square or round tubing strength after damage

[rb70383]

Not a question specific to anything i have just something I thought of. While watchin my programs on spike, it was mentioned that round tubing is stronger for chassis but more difficult fab because of its roundness, hence why square tubing is commonly used. Question is with a dent put in a given length of tubing square vs round. Which is more likely to fail? I would think the round, once dented is more prone to collapse. Where the square would be better off until the damage was severe enough to wrinkle the side walls as well.

Ideas? comments? Am i off my rocker?

[80proZ]

im pretty sure square tube is stronger then comparable round tube .If you do the math the square has more surface area.I think the problem lies in the bending process. The square tube deforms in the throat of the bend, whereas the round tube keeps its form, remaining stronger then the square tube at the bend.

[WS6]

the advantage of round over square is because the round tube has the same properties regardless of what direction a force is applied. Square depends on how the force is applied. Take a square tube and set it on an edge so it looked like a diamond. If you wanted to bend or damage a square tube, this is where you'd apply a force because that's the weak points. Along the flats square is strong.

It's really difficult to say square is better than round or vise verse when talking about a chassis. If the chassis has to fit a car without modifying the car, rectangle or square may prove to be stronger simply because of dimensional constraints dictating that a rectangle shape fits best and provides the most strength. The round tube that's as strong or stronger may not fit in the same area. Now, if you're talking a purpose built car where the body will be modified to fit a chassis, round is the way to go. Look at all the race cars built in this country, NASCAR, circle track, drag cars.

[Ratfink]

we don't have any trouble with dents in round tube.
https://static1.pt-content.com/images/pt/2009/11/dentedtube-1.jpg
this upper control arm has been like this for fourteen rounds of racing. I could take fifty more pictures of similar damage to round tube, but the point is often other aspects come into play and commonly engineering flaws, fabrication or time limitations, or fatigue cause other areas to fail first. The strength of a dented tube is not the limiting factor by any means.