Review of Shot Peened Surface Properties

Author:  David Kirk
Source:  The Shot Peener magazine, Vol 21 / Issue 4, Fall 2007
Doc ID:  2007028
Year of Publication:  2007
Abstract:  
DISCUSSION AND CONCLUSIONS This account has, of necessity, involved broad generalisations about the properties of shot peened surfaces. That is because component materials vary enormously in terms of their physical properties. Nevertheless it is felt that the general features described here are reasonable. The most important of these are that: 1) Multiple impacting invokes very high plastic strains with a maximum surface hardness being a characteristic feature. 2) The very high strain rates associated with dimple formation induce adiabatic heating that contributes to a degree of recovery of extreme-surface properties. 3) Heavily-deformed peened surfaces are thermodynamically unstable - requiring careful control of post-peening service temperatures. 4) A combination of strain-softening and surface temperature rise produces a reduction of the extreme surface compressive residual stress level. 5) Dimpling of peened surfaces can have a useful influence on high-load lubrication regimes. There is a temptation to apply the principle of "more is better" in commercial shot peening. This is contrary to evolving knowledge that indicates that optimum service properties are developed by applying coverage that is nearer to the nominal 100% than, say, 300%.