|
Other SAE Magazines Sites
|
|
Technology update
Automatic shot peening
-
Ths USF Vacu-Blast shot peener.
|
As a means of prolonging fatigue life of metal components used for aerospace applications, shot peening is an established technique. USF Vacu-Blast International has now supplied a special automatic precision peening machine to Italian company Sicam SpA for fatigue life improvement of the wheels and associated components fitted to the Eurofighter Typhoon. Sicam has a workshare partnership with Dunlop Aviation.
The Vacu-Blast machine has a 1500 x 1400 x 1200 mm processing enclosure incorporating four peening nozzles fitted to a two-axis roof-mounted blast nozzle manipulator. Components are attached to special fixtures on a variable-speed-powered turntable, which rolls in and out of the enclosure to facilitate manual loading and unloading. Maximum component processing envelope is 700 mm in diameter and 700 mm high. Steel shot or glass beads can be used, and the facility has an in-cycle magnetic media separation and classification system to provide total segregation between the two types of peening media. It also ensures that only high-grade media is recycled to the nozzles via the generator-reclaimer.
The shot-peening process involves the bombardment of a metal surface with a controlled stream of spherical media (steel shot, glass, or ceramic beads) that plastically deforms the surface of a metal part and induces a residual compressive stress in the surface layer. This can prolong the fatigue life of metal components operating under cyclic stress by a factor of two or more and inhibits stress corrosion cracking, according to Vacu-Blast. The process is the high-tech equivalent of an ancient armorer cold-working a sword or shield with a ball peen hammer to improve its strength.
Stuart Birch
Aerospace Engineering October 2000
|
|
|
