Originally Posted by
merlin55
The reality is that stiffness is determined by lots of other things besides diameter - things like choice of material, wall thickness and force distribution. And it doesn`t stop there! The same allow can have different heat treatments, any one of which will give it completely different specs. And even in composite construction like carbon fibre,? the weave direct plays a significant part.
FALSE! For the same material and wall thickness and loading the bending deflection decreases as a cube of the ratio of the diameter change. Different heat treatments do not change the stiffness, they reduce the ductility and increase the strength. Take a course in Engineering Materials at any College, if you want to know these sorts of things. Or Google Young's Modulus to learn the difference in stiffness between Steel, Aluminum, etc
Your posting has me really perplexed and if you hadn`t directly quoted me I would have simply ignored it.
But I`ve reviewed that part of my posting and in spite of a few spelling mistakes resulting from my crude attempts at posting from a cell phone, really can`t see anything that should have annoyed you. Maybe you should underline the exact words.
The other thing I don`t understand is your statement that a heat treatment doesn`t improve stiffness, it `reduces ductility and increases the strength`.
Actually that depends on the heat treatment. Some are intended to INCREASE ductility and DECREASE material strength. It all depends on the objective.
But I`d like to post a few definitions just for fun and stick with your statement.
DUCTILITY is a solid material`s ability to deform under tensile stress.
In material science, the STRENGTH of a material is it`s ability to withstand an applied stress without failure.
STIFFNESS is the resistance of an elastic body to deformation by an applied force along a given angle of freedom.
So maybe you can explain to me how you can decrease the ductility and increase the strength of a material without ending up with a stiffer material?
And your suggestion about taking a college course has been noted. I`m always up to learn. Do you think I can get any credit for the couple years spent scheduling an aluminum extrusion plant or the 20 years spent in engineering in the aerospace industry?
I`m on here to make a few friends and offer a bit of advice. You don`t have to agree with me but I`d really rather that you don`t get personal or insulting.