Which is stronger???

[blueoval557]

Yes...ANOTHER QUESTION! LOL Sorry guys! It seems I may have some competition in the fabrication of the suspension bars....although the competitions bars are not adjustabel at all . Anyways...he is using T6061 tubing, which has an OD of 1 inch and a wall of .125. I am using DOM, seamless mild steel tubing with a OD of 5.8 and a wall thickness of .120. Which would be stronger? not so much as to..."which would be easier to bend.." sorta thing...but if you were to have a machine pull the tubing apart until it broke(put the tubing under tension), which would be stronger? Also..which would give more? The bar will be under alot of compression then back to tension then back to compression thing...the control arm mounts are always trying to move in weird ways...in this case...would my mild steel give more or less than his 6061 aluminum? Just wondering!
THANKS!
Kyle

[asad]

look up the tensile strengths of 6061 and mild steel

calculate the cross-sectional area of each, and then multiply by the corresponding tensile strength

That will give you an idea of how much force it would take to pull a bar apart.

As for the 'give' -- take the 'stress', divide by the Young's modulus, and that will give you the change in length of the bar as a fraction of the overall length.

Of course, the forces on the bar are not going to be purely compression/tension...

And then remember that Aluminum has poor fatigue properties, and the tensile strength continues to diminish as the number of compression/tension cycles increases. Steels have the property that, as the number of cycles increases, eventually the tensile strength reaches a minimum and levels off.

Asad

[Dmaxeter]

I dont know what you are using these for, but I have a four link and air bag setup on my rock crawler and I used the DOM like you are using. I dont like aluminum to perform suspension dutys. I do however have an aluminum tie rod, but I have yet to see the benifits from this. I have used my link bars on purpose several times to act as sliders on the rocks and only bent one in the process, other outside forces were at work though. I would go with your steel ones in a heartbeat. I dont know what the tensile strength is though, but I bet the steel is the winner, for me at least, because its proven.

[Jim Kinney]

The answer is it depends. As the others stated, it depends on the load direction and life expectancy. 6061 has about half of the strength of DOM steel, and has about 1/3 the stiffness.

Based on the diffferent tubing sizes, for an axial (along the tube) load, the strength is about the same (6061 twice the area, half the strength). For a bending load, the steel tube has about 60% of the 6061's strength.

As also mentioned, the fatigue strength of steel is much greater, but for your application that may not make a difference.

If it was me, I would stick with steel, but go up a size to .75" x .120" wall.

Jim