REPUBLIC OF SERBIA

MINISTRY OF DEFENCE

www.mod.gov.rs

MINISTRY OF DEFENCE

Material Resources Sector

Defensive Technologies Department

Military Technical Institute

www.vti.mod.gov.rs

EFFICIENT COMPUTATION METHOD FOR FATIGUE LIFE ESTIMATION OF AIRCRAFT STRUCTURAL COMPONENTS

STEVAN MAKSIMOVIĆ

Military Technical Institute, Belgrade, Serbia,  s.maksimovic@mts.rs

MIRJANA ĐURIĆ

Military Technical Institute, Belgrade, Serbia, mina.djuric.12@gmail.com

ZORAN VASIĆ

Military Technical Institute, Belgrade, aig135@mts.rs

OGNJEN OGNJANOVIĆ

Military Technical Institute, Belgrade, ognjenognjanovic@yahoo.com

Abstract: This work considers efficient computation method for total fatigue life estimation of aircraft structural components under general load spectra. Total fatigue life of aircraft structure or structural components can be divided in two parts. The first part represents initial fatigue life up to crack initiation in which low cyclic fatigue properties are used and second part represents fatigue life during crack growth in which dynamic material properties are used. To obtain efficient computation method in this work the same low cyclic material properties, for determination of initial fatigue life and for residual life during crack growth, are used. Based on the strain energy density (SED) theory, a fatigue crack growth model is developed to predict the lifetime of fatigue crack growth for single or mixed mode cracks.  Presented computation results are shown that crack growth method based on strain energy density approach is in a good agreement with conventional Forman`s approach. This computation method for total fatigue life prediction can be used in practical design of metal structural parts of helicopter tail rotor blades as well as in service life extension of the G-4 Super Galeb aircraft structures.

Keywords: aircraft structure, total fatigue life estimation, SED, low cyclic fatigue properties.