Home Forums General Discussion Media, Shot, Beads, etc.

Dear All,
I would like to have information or references about the influence of the shot quality (shape, hardness, presence of broken and small defects, etc.) on the fatigue behavior of shot peened parts, particularly springs leafs.
Does the presence of angular shot’s and/or metallic defects is tolerated or not in new media (such us for example S330). If yes please give me the permitted percentage? And please give me the standard leading to check the shape of short peening media
What is the influence of the hardness shot’s? (Does the use of hardener media can induce and increase the media particle breakage phenomenon?) - Also does it leads to provoke degradation of the machine components?
Finally, what are the advantages and disadvantages of using cut wire shot for springs?
Thank you very much
--------------------
Prof. Raouf FATHALLAH
Ecole Nationale d’Ingénieurs de Sousse - TUNISIA

New media should NOT have any shape that is not spherical. Otherwise surface damage, cutting etc. will cause sites which may lead to high stress and fatigue failure. Refer to AMS 2431 for information on media types and requirements.
Harder shot is more prone to breakage at higher intensity but it may be necessary to achieve the designers depth of compression. Harder shot probably will be more deleterious to the machine, depending upon intensity and also machine construction (i.e. urethane wall liners etc.) Cut wire is a cleaner product (less dust) and more uniform in size distribution. It does not fracture but does eventually erode to smaller size which the screen separator will remove.