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  #16  
Old 02-19-2019, 01:17 PM
brianmay brianmay is offline
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Originally Posted by Silly Moustache View Post
mmm, A little while ago Murrmac (where are you?) reprimanded me on one of my videos because I said that after restringing you should ul them to stretch them ..he said "strings don't stretch, but they do settle" or something similar.

I doubt the guy in the video but I suspect he's as wrong as I was.
They stretch mate, if the pitch drops, they've stretched.

I tune a semitone sharp and leave them overnight before tuning to pitch.
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  #17  
Old 02-19-2019, 01:24 PM
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Originally Posted by charles Tauber View Post
It's an easy experiment to verify. Put on a new set of strings. Tune it to pitch and immediately put a mark on the string at the nut using a felt tip marker. As the strings stretch, and the guitar goes out of tune, subsequent retuning back to pitch will see the position of the marker move over time: it will move closer and closer to the tuning peg post. Removing the string tension does not return the mark to its original location. That is plastic deformation. Eventually, beyond a certain point, the mark won't move appreciably further.


Thanks Charles. That is interesting. The slow creep of a particular winding point towards the peg until an equilibrium / stasis.

Now I have another way to see when I loan a newly strung up guitar out how many hours of play it gets.

or

A new way to get to know what strings stretch faster than others.
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  #18  
Old 02-19-2019, 01:24 PM
maxtheaxe maxtheaxe is offline
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Originally Posted by mr. beaumont View Post
Can a string actually "stretch" though? They're metal...
This has been raised before, and it seems to me that if the string was incapable of stretching "because it is metal" then it would not be suitable for a guitar string, lacking tensile strength.

Lacking tensile strength, it would seem to me that the string would be too brittle and would simply break.

I understand that some, perhaps even most, of the 'settling in' is due to the wraps on the tuning post snugging up, but in my experience, the string also stretches, as it does with my electrics that have locking tuners and no more than 1/2 a wrap around the post...they still require some tugging to get them to stay in pitch.
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  #19  
Old 02-19-2019, 01:32 PM
charles Tauber charles Tauber is offline
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From our arm chairs, shall we next debate whether or not heavier objects fall faster than lighter ones?

Elastic deformation, plastic deformation, work hardening, elastic limits, yield strength, ultimate strength for metals are all well documented science. It isn't a question of who's opinion we prefer.

I offered a simple experiment that you can perform on your own instruments to easily confirm what science has figured out.


If you are interested, here is a video of standard tensile test for metals. Note the localized change in diameter/cross section - "necking" - that occurs after yield (into plastic deformation territory) and prior to failure (breaking). A similar rig is used to determine the tensile strength of steel strings/cables.

https://www.youtube.com/watch?v=67fSwIjYJ-E
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  #20  
Old 02-19-2019, 01:40 PM
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Rodger Knox Rodger Knox is offline
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Originally Posted by mr. beaumont View Post
Can a string actually "stretch" though? They're metal...
That depends on what you mean by "stretch". A string under tension is longer and thinner than it would be without. How much longer depends on Young's modulus, and how much thinner depends on Poisson's ratio, along with the tension and cross sectional area of the string.

Initially, it acts just like a spring, stretching a little in response to the tension, and then returning to it's original length when the tension is removed. This is known as elastic deformation, and is a property of materials. All materials exhibit this behavior to some degree.

As tension increases, it reaches a point where the string will not stretch any further. This is the elastic limit. Once the elastic limit is exceeded, one of two things will happen. A brittle material, like glass or cast iron, will break. A more flexible material, like rubber or steel, will continue to stretch, but it will no longer return to it's original length when the tension is removed, some of the deformation is permanent. That is known as plastic deformation.

Music wire is relatively brittle, so it usually breaks without much plastic deformation.

If "stretch" means elastic deformation, yes strings stretch. If stretch means plastic deformation, then they may stretch a little, but will more likely break.
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  #21  
Old 02-19-2019, 01:48 PM
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Reading this thread seriously made my head hurt. Now all you engineer guys know why my degree is in English. LOL
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  #22  
Old 02-19-2019, 02:08 PM
Glennwillow Glennwillow is offline
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Originally Posted by charles Tauber View Post
And, that is exactly what happens.




It is beyond its elastic limit into the range of plastic deformation. In the plastic deformation range, "work hardening" of the metal occurs making the metal increasingly more resistant to further stretching. The work hardening also increased the brittleness of the metal, one of the reasons that repeatedly bending and unbending a string - such as often occurs as the string leaves the tuning post - causes it to break. In short, it does stretch "a lot" initially, and progressively less and less.

It's an easy experiment to verify. Put on a new set of strings. Tune it to pitch and immediately put a mark on the string at the nut using a felt tip marker. As the strings stretch, and the guitar goes out of tune, subsequent retuning back to pitch will see the position of the marker move over time: it will move closer and closer to the tuning peg post. Removing the string tension does not return the mark to its original location. That is plastic deformation. Eventually, beyond a certain point, the mark won't move appreciably further.
If you say so...

I've not heard this theory before, but there could certainly be some truth in what you have written. Then again, I have been avoiding this kind of discussion lately. I should have stayed out of it.

However, this comment is just plain wrong: "New strings are at the highest tension then lose tension as they age!" They can't lose tension unless the player decides not to tune the guitar.

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  #23  
Old 02-19-2019, 02:39 PM
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Originally Posted by Glennwillow View Post

However, this comment is just plain wrong: "New strings are at the highest tension then lose tension as they age!" They can't lose tension unless the player decides not to tune the guitar.
Trying to follow the logic here.

Metal strings are elastic and will stretch under tension. This may be minimal with guitar strings, as their strength is sufficient to accommodate the required tension, but they will stretch.

If this is correct, then the statement that "new strings are at their highest tension" would be correct if you accounted for string length. New strings are at their shortest length while providing the required tension. As they age under tension, length will increase, and the slack will be taken up at the tuning pegs.

Is this correct?
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  #24  
Old 02-19-2019, 04:32 PM
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Reading this thread seriously made my head hurt. Now all you engineer guys know why my degree is in English. LOL
And mine is Photography!

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  #25  
Old 02-19-2019, 04:36 PM
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It turned out to be a pretty cool thread! Science is fun!
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  #26  
Old 02-19-2019, 04:44 PM
rick-slo rick-slo is offline
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Originally Posted by zmf View Post
Trying to follow the logic here.

Metal strings are elastic and will stretch under tension. This may be minimal with guitar strings, as their strength is sufficient to accommodate the required tension, but they will stretch.

If this is correct, then the statement that "new strings are at their highest tension" would be correct if you accounted for string length. New strings are at their shortest length while providing the required tension. As they age under tension, length will increase, and the slack will be taken up at the tuning pegs.

Is this correct?
No. They stretch under tension of the tuning but it's an elastic stretch. They return to their original length when the tension is released. They do not stretch more and more over time.
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  #27  
Old 02-19-2019, 05:43 PM
Glennwillow Glennwillow is offline
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Originally Posted by zmf View Post
Trying to follow the logic here.

Metal strings are elastic and will stretch under tension. This may be minimal with guitar strings, as their strength is sufficient to accommodate the required tension, but they will stretch.

If this is correct, then the statement that "new strings are at their highest tension" would be correct if you accounted for string length. New strings are at their shortest length while providing the required tension. As they age under tension, length will increase, and the slack will be taken up at the tuning pegs.

Is this correct?
Well, tension and string length are like comparing apples and oranges. They are not comparable because they are different mechanical features.

An old string should be no longer than a new string unless that old string has been exposed to stress beyond the material's elastic limit, called the yield stress. If an old string has been exposed to stress exceeding the elastic limit of the string, then yes, it may be slightly longer than a new string. But as you have noted, differences in string length can obviously be made up for with the tuning machines on the guitar. Once you tune the guitar to normal pitch, the tension on an old string should be exactly the same as the tension on a new string.

The original comment that Silly Moustache quoted stated, "New strings are at the highest tension then lose tension as they age!" This guy SM quoted was not discussing string length, but rather, tension. I am stating that if a string is tuned to pitch, old or new, it must be at the same tension. Therefore, this comment cannot be correct.

The author of this comment may be suggesting that the string loses strength as it ages so that the elastic stress limit of the string is lowered. I'm not sure if that is true or not, but it might be, once the string has been exposed to enough events of being stretched beyond its elastic limit.

The way I use strings, I can't imagine why they would be stretched beyond their elastic limit. But then it's pretty rare for me to break a string, so I probably don't stretch strings beyond their elastic limits.

I hope this makes sense.

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  #28  
Old 02-19-2019, 05:56 PM
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Reading this thread seriously made my head hurt. Now all you engineer guys know why my degree is in English. LOL
Iím a Physics Major, and *my* head hurts
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  #29  
Old 02-19-2019, 06:07 PM
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Reading this thread seriously made my head hurt. Now all you engineer guys know why my degree is in English. LOL
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Originally Posted by eatswodo View Post


I’m a Physics Major, and *my* head hurts

I'm not and my head hurts too.

I have an English degree too. Hmmm . . .

Wait . . . I did get a degree in Computer Science after I turned 50.

But my head still hurts.

Don
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  #30  
Old 02-19-2019, 06:19 PM
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Originally Posted by Glennwillow View Post
The author of this comment may be suggesting that the string loses strength as it ages so that the elastic stress limit of the string is lowered. I'm not sure if that is true or not, but it might be, once the string has been exposed to enough events of being stretched beyond its elastic limit.
Yes, that's really all I was attempting to get at. If there is any effect on the elastic property over time, so that there is not complete rebound, there will be some increase in length that requires compensation.

If a string used in normal guitar function doesn't lose any elasticity, it's a moot point.
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