Home Forums General Discussion Equipment, Machines, Accessories Almen strip for shot peening of holes

Hi,

I have to design an almen fixture to verify the intensity of shot peening an hole of 1.25" ID (rotary lance peening). The hole is 0.600" deep (open end). My current idea is to position the strip with it's 3" dimension aligned with the axis of the hole, but in this position I'll end up with approximately 1.2" of strip on each side of he hole not being shot peened. Do you have any recommendations?

Thanks!

David,

The proper method to measure the intensity of holes under .750" is to use a shaded strip.

You did not mention what your intensity range is. I'll use .004-.007A as an example.

First you have to develop a coloration. This is done by generating a saturation curve on a fully exposed "A" strip as you normally would. This can be done in any machine in any set up. Once you have established your intensity peen a shaded "N" strip ( in this example you would be exposing .600") in the exact same set up.

Lets say the intensity point for the fully exposed "A" strip was .0064A
The shaded "N" strip reads .0132N Therefore .0132N = .0064A


Now you can play around with the pressures and shot flow to come up with min / max limits
Example .0105N = .004A .014N =.007A

Now you can peen the shaded strip in your lance peening set up. As long as it is within .0105-.014N your good to go.

If your intensity range is over .009A then you can use an "A" strip for both. An "N" strip is used for .009A and below to give a larger arc reading.

Hope this helps,

-Walter

Thanks for such a great explanation! It's really appreciated although it doesn't really apply to my situation since the hole ID is 1.25".

I've found another solution though, I'll just use a different program for intensity verification and normal peening operations.

Thanks!

typically the aerospace industry peens holes using the same technique, quadrant peening.

by positioning the nozzle at 45 degrees and peening the hole from 4 quadrant positions (0, 90, 180, 270 degress) , both sides of hole.

if the hole is L/D less than 1, this enables line of site and eliminates the need to rotary lance peen the hole - and having to used masked strips.

To represent the hole, you can lay the almen strip flat over the hole , not along the hole axis, since you are peening at approx. 45 deg.