Strength Testing and Analysis of Fatigue Crack Growth in Selected Aircraft Materials

The study has been intended to determine the most essential mechanical and fatigue properties as well as impact strength of the 30HGSNA steel, to gain own data on the above-mentioned characteristics of materials to be used further on in numerical analyses of life estimates of aeronautical structural components. The scope of the study comprised the following assignments:
- determination of the most fundamental mechanical properties and impact strength of materials,
- low-cycle fatigue testing and evaluation of the Manson-Coffin curves,
- high-cycle fatigue testing and evaluation of the Wöhler curves,
- investigation into fatigue crack growth rates at constant and variable load-cycle amplitudes (determination of curves da/dN = f(ΔK, R), coefficients in Paris and NASGRO equations, coefficients in the Wheeler models of delay, the value of K_th(R)),
- crack toughness testing under the plane-state-of-strain conditions at room temperature (determination of the K_Ic(R)). The strength/fatigue testing was carried out in the Laboratory for Materials Strength Testing of the AFIT’s Division for Aeronautical Systems Reliability and Safety, the lab being accredited by the Polish Centre for Accreditation (Accreditation Certificate No.: AB 430).