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Hi Dan, Yes it was me that instructed Chuck not to spend time on this right now. As we discussed earlier, the most effective way to find the natural frequencies of the cathode plane would be to perform a test using the equipment that you said you have access to. This would involve setting up an acoustic driver at varying frequencies and observing the vibration of the cathode. One of the unknowns is the tension in the plane. This will directly affect the natural frequencies. A hand calculation can give some ballpark estimates of the natural frequency and subsequent modes. This again depends on the tension. Assuming the tension is very low (on the order of a 1 lb/foot of circumference), the1st natural frequency mode is in the single digits hz. If we want to get a better feel for the tension, a sag measurement under gravity alone can be made and the tension could be backed out. In my opinion, before any finite element model can be effective, these measurements should be made. Also, these measurement will be more accurate than an FEA model. I do not believe the natural frequencies will be a problem, and if it turns out to be, it can be easily solved. The first order frequencies we would need to avoid is 60hz and 120 hz. Cheers, Tim Chuck Hutton wrote: I have been instructed not to worry about this right now and to focus on more pressing issues. |
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