Heat treat AD rivets 1

[Rob130]

Recently heard one of our customers heat treat AD rivets to about 200 F for one hour prior to installation so they drive easier. As a structural repair tech and current instructor I have never heard of this practice. My concern is they are annealing the rivets and they will never handle the design loads. I told them it is unnaproved process they are using. At least leave the rivets to age harden again, and if still soft they are screwing up big time. I would appreciate some feedback from the engineer group on an explaination on why this process is acceptable or not.

Thank, Rob

 

[rb1957]

this sounds really odd ... AD rivets should be pretty easy to drive. I agree that this is an unapproved procedure, unless they have test data (yeah, right !) although 200degF probably isn't enough to anneal the rivet material. Will (Taylor) can give us chapter and verse !

another day in paradise, or is paradise one day closer ?

 

[WKTaylor]

Rob130... I thought I'd heard every conceiveable rivet heat-treat 'scheme' ... but this one is a real head-scratcher.

I totally agree with RB1957 in every aspect and can only add the following comments...

Baking AD rivets [any size] at 200F for 1-hour will have no discernable metallurgical effect on these parts what-so-ever... hence no value... but, thank God, no likely harm either [metallurgical or finish].

Rob130... Any way to find-out WHY Your customer is doing this operation? Curiosity is killing me. I suspect that there is a "wives tale" at work here; and most-certainly no valid/tested process spec.

NOTE.
I've had several friends in the fastener business, who've tested solid rivet driving forces [bucked or squeezed] VS deformability and factors such as cracking or chipping. This was a high priority from a production and quality perspective. These guys noted that when significant force variations or quality discrepancies were noted, then there was a fundamental issue with the rivet alloy or basic heat-treatment.


Regards, Wil Taylor

Trust Me! I'm an engineer!

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.

Unfortunately, in science what You 'believe' is irrelevant – "Orion"

 

[Rob130]

I agree with both of you guys. Their stated purpose of the heating is "they drive easier" which is crazy. Over driving was always the problem I encountered.

I do not want to disparage a particular customer re:Country Air Force, but they are notorious for over thinking the C-130 and thinking they are smarter than the dolts who designed the plane and wrote the manuals. Funny thing was when I started training them they were looking for validation of some of their repair designs and procedures. Seems like a particular Lockheed Service Center was continually charging them to undo repairs they had accomplished at the squadron level. After learning the SRM they realized that Service Center was right. This was quite a few years ago and I thought I had broken them of bad habits and now this rivet thing pops up!

Some amplifying info I picked up from them. They are heat treating the AD rivet to the same spec as DD rivets, quench then drive. Not sure of their quality control or detrimental affect this would have on an AD rivet. They are a couple of young guys who know just enough to be dangerous and they like to experiment.

I'm in Japan right now so pardon the delays.

 

[rb1957]

that sounds effing bad ... no-one, No-one, in the industry does this. Do you think Everyone else is as dumb as door posts ? If they do think this is a better process, then qualify it; maybe even trade-mark it ?

possibly the other way to look at it is are they creating a DD type rivet ? with the quench, i don't think so, but i'll let Will lay in.

another day in paradise, or is paradise one day closer ?

 

[WKTaylor]

Rob130... Are You at DNA?
----------------
THIS IS AN AIRWORTHIENESS EMERGENGY.

Re-heat-treating AD rivets was discussed ~10 years ago. VERY BAD IDEA, in theory and practice... especially when done by the techs who would attempt this non-standard process.

http://www.eng-tips.com/viewthread.cfm?qid=103368

This process has destroyed the corrosion protective finish on the AD rivets! Most have chemical conversion coating, which will oxidize [disappear] and which likely contaminate/damage the rivet alloy surface. Clear anodize is the only finish that will survive the solution heat treat process. Anodize is applied to all DDs. Anodize is applied to SOME Ds which can be re-heat-treated [bucked in the -W temper].

Situation will be aggravated [temper/strength fail] if AD rivets are heat treated per AMS2770 or AMS-H-6088 per DD [2024] rivet processes... due to differeing SHT soak temperatures.

What troubles me most is that techs who 'think heat-treating ADs is acceptable', generally fail to grasp how important every aspect of the "conventional riveting" and "ice-box-riveting" process is to obtain the appropriate strength/toughness/swell/etc of the simple solid driven aluminum alloy rivet!

Murphy is alive and well...





Regards, Wil Taylor

Trust Me! I'm an engineer!

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.

Unfortunately, in science what You 'believe' is irrelevant – "Orion"

 

[Rob130]

Will. I agree with you in all regards. Thanks to you all I can give them engineering feed back. I said I was in Japan but it's not them. I am relaying this info from my colleague who is covering my classes back in Tampa. I am not at DNA. I wotk for CAE USA in Tampa. We train C-130 aircrew and technicians from many countries and commercial operators. I am a retired USCG metalsmith/flight engieer.

I am dumb struck that they would attempt this. If you pm me I can divulge the customer but for obvious reasons I want them to remain anonymous.

Thanks to all for feedback.

 

[402doctor]

As a structural/stress engineer I can say that the rivets must be removed and replaced immediately. I would consider the rivets as altered hardware. AD rivets should never be hard to drive. Try using a squeeze. If that is not an option then the equipment being used must be reviewed to see if it is acceptable.

 

[ABV97]

I also agree, AD rivets are not hard to be driven, and we have never heat treated them as well! This is dangerous and the repair should not be approved by the authority!