steel 4130

[Philippe Vessaire]

Hello,

when I read 90,000 lb/sqi for strength,
is it just before the part is broken or is it the elastic limit?

Thanks
--
Philippe Vessaire ҿӬ

[Cam]

That would be UTS , ultimate tensile strenght. I think yeild
strength is at what point the material starts stretching.

Personally, I've had a problem with numbers, so i tend to
do destructive testing with a pull ram and a pressure gauge. As far as
chromolly steel goes, it seems to "snap"
right at the point of stretching. So I'd imagine its Yeild Strength is very
close to its UTS .

If you see two numbers for strength, pick the lesser one and halve it , and
design from that .

Cheers (no qualifications) Cam...


> when I read 90,000 lb/sqi for strength,
> is it just before the part is broken or is it the elastic limit?
>
> Thanks
> --
> Philippe Vessaire ҿӬ
>

[Paul Lee]

Wicks aircraft catalog gives two values for 4130:
min tensile (breaking) 95,000 and min yield (where it starts
distorting) 75,000. Usually the initial yielding will have quite
a bit of strength giving you a chance to get back down. But
repeated cycles will weaken it and rupture. Check the structure
for any cracks and fix it.

----------------------------------------------------
Paul Lee, SQ2000 canard project: www.abri.com/sq2000

Philippe Vessaire > wrote in message -moi>...
> Hello,
>
> when I read 90,000 lb/sqi for strength,
> is it just before the part is broken or is it the elastic limit?
>
> Thanks

[O-ring Seals]

On Sat, 18 Oct 2003 03:46:35 +1300, "Cam" > wrote:

>That would be UTS , ultimate tensile strenght. I think yeild
>strength is at what point the material starts stretching.
>
>Personally, I've had a problem with numbers, so i tend to
>do destructive testing with a pull ram and a pressure gauge. As far as
>chromolly steel goes, it seems to "snap"
>right at the point of stretching. So I'd imagine its Yeild Strength is very
>close to its UTS .
>
>If you see two numbers for strength, pick the lesser one and halve it , and
>design from that .
>
>Cheers (no qualifications) Cam...
>
>
Cam,

While that might sound like a good (and conservative) approach to the
design, he probably wants to build something that will be able to get
off the ground. If your suggested technique were to be used
throughout the aircraft, it would probably be too heavy to fly.

O-(some qualifications)Ring

[Corrie]

(O-ring Seals) wrote in message >...
>If you see two numbers for strength, pick the lesser one and halve
it , and
> >design from that .
> >
> >Cheers (no qualifications) Cam...
> >
> >
> Cam,
>
> While that might sound like a good (and conservative) approach to the
> design, he probably wants to build something that will be able to get
> off the ground. If your suggested technique were to be used
> throughout the aircraft, it would probably be too heavy to fly.


Depends on your risk tolerance. Bridges use 200%+ risk factor.
Airplanes generally use 150%. So multiply times 1.50.

CB