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Great pont about blasting stuff. Yes, Correct, There is cleaning of pits at low pressures with angular media and there is inducing compressive stress at higher pressures with rounded shot.
Intensity is key. No need for blasting a 2024 skin at 120psi right out of the compressor. Check with Piper. Regulated 40-50ish psi with angluar 180 grit AlOx should be all you need. If in doubt run an Almen strip to test intensity before you blast your plane. A normal "N" strip shoud work. We are limited to 50 psi with the 180 AlOx and limited dwell time in any one area. Good Point. Make an Almen strip and check intensity.
Metal Improvement used to have some fantastic on-line data about compressive stress through peening and now the Big Bad Curtiss Wright corporation has fvcked that up and removed it from their web site. Metal Improvement Corporation (bought by CW) invented shot peening btw, Buick valve springs, in the 1920's off the top of my head. Peening is a fascinating part of my job relating to propellers.
[URL unfurl="true"]https://cwst.com/shot-peening-overview/reasons-to-shot-peen/metal-fatigue/[/URL]
Edit: I wasn't going to bring it up but...
[URL unfurl="true"]https://apps.dtic.mil/dtic/tr/fulltext/u2/a274817.pdf[/URL]

<blockquote data-quote="propjoe" data-source="post: 321519" data-attributes="member: 14912">Great pont about blasting stuff. Yes, Correct, There is cleaning of pits at low pressures with angular media and there is inducing compressive stress at higher pressures with rounded shot.Intensity is key. No need for blasting a 2024 skin at 120psi right out of the compressor. Check with Piper. Regulated 40-50ish&nbsp; psi with angluar 180 grit AlOx should be all you need. If in doubt run an Almen strip to test intensity before you blast your plane.&nbsp; A normal &quot;N&quot; strip shoud work. We are limited to 50 psi with the 180 AlOx and limited dwell time in any one area. Good Point.&nbsp; Make an Almen strip and check intensity.Metal Improvement used to have some fantastic on-line data about compressive stress through peening and now the Big Bad Curtiss Wright corporation has fvcked that up and removed it from their web site. Metal Improvement Corporation (bought by CW) invented shot peening btw, Buick valve springs, in the 1920&#039;s off the top of my head. Peening is a fascinating part of my job relating to propellers.[URL unfurl=&quot;true&quot;]https://cwst.com/shot-peening-overview/reasons-to-shot-peen/metal-fatigue/[/URL]Edit: I wasn&#039;t going to bring it up but...[URL unfurl=&quot;true&quot;]https://apps.dtic.mil/dtic/tr/fulltext/u2/a274817.pdf[/URL]</blockquote>

[QUOTE="propjoe, post: 321519, member: 14912"] Great pont about blasting stuff. Yes, Correct, There is cleaning of pits at low pressures with angular media and there is inducing compressive stress at higher pressures with rounded shot. [B][U]Intensity[/U][/B] is key. No need for blasting a 2024 skin at 120psi right out of the compressor. Check with Piper. Regulated 40-50ish psi with angluar 180 grit AlOx should be all you need. If in doubt run an Almen strip to test intensity before you blast your plane. A normal "N" strip shoud work. We are limited to 50 psi with the 180 AlOx and limited dwell time in any one area. Good Point. Make an Almen strip and check intensity. Metal Improvement used to have some fantastic on-line data about compressive stress through peening and now the Big Bad Curtiss Wright corporation has fvcked that up and removed it from their web site. Metal Improvement Corporation (bought by CW) invented shot peening btw, Buick valve springs, in the 1920's off the top of my head. Peening is a fascinating part of my job relating to propellers. [URL unfurl="true"]https://cwst.com/shot-peening-overview/reasons-to-shot-peen/metal-fatigue/[/URL] Edit: I wasn't going to bring it up but... [URL unfurl="true"]https://apps.dtic.mil/dtic/tr/fulltext/u2/a274817.pdf[/URL] [/QUOTE]

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