"Ultrasonic Impact Technology" another name for "Vibratory Stress Relieving"?

Hi,

to my understanding there is a fundamental difference although both procedures are aimed at stress relief:

ultrasonic (or sonic) impacts act as in shot peening: locally compressing the surface, compression is transforming any stress near the surface into compression.

Weight, velocity, energy per pulse and form of impactor has to be chosen carefully to avoid damage. (you don't like a mechanical woodpecker work on your surface).

Surface coverage must be total in and near critical areas (the highly stressed zones).

Vibratory stress relief acts with mechanical oscillations that are amplified by resonances, so there has to be a suspension where and how to attach the part with low damping, a search for resonances by coupling the exciters to different points of the structure and a scan (sweep) in frequency to localise the resonances and the related dampings: give the structure a lot of stress but not as much as will cause damage. (fatigue stress well to be avoided) If the cyclic sinusoidal stressing is done with first rising and the decaying amplitude the stress in the cyclically stressed areas is relieved if the sum of internal stress plus cyclic stress was above the yield limit.

All this is difficult to optimise - same with thermal stress relief.

RHABE

Thanks Rhabe,

Thanks for your advice (which gets my GA vote).

Regards

Malcolm

"Ultrasonic Impact Technology" another name for "Vibratory Stress Relieving"?

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Dear Mr. Stephen,

I worked a few years as a consultant in Europe for the Ultrasonic Impact Technology so I know something about this issue.

The only comparisment between UIT and Vibration Stress Relieving (VSR) is that both technlogogies work with high frequency vibrations. When looking at VSR you need to bring the complete construction into resonances and the parameters completely depend on the structures dimensions and it is applied after te structure is finished. UIT however is only applied on small areas such as weld and HAZ and when it is used for stress relieving it should be applied on every single weld layer in order to reach max. stress relieving, this because the ultrasonic effect is only working up to max. 12 mm depth (depends on the materials properties). Here also you need to adapt the parameter according to the material to treat but it is less complex as for VSR.

If you want to use UIT for stress relieving issues than you need to be aware of the fact that this is not general accepted in regulations as a method for stress relieving and therefore you will need an approval in front from a customer or any inolved notified body. In some cases (when it concerns repairs) you can easy get such approval especially when normal PWHT is not possible for some reason.

If you have investigate the application areas of UIT you will see that it's mostly used for increasing fatigue strength of welded structures such as bridges and train boogies or other dynamic loaded structures.

So if you need some more detailed information you can always asked for.

Best Regards,

Herman Pieper

Thanks Herman,

Thanks for your advice (which gets my GA vote).

Regards

Malcolm

dear Herman,

could you please provide the details of known service providers of UIT. We have a situation where in local PWHT is not practical on the small repair weld of a process equipment & hence we would like to suggest UIT by expert service provider.

regards

gireesh