A new paper from Dr Wei Tan's group is published! A new fatigue crack growth model considering the effects of load interaction and low velocity impact damage of aluminium-alloy thin-sheets was proposed. Our theoretical model and test results can provide guidelines for the impact damage tolerance design and fatigue life prediction of aeronautic aluminium-alloy structures. See the paper published in the top Fatigue journal: International Journal of Fatigue.

Aeronautic aluminium-alloy thin-sheets are the primary structural material for aircraft skins. During aircraft take-off, landing and maintenance, aircraft skins are inevitably and occasionally encounter low-velocity impact (LVI) events from foreign objects, such as flying runway gravel, accidental tool drop, and collision with ground vehicles. LVI indentation, as a typical damage type of aircraft skins, is one of the main reasons that affect the ultimate strength and fatigue life of aircraft structures. At present, reliable evaluation for the LVI damage on the fatigue life of aircraft remains a challenge to the aviation industry.

The main novel contributions of this paper herein are: (i) For the first time in the literature, constant amplitude FCG tests at different stress ratios and block spectrum loading were performed on 7075-T62 aluminium-alloy thin-sheets with LVI damage. (ii) A new FCG model considering the effects of load interaction and LVI damage was proposed, and the accumulative methodology of FCG life was established to assess crack growth life of post-impact aluminium-alloy thin-sheets under spectrum loading. (iii) Mechanisms of LVI damage on sequent FCG behaviours of aluminium-alloy thin-sheets were revealed. Our theoretical model and test results can provide guidelines for the impact damage tolerance design and fatigue life prediction of aeronautic aluminium-alloy structures.

Reference: Cheng, Z.Q., Xiong, J.J. and Tan, W., 2021. Fatigue Crack Growth and Life Prediction of 7075-T62 Aluminium-alloy Thin-sheets with Low-velocity Impact Damage under Block Spectrum Loading. International Journal of Fatigue, p.106618.

https://doi.org/10.1016/j.ijfatigue.2021.106618

Updated by: Wei Tan