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Material Allowables Question

Material Allowables Question

Material Allowables Question

I want to use 4140 Steel Plate per ASTM A829, but I can't find strength allowables (Ftu, Fty, Fsu, all that good stuff) for this spec.

I do have material allowables for a different spec, which are MMPDS allowables for AMS 6395. But I'm not sure if these allowables apply to ASTM A829.

My questions are as follows:
1. Are there any allowables available specifically for 4140 per ASTM A829?
2. Any industry substitution documents that state allowables are the same for AMS 6395 and ASTM A829? Or acceptable conversion factors?
3. In more general terms, for 2 different specs that meet the same AISI/SAE Alloy, how much does the material strength differ?


RE: Material Allowables Question

Have you bought the ASTM spec ?

Using my friend (everyspecDOTcom), your spec supercedes QQ-S-626. This earlier spec shows that, common with steels, the properties depend on the heat treat you specify (Annealed, Normalised, 1/4 Hard, Fully Hard, …)

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

RE: Material Allowables Question


Broadly speaking... HOW the material is processed [to what specifications] is everything in aerospace.

The only way allowables from MMPDS can be used in an instance like this... is if the MILL MARKINGS on the raw stock and the accompanying material certification paperwork supplied with the raw-stock [from a REPUTABLE vendor]... include qualification to meet ASTM A829 and AMS6395 and/or other valid MIL/AMS specs that have been commonly used in aerospace grade forms... and those forms had allowables [currently or previously] published in MMPDS or MIL-HDBK-5.

ALSO.. any/all subsequent manufacturing processing... especially heat-treat processing... MUST be done in accordance with established aerospace specs and practices.

I do believe that there is/are published basic material allowables [mechanical, physical] data for the commercial stock materials [ASTM] using ASTM heat treatments, etc... but unsure where to direct You. Perhaps a better place to post this question is the Metal and Metallurgy Engineering forum... https://www.eng-tips.com/threadminder.cfm?pid=330

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

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