I am very confused with some of the results that I am getting using a static frequency analysis.
Frequency is calculated as the squareroot of stiffness devided by mass (as found here towards the bottom: http://en.wikipedia.org/wiki/Fundamental_frequency).
My question: when I run an analysis on the same beam but using a different material, say steel (ASTM 36) vs aluminum (6061 alloy) vs plastic (Nylon 101) I get almost the exact same results (difference of 27.61Hz vs 27.65Hz vs 27.48Hz). Can sombody explaine to me why I might get approximately the same result even though the masses are significantely different fro each of these 3 materials?
Thank you in advance!