Experience It Yourself: An Introduction to Problem-Based Learning
Problem 1 Brazil Problem 1 – Invent Yourself that you can...
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BrazilProblem 1 – Invent Yourself
Team of BrazilBRAZILIYPT 2018
Problem 1
Invent YourselfReporter: Victor Cortez
Construct a simple seismograph that amplifies a local disturbance by mechanical, optical or electrical methods. Determine the typical response curve of your device and investigate the parameters of the damping constant. What is the maximum amplification that you can achieve?
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BrazilProblem 1 – Invent Yourself
CONTENTS
BrazilProblem 1 – Invent Yourself
1. Theoretical Introduction
Basic Concepts
The Seismograph
Theoretical Model
2. Experiments
Experimental Materials
Experimental Set-up
Experiments
3. Conclusion
Summary
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BrazilProblem 1 – Invent Yourself
Introduction The Seismograph Theoretical Model
Vibrations Amplification
Mechanical
Optical
Electrical
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BrazilProblem 1 – Invent Yourself
Introduction The Seismograph Theoretical Model
The Seismograph
D
d
Amplification Optical
ScreenLaser
Figure 1: Laser scheme.
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BrazilProblem 1 – Invent Yourself
Introduction The Seismograph Theoretical Model
D
d
Mirror
Laser
Screen
Figure 2: Scheme of an optical system with multiple mirrors.
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The Seismograph
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BrazilProblem 1 – Invent Yourself
Introduction The Seismograph Theoretical Model
D
d
MirrorLaser
AProjection
D
Screen
Mirror
Virtual Laser Image
Figure 3: Scheme of the optics of the problem.
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The Seismograph
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BrazilProblem 1 – Invent Yourself
Introduction The Seismograph Theoretical Model
F
Young’s Modulus
Figure 4: Damped mass-spring system.
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Theoretical Model
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BrazilProblem 1 – Invent Yourself
Introduction The Seismograph Theoretical Model 8
Theoretical Model:
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BrazilProblem 1 – Invent Yourself
Introduction The Seismograph Theoretical Model
Overdamped
Critically damped
UnderdampedTime
Po
siti
on
Underdamped
Critically Damped
Overdamped
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Theoretical Model
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BrazilProblem 1 – Invent Yourself
Introduction The Seismograph Theoretical Model
Figure 5: Function x(t) using the indicated parameters.
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Theoretical ModelA
mp
litu
de
(u.a
.)
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BrazilProblem 1 – Invent Yourself
Introduction The Seismograph Theoretical Model
General case:
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Theoretical Model
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BrazilProblem 1 – Invent Yourself
Introduction The Seismograph Theoretical Model
Damping Sensibility Response
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Theoretical Model
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BrazilProblem 1 – Invent Yourself
Experimental Materials Experimental Procedure Experiments
1 - Well polished mirrors held by stable supports;
2 - Powerful green laser beam;
3 - Stable supports;
4 - High frame rate camera (240 fps);
5 - White screen;
6 - Computer for data analysis.
Figure 6: Mirrors held by stable supports.
Figure 7: Seismograph.
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Experimental Materials
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BrazilProblem 1 – Invent Yourself
Experimental Materials Experimental Procedure Experiments
Analyze dataCause
perturbationsFilm the experiment
Place the cameraAlign the beamPlace the Mirrors
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Experimental Procedure
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BrazilProblem 1 – Invent Yourself
Experimental Materials Experimental Procedure Experiments
Processing
Figure 9: Laser projection over the screen.
Figure 8: Scheme for experimental set-up.
Mirrors
Screen
CameraLaser
15Figure 10: Typical signal.
Experimental Procedure
Time (s)
Rel
ativ
e p
osi
tio
n
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BrazilProblem 1 – Invent Yourself
Experimental Materials Experimental Procedure Experiments
Luminosity scale
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Experimental Procedure: Data Analysis
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BrazilProblem 1 – Invent Yourself
Experimental Materials Experimental Procedure Experiments
Figure 11: Seismograph response to random perturbations.
Time (s)
Rel
ativ
e p
osi
tio
n
Random vibrations captured through the Y axis.
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Experiment 1: Random vibrations
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BrazilProblem 1 – Invent Yourself
Experimental Materials Experimental Procedure Experiments
Controlled Vibration
C
2 Kg weight
Concrete table
h = 0.1m
Laser
D = 0.8 m
Measuring parameters
Stable support
Figure 12: Experimental scheme.
2 Kg
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Experiment 2: Controlled vibrations
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BrazilProblem 1 – Invent Yourself
Experimental Materials Experimental Procedure Experiments
Figure 13: Response curve to a controlled vibration.
Controlled vibrations captured through the X axis
Time (s)
Rel
ativ
e p
osi
tio
n
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Experiment 2: Controlled vibrations
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BrazilProblem 1 – Invent Yourself
Experimental Materials Experimental Procedure Experiments
Experimental
Theoretical
Rel
ativ
e p
osi
tio
n o
n t
he
X a
xis
Time (s)
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P wave:
S wave:
Experiment 2: Controlled vibrations
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BrazilProblem 1 – Invent Yourself
Experimental Materials Experimental Procedure Experiments
Controlled distance
C5 Kg Sandbag
Concrete table
h = 0.3m
Laser
D
Measurement of the decay
Stable support
Figure 14: Experiment scheme.
h = 0.5m
h = 0.7m
D = 1.00 mD = 2.00 mD = 3.00 mD = 4.00 m
Laser trajectory: 39.03 m
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Experiment 3: Controlled distances
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BrazilProblem 1 – Invent Yourself
Experimental Materials Experimental Procedure Experiments
Specific vibrations
C
ExperimentalTheoretical
Rel
ativ
e am
pli
tud
e o
n t
he
X a
xis
Distance (m)
Figure 15: Computational fitting for the experimental plot from 50cm launches.
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Experiment 3: Controlled distances
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BrazilProblem 1 – Invent Yourself
Experimental Materials Experimental Procedure Experiments
Laser
DC Motor
Frequency Generator Oscilloscope
Camera
Screen
C DFT
Response curve
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Experiment 4: Response curve
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BrazilProblem 1 – Invent Yourself
Experimental Materials Experimental Procedure Experiments
Frequency (Hz)
No
rmal
ized
res
po
nse
am
pli
tud
e
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Experiment 4: Response curve
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BrazilProblem 1 – Invent Yourself
Experimental Materials Experimental Procedure Experiments
Relative amplitude as a function of the laser’s physical path.
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Experiment 4: Controlled vibrations
[5]
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BrazilProblem 1 – Invent Yourself
Dd
MirrorLaser
Screen
Underdamped
Critically Damped
Overdamped
P wave
S wave
26
Summary: Theory
Time
Po
siti
on
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BrazilProblem 1 – Invent Yourself
ExperimentalTheoretical
Rel
ativ
e p
osi
tio
n o
n X
axi
s
Time (s)
Experimental
Theoretical
Rel
ativ
e am
pli
tud
e o
n t
he
X a
xis
Distance (m)
Mirrors
Screen
CameraLaser
Frequency (Hz)
Response Curve
No
rmal
ized
res
po
nse
am
pli
tud
e
27
Summary: Experiment
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BrazilProblem 1 – Invent Yourself
Bibliography
[1] Kim, Dong-Soo, and Jin-Sun Lee. “Propagation and Attenuation Characteristics of Various Ground Vibrations.” Soil Dynamics and Earthquake Engineering, vol. 19, no. 2, 2000, pp. 115–126, doi:10.1016/s0267-7261(00)00002-6.
[2] G. E. General Seismology. Lecture. Retrieved March 26, 2018, from https://www.youtube.com/watch?v=2wiV0Ow5oT0&t=1684s.
[3] H. Moysés Nussenzveig, Curso de Física Básica, vol. 2, Editora Edgard Blücher, LTDA (1999).
[4] Gutowski, T. G., & Dym, C. L. (1976). Propagation of ground vibration: A review. Journal of Sound and Vibration, 49(2), 179–193. https://doi.org/10.1016/0022-460x(76)90495-8
[5] Novotny, Oldrich(1999). Seismic Surface Waves, Lecture notes for post-graduate students [Pdf File]. Retrieved from http://geo.mff.cuni.cz/vyuka/Novotny-SeismicSurfaceWaves-ocr.pdf
[6] Romney, C. (1959). Amplitudes of seismic body waves from underground nuclear explosions. Journal of Geophysical Research, 64(10), 1489–1498. https://doi.org/10.1029/jz064i010p01489
Figure: Oleg Alexandrov, 2007
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BrazilProblem 1 – Invent Yourself
Thank you!
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BrazilProblem 1 – Invent Yourself
Appendix: Experiment 3 - Controlled distances
C C
C
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