Lasershot peening

Citation

(1999), "Lasershot peening", Aircraft Engineering and Aerospace Technology, Vol. 71 No. 6. https://doi.org/10.1108/aeat.1999.12771fab.001

Lasershot peening

Keywords Materials World, Lasers, Peening, Aerospace industry

A new technique for improving the mechanical properties of the metals and alloys used in the aerospace industry is being developed by the Metal Improvement Company (MIC) and the Lawrence Livermore National Laboratory (LLNL), part of the University of California. The technique, known as lasershot peening, uses LLNL's solid state laser to give repeated "shocks" to the surface of the material, improving the material's tensile strength and crack resistance properties.

The lasershot peening technique works by generating a plasma at the surface of the material. Laser intensities of 200 Joules per square centimetre in a pulse lasting 30 nanoseconds can generate shock pressures of up to 109 atmospheres when absorbed on a metal surface. The precise depth of residual stress introduced into the surface can be controlled by applying successive shocks to the same area, driving the residual stress progressively deeper without damaging the material at the surface.

Deep residual stress is important for safety critical components such as turbine blades in aeroplane engines. Tests on lasershot peened turbine blades have reportedly shown that the surface engineering technique has a marked effect upon the properties of the material. On two lasershot peened blades, V-shaped notches were cut 3.8 mm into the material. We are informed that after 10 million cycles of the blade at optimum speed and vibration no cracks were detected in the material, demonstrating a high level of fatigue resistance in the critical surface area. In tests with blades with 6mm notches, the fatigue strength of the blades was said to be more than double that of conventionally shot peened steel.

Details available from Materials World, The Institute of Materials. Tel: +44 (0) 171 451 7395; Fax: +44 0 171 839 2289; E-mail: Andrew-Mclaughlin@materials.org.uk