Dear dr. Peener,
We know that the shot peening introduces compressive residual stresses on the parts subjected to this process.
We know that the values of these residual stresses depend on the parameters of the process.
Can the shot peening process introduce (in surface or depth) also shear stress?(I'm considering carburized and quenched gears)
If the answer is positive, what are the parameters that I need to change, to eliminate or reduce the shear stress?

Thanking in advance

Austenite

This is really a 'mechanics' question. For any shot-peened surface there is a residual stress system that has several components. The 'normal' stresses are those that are usually considered. There must always, however, be a shear stress system that is related to the magnitude and direction of the normal stresses.

For carburized and quenched gears another important factor is the effect of peening on the retained austenite content. Peening reduces high retained austenite levels - by transformation to martensite - which usually produces improved service performance.

Dear Dr Peener,

The goal of shot peening is obtaining compressive residual stresses that give benefit on fatigue life .
The presence of shear stresses is detrimental for fatigue resistance. How can I reduce tre presence or the value of shear stresses ?
Are there some shot peening process techniques in order to reduce shear stresses value? ( for example angle of impact of shot against the surface or other ?)


Thanking in advance for your answer

I'm not an expert in stress analysis but I believe that resolved shear stresses are unavoidable for any residual stress system.