Figure 891 two mass spring system problem sketch

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Unformatted text preview: se description is the same as that for VM86 except for the assumption on damping. Assume that all damping is in the form of equivalent structural damping and there is no element damping. Figure 87.1 Structural Damping Problem Sketch Analysis Assumptions and Modeling Notes The structural damping factor is γ = 2 ξ ω/ωn where ξ is the damping ratio and is equal to c/2m ωn. Therefore, γ = c/(m ωn) = 6/(0.5 x 20) = 0.6 since ω = ωn. The frequency-dependent multiplier β is calculated as β = 2 ξ/ωn = γ/ω = 0.6/20 = 0.03 seconds. The node locations are arbitrarily selected. One master degree of freedom (MDOF) is selected at the mass in the force direction. Results Comparison Target Amp, in ANSYS Ratio 0.083333 0.083333 1.000 ANSYS Verification Manual . ANSYS Release 9.0 . 002114 . © SAS IP, Inc. 1–198 VM87 Target angle, deg ANSYS Ratio -90.000 -90.000 1.000 ANSYS Verification Manual . ANSYS Release 9.0 . 002114 . © SAS IP, Inc. 1–199 VM88: Response of an Eccentric Weight Ex...
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