Shot peening is a cold working process used to produce a compressive residual stress layer and modify mechanical properties of metals. It entails impacting a surface with shot (round metallic, glass, or ceramic particles) with force sufficient to create plastic deformation.
Why Almen Intensity Matters
In quality-critical industries such as aerospace and automotive manufacturing, merely running shot peening equipment without verified calibration introduces catastrophic risks of under-peening (failing to prevent fatigue failure) or over-peening (inducing micro-cracks). The Almen system provides a standardized, repeatable metric to gauge the kinetic energy of the shot stream.
The Three Standard Strips: A, N, and C
- A Strip: Standard intensity applications, medium hardness components.
- N Strip: Low intensity applications, thin components, or softer alloys.
- C Strip: High intensity applications such as heavy structural shafts and landing gears.
Establishing the True Saturation Point
Saturation is defined by SAE J443 as the earliest point on the arc height vs. exposure time curve where doubling the peening exposure time results in no more than a 10% increase in arc height. Modern computerized saturation software eliminates manual graphing error and ensures compliance during FAA and ISO audits.
