Rehashing "flex"

Karl I believe Nathan already touched on it in his post, but just to make sure you are covered I would suspect that what you are observing is a result of work hardening. I am not sure I am grasping exactly what you are seeing but when a piece is steel is taken to the yield point one can image the elastic line on the chart above moving to the left until its new position coincides with where the proportional (elastic) limit was reached the first time. This reflects how work hardening can mimic some of the same things that a hardening heat treatment can do. Deforming the metal once will push the yield point up and reduce the plastic range so that on the second bend the metal will resist bending a little longer but will have less ability to stretch or bend before breaking. This is exactly how and why one can break a piece of wire by repeatedly bending it back a forth. on each bend the wires plastic range is decreased until it snaps almost immediately upon exceeding the elastic range.

This also touches on the ideas of fatigue strength. It would be erroneous to think that making steel softer would increase fatigue strength after a certain point. If the part can cycle entirely within the elastic range of the steel then very little strain can be induced thus it will not accumulate the issues that will eventually lead to its demise. If however you soften the metal to where the use will cycle it into the plastic range every repeat of that action will induce strain hardening effects and the part will fail rather quickly. I have likened it to dealing with trojans and spyware on your computer by just getting the largest hard drive you can find so that you can handle all the accumulated junk and still have your computer run, I would rather have a good firewall that stops the accumulation to begin with.

On the other hand it is true that the absolutes we like to deal with in our thought processes are never present in real life and the chances are that every time you flex a blade with no apparent effect as it returns to true, there is probably energy being introduced and stored in the material to some point, and for this reason I tell people that it is not the best idea to go flexing swords all the time to show how high quality they are. First of all you will probably be affecting the blade in imperceptible ways, but most of all it doesn’t really show anything except how little you know about elasticity.
 
Kevin R. Cashen said:
I hope that paragraph of smooth talking helps alleviate any tensions before mete gets a hold if it;). If you think cryoed bainite would cause me to go spastic you should see what would happen if you tell a metalurgist about molecules in steel, and spell it metalurgist in the process:D
Click to expand...


Ga! Mete!

metalurgist heh

Seriously though. No tensions here. I knew what he meant, I guess I was casting bait... Shame on me
 
Tai Goo said:
O.K., maybe I didn't say it "metallurgically correct". I was using the term in the broadest general sense (teeny tiny and itsy bitsy),... but what about the point I'm trying to make about fatigue and failure?
Click to expand...
Its a valid point. Fred
 
Cryo bainite and you can reduce the retained austenite in the bainite. That Cambridge U website has some very interesting stuff that makes you think things all over again. You're shocked at that and the fact that low carbon martensite can have RA also !! Gotcha !!!
 
Fred.Rowe said:
Its a valid point. Fred
Click to expand...

O.K. from now on I promise not to use the "M" word. From now on it's "teeny tiny itsy bity". :D

It was the only point I could think of to add to what Kevin was saying about flexing, bending, deforming etc...

Is there a simpler way to say what Kevin is saying without all the metallurgical lingo?
It seems somewhat paradoxical and philosophical at first, but the essence does make sense. I’m just trying to simplify it in my mind, and grasp the big picture here.

Is it that, heat treating won't effect the amount of force needed to introduce the elastic effect,... just geometry? I'm not sure I said that right, but is that it,... or is there a better way of saying it?

I've always had a gut feeling that "geometry" was the bottom line...
 
I keep slipping in the term “proportional range” instead of elastic, I do this for a reason, because I like the things that it tells us about the whole topic. It is called the proportional range because anything short of the yield point will deform directly proportional to the amount of load applied. If at any point you stop applying load and hold, the deformation or strain will stop as well, as it is proportional to that load. So if the steel is clamped horizontal and you hang 20 lbs. on the end of it, it deflects a certain amount of inches. Adding no more weight the steel will just sit still and hold its own. If you remove the weight the steel will return to true. But if you continue to add weight to the end of the steel eventually you will reach the limit at the yield point. It is here that if you add just one more ounce the steel will continue to deform and droop toward the floor some even though you are not adding any more weight. After the yield point the stress versus strain is NOT proportional.
 
mete said:
Cryo bainite and you can reduce the retained austenite in the bainite. That Cambridge U website has some very interesting stuff that makes you think things all over again. You're shocked at that and the fact that low carbon martensite can have RA also !! Gotcha !!!
Click to expand...


Ga! Its Mete! and he is talking about retained austenite in cryoed bainite! Run away!


...wait. I don't get it....
 
O.K.

So,... is "Strength" the ability to resist deformation, the ability to tolerate deformation,... or both or neither,... philosophically speaking? :D

I don't know where I'm going with this,... but it's fun! :)
 
Tai Goo said:
O.K. from now on I promise not to use the "M" word. From now on it's "teeny tiny itsy bity". :D

It was the only point I could think of to add to what Kevin was saying about flexing, bending, deforming etc...

Is there a simpler way to say what Kevin is saying without all the metallurgical lingo?
It seems somewhat paradoxical and philosophical at first, but the essence does make sense. I’m just trying to simplify it in my mind, and grasp the big picture here.

Is it that, heat treating won't effect the amount of force needed to introduce the elastic effect,... just geometry? I'm not sure I said that right, but is that it,... or is there a better way of saying it?

I've always had a gut feeling that "geometry" was the bottom line...
Click to expand...

Indeed in matters of stiffness geometry is the bottom line. Increasing the ammount of material to resist tensile forces on one side and compressive forces on the other is how you make things stiff. And it does't have to be pure mass, one can play games with distances from the center line where the two forces are divided, as in "I" beam type shapes, the mass is not the key as much as the distance from the centerline that the materil extends thus requiring more force to overcome it. This comes into play with rapiers. Real rapiers are not these flippy flimsy whip like foils that we so often see, they are rigid and as stiff as they can be made and this has nothing to do with their heat treatment. Good old rapiers had heavy fullering or even sometimes star shaped cross sections to give rigidity in order to drive them through their targets.

*I always keep it simple and focus on the big picture when discussing this topic so the only real relevent forces are tensile and compressive, however techno geeks can (and do) pick my descriptions arpart because I do not include shear and other factors in the picture, but this comes into play at a very much smaller scale and would only muddy the waters with complication that is not necesarry to get the point across.
 
Tai Goo said:
O.K.

So,... is "Strength" the ability to resist deformation, the ability to tolerate deformation,... or both or neither,... philosophically speaking? :D

I don't know where I'm going with this,... but it's fun! :)
Click to expand...

I thinkI would say strength is the ability to resist plastic deformation and toughness is the ability to "tolerate" deformation. 1018 is ductile and very soft so it can tolerate getting smacked with a hammer and taking a bend without breaking, it is tough. While hardened 5160 is strong and can resist the bending under the blow but once the bend is inevitable it will not tolerate it very well.

I actually prefer the more generic and philosophical terms to describe these things as it makes it a little more interesting to discuss and understand.
 
If you were to start with 3 pieces of ¼ inch round 01 drill rod by two inches long, hardened one, hardened and tempered one, and annealed the other,… would it require an equal amount of force or energy to take each one of them to the breaking point through flexing or bending? Or,… is one “stronger” than the others?
 
If all three were fastened at one end on a bench and then had 20 lbs suspended off the other end they would all deflect exactly the same under 20 lbs. As you increased the weight the annealed one would be the first to bend and not return to true if the weight is removed. The other two would take much much more force to reach that point, but the tempered one would still have a little life left after it began to yield while the fully hardened one would just snap with very little if any deformation. It is kind of as if there is only so much the steel can handle until ultimate failure, with "X" being your starting point and "Z" being ultimate failure and the distance between the two is the same for any of the rods, but "Y" is a point somewhere in between that divides elastic from plastic. All heat treating can do is slide "Y" up or down the scale giving more of one at the expense of the other. Indeed on a stress strain curve the point at which the material just gives up entirely and dies in fracture is known as the "ultimate strength".
 
Tai Goo said:
If you were to start with 3 pieces of ¼ inch round 01 drill rod by two inches long, hardened one, hardened and tempered one, and annealed the other,… would it require an equal amount of force or energy to take each one of them to the breaking point through flexing or bending? Or,… is one “stronger” than the others?
Click to expand...


If you hung a the same amount of weight from the end of each rod they would all flex exactly the same amount until you had added enough weight to reach the elastic limit of the annealed bar. That one would then bend even further than the other two with the same amount of weight . If you kept adding weight to the tempered and the fully hardened ones they would still flex exactly the same amount until the elastic limit of the tempered bar was reached. Then that one would start to bend farther.
If at any point you remove the weight the bars would all return to true unless they had reached that elastic limit in wich case they would return to less than true.

So the "harder" bars would take more weight to break or permanently bend but take the exact same force up to the elastic limit of the weaker one.
 
It goes back to what I was saying about ball bearings,... the only thing that changes on a ball bearing is the reflection of light off of any given angle back to the eye of the beholder.

The "object" itself never changes...
 
Tai Goo ,you've obviously never seen a bearing after catastrofic failure !!..... Back in my fencing days when we bought epee blades we chose the stiffer ones. Otherwise you point the sword to one direction but the point may go somewhere else !!
 
You must log in or register to reply here.
Back
Top