A sub-surface compressive residual stress profile is measured using x-ray diffraction measuring equipment.

The X-axis is the measurement of the depth in mm or inches the Y-axis is measure of residual stress in ksi or MPa.

The maximum residual stress profile can be affected by changing the known factors of the shot peening process; these include:

• component geometry
• component material
• shot material
• shot quality
• shot size
• shot intensity
• shot coverage

The compressive residual stress in a metal is produced by the transfer of kinetic energy from a moving mass (of the shot particle) and discharging the energy into the surface of a material, to plastically deform the surface.

The residual stress profile is also dependent on the density of coverage or saturation.

The mechanics of the impacts involve the properties of the shot hardness, shot shape, and structure; as well as the properties (ref “young’s modulus”) of the component material.

Factors to consider to enable further development of the peening process and the control for kinetic energy transfer are:

• shot velocity (shot speed delivered by the diameter and blast wheel / turbine speed (RPM) or air pressure/nozzle design)
• shot mass
• shot chemistry
• impact angle
• components metallic properties

Click on links to read

1 – What Will Peening Do For My Components?
3 – How to Measure Residual Stress
4 – MPa and Relationship to Almen Strips

Click here for information on x-ray diffraction measuring equipment.

For more information on shot peening please visit www.rosler.com

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Post written by
Haydn Kitchen
Shot Blasting Technical Manager