Interesting and Insightful COSMOSWorks answers, Part I

We here at Graphics Systems regularly come across COSMOSWorks related questions whether it be during training or everyday Technical Support.  So for the next couple of posts, I will attempt to provide Interesting and Insightful answers to a few of the more interesting questions.

We'll begin with three questions related to Frequency Studies.  Frequency studies provide the user with the natural frequency response of a system and with these frequencies, engineers can design around them... hopefully avoiding the dreaded RESONANCE FREQUENCY with such components as motors.

1. Which equations to the Direct Sparse and FFEPlus solvers use to find eigenvalues?  The answer also applies to Bucking studies (but that's another post). Both solvers use the following equation to calculate resultant structural stiffness:

   [K_E + λ_iK_S][φ_i] = 0; K's of E is the elastic stiffness matrix, K's of S is the stress stiffness matrix, lambda of i are eigenvalues and phi of i are your eigenvectors.

2. Are modal participation values calculated? Mass participation factors can be retrieved from the study by right-mouse clicking the Results folder for the study in question.

3. Are the units for gravity calculated in "G's" or m/v? With all studies, unless gravity is a boundary condition set-up by the analyst, gravity is not calculated in. Should gravity be included as a boundary condition, the system of units to describe gravity are the same for any other load or restrain: English, Metric, SI. (I prefer m/s^2 personally) [on the first pass, I had the wrong units; sorry, brain fart]

Thanks for the questions, folks. And keep them coming.  In the next few posts, I'll deal more with Buckling, some items pertaining to mesh quality, and even one or two questions regarding "soft springs."  Stay tuned!