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Rayleigh Damping

Question asked by 1-L5M1MV on Sep 22, 2009
Latest reply on Sep 25, 2009 by Brian Zias

Using the ANSYS technical manual and checking through other sources, I've been able to come up with the equations used to determine the Rayleigh damping coefficients.  My problem is that I always seem to get a significantly larger alpha coefficient than beta when using the natural frequencies of my models.  The manual suggests that the alpha coefficient is uaully small enough to neglect, which makes me question my results.


I'm trying to figure out if maybe I'm using the wrong natural frequencies in my equations.  I assume that I should determine my upper bound of the range of natural frequencies based on mass participation, but I don't know where to draw the line.  Also, I'm not sure if changing the upper or lower bound will ever make alpha smaller than beta.


If anyone can shed some light on this subject for me it would be greatly appreciated.  If needed, I can provide a chart of natural frequencies and mass participation for a sample model.