach and testing for life extension.