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Characterization of C Pod

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1 Characterization of C Pod
Measurement Report on Vibration Isolation of C Pod Department of Physics, University of British Columbia, Vancouver PI: Dr Yan Pennec Student: Vincent Wong

2 SolidWorks model – C Pod
Suspended by 4 isolators (Model #) Volume: m3 Density: kg/m3 Mass: E4 kg % Concrete: 94.5% Young Modulus: 3.94E10N/m2 Poisson Ratio: 0.17

3 Concrete Block Properties Deduction from Threshold Pressure
Isolator Dimension Chamber Diameter: 15.7in Total Effective Area: in2 * 4isolators Threshold Pressure: 89psi Threshold Supporting Force: lbf Equivalent to N Measured Mass: kg Measured Density: kg/m3

4 Experiment Protocol - Slab Excitation
Reference Accelerometer Data Point

5 Slab Excitation – Acceleration Amplitude z-axis damping for the slab
Time Constant ~100ms y = A1*exp(-x/t1) + y0 y0= ms-2 A1= ms-2 t1= s

6 Slab Excitation – Average PSD in z-axis(1-1kHz)

7 Slab Excitation – Average PSD in z-axis (200-400Hz)
Twisting 1 Bending 1 Bending 2 Flapping support

8 Modal Resonance - Twisting Mode
Measured 228Hz FEA 233 Hz (1st mode in FEA)

9 Modal Resonance - Bending Mode
Measured 289Hz FEA 283Hz (2nd mode in FEA)

10 Modal Resonance - Flapping Support Mode
Measured 338.5Hz FEA 340Hz (3rd mode in FEA)

11 Damping by Isolators – x-axis acceleration amplitude
Time Constant ~14.9s Natural Frequency ~1.02Hz y = A1*exp(-x/t1) + y0 y0= ms-2 A1= ms-2 t1= s

12 Damping by Isolators – y-axis acceleration amplitude
Time Constant ~11.5s Natural Frequency ~1.02Hz y = A1*exp(-x/t1) + y0 y0= ms-2 A1= ms-2 t1= s

13 Damping by Isolators – z-axis acceleration amplitude
Time Constant ~2.14s Natural Frequency ~1.4Hz y = A1*exp(-x/t1) + y0 y0= E-4 ms-2 A1= ms-2 t1= s

14 Transfer Function in z-axis - Isolators

15 Transfer Function in z-axis – Room Isolation

16 Seismic Vibration in z-axis – velocity PSD open room

17 Seismic Vibration in z-axis – velocity PSD closed room (1 hour run)

18 Sound Pressure Level – closed room

19 Sound Pressure Level – Excited
19Hz 38Hz 25Hz

20 Acoustic Resonance Assumption: speed of sound = 350m/s
Expected Resonance Mode: 3.5m -> ~47Hz 3.8m -> ~43Hz 4.8m -> ~36.5Hz 5.2m -> ~31.7Hz 5.9m -> ~29.6Hz 6.1m -> ~27Hz 7.1m -> ~24.6Hz


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