undriven and driven rivet 3

[TAL2014]

HELLO,
All rivets must be sufficiently driven to fill the rivet hole at the shear plane. Driving changes the rivet strength from the undriven to the driven condition.
i need more information and or document about the undriven and driven rivet.
thanks.

 

[WKTaylor]

TAL2014. WHY???

The rivet procurement specs, and the raw-wire specs, provide undriven shear values [example NASM5674, QQ-A-430, AMS4982].

MMPDS provides allowables for solid driven rivets. Solid driven allowables can change [increase or decrease] over undriven shear values for (3) basic resons.

A. The holes are larger than the rivet which has to swell to fit it. Hole size generally determines installed-rivet shear-area [alignment and other factors in-play].

B. There can be some hardening and/or spring-back [relaxation] effects from the bucking/squeezeing process.

C. HOW the rivet is driven... combined with the rivet configuration and the rivet alloy-temper... among-other-things... can make for some wild +/- statistical variations in shear strength [FSu, FSy] that have to be accounted for in allowables table by a LOT of variables-testing and statistical analysis of the test results.

Fasteners are not nearly as 'simple' as they seem: even/especially the lowly bucked solid rivet.


Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true.
o For those who believe, no proof is required; for those who cannot believe, no proof is possible.
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can break them like an artist. [Picasso]

 

[crackman]

TAL2014

This is a valid question. What you are looking for is the Upset Diameter Specifications. This typically varies from OEM to OEM and is documented in their Fastener Installation Specifications. If you are working with an OEM you should be able to ask them for the specification. The Upset Diameter requirements relate to not only the static strength of the joint but also the fatigue qualities of the joint. Particularly, with regards to static strength, this impacts the tension strength of joint related to diagonal tension in the panel. Note that tension allowables for rivets (ie 1097) are not easy to come by. With regards to fatigue, it has a very drastic impact on fatigue life. Many years ago I conducted fatigue testing of joints at the low, mid and high end of the Upset Diameter specifications. The low end fasteners pretty much performed no better than a blind rivet which had a significant reduction in fatigue life.

Anyways, I recommend you consult with the OEM or search some of the industry literature as what you are looking for is related to test based allowables.

Good luck

Crackman

 

[dgapilot]

Pull up the drawing for MS20470 or any of the other rivet part numbers on Quick Assist

http://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=39808

See AC43.13-1b Chapter 4 for rivet installation techniques, and MIL-HDBK-5 or MMPDS for drill size and other physical characteristics.

 

[rb1957]

responses are all over the map 'cause the original question is too vague.

what do you want to know about driven and undriven rivets? yes, Fsu changes by a couple ksi by driving, refer AR-MMPDS-01, table 8.1.2(b).

How much research have you done on your own ?

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

 

[WKTaylor]

TAL2014 is a newby... clicking on his name, this is 'first post'... with no post replies listed.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true.
o For those who believe, no proof is required; for those who cannot believe, no proof is possible.
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can break them like an artist. [Picasso]

 

[tbuelna]

TAL2014-

Below is table 8.1.2(b) from MMPDS-01 that gives the information you seem to be looking for. You can also refer to these older MIL-specs (MIL-R-47196 and MIL-STS-1759) for further information about hole preparation and rivet material properties.

Maybe your question was purely academic. But it seems a bit unusual to some because, as wktaylor noted, a commonly accepted approach used in the US aerospace industry for analyzing riveted joints is that described in section 8.1.2 of MMPDS. If you follow the guidelines listed in MMPDS for your rivet joint analysis, then you should have no problem passing a design review. But if you plan to use rivet material properties that exceed those listed in MMPDS, you had better be prepared to perform some costly and time-consuming testing to validate those properties.

 

[WKTaylor]

TAL2014.. to enhance what tbuelna was discussing.

MMPDS-09 Table 8.1.2.(a) lists drilled hole ssizes for these standard rivet sizes. These standard holes were/are used for all nominal diameter rivet tests.

NOTE. Per NAS907 DRILLS, HIGH SPEED STEEL AND COBALT, 1/16 INCH THRU 1/2 INCH, drill bit tolerances are listed in the table on page 19/25 DIMENSIONAL & ELEMENT TOLERANCES FOR TWO FLUTE TWIST DRILLS

1/16 TO 1/8 INCLUSIVE | MINUS 0.0000 INCH TO MINUS 0.0025 INCH

OVER 1/8 TO 1/4 INCLUSIVE | MINUS 0.0005 INCH TO MINUS 0.0030 INCH

OVER 1/4 TO 1 INCLUSIVE | MINUS 0.0005 INCH TO MINUS 0.0045 INCH

NOTE. This table basically states that the drill bit should create a hole that is nominal size... or slightly smaller, within limits noted.

NOTE, for grins...

A similar table in NAS897 REAMERS, CHUCKING, RIGHT-HAND CUT, 0.0938 THROUGH 1.5000 INCH, on Page 16/23, reamer tolerances are listed as much tigher, thus...

Decimal Equivalent| [Dia] Range | Tolerances
Diameter | 0.0938--0.5000 | + 0.0002/-0.0000
| 0.5001--0.7500 | + 0.0003/-0.0000
| 0.7501 to 1.5000 | + 0.0004/-0.0000

These two tables graphically illustrate the nature/quality of drilled VS Reamed Holes.

IF rivets were always installed in holes reamed-to exact required diameter, then riveting shear variations would virtually disappear. In the real world, drilled holes, this is obviously NOT the case.

And likewise, close tolerance lock-bolts, Hi-Loks, Bolts, Etc shoul always be installed in reamed holes for optimum performance.

NOTE.
On rare occasions I have mandated that blind-bolts [especially multiple blind bolts] be installed in close-reamed holes... even if that means a slight press fit to set the bolt before 'pulling-'em'... simply to reduce 'sloppy tolerances'.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true.
o For those who believe, no proof is required; for those who cannot believe, no proof is possible.
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can break them like an artist. [Picasso]

 

[MOHR1951]

Ok,I just want to make something real simple to myself.
The rivet is inserted in a close to gauge hole.
By driving and bucking the rivet,it in essence fills internally the hole.
By performing this operation,one might or can assume that there is no longer a discontinuity there,its as if the hole did not exist,its basically a piece of whole material,no stress risers.Our design calculations are being based on this,because the closely gauge hole was filled with a snuggly fit rivet and then bucked to fill exactly the void.So all is lack of voids.Is that what our theory is saying and are we,have we been for eons been using that theory ?
That's what I think I've been taught.And then to compensate for any uncertainity we'll add some stress riser corrections,some other safety factors and all will be well.Am I reading this right or completely off base,Please sincere truthful answers.

 

[crackman]

I would add one footnote to tbuelna an wktaylor's responses which I fully agree with. When working with older aircraft and in particular dimpled riveted joints, the basic rules are somewhat different. Current MMPDS does state the final shear capability of the joint as the fastener shear allowable. However, older ANC5 and MilHdbk5 actually produced dimpled joint allowable tables where the capability of the joint is actually higher than the shear allowable of the fastener (compare tables 8.1.2.2). This is because they are based on testing and in the tests the dimple lip actually has a limited amount of shear capability. Just wanted to note this as it has created a few problems in the past when working older aircraft since if one uses the current MMPDS values it will reduce the allowable and hence margins could go negative.

good luck

 

[MOHR1951]

Sorry friends,I don't see the clear cut answer I was in search of.The theory I suppose is what I am in search of.Can the insertion of a correct size rivet or fastener,properly installed,in the correct hole size be assumed to create for design purposes a section that is uniform and continuous with no voids.

 

[WKTaylor]

MOHR1951...

Simple answer.

Hand Drilled, eye inspected and hand-bucked/squeezed, conventional aluminum solid rivets: statistically improbable to have a pressure/fluid tight installation, although these installations may have good static-strength and fatigue-durability. Hole filling will be fairly decent, however human repeatability... for a routine task like riveting is... hit/miss. Some mechanics will focus it and learn to 'hit-the-mark' with a high precision; however, these are not the average mechanic: most will do a good job, but 'robotic-precision' in a task like this is not possible. Some internal gaps/voids are likely, however they will not affect mechanical performance of joints.

Machine clamped, machine-drilled, electronically inspected, machine-driven/squeezed dimensionally-precise aluminum solid rivets with stable alloy/temper/finishes: +99.9999% probability of highest static strength, highest fatigue durability and highest hole-filling ^100% for fluid/air leak resistance. Most aircraft OEMS have adopted these assembly methods for critical primary structure assembly with integral pressure and fluid leak resistance needed for a lifetime [+100,000-Hrs, +25-years]. These assemblies will be 100% dry [no primer or sealing due to the mess it creates with automated equipment]; however, sealant may be applied prophylactically for internal part gapping at pressure joints [integral tank-dry bay separations, etc] around fay-joint edges and fastener-overcoat… especially for threaded bolts [HLs, etc] and non-threaded bolts [lock-bolts and special fasteners].

CAUTION. Flush riveted installations are the hardest to attain good hole fill with proper head/tail geometry which leads to highest pressure/corrosion-resistance with maximum strength/durability. Special rivet installations in wing skins, and certain fatigue sensitive joints, may be accomplished using specialty rivets and/or riveting methods such as: (a) NACA/modified NACA head rivets for fluid/pressure/corrosion resistance; or (b) use of the NACA-method for conventional/NACA-head driven rivet installations [protruding head rivets installed so that head is internal and tail is bucked/squeezed into the countersink (milling the bucked-tail flush-to-skin is required).

IF this is a real concern, then suggest You have several hundred hand-installed and machine-installed rivets compared side-by side for strength, fatigue and fluid/air leak resistance. HOWEVER, you must retain a small population of each installation for metallurgical sectioning after installation; which will reveal installation weaknesses or strengths.

NOTE.
Blind rivets are notorious for slight shank and head gapping [poorer fit overall relative to driven rivets], leading to lower install strength and substantially higher probablility of leaking. SOME aircraft OEMs prohibit all blind fasteners from being installed where pressure/fluid-leak resistance is required.

Pop-Quiz: how can You tell if any fastener is becoming loose in-service?

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true.
o For those who believe, no proof is required; for those who cannot believe, no proof is possible.
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can break them like an artist. [Picasso]

 

[MOHR1951]

Ok then,I will tell by 16 yeat old that's heavy into STEM,and trying to decide between AE and ME that for design theory engineering assume that no holes or fastners exist.Since we are always dealing in real world applications and we know our theories are not 100% realistic,we add fudge factors to hopefully and to the best of our engineering ability compensate for what uncertainty may exist.Does that sound like a fair and truthful statement to make.It's important.he's going to make a career choice based on what I tell him.

 

[rb1957]

why tell a 16yo considering starting a career in AE or ME such a small detail. Very little in engineering is "truth" ... if you want "truth" then go into theology ('cause even science approximates "truth").

But as for your detail, in my experience we generally don't count of a bucked rivet filling the hole to make it "disappear". For static design, under tension loads you could use the net section (consider the hole area ineffective in tension) ... MEs might include the Kt of an open hole, I wouldn't) under compression loads you might consider the rivet effective. For fatigue/DT, you'd typically assume it to be an open hole ('cause that's what most models for crack geometry assume) ... it could be an open hole with a pin load (as counter-intuitive as that sounds).

For me the key difference between AE and ME is ... do you Love aircraft ?

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

 

[Andries]

Tal2014,

You sure received value for your money here!

Andries

 

[rb1957]

TAL seems to have given up (or does know to mark threads for attention)

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