Which is stronger?

Hi,
Can anyone tell me which tube would be stronger as far as bending or buckling, 304 stainless 60mm diameter with a 1.5mm wall or 6082 T6 2 1/4 inch with a 3.2mm wall and anodized. I will take educated guesses.
Thanks,
Ishy

i guess lockypoo

wippin' boy said:

i guess lockypoo

Click to expand...

Obviously a little education deprived.....

ISHY said:

Hi,
Can anyone tell me which tube would be stronger as far as bending or buckling, 304 stainless 60mm diameter with a 1.5mm wall or 6082 T6 2 1/4 inch with a 3.2mm wall and anodized. I will take educated guesses.
Thanks,
Ishy

Click to expand...

I'm not an engineer, nor have I played one on TV but consider this: you have two materials and two regimes of loading.

Buckling is a matter of the material's intrinsic stiffness combined with the yield strength of the material. It's a local failure mode often sudden in onset. A stressed member under eccentric loading may buckle and fail in a fraction of a second. It always affects the compression side.

In a beam, deflection can be seen as load increases and an observer can stop the loading or holler depending on his role.

Without getting into numbers, my guess is your 60 mm stainless tube will likely support greater load as a column than the 2 1/4" aluminum merely because of its greater stiffness in spite of its thinner wall. Much depends on the column height, end termination, and laterial bracing if any.

The length of height of the beam or column can't be adequately addreessed. Whatever the material, if the tube is used for too long a beam or too tall a column without laterial bracing, buckling will be exacerbated depending on end and lateral restraint.

It looks to me that you have two candidate materials in hand and you'd like to pick the best one for a proiject but you need to know which is best suited for the job. You can't afford a guess. You need hard data. The very fact that you have to ask this question make me think you need to run the WHOLE problem past someone skilled at stress analysis.

Do you want a real answer or simply an educated guess?

If the former, then you must provide many more details before an meaningful analysis could be done.

Forrest touched on some of them, there are more required however. Questions such as this one make me run away. I like my PE license and hate courtrooms!

OK I'll rephrase the question, if both tubes were the same height and mounted solid on the floor and I pulled them towards me which one would bend or break first?
Thanks,
Ishy.

If my math is correct (pls check)...

Moment of inertia, I=.049(D^4-d^4) for cylindrical tube from mach Handbook

6082 alum tube: I=1.98 M^4
SST 304 tube : I=1.18 M^4

Yield strength (6082) 250 MPa
Yield strenngth (304) 207 MPa

The most simplistic answer just by looking at numbers only, (no design criteria provided) the alum tube will withstand about 2X the bending moment that the 304 tube will take before yield. Don't know about buckling.

The M of I of the 6082 tube is about 65% greater than the SS

The yield strength of 6082 alum is about 20% gretaer than the 304

My math is rusty, so hopefully someone will confirm what I say.

morsetaper2 said:

If my math is correct (pls check)...

Moment of inertia, I=.049(D^4-d^4) for cylindrical tube from mach Handbook

6082 alum tube: I=1.98 M^4
SST 304 tube : I=1.18 M^4

Yield strength (6082) 250 MPa
Yield strenngth (304) 207 MPa

The most simplistic answer just by looking at numbers only, (no design criteria provided) the alum tube will withstand about 2X the bending moment that the 304 tube will take before yield. Don't know about buckling.

The M of I of the 6082 tube is about 65% greater than the SS

The yield strength of 6082 alum is about 20% gretaer than the 304

My math is rusty, so hopefully someone will confirm what I say.

Click to expand...

Thank you very much indeed.
Ishy.