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Unformatted text preview: Fixed-Fixed Beam Harmonic Analysis Workshop Harmonic Analysis Workshop …Fixed-Fixed Beam Description: Workshop Supplement DYNAMICS DYNAMICS Determine the harmonic response of a steel beam carrying two rotating machines which exert a maximum force of 70 Ib at operating speeds of 300 to 1800 rpm. The beam, 10 feet long, is fully fixed at both ends and the machines are mounted at its “one-third” point. Assume a damping ratio of 2%. November 3, 2003 Inventory #001969 W4-2 Harmonic Analysis Workshop …Fixed-Fixed Beam Instructions 1. Create the beam model. 2. Specify harmonic analysis (full method). Workshop Supplement DYNAMICS DYNAMICS 3. Fix the two end of the beam and apply the two in-phase harmonic forces of FY=70Ibs each at the 40-inch and 80-inch points along the beam. 4. Specify a damping ratio of 0.02(i.e. 2%). Solution> Load Step Opts > Time/Frequenc > Damping 5. Specify 25 solutions between 5 and 30 Hz(300-1800 rpm). Solution> Load Step Opts > Time/Frequenc > Freq and Substps… 6. Obtain the harmonic solution. 7. In Time history post processor plot UY displacement versus frequency for the two nodes at which the forces were applied. 8. Find the critical frequency and phase angle. November 3, 2003 Inventory #001969 W4-3 Harmonic Analysis Workshop …Fixed-Fixed Beam Workshop Supplement DYNAMICS DYNAMICS 9. In General Post process review the deformed shape of the beam at the critical frequency and phase angle. 1. Find the load step and substep for the critical frequency: General Postproc> Result Summary 2. Issue the HRCPLX command to read in the results at the critical frequency and phase angle: HRCPLX,1,4,-25.3743 November 3, 2003 Inventory #001969 W4-4 Harmonic Analysis Workshop …Fixed-Fixed Beam 9. (continue). 3. Plot the UY displacement: Workshop Supplement November 3, 2003 Inventory #001969 W4-5 DYNAMICS DYNAMICS ...
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28 beamí•˜ëª¨ë‹‰ì‘ë‹µ[1]

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