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#155 10/19/05 06:40 PM
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Hey Jack and others. This Mike from MOOG in Torrance. Jack if you remember John Camment and yourself came out for some in house training in 2004.

If you remember from your visit we used a static almen stand to generate intensity curves. The stand held the strip at the same stand off distance as the part surface. We generated the intensity following the rules and then we would replace the stand with the part and determine the time for our coverage requirements. This separated the intensity determination from the coverage nicely.

The rotation of the part should only affect the coverage. This is my understanding. So why is it that I am required to rotate a PVT under the shot stream? This rotation is now changing our coverage times and shifting our saturation points with all the pararmeters remaining the same.

If you guys could give me an answer to this I would really appreciate it. I have some studies that are going to require some more detailed questions that I am hoping to get answered at the workshop next month.

#156 10/20/05 06:51 PM
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Mike,
Can you elaborate a little bit more on this setup? What is pvt?

#157 10/20/05 06:53 PM
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Thanks for the response Jack. I am in the middle of putting all this stuff together and it is giving me fits.

I started off with a general question and I was going to work from there based on your answer. For the purposes of this question the PVT is a custom tool that has two almen blocks that simulate the two peened diameters on the piston. Off the top of my head the diameters are 1.11 and 2.11 for the head. The overall length of the PVT is the same as the piston and uses the same tooling to drive it under the shot stream. Not a scrap part, but an accurate stand in.

This piston requires .004-.007A intensity and 200% coverage. Using the static almen stand I settled in comfortable at about .0050A at 2 passes for the shaft and .0054A for the piston head. It is a little closer to the nozzle. Since we rotated the part so slowly we were able to peen the entire surface under a single program.I felt that this was an accurate intensity rating and was very repeatable.

I am now rotating the PVT under the same conditions as the part. The same settings on pressure, shot flow, stand off, and angle of impingement are now producing intensity ratings for the shaft at about .0064A at 8 passes and .0061A at the head at 16 passes. I am still trying to nail down why the intensity rating would increase with the rotation of the PVT. The shot stream has not increased in intensity in any way. The shot is still coming in at the same velocity and at the same angle. I understand the difference in exposure time for the two surfaces, the head has almost twice the surface velocity as the shaft at the same RPM. In both cases the traverse rate of the nozzle is the same, I cannot change that on the machine at all.

It appears to me that spinning the PVT has changed the dynamic of the strip coverage. Which is the more accurate intensity? That is what is bothering me. If would like to see some numbers I should have some in the next day or two and perhaps I am missing something that you will pick up.

#158 04/03/06 01:38 PM
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have the same problem, I did an experiment and did 2 saturation curves 1- with static Almen (4 strips) the time parameter was passes. 2- with a rotating Almen (4 strips) and the time parameter was number of cycles and I got approximately the same intensity 1- 6.8 2-7.0
Because you can not determine the exact time exposure of the rotating Almen you can not compare them.
Jack correct me if I am wrong
Best Regards


Shlomi Kisluk
Bedek-Engines Div. Material & Process Engineering
ISRAEL AEROSPACE INDUSTRIES
972-3-9358300
972-52-6040517

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