Function: What does it do?
Shot peening machines bombard a part with tiny beads that each act like ball-peen hammers, creating dents in the surface of the part that relieve tensile stress, strengthen the part against wear, and improve surface finish. It can perform a similar function to sandblasting (in that it cleans and finishes a part quickly) or to some forms of heat treating (in that it strengthens a part against repeated wear or fracture).
Application & Benefit: What can I use it for?
Cracks in a component occur in areas where there is a high amount of tensile residual stress. By compressing these areas with the shot peening media, the tensile stress is converted to compressive stress, which strengthens the part rather than weakens it. This process is used extensively in the production of all types of springs, which are especially vulnerable to fractures from repetitive wear.
Shot peening is incredibly effective in increasing component life. It can increase gear life by more than 500%, and spring life by up to 1200%. 1
Aerospace Automotive Springs Gears
Common Processes 2
- Landing gears
- Ring and pinion gears
- Spur gears
- Compressor disks
- Turbine disks
- Compressor airfoil and roots
- Aircraft wheels
- Aircraft wing skins
- Connecting rods
- Coil springs
- Leaf springs
Process: How does it work?
Shot peening is subject to a wide variety of methods and processes, but they all contain the same basic elements: the media, the chamber, the recovery system, and the propellant system.
The media are the small objects that create the dents in the surface of the component. They come in various sizes and can be made of glass, ceramic, or iron, but are most commonly made of cut wire which does not shatter into jagged fragments.
This media is shot out by the propellant system using any of a range of methods, such as air compression or centrifugal force, and the stream of propelled media is directed onto the component being peened while enclosed in the chamber for safety.
The media are then recovered and are often able to be used again.
While this process is very straightforward it can be supplemented by many different pieces of equipment in order to increase efficiency, speed, and cost effectiveness.
Major Shot Peening Machine Manufacturers
- Jason Johnson, Albert Whetstone, Juston Johnson. "Shot Peening." http://www.webpages.uidaho.edu/mindworks/Machine_Design/Posters/PDF/Peening_Poster.pdf ↩
- http://www.progressivesurface.com/shotpeening/process.htm ↩