Yield strength conversion to shear strength. 4

[FranLopez]

Blueprint called out for material corrosion resistant steel A286 per AMS5732with a 95,000 PSI minimum shear strength. The material Cert shows only Yield strength: 121,000 PSI and Tensile strength: 161,000 PSI.

The mill company said AMS 5732 does not call for shear strength. I dont have the spec, and It would take a day to get one. what is the formula to convert Yield strength to Shear strength? or would be better to send the material for shear strength test anyway?

 

[rb1957]

shear = .57*tension (for your case UTS*.57 = 91 ksi)

Quando Omni Flunkus Moritati

 

[TVP]

Is this for a fastener? Fastener drawings that specify shear strength need to be tested in shear, not just tension.

 

[FranLopez]

Its a pin straight headed. I believe it is.

 

[Screwman1]

You have to have finished part tests for a pin, not just a material cert tests, because processing will change the values.

TVP is right that you can't just do a conversion; you have to actually get test results for shear. Depending on length it might be a double or single shear test. Headed pins are intended for shear loading in service, so that is why you have to get actual shear results to ensure proper HT response.

 

[rb1957]

i think that's the joint strength ... will the pin bear against the sheet ? bending of the pin, etc

the pin itself has a strength ... if UTS = 160ksi, USS = 91 ksi (as a rule of thumb, looking at the tables it seems more like 95 ksi)

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[FranLopez]

will do, Im sending the part for test. converting the yield is not giving me the min. PSI.

 

[rb1957]

can't you say that if the fasteners are certified to the AMS, then they meet the AMS standard ? I suspect that the AMS was written thinking there is a fixed ratio between Fsu and UTS, so if we control UTS we'll be quite certain of getting an acceptable Fsu.

if the fasteners are certified to the AMS, then they meet the AMS standard (IMHO).

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[Screwman1]

RB; all the pins that we have done have a single or double shear test requirement, since that will be the failure mode. AMS is a raw material spec, I can get all sorts of different finished part tensile strengths out of AMS5732. You always have to provide test results to the finished part requirement, in this case they want shear, which is not specified in that document, so he is going to have to go out and have some parts sheared.
On aerospace fasteners, almost every lot of finished parts requires a shear test (except for those parts that are too short, small, big, etc.) since the majority of parts are designed for shear loading and a shear test is an easy way to validate proper heat treat.

 

[FranLopez]

Document control people is getting my copy of AMS5732 tomorrow, until then I can read the spec, Im sending the material to get shear yield tested. If passes or fails I need to know asap, in order to get more and get the right material, the pin's are 2".5 long

 

[rb1957]

if shear is so critical, maybe the engineers should change the spec (to a process that directly verifies the shear strength); but then you're probably working with other people's parts. but then, if it fails, shouldn't you return to the supplier as not meeting drawing requirements. then of course you'll have a "bun fight" on your hands ... "it meets the ASM standand", "but it doesn't meet the drawing requirements", ...

but if you are working with other people's parts, then hasn't the other person certified that the part is good ?

if you're working with your own part, then the engineering definition should match the design intent. in this case it sounds like they don't match explicitly; either change the stregth call-out for specify UTS (which defines the heat treat, no?) which is tested by the ASM, or change the ASM to one that tests shear strength.

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[FranLopez]

The Drawing requirements are more important than a SAE-AMS spec. Drawing requirements are for only that specific part, a AMS spec is in general with that type of material. the raw material haven't yet sent to the supplier for machining. the Mill company only does the test according to the spec of material. If the material spec does not call out for shear strength then they won't do the test, and the material spec on the drawing can't be change, thats only for the NASC to change.

thank you guys for your help.

Regards

 

[rb1957]

you're talking about an MS or NAS or standard spec fastener ?

if it certified, it is good and meets the spec requirements and additional testing to verify properties not expressly tested is, IMHO, unnecessary.
if the UTS is 160 ksi and the spec drawing calls up 95 ksi Fsu, i don't think there's a problem because 0.57*UTS = 91 ksi.

if it's a fake cert, then your testing will reveal it (just as if you repeated the UTS test required by the spec).

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[FranLopez]

naval air systems command. not MS or NAS, the material is per SAE- AMS

 

[rb1957]

ok, it's a part designed by your own people (as opposed to a vendor/supplier) ... for where i am you're all tarred with the same brush (and that's NOT a racial slur).

maybe it's another command, but for where i am you're all tarred with the same brush (and that's NOT a racial slur).

maybe it's a tonne of paperwork to get another command interested in this, maybe this is just a windmill (to tilt at).

but if you're interpreting the certificates as saying "i've checked UTS" and not as "i've complied with the spec",
and so continue "i need to verify Fsu" and not "Fsu is defined by having on-spec material"
because you see a disconnect between what's specified (Fsu min) and what's tested by spec (UTS)
then IMHO it makes sense to either ask NASC is the certificate accept for demonstrating on-spec material (and so meeting the Fsu required),
or tell NASC the spec choosen doesn't test the key engineering feature (Fsu) so change the spec to one that does (ie align the test with the spec);
clear as mud ?

but as i've opinioned, several times, i think your material meets the spec requirements and i'd be surprised if someone backs you up, supports either your requ for further testing or your request for drwg change.


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[jagad5]

Per MIL-HDBK-5J (the last free version) AMS 5732 has an ultimate strength of 130 and a yield strength of 85 ksi at room temp. The Shear ultimate is 85 ksi. All these are S-Basis. So I seriously doubt that you'll meet your print requirement for a shear strength of 95 ksi. The cert numbers are individual data points and have little to do with the appropriate design minimum values.

Doug

 

[Screwman1]

It is very common for the part print to have additional requirements beyond what is included in the AMS spec. AMS speaks to material, and the part print speaks to functionality. A good example would be NAS1580 for the part print, which has the Fsu on it for the various materials (alloy, Cres, Ti),then the required testing is covered under the procurement spec: NAS 4003, 4004 etc. The required AMS materials listed on NAS1580 do not make reference to Fsu in the finished part, since at the material level it is unknown which particular HT spec will be applied to the material.
I don't understand why you want Fran to try to get a change; this is the normal practice for fasteners. We deal with it all the time, you certify the material to the requirements of AMS and then after fabrication you test finished parts to the part print requirements, which can be in addition to requirements listed in AMS.

 

[rb1957]

that's what AR MMPDS-01 has too ... Fsu = 85ksi
but i notice that AMS5737 has Fsu = 95ksi ... typo ?

it sounds like there's an engineering problem between the drawing call-out (95 ksi min) and the process spec ? (I had assumed that they were compatable)

now for this detail part, additional testing will probably clear the drawing requirement (which doesn't look to be met by the process spec)

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[jagad5]

The various AMS specs for A286 have WIDELY differing design properties. There are AMS specs for versions of A286 that are nearly twice as strong as AMS 5731.

Doug

 

[FranLopez]

@ screwman, You are correct , I can't get this material released to the shop floor with out meeting the requirements of the print.
@jagad5, Im thinking the same. I dont think this material will pass the shear test, will wait until the results from the Lab come back.
@rb1957, this is a CSI fastener, I can't place an EO for this shear strength requirement.