Failure analysis of the wing-fuselage connector of an agricultural aircraft

This paper presents an analysis of failure of the wing-fuselage connector for the agricultural aircraft. From the visual examination of the fractured surface, it was possible to observe beach marks, typical for fatigue failure. Careful observation showed that the crack origin surface was covered by corrosion products, therefore the failure had a character of fatigue combined with corrosion. A nonlinear finite element method was utilized to determine the stress state of the connector under operating condition. High stress zones were found at the region of the wing lug, where the failure occurred. Obtained results were next put into total fatigue life (S–N) and crack initiation (ε–N) analyses performed for the load time history equivalent to 10-minute operating flight. In these analyses, the number of flight hours to the first fatigue crack and also to total damage of the wing lug were estimated. Moreover the influence of many factors such as: heat treatment, surface treatment, corrosion and overload on the fatigue life of the connector were analyzed.