Small Tension Test Specimens 1

[mcclain]

Has anyone ever taken a tensile test specimen (ASTM E8) from a broken fracture specimen (ASTM E1820). It appears that some of the small specimens could be taken from a broken half of a CT specimen.

Is there any reason why you could not do such a thing.
Any test houses in the US who have done this?

Thanks

 

[CoryPad]

That would need to be a fairly large CT specimen.

There is no fundamental reason why you couldn't make such a specimen.

I would ask Westmoreland - they are the leader in fracture mechanics testing.

http://www.wmtr.com/

Regards,

Cory

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[EdStainless]

You will get low elongations, and maybe wrong yield strengths with small tensile samples. The effect of grain size will be an issue if you get very small.

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Plymouth Tube

 

[mcclain]

EdStainless,
Would the small specimen give a reasonable elastic modulus?

 

[EdStainless]

It may not. If a couple of grains with a particular orientation made up most of the gage length then you might get the modulus in that orientation. With many alloys it doesn't matter, but some can have heavy directional effects.

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[CoryPad]

Time to provide some details: how big is the CT specimen, and what is the alloy and thermomechanical processing history?

Regards,

Cory

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[mcclain]

Titanium 6AL-4V (ELI) AMS 6932
Recrystallization Annealed per SAE AMS-H-81200A
Size of typical CT specimen:
Thickness = 1"
W = 2"
Would a different type of specimen be better?

Thanks

 

[CoryPad]

If W = 2", then that is a mighty small tension specimen. You really have no room for the grips.

There are beam and sheet specimens used for fracture mechanics that might be more suitable for subsequent tension specimen removal.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[metengr]

You can probably obtain sub-size tensile specimens for tensile testing in accordance with ASTM E8. Based on what you reported regarding a CT specimen, and attempting to remove standard or subsidize tensile specimens, I would not recommend it.

In my opinion, material for tensile testing should be as close to what was either in service or if new material, as is. Attempting to obtain tensile data from "test used" specimens is not good engineering practice. I have seen reconstituted specimens from CVN testing where tabs are welded, but this is remote from the notch and is still subject to scrutiny, in my opinion.

 

[EdStainless]

Since Ti is a hex structure it is very direction sensitive. I don't like the sound of this. It would be too easy to be misslead.

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Plymouth Tube

 

[mcclain]

Thanks to all for your valuable insights and experience.
We are going to simply take more standard specimens from the fracture specimen parent stock.