Framebuilders - Tube denting (equations?)

Anybody know of any equations to determine relative denting resistance to dynamic impact between two different tubing materials? Particularly as it relates to equal-weight options (IE, a 150g 3040 steel tube of 24" vs a 150g 7075-t6 aluminum tube of 24"). Obviously there are a lot of things that go into this (hardness, work hardening, wall thickness, diameter, etc.), but the more detail the better!

I know this has been touched on in the past (see: http://www.bikeforums.net/archive/index.php/t-290453.html ) but it stopped a bit short of the really juicy stuff :)

Cheers

I suggest you ask a more meaningful question. All of us engineers know that steel's density and Youngs modulus is 3 times greater than Aluminum, but what exactly is your issue, I doubt that you are designing a tube denting device. I guessing you are trying to build something from tubing, and are trying to decide between the two materials, but without really knowing....

this actually is a difficult problem, at least it looks like it would require some thought. Generally speaking, the thicker tube is going to win.

this actually is a difficult problem, at least it looks like it would require some thought. Generally speaking, the thicker tube is going to win.

Higher strength matters too - steel tubes for bicycles range in strength greatly.

I suggest you ask a more meaningful question. All of us engineers know that steel's density and Youngs modulus is 3 times greater than Aluminum, but what exactly is your issue, I doubt that you are designing a tube denting device. I guessing you are trying to build something from tubing, and are trying to decide between the two materials, but without really knowing....

I would argue this is a very meaningful question - how to chose between two materials (assuming isotropic, non-composite materials) when dent resistance is an important factor?

For example, given two steel tubes of equal ultimate tensile strength and equal density, which one wins - the harder material, or the one with more work hardening potential? Or, for example, given constraints of equal outer diameter and equal weight, which is more dent resistant - aluminum 7075-T5, 6061-T5, Reynolds 953, 6/4 Ti, or an AZ-91D magnesium alloy? Ignoring weldability etc.

I'm not necessarily trying to decide between two materials, i'm trying to come up with a way of looking at a sheet of materials and saying "These materials will probably be more dent resistant than what we use now and should be tested further, while these ones are likely less dent resistant and should not be tested".

And for the record, I am actually going to be building a "tube denting device" as part of this testing :D

I would argue this is a very meaningful question - how to chose between two materials (assuming isotropic, non-composite materials) when dent resistance is an important factor?

For example, given two steel tubes of equal ultimate tensile strength and equal density, which one wins - the harder material, or the one with more work hardening potential? Or, for example, given constraints of equal outer diameter and equal weight, which is more dent resistant - aluminum 7075-T5, 6061-T5, Reynolds 953, 6/4 Ti, or an AZ-91D magnesium alloy? Ignoring weldability etc.

I'm not necessarily trying to decide between two materials, i'm trying to come up with a way of looking at a sheet of materials and saying "These materials will probably be more dent resistant than what we use now and should be tested further, while these ones are likely less dent resistant and should not be tested".

And for the record, I am actually going to be building a "tube denting device" as part of this testing :D


Given the same impact, I'd think the material that can stand more deflection and remain elastic (i.e. will spring back to original dimensions after the stress) will better resist denting, for two tubes with the same mechanical properties. That last phrase makes it complex, however. What are the significant properties and what is the shape? A tube will behave differently from a sheet. I'd also expect how the sheet is supported is rather significant.

'Luck!

Seems to me like a problem where a denting machine could be devised and used in less time than talking about it here, except for the need to accumulate the different samples.

I would argue this is a very meaningful question - how to chose between two materials (assuming isotropic, non-composite materials) when dent resistance is an important factor?

For example, given two steel tubes of equal ultimate tensile strength and equal density, which one wins - the harder material, or the one with more work hardening potential? Or, for example, given constraints of equal outer diameter and equal weight, which is more dent resistant - aluminum 7075-T5, 6061-T5, Reynolds 953, 6/4 Ti, or an AZ-91D magnesium alloy? Ignoring weldability etc.

I'm not necessarily trying to decide between two materials, i'm trying to come up with a way of looking at a sheet of materials and saying "These materials will probably be more dent resistant than what we use now and should be tested further, while these ones are likely less dent resistant and should not be tested".

And for the record, I am actually going to be building a "tube denting device" as part of this testing :DI think you want to compare yield strength.