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Periodic beam structures

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Periodic beam structures

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  1. An investigation of a periodic structure to suppress the transmission of energy in an elastic tube, and experimental 6 DOF techniques to detect itOle Holst-Jensen1*, Sergey Sorokin et al21Minus10dBStokrosevej 29, 8330 Beder, Denmarkole.holst@minus10db.dk2Department of Mechanical Engineering, Aalborg UniversityPontoppidanstraede 101, Aalborg East, DK 9220, Denmarksvs@ime.aau.dk

  2. Periodic beam structures • Organisation: Makunet • Machine acoustic network • Major Danish industrial partners • Institute of Mechanical Engineering at Aalborg University Denmark • Purpose of this project • Use periodic structures to control pipe vibration in pipes and plates • Develop engineering tools for the design of periodic structures • Theoretical optimisation tool • Measurement tool • Background • Experimental setups • Pipe with highly damped termination • Beam with reflecting termination • Theory • Results with damped termination • 6 degree of freedom experimental technique • Application to beam with reflecting termination • Conclusion

  3. Transmission control

  4. Background Red: Motor spectrum Blue: impact spectrum Varying speed drive Operating range: 20 to 60 Hz shaftspeed Example: 38 Hz

  5. Tube ø 34 / 27, steel Length: 4000 mm Blocks: 75 x 75 mm h: 220 mm Block weight: 4000 g Damping stiffening: 19 x 19 mm Pipe with highly damped termination

  6. Pipe with highly damped terminationEffect of damping Undamped Damped

  7. Beam with reflecting termination Måling og analyse i 6 frihedsgrader

  8. Theory: Boundary equations

  9. Experimental Insertion Loss 3, 2 and 1 blocks 3: Heavy, light, medium blocks

  10. Comparison Insertion Loss

  11. Background6 Degree of freedom measurement • Simple method of separating modes • Torsional modes are often not recognized in simple measurements • Evolution of vibration measurements: • One axis • Three axis • 6 axis • Mulitchannel digtal techniques makes realtime 6 DOF possible

  12. Test setup • Comparison of plainbeam and beamwiththreeblocks • Two types of blocks • Aluminium 10 x 10 x 100mm beamwiththread • Block1: 47 g weighton top • Block 5: 156 g weightontop • Axes • X – verticalxx – bendinghorizontal plane • Y – horizontalyy-bendingvertical plane • Z – longitudinalzz –torsion longitudinal

  13. Setup7: 0 blocks- 3 block1 47 g

  14. Setup7: 0 bloks - 3 block5 203 g

  15. Conclusions • Pipe with highly damped termination • Eigenfrequencies match theory • Insertion loss show agreement between theory and experiment with stop bands, when using energy and acceleration levels • Beam with reflecting termination • 6 DOF measurement on rigid body termination can separate modes • Eigenmodes are suppressed • Further investigations: • Parametric studies • Application to industrial setting

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