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Post by Kuri on Feb 22, 2013 14:13:37 GMT
I have going through the SBG forum for a while now (great resource), and have noticed that terms such as strength and toughness are commonly being used.
Coming from an engineering background, I equate these against very specific material properties. I often wonder whether people using these terms understand the meaning or are using their interpretation (lay usage?) of the words because they simply don't know any better.
I've searched the forum to see if anyone has provided definitions, but there doesn't seem to be a consolidated list. Is it worthwhile putting commonly used words and their meanings together, or is it simply understood what people are trying to comminicate?
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Post by OttoVonFaart on Feb 22, 2013 15:06:52 GMT
In general, this forum seems to use standard definitions for strength & toughness. i.e, Strength: Definition: Strength is a measure of how well a material can resist being deformed from its original shape. Generally blade resilience to deformation and/or bending.
Toughness: Definition: The ability of a metal to rapidly distribute within itself both the stress and strain caused by a suddenly applied load, or more simply expressed, the ability of a material to withstand shock loading. It is the exact opposite of "brittleness" which carries the implication of sudden failure. A blade that easily chips or cracks is said to be brittle or not as tough as one which is resistant to chipping.
I have read almost every post & sword review in this forum over the past 5 months and the definitions above seem to be consistent with the way these terms are used here.
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Post by Kuri on Feb 22, 2013 23:12:49 GMT
Definition of strength is related to loading, not deformation. It can deform a little or a lot. How much it deforms is related to the material (ie. elastic modulus) and the cross sectional shape. Just note that you are relating it to the load taken at the proportional (yield) limit (ie. ability to return to original shape). There is also ultimate strentgth which is the maximum load that it can carry, and this is beyond the yield point.
Your definition of toughtness is not quite there. Toughness is the material's energy absobing capacity through the elastic (ie. go back to original shape) and inelastic (permanantly deformed) through to destructive failure (ie. break). It is for any loading, not just "shock".
Ductility and brittleness are antonyms (not toughness). It's a measure of how far beyond the elastic limit a material can go before destructive failure. It's the ratio of deformation at failure point to yield point. If this ratio is close to 1, then it's brittle (sudden failure). Much larger number, then it's ductile. So cast iron is quite brittle, while copper is very ductile.
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Post by Shrugger on Feb 23, 2013 0:08:28 GMT
Strength: Being heavy! Toughness: Not breaking! I be smart man. Me use smart words!
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Post by Kuri on Feb 23, 2013 0:49:07 GMT
Beefy and can dish it out Takes an absolute beating before calling it quits
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avery
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Post by avery on Feb 23, 2013 1:18:50 GMT
Unfortunately and fortunately, these terms are a bit relative here. We could discuss the shear point of T 10 tool steel with all the apropriate measurements and temperature factors till we're blue in the face. Will a beginner understand and equate that? Certainly not. Even something as simple as Rockwell Hardness is lost on many people, but when one reads a review that has video along with it, one gains a multitude of insight that may other wise be lost on them. Remember, this place is mainly for beginners, a stepping stone if you will. Some go on to more specific or dedicated mediums as their knowledge grows. Some simply stay here and learn over time. Dealing with molecular structures in iron such as ferrite can take a lot of time to understand. Get into pearlite, martensite, dendrites or face centered molecules vs body cemtered molecules and people will stop listening. Show them a video of the sword in action and they will say "ahah, that's what I'm after".
The "strength and toughness" of a blade is often times miscalculated; you'll see it tested on a metal barrel or cinder block. The beauty of the sword is that is designed for one thing and that is cutting human flesh. It's not like a hammer or any other tool that is multi functional. What a sword can do to flesh is what defines that sword as being tough enough or strong enough.
Now, having said that, I'm all for a discussion on what makes that blade "tough" enough and we can get into the particulars, but that horse has been beaten to death. Through hardened vs Differentially hardened, European design vs Eastern design, who made wootz first and was it really wootz.. What is wootz, the difference in the strength of a pattern welded blade vs a Damascus blade. The molecular edge between making Crucible Steel and cast iron, the list goes on and on.
Bottom line is, show someone what a blade can do and let them decide if its strong or tough enough for them.
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Post by Kuri on Feb 23, 2013 2:07:57 GMT
Thanks Avery As you said, getting a firm grasp of material properties and mechanics of solids requires a lot of study and research. If there were simple explanations of common terms, it's a starting point for begineers to get a basic understanding of swords/knives and everyone can talk the same language.
People ask for advise and say they want something strong, durable, tough or hard. They know what they mean, does everyone else?
Yeah, there's nothing like a demonstration to show the limits of the sword/knive or the individual wielding it.
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Post by frankthebunny on Feb 23, 2013 2:39:19 GMT
I think we all understand these terms well enough to express ourselves and understand the points being made. generally we would rather pick apart comments on steel composition and claims of performance question - issa slingblade tough or issn it strong? now iffn' youwel excuse me, I rekon Immagonna go git me some of them french fried pertaters ...mmmm hmmmm
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Post by OttoVonFaart on Feb 23, 2013 2:52:25 GMT
The issue I have with Kuri's no doubt correct definitions is that those definitions are the sort of thing the teach in engineering school. You damn near need a degree in engineering to understand the terms used to define the definition. "Elastic modulus" WTF? Nobody here is doing the math. Most here do not have degrees in either engineering or metallurgy what they do have is a desire to have a sword that won't permanently bend, i.e., take a set or deform when laterally stressed. That's a testable quality, can I bend it 45° without permanently warping/bending it? If I bend it 47½ degrees? What then? Does it stay bent or return to true? Does it break?
Another thing people want is a sword that won't chip or roll the edge when struck against a reasonable non-living animal/human target. Again, testable. Hit a concrete block? Ah, it chips. Hit a bunch of wet, rolled tatami mats or green bamboo? The blade shouldn't chip or roll over. One sword manufacturer/vendor has been known to chop whole pigs into pork chops in his demo videos. Trust me, no one asks questions about his sword's elastic modulus or the cross sectional shape. He sells a lot of swords. Some want to test their blades on zombies but we're waiting due to a current shortage of zombies.
Of course sword making is an art as well as a science. It's probably easier to understand and appreciate the art, I'm happy to leave the science of it to guys like Kuri.
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George
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Post by George on Feb 23, 2013 11:06:05 GMT
Hmmm i never use the term 'strength' or strong, as i know for metal that can be 1000 things. Toughness on the other hand i use as simply a sword term. Tough against bending, snapping or rolling. I guess you could use strength the same way. End of the day we all know what we mean i think
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