LIFE ASSESSMENT AND ANALYSIS OF CRACK PROPAGATION FOR AIRCRAFT STRUCTURAL ELEMENTS UNDER A GENERAL LOAD SPECTRUM

Aircraft structural components are exposed to cyclic loads during their operational life. Life assessment ofstructural elements can be divided into two phases. Phase one, life to crack initialization, and phase two, crackgrowth. The crucial issue is the determination of a reliable computational procedure for life assessment ofaircraft structural elements. For this purpose, it is essential to determine fracture mechanics parameters, suchas stress intensity factors (SIF). The computational method presented in this investigation uses singular finiteelements, incorporating the load spectrum over a number of cycles or blocks up to failure. In this paper, theStrain Energy Density (SED) method is used for crack initialization and for crack growth, with the aim ofdetermining the total fatigue life. SED is a comprehensive and efficient method that uses low cycle fatigue(LCF) properties for crack initiation and crack growth analysis. These advantages reduce the experimentaltesting. The focus of this research is on establishing the analytical expression for stress intensity factors (SIF).Crack growth analysis of damaged structural elements is based on conventional Forman's low and StrainEnergy Density methods. Validation of the computational procedure has b