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safety of carabiners under dynamic load
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pro_alien


Jan 11, 2009, 4:01 AM
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safety of carabiners under dynamic load
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New Publication:

Schambron T & Uggowitzer PJ. Effects of wear on static and dynamic failure loads of aluminium-based alloy climbing karabiners. Sports Eng. Published online: 13 November 2008.

For those with access, or willing to pay $34:
http://www.springerlink.com/...tent+Status=Accepted

Short article in German:

http://www.ethlife.ethz.ch/...Karabinerhaken/index

Brief summary:

- EN norm only requires static load test. In their tests, dynamic breaking load was about 25 to 50% less than static load, suggest adding dynamic load requirements to the norm.

- Moderate damage like small chinks or rope wear did not reduce breaking load significantly.

- The author recommends wire gates. In critical locations, multiple and/or locking biners should be used.

- In high wear situations like climbing halls or top anchors, steel hardware should be used and regularly inspected.


adatesman


Jan 11, 2009, 7:05 AM
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JimTitt


Jan 11, 2009, 11:31 AM
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Re: [adatesman] safety of carabiners under dynamic load [In reply to]
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Typical students, do research without doing research:
"Until now the relationship between static and dynamic breaking strength has not been researched". (my translation).
Except for http://personal.strath.ac.uk/...lie_Jackson_2008.pdf
and for wear and damage http://personal.strath.ac.uk/...han_Garratt_2007.pdf
as the first that I can think of but I can find some more if you want!


gosharks


Jan 11, 2009, 1:26 PM
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Re: [JimTitt] safety of carabiners under dynamic load [In reply to]
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JimTitt wrote:
Typical students, do research without doing research:
"Until now the relationship between static and dynamic breaking strength has not been researched". (my translation).
Except for http://personal.strath.ac.uk/...lie_Jackson_2008.pdf
and for wear and damage http://personal.strath.ac.uk/...han_Garratt_2007.pdf
as the first that I can think of but I can find some more if you want!
As far as I can tell, neither of those were published or peer-reviewed in the typical sense. That is what people mean when they say "has not been researched" in a peer-reviewed publication.


JimTitt


Jan 12, 2009, 1:37 AM
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And your point is?

If those in the ivory towers of academia wish to abuse the word `research´ by attatching their own definition to it that is their affair. Of course discounting `research´ perfomed by industry, private individuals, other academics, NGO´s, Government organisations, the military etc because it does not conform to their rules of what defines `research´ leaves them the poorer, not us.

The only peer reviewed publication on climbing equipment from the several hundred others I have on file is utterly flawed, based on a false premise and the conclusions drawn are completely wrong so perhaps peer review is not the gold standard some might hope!

Since the authors of the paper in question have followed the regrettable modern trend of expecting us to pay to read research funded by the taxpayer I for one will never know the value, accuracy and worth of their work.


I_do


Jan 12, 2009, 10:53 AM
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Re: [JimTitt] safety of carabiners under dynamic load [In reply to]
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JimTitt wrote:
And your point is?

If those in the ivory towers of academia wish to abuse the word `research´ by attatching their own definition to it that is their affair. Of course discounting `research´ perfomed by industry, private individuals, other academics, NGO´s, Government organisations, the military etc because it does not conform to their rules of what defines `research´ leaves them the poorer, not us.

The only peer reviewed publication on climbing equipment from the several hundred others I have on file is utterly flawed, based on a false premise and the conclusions drawn are completely wrong so perhaps peer review is not the gold standard some might hope!

Since the authors of the paper in question have followed the regrettable modern trend of expecting us to pay to read research funded by the taxpayer I for one will never know the value, accuracy and worth of their work.

I think I can partially agree with you but it's hard to asses any work not peer reviewed. If it's in a respected peer reviewed magazine I know it holds up to a certain standard. Not saying it's always correct far from it, even as a student I can find many flaws in many publications but I'll take it over research done by most other party's unless it's an organization I think I can trust but never had the need to resort to that in my field of work.


nthusiastj


Jan 12, 2009, 11:16 AM
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Re: [I_do] safety of carabiners under dynamic load [In reply to]
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So uh, what I'm getting from this is that nothing about what we know of carabiners has changed. Just like always I shouldn't be concerned with my gear exploding when I look at it.


kimbill


Jan 12, 2009, 11:25 AM
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I_do wrote:

I think I can partially agree with you but it's hard to asses any work not peer reviewed.

It's particulary hard when the article is pay-per-view!

Even without peer review, if you have some background in the subject, you can look at the experimental set-up and procedures, the characteristics of the sample tested (number, type, condition), and form a working idea of the validity of the results.

If you are like Jim Titt and have a lot of background in the field, then you ARE a peer and thus can do your own review!


I_do


Jan 12, 2009, 11:32 AM
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kimbill wrote:
I_do wrote:

I think I can partially agree with you but it's hard to asses any work not peer reviewed.

It's particulary hard when the article is pay-per-view!

Even without peer review, if you have some background in the subject, you can look at the experimental set-up and procedures, the characteristics of the sample tested (number, type, condition), and form a working idea of the validity of the results.

If you are like Jim Titt and have a lot of background in the field, then you ARE a peer and thus can do your own review!

And there's definably subjects in which I am confident I can asses whether or not a certain research paper is at all dependable. But being a student I can get the papers for free through the university and I need to know before I start reading whether or not I could use an article otherwise it's just a waste of my time figuring out if it holds up to my standards.


Wal


Jan 13, 2009, 3:32 AM
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Re: [I_do] safety of carabiners under dynamic load [In reply to]
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Hi there all,

RE: access to scientific papers & pay-per-view

As a scientist and an rock climber I am interested in this article. I intend to get around the pay-per-view by emailing the author - thomas.schambron@alumni.ethz.ch (address listed on the abstract page) - for a pdf reprint of the paper. This is a widely accepted practice in scientific and academic circles and scientists are generally very happy to supply copies of their work (it shows us that people are actually interested in what we do!).

Hope this helps.


JimTitt


Jan 14, 2009, 1:41 AM
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Re: [adatesman] safety of carabiners under dynamic load [In reply to]
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Well, I do have a possible theory about why karabiners fail at lower loads under dynamic testing than quasi-static. To test it practically is going to be difficult, though a few possibilities exist to see if this `toilet-seat´theory is going in the right direction.
Someone with access to a good dynamic finite modelling package could probably get quicker and better answers if they could get a model from one of the manufacturerers.

A possible failure mechanism is related to the gate/nose system in karabiners which initially fails allowing catastrophic failure of the spine.
As the load comes on the karabiner the nose area moves outwards (due to clearance in the nose/pin area) until it hits the pin of the gate. This is easy to see in micro-strain graphs where the outside radius is first under compression and then changes to tension after about 50ms. The nose is moving considerably faster than the loading point due to the shape of a karabiner and the leverage, probably by a factor of 4 or so depending on the design and the strain on this point is applied considerably faster than in a quasi-static test. (In the micro-strain gaphs we can see that after some initial bouncing the rise in the strain is very rapid.)
A feature of the alloys used in karabiners is the variation in strain rate sensitivity (this is related to the crystaline structure), depending on the heat treatment this more or less pronounced but it is probable that at the sort of speed the strain is applied in dynamic testing we are in an area of negative strain rate sensetivity. This would cause the karabiner nose to fail at lower loads than usual.

Experimentally, if this is so I would expect a more traditional karabiner with less heat treatment to be stronger in a dynamic test but the exact heat/ageing treatments are usually industrial secrets so its hard to know what one is working with. Possibly an easier way to see would be to check the difference between solid gates and wiregates as wire gates have a lot more give in them thus one would expect the strain on the nose to be applied more slowly.

As I said, this is only a rough theory, maybe someone who makes karabiners can tell us more.


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