Structural fatigue and joint degradation

This paper deals with three subjects on fatigue behavior of single lap joint structures based on the test results to discuss the structural integrity problems of aging aircraft. Firstly, the effect of the following factors on fatigue life were examined; fastener type, fastener row, squeezing force, overload, underload as well as corrosion. Secondly, the simulation problems of fatigue behavior of fuselage structures by uni-axial laboratory test using stiffened panel specimen are discussed. Thirdly, the effects of service load components on fatigue behavior of fuselage structure are examined using 1/3 scale model of a B-737 aircraft. Model specimens were tested by pneumatic cycles with and without synchronized bending. Test results suggested that fatigue behavior of fuselage structure can be estimated by evaluating the largest principal stress under complex stress conditions.