Researchers developing new method to test metal fatigue

Siegen / Portsmouth: University scientists in Germany and the UK are developing a new method for testing aircraft components that should result in air travel becoming safer and cheaper.

The team is trying to develop state-of-the-art computer modelling programs that show how aircraft components react under the stresses of flying. The program tries to tackle the problem of "metal fatigue" or " fatigue crack growth." The program is intended to replace costly mechanical testing that components currently undergo.

Metal fatigue is a process whereby small cracks, inherent in the metal components making up aircraft engines, grow over time. In the past this phenomenon has been the cause of tragic accidents, such as the 1989 United Airlines crash in the US which resulted in the loss of 112 lives. Investigation into the crash resulted in the discovery that the piece of metal holding the engine's fan blades together had shattered, destroying the craft's hydraulics, and causing it to cartwheel across the tarmac as it tried to land.

According to University of Siegen scientists, up to 90 per cent of a component's lifetime is spent in the stage of the initiation and early growth of short cracks. Throuigh this program materials scientists at the German university will examine dislocation structure, and other microscopic changes in components, using a powerful transmission microscope.

According to professor Jie Tong, lead researcher from the University of Portsmouth, since the parts of engines in any aircraft go through a complex combination of stresses and vibrations, it needs to be discovered how the inherent cracks in the metal are going to be affected.

Tong says that the safety of aircraft depends on engineers knowing when the cracks are going to become a problem so that plans can be made to replace components during regular inspection cycles. "The scheduling of these inspections critically depends on the precise knowledge of crack growth mechanisms and growth rate,' says Professor Tong.

According to the researchers, their work will not only improve air safety, but also  reduce maintenance costs, that currently run into billions of dollars worldwide. All this will lead to cheaper and safer air travel for all.