PSN-L Email List Message

Subject: Re: Material Creep
From: S-T Morrissey sean@...........
Date: Sun, 12 Sep 1999 16:59:11 -0500 (CDT)


A bit of historical info:

For several decades the "zero-length" springs of long(ish) period
seismometers with large (gt. 5kg) masses were shipped with a stretcher
rod on the inside of the coil spring.  (These seismometers are too
large to be shipped with the mass and spring installed).
The length was the working length of the spring, and although it
was quite necessary just to get the spring installed, the main reason
was to pre-stress the spring to minimize creep after the instrument
was installed. The sensors still needed several days to stabilize.

Newer VBB leaf-spring designs are "factory aged" before final determination
of constants is done. Some are still notorious for needing a "settling
in" period of several days to weeks every time they are installed.

Regards,
Sean-Thomas

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Larry Cochrane <cochrane@..............>