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janeclimber:湿绳和结冰的绳子的安全性研究

湿绳和结冰的绳子的安全性研究

湿绳和结冰的绳子的安全性研究
La Rivista del Club Alpino Italiano (CAI) 意大利登山协会对湿绳和结冰的动力绳的强度,缓冲有效性进行了详细的研究。这篇文章最初发表在2001年UIAA的期刊上,作者:Gigi Signoretti, 英文译者: Anna Maria Torresan,Singingrock 转载了英译全文,网址:www.singingrock.com/en/tech_net/metodic_ropes_002.php

这里简要介绍一下文章的精华
(中文摘要从英文转译,译者:Jane Y. Howe)。
测试方法:UIAA 标准方法
标准绳(用于对照)
湿绳(水浸48小时,常温)
结冰的干绳(水浸48小时后,在-30度冰冻至少48小时,然后取出绳子测试)
湿过后晾干的绳子(水浸48小时后照一般情况晾干)
湿过后特别晾干的绳子(水浸48小时后甩干机甩干,再在真空中用化学干燥剂晾干)

实验结果
湿绳:耐冲击次数只有标准情况下的1/3,缓冲有效性大大降低!
结冰的干绳:耐冲击次数只有标准情况下的一半,而缓冲有效性略有提高!
湿过后晾干的绳子:恢复到标准情况
湿过后特别晾干的绳子:比标准情况略有下降

主要结论:
1. 湿绳的耐冲击性能下降到只有最初值的30%,不管是干绳,普通绳,新绳或旧绳。
2. 绳子浸水后伸长5%, 这可能是缓冲有效性降低5-10%的原因。
3. 水的负面效应十分显著,即使是泼上水或短时间浸泡影响也很大。
4. 水的负面效应主要是水影响了尼龙绳的晶体结构。
5. 水的负面效应是暂时的,一旦绳子干了之后则几乎完全恢复。
6. 取决于不同的晾干方法,绳子长度缩短4-8%,这可能是缓冲有效性略有下降的原因。
7. 浸湿后再结冰的绳子性能有所降低,但没有湿绳那么严重。

使用建议:
一根好的,正常服役中的绳子干的时候可以承受4-5次大系数冲击,但是湿的时候只能经受1-2次(比如在突遇一场阵雨,这种情况在野外经常遇到)。在冰雪活动时绳子结冰的情况比湿绳子要好一些。但气温很重要,一旦气温高于冰点,冰绳就马上变成了湿绳!

根本结论:常常更新你的绳子!


灰灰:请解释一下这句话...

原文:“结冰的干绳:耐冲击次数只有标准情况下的一半,而缓冲有效性略有提高!”其中“缓冲有效性略有提高”是针对谁而言?是湿绳还是干的绳子?为什么?
常规情况下,人们的感觉是:干的绳子延展性好,冻硬的绳子延展性极差。



janeclimber:材料和结构设计

动力绳一是要有高的抗拉强度(耐冲击次数),更重要的是要求有良好的减震特性(缓冲有效性)。动力绳是尼龙做的,一种高抗拉强度材料。而良好的减震特性则是通过特定的结构设计来达到。动力绳的由外皮和内芯构成。外皮耐磨,内芯是特殊编结成的,受力后总长能延伸~8%,以此吸收冲坠的能量(而不是人的脊椎)。所以在衡量动力绳的性能时必须同时测定其耐冲击次数和缓冲有效性。
(在家里做个实验,在鞋带的一头拴上个重物,鞋带的另一头握在手里,然后让重物自由落体,把鞋带换成橡皮筋,重复,你手上的感觉是两样的)
尼龙绳的材料是Nylon-6, 这是一种极性晶体高分子材料。晶体高分子材料并不是100%的晶体,其结晶程度一般只有70-90%,其余的是非晶态。尼龙的结晶程度(有序化程度)直接受温度和物理化学环境的影响。尼龙在常温下浸水之后有序化程度降低,抗拉强度下降。据UIAA测定,湿绳在常温下的表现相当于干绳在70-80度的情况。就好比是软绵绵的橡皮筋,不经拽。而在低温下的绳子由于低温限制了非晶态分子的自由运动,绳子可能“变脆”,但弹性不减,甚至有可能增加。

灰灰:一些细节

绳子在80公斤重物冲坠时的延展度:单绳小于8%,双绳小于10%。可承受坠落系数2的冲坠次数大于5次。
人在攀登坠落时,最易拉伤的部位是腰部两侧韧带,其次是肋骨8—12然后才是腰椎。所以再攀登之前必须活动一下腰部。



mh:8%,10%等指标是挂标准重量静态延长,不是冲坠时


Kristian:冲坠时可能达到20-30%。


janeclimbe:Q&A

“缓冲有效性略有提高”是针对谁而言?是湿绳还是干的绳子?
冰绳的缓冲有效性比干的绳子略有提高。

湿绳的缓冲有效性比干的绳子略有下降。

灰灰:这么说下次玩动力绳蹦极,应该在冬天,用冻的僵硬的绳子了?!?

janeclimber:大系数冲坠后冰绳温度升高,嘿嘿

能量转换,动能转变为热能。


mh:人们的感觉是很有局限的

人们掉下来的时间很短,在绳子结冰情况下掉下来次数也
不多。所以人们对绳子的感觉一般都和冲坠时绳子的情况
不相干。这个报告的的可靠性还是很好的(UIAA发表的),
其结果我一直想介绍到国内。现在由一个材料学家介绍是
再合适不过的了。
不过和通常情形一样,绳子强度对一般攀登关系不大,没有
人因为冲坠把现代绳子给拉断(断了的都是因为切割或擦)。
所以除非你确保一个80公斤的人,而那人有可能出现系数2
的冲坠,你不用太关心绳子是不是有水。我们关心的问题
主要是冲击力(绳子的弹性),报告中指出有水的绳子有
5-10%损失。
本贴由于2004年2月05日11:53:48在〖岩与酒〗发表.


灰灰:Dan Osman 去世于98年11月23日...

你忘了,Dan Osman 于98年11月23日,在高于1000英尺的登山绳冲坠中,由于登山绳断裂而死。
原因可能是:Osman 最后一跳的角度最终使连接绳子的绳结断裂。12月28日,200多个朋友在寒冷的、飘着雪的天气中悼念他。
(真的和气温没关系吗?)

mh:我原文包括“摩擦”时想的就是Osman例子

不知怎么“摩擦”的“摩”没打上去。
见BD的关于Osman器材失效报告。



Kristian:那仅仅是感觉而已

绳子冻硬以后,用手是拽不冻了,似乎“失去了弹性”;
事实是,冲坠的能量是转化成热量了,而结冰的绳子恰恰有助于“消化”这些热量。



裂缝:缓冲有效性降低5-10%是“大大降低”还是“略有下降”?


这在文中都提到过。

有没有直观的结论,比如湿绳不要承受冲坠系数超过??的冲坠,或是冲击力不超过??kn等等?


mh:我觉得是略有下降

但很少有发生系数2坠落,一般要是不用GRIGRI确保的话,
确保有一定的动态特性,比UIAA测试要冲击小些。而且
我要是到了80kg大概也爬不动什么了。所以我会记着这
个测试结果,别让什么因素都凑巧发生(比如背20公斤
的包在静态确保的情况下在湿透的绳子上发生系数2的
冲坠),但平时不担心。
注意这个测试中没有提较小坠落系数(0.1-1)下湿绳
冲力大了多少,对这我更想知道。

janeclimber:failure analysis on Dan Osman's rope

www.adventureguides.com.au/PDFs/Dan%20Osman%20Rope%20Failure%20Analysis.pdf


自由的风:把内容抄过来

Subject: My Dan Osman Rope Failure Analysis
From: Chris Harmston
Newsgroups: rec.climbing
Date: Fri, 16 Jul 1999 12:09:11 -0600
I think it is time I spoke up publicly. I have reviewed Dano's rope in
some detail. My findings and theory support those published by Kevin
Worrall in Climbing (No 183, March 1999, Pg 90).
This statement is mine personally and NOT that of Black Diamond Equipment!
This is obvious as you read below.
Irrelevant Background:
I am a Materials Engineer with BS degrees in Physics and Materials
Engineering and a ME in Materials Engineering (I nearly finished a PhD but
bailed once I learned I did not enjoy being a scientist any longer). I
know lots about atomic layer semiconductor crystal growth. I have been
the Quality Assurance Manager for Black Diamond Equipment for 6 years. My
primary responsibility is the testing and analysis of climbing equipment,
among other stuff. I have been involved in the ASTM climbing and
mountaineering standards development for the last 4 years. I investigate
all accidents I hear of involving equipment failure, whether they are BD's
or not. I review rec.climbing every day looking specifically for posts
related to accidents, gear, misuses of gear, issues about BD, etc. I, and
others at BD, go out of our way on this news group to publish information
above and beyond what is required by the standards that climbing gear is
designed to (see the recent lame thread on "Gear Safety" which I will not
respond to specifically. See Karl Lew's web site. Search under my name
on dejanews for examples). I do not post to this news group as a general
rule unless I think that posts from various people are specifically wrong
or misleading, as is the current case (in fact I try to avoid posting
because of commercial conflict of interest). I respond to individuals on
this news group constantly and my comments to these people come back into
this group (see the current RP thread on soldering cable fatigue). I
respond in detail to individuals who ask me questions, even when they do
not like what BD is about (see recent Camalot threads and failure analysis
associated with this thread).
Even more irrelevant background:
I have been rock climbing since 1981, and am primarily a trad climber. I
am a risk taker because I climb. Climbing IS dangerous and anyone who
thinks otherwise if fooling themselves. Anyone who climbs is a risk taker
in my opinion. I climb 5.12 on any rock type (that I have been on) and
style (except offwidth, so far) and have onsighted up to 12c/d. I climb
WI6 and possibly harder (ice is either hard or easy to me and is my
primary passion). I climb M8. I establish new rock, ice and mixed
routes ground up with and without bolts. I have no aid or alpine
experience. I weight 190 lbs and take upside-down 40 to 60 footers
without my helmet on. I have nearly killed myself several times due to
falling off 5.8. I am a climber, climbing eventually involves falling,
which may very well kill or maim me. Most people, including myself, would
consider me to be reckless because of how I climb. I climb for my own
reasons and no one else's. I don't care what people think about me in
general. Why Dano jumped off cliffs is his own personal choice that
nobody has a right to argue against, even if he had children in my
opinion. I certainly have no right to judge his reasons for doing what he
did. I respect Dano for pushing the limits way way beyond where they had
been previously. I met Dano twice but did not know him. I know many of
his friends.
Relevant Background:
My expertise in the analysis of broken climbing ropes is very limited.
This is due to the fact that climbing ropes very rarely break or cut in
actual use. The only previous experience I have with rope failure
analysis was that of Matt Baxter who died on El Cap several years ago when
his rope was cut by a flake after a carabiner had broken (see dejanews for
more info on this, send a Freedom of Information Request to the NPS-I
recommend you do it for the Dano accident as well and then you can have a
copy of my official report, or look at ANAM). I have also reviewed
several ropes with sheaths shredded due to the open back regular carabiner
gates in minor axis. This lack of experience could indicate that my
findings are incorrect or suspect.
I first became involved in Dano's accident when news of Dano's death
spread across this news group with the associated rumors that the NPS
might have purposely cut his rope. On December 9, 1998 I sent an email to
John Dill (YOSAR director) letting him know of these rumors on this news
group and offered my assistance in the analysis of Dano's equipment. John
responded back that Yosemite Law Enforcement (YLE) was investigating the
accident and that they had to finish their investigation before I might be
able to see the ropes (they too knew of the rumors of murder and were
investigating this as well I suspect). As you all should know Dan's ropes
stayed on the wall for over a month and YLE was unable to recover them.
Given the rumors of tampering by the NPS a climber took matters into his
own hands. He recovered the ropes and sent them directly to BD. As soon
as I received the ropes I contacted YLE because I was in possession of
stolen federal evidence from an active investigation. I was told to
return the ropes immediately and reveal the name of the person who sent me
the ropes. While on the phone with the lead investigator another phone
call came into BD from "someone within YLE" stating that the FBI would be
at BD to arrest me if I did not send the ropes back the next day. I was
freaking out to say the least. Meanwhile I looked at the rope in some
detail. It was melted through. It looked as if there were the
possibility that someone had hot cut the rope. When I called YLE back and
told them this they wanted me to conduct my full investigation and allowed
me to keep the rope for two weeks. No FBI showed up to haul me away.
Analysis:
I only saw the one section of rope that was cut down and contained the
failure point. I did not see the rigging, retrieval rope, or the section
that was attached to Dan directly.
Everything I did was visual examination. I did not untie any knot or
tamper with the rope in any way other than prying the knots to see inside.
With some insight from Doug Heinrich I concluded that the failure of Dan's
rope was not due to tensile overload or from being tampered with. I
strongly believe that Dan did miscalculate on his last jump. For some
reason he moved his jump site. In doing so he crossed the ropes (either
on the retrieval line or on the main jump line). When he jumped the first
knot above the one he was tied in with slid down a section of rope several
lengths up. The sheath was heavily melted and removed in several sections
on this upper part of the rope. The knot that slid down the rope was
melted in multiple locations and was melted nearly completely through,
deep inside the knot. This knot was not tight, yet others in the system
were (this is the one open question that is unresolved as far as I know).
It is my conclusion that Dan's rope was cut by his own rope sliding
against itself. Use of a magnifying glass indicated to me that the cut
surface was due to sliding action in one direction. There was no evidence
of hot cutting with a knife or other type of instrument. I conducted
further experiments in my lab to see if tensile overload could have caused
this failure. The samples I tested were significantly different in that
they were heavily frayed and tattered. My analysis of Dan's ropes in
general was that they were in great condition. There was no evidence to
me of damage due to previous falls, uv exposure, or weather. I would have
climbed on these ropes without any hesitation had they not been from this
accident. I do not believe that the condition of the ropes had anything
at all to do with the failure of the ropes. Nor do I believe that Dan's
basic shock absorbing setup was incorrect. Crossing the ropes was the
problem.
I was asked by YLE not to make my findings public until they had finished
their criminal investigation. They forced me to tell them who sent me the
rope and they pressed charges against this individual (I will have to live
with the fact that I was unable to keep this information confidential). I
still have not heard back from YLE about closure of this accident and
decided to make my findings public now due to the vast numbers of
misinformed posts relative to this subject. Maybe my analysis will stop
some of the useless bickering many of you are currently engaged in.
Conclusions:
What is to be learned from this accident? NEVER LET NYLON SLIDE AGAINST
NYLON! You should already know this.
I also know that Dano's rigging setup was reviewed by more than a couple
of technically competent people. I also know that he tested it multiple
times. I personally do not think that what Dan was doing (when done
properly as he had done on earlier jumps) was any more dangerous than
modern ice climbers doing hard thin ice routes (like in Maple Canyon and
elsewhere), in fact his setup was most likely safer in my personal
opinion. Dan's death was a tragedy and an accident.
Again, this summary is mine personally and not that of Black Diamond.
Chris Harmston (chrish@bdel.com).
Quality Assurance Manager. Materials Engineer BS, ME.
Black Diamond Equipment Ltd.
2084 East 3900 South, SLC, UT 84124 phone: 801-278-5552
DISCLAIMER: Unless otherwise indicated, this correspondence is personal
opinion and NOT an official statement of Black Diamond Equipment Ltd.


自由的风:他的结论是
不要让尼龙摩擦尼龙!

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