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Message ID: 3246     Entry time: Mon Jul 19 16:11:17 2010
Author: Gopal 
Type: Update 
Category: Optic Stacks 
Subject: Eigenfrequency Analysis of Full Stack 

Expanding on the single-layer model, I added the second, third, and fourth layers to the stack in COMSOL. Eigenfrequency analysis run times increased exponentially as the model multiplied in complexity. The following images document the some of the important eigenfrequencies:


First Eigenmode: y-translational, 3.34 Hz:

Eigenfrequency_1_4Stacks.png


Second Eigenmode: x-translational, 3.39 Hz:

Eigenfrequency_2_4Stacks.png


Third Eigenmode: z-rotational, 3.88 Hz:

 Eigenfrequency_3_4Stacks.png


Sixth Eigenmode: z-translational, 8.55 Hz:

Eigenfrequency_6_4Stacks.png


As expected, the eigenfrequencies are generally lower, but still in the same range, as the single-layer model, because of greater mass but constant weight-per-spring distribution.

Next Steps:

1) Extend a single stack to the full stack system, which consists of three stacks like this. Perform similar eigenmode analysis.

2) Analyze the mirror suspension system and incorporate a similar pendulum on the top plate.

3) Make transfer function measurements between seismic and mirror motions.

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