Re: I had a sort of opposite problem

Post #41,688

6/8/02 11:20:46 PM

6/9/02 12:03:11 AM

That is interesting - 'They don't look right" so don't want em. Sheesh

Am interested as to what the 'shot peen' process involved. Am guessing that
peen means 'hitting' & shot implies using ball bearings to do the hitting ? am also guessing that
this was a hardening process after machining.

Cheers

Doug

UPDATE#1
LOOKED IT UP ON THE WEB ...

Shot Peen Forming [link|http://www.curtisswright.com/segments/metal_treatment/shot_peen_forming.asp|Shot Peen forming]

Peen forming is a dieless forming process performed at room temperature. During the
process, the surface of the workpiece is impacted upon by small, round steel shot.
Every piece of shot impacting the surface acts as a tiny peening hammer, producing
elastic stretching of the upper surface and local plastic deformation that manifest
itself as a residual compressive stress. The surface force of the residual compressive
stress combined with the stretching causing the material to develop a compound,
convex curvature on the peened side.

Parts formed by peen forming exhibit increased resistance to flexural bending fatigue.
Another distinct advantage with peen forming, unlike most other forming methods, it
that all surface stresses generated are of a compressive nature.

Edited by dmarker2 June 9, 2002, 12:03:11 AM EDT

Re: I had a sort of opposite problem

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Post #41,696

by Andrew Grygus

6/9/02 12:47:31 AM

6/9/02 12:58:20 AM

Only the last sentence is relative

Shot peening of (very hard and not at all formable) critical structural parts is done with very tiny steel shot at high velocity. The objective is to create those compressive stresses on the surface, similar to the stresses induced in tempered glass.

Grinding after shot peen tends to relieve these beneficial stresses through removal of material and heat, and introduces microscopic cracks and unwanted grinding stresses. Properly, there should be a heat cycle after grinding operations to remove the stresses produced by that process, but any such heat cycle would also remove the beneficial stresses from shot peening. On the other hand, shot peening can be used to relieve grinding stresses if a heat cycle is not possible due to metalergical (temper) requirements.

[link|http://www.aaxnet.com|AAx]

Edited by Andrew Grygus June 9, 2002, 12:58:20 AM EDT

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