Ductility, strength, toughness, flexing and bending

bluntcut said:
I interpreted chart as: 'plastic deformation' line/curve corresponding to yield strength and 'total deflection' to fracture strength. Perhaps you have a better or right way to interpret the chart? Please just state your opinion rather than being young about it.
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You took a line labeled “plastic deformation” and instead called it “elasticity.” You interpreted the whole thing backwards.
 
Actually, it could be that you got it backward because there isn't a 4th axis for permanent bend distance. Plus based on experiences - 'plastic deformed'/'permanent bend' is not that wide. Thus it is more reasonable to interpret 'plastic deformation' as 'elasticity'. Having said this, how do you interpret 'plastic deformation' curve/line?

Larrin said:
You took a line labeled “plastic deformation” and instead called it “elasticity.” You interpreted the whole thing backwards.
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bluntcut said:
Actually, it could be that you got it backward because there isn't a 4th axis for permanent bend distance. Plus based on experiences - 'plastic deformed'/'permanent bend' is not that wide. Thus it is more reasonable to interpret 'plastic deformation' as 'elasticity'. Having said this, how do you interpret 'plastic deformation' curve/line?
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I interpret the “plastic deformation” line as “plastic deformation.”
 
Deflection axis in context:
https://en.wikipedia.org/wiki/Four-point_flexural_test
https://en.wikipedia.org/wiki/Flexural_modulus

Here is pic of 3 points bending test:

440px-Flexural_modulus_measurement.png

That "plastic deformation" line most likely means = when deflection goes this far plastic deformation start/begin.

I am done with common sense... geez!
 
bluntcut said:
Deflection axis in context:
https://en.wikipedia.org/wiki/Four-point_flexural_test
https://en.wikipedia.org/wiki/Flexural_modulus

Here is pic of 3 points bending test:

440px-Flexural_modulus_measurement.png

That "plastic deformation" line most likely means = when deflection goes this far plastic deformation start/begin.

I am done with common sense... geez!
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Your link is to "asfault" mixtures. I'm interested in "apples to apples" comparisons. You can't just substitute "elastic" for "plastic". Although similar, they are not equal or the same.
 
Unfortunately Uddeholm is the one labeled this curve/line a little bit confusing however deflection in context of bending test as I stated.

Bottom of page 4. * I used an older version but more less same data.
https://www.uddeholm.com/files/PB_Uddeholm_vanadis_4_extra_english.pdf

Solid lines are hrc vs strength/force. Dash lines are hrc vs deflection.

danbot said:
Your link is to "asfault" mixtures. I'm interested in "apples to apples" comparisons. You can't just substitute "elastic" for "plastic". Although similar, they are not equal or the same.
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That chart is a bit confusing for someone who's new at all of this, but I think I get it for the most part.

Thanks everyone,

Bo
 
danbot said:
Because they mean different things in metallurgy. Plastic deformation is permanent and elastic deformation is not. Apples and oranges my friend. Reference requires correlation not substitution.
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Well, my plastic is more elastic than yours.....:D
 
danbot said:
Because they mean different things in metallurgy. Plastic deformation is permanent and elastic deformation is not. Apples and oranges my friend. Reference requires correlation not substitution.
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Wait a second here....am I reading this right??? Marvin the Martian is the voice of reason???
No way!!!
:D
 
If my edge chips under use, then it's not tough enough for me. If I bend my blade and it stays bent, then it has high ductility, but at the same time, it has also experienced plastic deformation. I like a middle-of-the-road between the upper extremes of those two qualities in a knife steel.
 
91bravo: wait, if you bend a knife and it stays bent, it has high ductility? I thought it had high ductility if it didn't stay bent. Are ductility and toughness the same thing?

Thanks,

Bo
 
Or is ductility the ability to bend a metal and it not chip or break? I can't quite remember, I'd have to find that answer in my long list of blade forums answers I've written down.

Bo
 
Bo-dacious said:
Or is ductility the ability to bend a metal and it not chip or break? I can't quite remember, I'd have to find that answer in my long list of blade forums answers I've written down.

Bo
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Toughness measure's a metal's ability to maintain its integrity while being pressed, pulled, or deformed. A metal that can be bent without breaking is tougher than a metal that will break rather than bend. Ductility is a metal's ability to be stretched.

For knives, I think it's much better to use the term "toughness." Tough blades have a high ability to resist breaking, chipping or cracking.

Strength is the ability to prevent permanent bending, rolling or denting.

Those two terms, toughness and strength, really define a knife steel. You can add in wear resistance.

A blade/edge with good edge stability is one where both strength and toughness are high. It other words, good edge stability is a characteristic of well balanced steels, at least in regard to knife science. Some people would include wear resistance, but not all.
 
Twindog: yes, hardness/strength, toughness, and wear resistance make up edge retention, am I wrong?
Good info, man.

Thanks,

Bo
 
Bo-dacious said:
Twindog: yes, hardness/strength, toughness, and wear resistance make up edge retention, am I wrong?
Good info, man.

Thanks,

Bo
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Yes. I'd call it edge stability rather than edge retention, but pretty much the same thing.

Hardness is correlated to edge wear, so some people don't include wear resistance in edge stability. But with today's high-alloy steels where the alloys add a ton of edge wear, I feel it's fair to call it the third element of edge stability.
 
Yes, ductility is the ability to deform under under tensile strength. I guess the term "toughness" would be more appropriate when it comes to knife blade performance.
 
Twin: okay, great.

91bravo: that's deforming without chipping or cracking, right?
If ductility is the ability to deform under tensile strength, what is the ability to deform under compression and shear strength?

Thanks guys,

Bo
 
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