stretching wire

[John Delacour]

At 00:13 -0500 20/4/08, kurt baxter wrote:

>>I'd like to see what the guy has to say about the direct case of 
>>Êpiano wire well under the yield limit and kept at ambient 
>>temperatures and see what he has to back it all up with.
>
>
>Agreed. From the actual scientific article: ...

The following link lets you download a full pdf article that deals 
with "relaxation" in patented wire, which seems to be what we are 
talking about.  Certainly the term is descriptive of what I have in 
mind.

<http://www.journalarchive.jst.go.jp/english/jnlabstract_en.php?cdjournal=isijinternational1966&cdvol=26&noissue=12&startpage=1059>

The relaxation test is carried out at 20 degrees celsius over a 
period of 10 hours with an initial load of 70% of tensile strength, 
the sort of tensions we use in the piano.

Here is an extract from the paper:

"Figure 7 shows the relaxation curves of Si-Mn and
plain high-carbon galvanized steel wires. The relaxa-
tion value of Si-Mn steel wire was 1.2 % in 10 h
which is one-third of that of the other, which was
3.6 %. This is presumably because in the case of
Si-Mn steel wire, lattice strain increases due to the
solid solution hardening of Si in ferrite and makes
dislocation movement difficult. According to S.
Taira, there is a proportional relationship between
the relaxation and the creep characteristics of high-
carbon steel wires, and decrease in the value of relaxa-
tion can be attributed to decrease in creep strain.
Therefore, in applications such as those in the con-
struction of suspension bridges, in which a low creep
characteristic is required, it is advantageous to use
high-strength steel wire strengthened by addition of
a high Si content..."

JD


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