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Tony
10-24-2002, 06:38 PM
anyone out there have any experience with removing residual stress using vibrations?

there are a few companies out there that claim to remove residual or "machined" stress using some sort of high frequency vibrations -- no heating, no furnace, etc.

from what i've been able to learn this is used mostly for machined/ground plates (ie, presses, dies, etc)

first hand experience anyone?
does this stuff really work?
other possible applications? (other than plates?)

roberlt
10-25-2002, 12:12 AM
I understand that NASCAR engine blocks are stress relived in this way.
Perhaps contact one of the major suppliers of racing motors for info.
Rob

Forrest Addy
10-25-2002, 01:27 AM
Yup. I've done lots of it in production.

The object is to induce circulating cyclic stresses by mechanically vibrating it in one or more planes. The process is suited to parts having natural resonances in multiple modes. Stiff solid parts are resistant to vibratory stress relief because their natural resonances are higher in frequency than obtainable by present day mechanical vibratory systems. It may be that recent developments in higher powered peizo electric drivers or contact tranducers have broken this perceived barrier.

I've machined a lot of identical castings shaken and not and notice no significant in dimensional stability.

One thing never mentioned in the vibratory stress relief literature is that the circulating stresses are not uniformly distributed through the mass of the component. Exciting the component to higher amplitudes of vibration in an effort to obtain a stress relief "effect" further into the mass has the effect of overstressing the "nodes" possibly to point of reduceing it's fatigue resistant or causing stress cracks.

Nope. Every bit of my experience in vibratory stress relief convinces me it's a good idea that's been poorly implemented. Newer and better equipment driving to high frequencies and part instrumation that does a better job of mapping dimensional changes and stress relaxation might make the processing more predictable and effecatious. But we aint there yet except in a few special cases.

The equipment I used was about as effective in reducing locked-in part stresses as a crucifix in reducing pre-marital sex.

It seems like a lot of fuss and feathers to avoid a simple thermal cycle stress relief.

Tony
10-25-2002, 05:39 AM
from what i've gathered it seems that the vibration treatment is not a 100% replacement for thermal stress relieving.

ie.. it is only effective for certain material with particular geometries.

i was hoping to learn more about which materials and what geometry?

according to the websites they say vibration can be equal to, or even better than, heat treatment (to reduce stress, not for metallurgical changes)for in some instances.

sounds like theres alot of cost savings in there.. shipping / energy costs / etc.

decoy91288
10-25-2002, 12:09 PM
I've a girlfriend who swears that vibration is the best stress reliever ever invented.

Dave Burnett
10-25-2002, 06:31 PM
Our company tried the vibrotory stress relieving years ago on mold blocks and all of the big three auto companies made us stop and go back to thermal stress relieving. They said vibrating did not work.

Thrud
10-26-2002, 09:38 PM
decoy91288:
Buy her a Harley and she will leave you.