1. A N INVESTIGATION OF A PERIODIC STRUCTURE TO SUPPRESS THE TRANSMISSION OF ENERGY IN AN ELASTIC TUBE, AND EXPERIMENTAL 6 DOF TECHNIQUES TO DETECT IT Ole Holst-Jensen 1*, Sergey Sorokin et al 2 1 Minus10dB Stokrosevej 29, 8330 Beder, Denmark ole.holst@minus10db.dk 2 Department of Mechanical Engineering, Aalborg University Pontoppidanstraede 101, Aalborg East, DK 9220, Denmark svs@ime.aau.dk RASD July 20101

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 RASD July 20102 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 RASD July 20103

4. Background RASD July 20104 Red: Motor spectrum Blue: impact spectrum Varying speed drive Operating range: 20 to 60 Hz shaftspeed Example: 38 Hz

5. Pipe with highly damped termination RASD July 20105 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

6. RASD July 20106 Pipe with highly damped termination Effect of damping Undamped Damped

7. Beam with reflecting termination RASD July 20107 Måling og analyse i 6 frihedsgrader

8. Theory: Boundary equations RASD July 20108

9. Experimental Insertion Loss RASD July 20109 3, 2 and 1 blocks3: Heavy, light, medium blocks

10. RASD July 201010 Comparison Insertion Loss

11. Background 6 Degree of freedom measurement RASD July 201011 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 RASD July 201012 Comparison of plain beam and beam with three blocks Two types of blocks – Aluminium 10 x 10 x 100mm beam with thread – Block 1: 47 g weight on top – Block 5: 156 g weight on top Axes – X – verticalxx – bending horizontal plane – Y – horizontalyy- bending vertical plane – Z – longitudinalzz –torsion longitudinal

13. RASD July 2010 13 Setup7: 0 blocks - 3 block1 47 g

14. RASD July 2010 14 Setup7: 0 bloks - 3 block5 203 g

15. RASD July 201015 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