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#1040 - 12/09/13 02:53 PM Will peening result be equal for different medias?
Jack Champaigne Offline


Registered: 04/20/99
Posts: 325
Loc: Mishawaka, IN, USA
I have been asked on several occasions about the substitution of media. If one substitutes ceramic bead for glass bead (same size and propelled at velocity to achieve same intensity)will you get the same peening benefit?
Also, if you substitute cut wire media for cast steel shot, such as CW14 for S-110, using same hardness, can you expect to get equivalent peening results?
In short, if you deliver media at the same intensity (Almen saturation curve etc) or if you get a certain size dent from one media and then get the same size dent when using another media can you expect that the target material and therefore the peening benefit will be equal?


Edited by Jack Champaigne (12/11/13 01:08 PM)

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#1041 - 12/12/13 10:30 AM Re: Will peening result be equal for different medias? [Re: Jack Champaigne]
Socrates Offline


Registered: 02/20/06
Posts: 108
The similarity of peening benefit depends on the similarity of the peening media - other things being equal. Ceramic and glass beads CAN have very similar properties in terms of density and shape. This would lead to a prediction of very similar peening benefits. As-cut steel wire, on the other hand, has a very different shape from that of cast steel shot so that close similarity of a property such as fatigue life would not be expected. Spherical-conditioned cut steel wire has a similar shape to that of cast steel shot and hence one would predict similar peening benefits.

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#1215 - 05/25/16 06:44 AM Re: Will peening result be equal for different medias? [Re: Jack Champaigne]
Blomberg Offline
Member

Registered: 11/15/13
Posts: 10
Loc: Sweden
Interesting question. I would like to know for sure also. I would like to replace cw14 with ceramic shot to get a smoother surfacefinish.
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Shotpeen Engineer

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#1216 - 05/25/16 10:40 AM Re: Will peening result be equal for different medias? [Re: Jack Champaigne]
Jack Champaigne Offline


Registered: 04/20/99
Posts: 325
Loc: Mishawaka, IN, USA
I presume (with no data in front of me) that if you use the same size ceramic media and propel it at higher velocity (less energy due to less density/mass) then you may get the same peening results (depth of compression) and probably a smoother surface. Another way to get smoother surface is to use larger media size. Small media at high velocity to get the intensity will go deeper into the surface making it rough. Larger media, making the same diameter dent (factor of intensity) will have shallow dent thus smoother surface. Be sure to experiment with steel media and ceramic media to be sure you get the results you are expecting.

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#1217 - 05/27/16 09:10 AM Re: Will peening result be equal for different medias? [Re: Jack Champaigne]
Charlie Offline
Member

Registered: 09/23/14
Posts: 16
Loc: USA
I would argue that if you reach the same intensity with two different medias then you have provided the same peening results to the almen strip. Saturation and therefore intensity by definition would show that if you gained full coverage on that almen strip then the arc height would be the same (within a reasonable tolerance) for both medias. The almen strip being in the same condition would support the argument for same peening benefit. There have been articles published in the shotpeener with data and analysis to support this.

Fortunately for me, all of my customers generally require that surface finish be controlled prior to shotpeen only. It is possible also that if you are peening at such an intensity that surface finish is a concern, then you also have rollover or dimensional concerns, and may need to polish either way. We frequently have to polish or hone surfaces and holes after shotpeen to meet final dimensions, within stock removal allowances. There is data to support light polishing actually providing positive benefits to the shotpeened surface.

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#1218 - 05/27/16 09:48 AM Re: Will peening result be equal for different medias? [Re: Jack Champaigne]
Jack Champaigne Offline


Registered: 04/20/99
Posts: 325
Loc: Mishawaka, IN, USA
You are exactly right.
Components like to have a smooth surface. No scratches, sharp filet radius, etc. But, when you shot peen you made dents. Dents are not nice. They become locations for fatigue failure initiation. We tolerate the dents because we have the compressive layer to retard the progress of any surface dents. It is better to lap or hone the surface and remove the dented surface and make it smooth again. This practice gives you the best performance.

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