Chisel Peening Theory

[Bambie]

Please review thread378-319665.

Aeronautical Engineers may be more familiar with limitations and applications of chisel peening.

 

[berkshire]

Bambi,
Whilst chisel peening is used as a means of staking bearings into an aluminum housing, the application you are asking it to do, in your other post is fraught with dangers.
Do you know the hardness, material spec and temper of the Aluminum housing you want to peen?
If it is a hard aluminum are you prepared to see a chunk fly off as you peen it?
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[Bambie]

B.E.

The consequence of chisel peening an aluminum casting, in the hands of a competent specialist, will be immediately evident.

Can you refer me to any calculations associated with 'staking bearings into an aluminum housing'?

 

[berkshire]

Best I can do is refer you to a picture.

http://www.americanprecisionassembl...g_url=/uploads/files1/DSC00965a_resize400.jpg

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[Bambie]

Thank you for the picture B.E.

 

[rickweld]

Bambie,
Please understand that I am getting involved in this question late in the game. If you are trying to "stake" the bearing for retention purposes two options exist that I know of that are not of the caveman hammer and chisel variety. 1) roller staking, and 2)compression staking have both been used for many years in the aircraft industry. Roller staking uses a slow rotating mandrell that is piloted by a pilot diameter of the mandrell that pilots on the id of the bearing. It can have single or multiple rollers that have a small radius machined into the od of the roller wheel. As the mandrell is rotated in a drill press or similar machine pressure is excerted in a downward motion displacing the material in towards the bearing bore. In compression staking a tool is made that can be either solid or notched out with a similar small radius. It also has a pilot that engages the bearing and is pressed downward to dimple the surface. This leaves a surface that looks like a "hidden line" on the surface of the part.

 

[Bambie]

Rickweld,
Thank you for your comments. Do you have any references to the analytical methodology used to calculate the compressive stresses generated by roller or compression staking?

 

[WKTaylor]

Bambie...

Rickweld explained it correctly: what You have a photo of is partial ring-staking.

NOTE.
There are multiple ways to install aerospace bearings correctly: and a 1000+ways to install them using highly damaging [caveman] methods.

Ring-staking is just ONE-not-so-common method [anymore]. The more common methods for staking the housing over the chamfered edges of a bearing are roller-swaging and ball-staking.

Then there is the later generation installation method where the bearing has grooves on each outer-race edge, so-that the [soft] edge of the bearing is swaged over the (2) chamfered edges of the housing bearing bore. This virtually eliminates housing damage due to installation practices.

Then there is the sleeve-method where a thin sleeve is inserted in the housing bore, with one 2X flanged edge. The bearing is pressed into the open end of the sleeve and that end is then staked/roller-swaged over the chamfered edges of the housing and the bearing.

In all cases the impressions [stake/swaged-groove or ball-impressions] have very low stress concentrations... with adequate press-out [axial] resistance.

Further retention can be aided by anerobic adhesive retaining compounds. Also, these bearings can also be inserted with sealant or primer for increase corrosion and moisture resistance.

REF installation specs [AIA]:

NAS0331 Bearing Installation and Retention by Swaging or Staking
NAS0332 Bearing Retention Sleeve, Grooved Outer Face

Most aircraft manufacturers have great manuals for bearing installations in their assemblies. Since everything from sealaing and corrosion resistance and interference/clearances are all different... these might be Your best resources for specific assemblies.

NOTE. There are several great USAF/USN/USA T.O.s/NAVAIRs/TMs for bearings that are close to solid gold... If You can get access to them!

As far as stress analysis: once the method is stabilized using a low Kt method and all other installation variables [interference, clearance, housing matreials, etc] are known, a good stress guy should be able to figure it out impression stressed for You: if any exist.

Regards, Wil Taylor

Trust - But Verify!

We believe to be true what we prefer to be true.

For those who believe, no proof is required; for those who cannot believe, no proof is possible.

 

[Bambie]

Wil,

That's the problem...I can't seem to find 'a good stress guy'.