LIGO Seminar

Crystalline and poly-crystalline material, such as metals, are usually
assumed to behave in a linear elastic manner when stressed below their
yield limit. When the stress approaches the critical point, such
systems are known to exhibit non linear behaviors. Beside the
deviation from a linear stress-strain relation, materials can respond
to varying external stressed in a discontinuous way, exhibiting
discreet release of energy. This crackling noise has been extensively
studied both experimentally and theoretically close to the critical
yield stress.
The Advanced LIGO suspension system contains a large number of parts
that are under time varying stress, even though far from the yield
point. In this seminar we'll describe how we are investigating
experimentally if the maraging steel used for the suspension
cantilever blades exhibits any non-linear behavior. Indeed, discrete
responses of the metal cantilevers might prove to be a limiting factor
for the detector final sensitivities, mainly due to non-linear
up-conversion of low frequency residual seismic motion to the
frequencies of interest for the gravitational wave observations.

We plan to broadcast these talks using TeamSpeak. Use a sub-channel of
"--- LIGO Lab---" , and is not password protected.