RESEARCH PROGRESS AND DEVELOPMENT TREND OF MAJOR FATIGUE PROBLEMS IN AIRCRAFT STRUCTURES

Aircraft structures frequently endure complex service loads during long-term operation and maintenance, including single or coupled effects of cyclic static loads, mechanical vibrations, impact loads, alternating thermal loads, and corrosive environments. These loads shall highly lead to aircraft structural damage and fatigue failure, which serves as the main research focus closely monitored in the aircraft design and manufacturing period. This study systematically reviews typical fatigue modes of aircraft structures including conventional fatigue, vibration fatigue, impact fatigue, corrosion fatigue and thermo-mechanical fatigue (TMF). It comprehensively elaborates the main characteristics, sources of loading, and critical structural areas associated with various types of fatigue problems in aircraft structures. This study briefly outlines the design and testing requirements regarding the fatigue of aircraft structures, which are stipulated by standards and specifications such as the military aircraft structural integrity programs, civil aircraft airworthiness regulations and so on. This study presents the current research overview, technical differences, and representative research progress concerning various fatigue issues in aircraft structures from the perspectives of fundamental fatigue theories, damage evolution and accumulation models, structural failure mechanisms and fatigue life prediction methods. At the same time, this study summarizes the experimental methods, objectives, and apparatus for investigating fatigue tests in aircraft structures from material, structural component, and full-scale aircraft structural levels. It introduces key experimental technologies such as the measurement and evaluation of multi-source heterogeneous parameters, efficient damage detection and intelligent structural health monitoring. This study also presents representative case studies in real engineering. Finally, by taking the technical demands of new-generation aircraft development, the daily operation as well as the long-term maintenance in the lifecycle run of aircraft structures and so on, this study outlines the future development trends in aircraft structural fatigue technology. It provides valuable technical references for subsequent research and engineering optimization in the field of aircraft structural fatigue.