shot peening???

[dohcfiend]

for the sake of speculation let's say the stock rods and crank are only good for 350 hp.

how much more could they withstand if they were shot peened?

or if the rods were shot peened and the crank nitrided?

[Lyle's GTP]

RE: shot peening???

I'm not an expert on this subject. But I think shot peening is no an exact science. It would totally depend on the metal, the length of time it was shot peened, etc.

Lyle

[BMFH]

RE: shot peening???

Hello All

Shot Peening does not make the rod stronger, it makes it more durable, (it will still pull apart), what it mainly does is ruff up the surface of the rod to stress relieve the surface so that there are not any stress risers and or sharp edges to give a place for cracks to start.

Before shot peening can be done, the rod needs to have the beam outer surfaces and sharp edges prepared by removing the forging marks on a belt sander or with a sanding or buffing wheel in a way that will not leave heavy groves in the surface (all sanding should be done so that all the sanding marks are paralel to the length of the rod) rounding and blending all the sharp edges is also needed before the shot peening operation.

After shop peening, the rod needs to be resized/reconditioned and new rod bolts and wrist pin bushing installed and fittted if there was one. They need to be ballanced as a SET, if you are going to the effort to shot peen the rods, then they should also have their weights adjusted to make them a BALLANCED matched set of rods.

Hope this helps,

John

[sspeedstreet]

RE: shot peening???

Shot peening is not a stress relieving process, it is a stress inducing process. Peening puts the entire surface of the part into compression making cracks caused by metal fatigue less likely to occur.

[your_I.D.]

Re: RE: shot peening???

Shot peening is not a stress relieving process, it is a stress inducing process. Peening puts the entire surface of the part into compression making cracks caused by metal fatigue less likely to occur.

nasa agrees:
INTRODUCTION
It has been recognized for a long time (Ref. 1) that the introduction of residual compressive stresses in metallic
components leads to enhanced fatigue strength. Many engineering components have been surface-treated with the
fatigue strength enhancement as the primary objective or as a by-product of a surface hardening treatment.
Examples of the former type of treatment are shot-peening, laser shock peening (LSP), and cold working; examples
of the latter type of treatment are nitriding and physical vapor deposition.
In shot peening, a high velocity stream of hard particles is directed at a materials surface often resulting in
compressive residual stresses being produced at and below the surface of the material with a peak value being
reached at some depth below the surface (Ref. 2,3,4). This peak value can reach a value as high as 60 % of the
materials ultimate strength. Because of the direct impact of the particles on the metallic surface, significant surface
roughness can result with a thin layer at the surface being work hardened. The net result of shot peening is often a
noticeable improvement in fatigue properties (Ref. 5). Shot peening under a prestress can produce an even higher
level of compressive stresses (Ref. 3).
Laser-shock peening (LSP) was first used by Battelle Columbus Laboratories in 1974 (Ref. 6). In this process, the
surface of the material is covered with a thin layer of opaque material (such as black paint) and over this layer a
thick layer of transparent material (such as water) is placed. The laser beam passes through the transparent material
and causes a thin layer of the opaque material to vaporize. The rapidly expanding gas is confined by the transparent
overlay and creates very high pressures. The surface pressure propagates into the metallic substrate as a shock
wave, causing plastic deformation and subsurface residual compressive stresses. LSP is reported not to cause
surface roughness. While the residual stress across the treated laser beam spot is mostly uniform and compressive, it
changes to tension towards the periphery of the spot and beyond. But, when large areas are treated by overlapping
laser beam spots, there is no indication of tensile residual stresses in the overlap regions; the distribution of residual
stress is said to be relatively uniform on the surface, while the distribution below the surface is similar to that of
shot-peening.
1) Senior Aerospace Engineer and Aerospace Engineer, Army Vehicle Technology Directorate, ARL; 2) Professor,
Old Dominion University; 3) Senior Scientist, NASA Langley Research Center; 4) Consultant.