behavior of ultrasonic wave propagation...
TRANSCRIPT
BEHAVIOR OF ULTRASONIC WAVE PROPAGATION IN PRESENCE OF HOLES ON PEQUIÁ (Aspidosperma
desmanthum) WOOD
• Authors: Drª Raquel Gonçalves;
• Drº. Domingos G. P. Cerri;
• Msc. Chiara B. Secco;
• Fernando A. F. Batista,
•
17th International Nondestructive Testing and Evaluation of
Wood Symposium
September 14th-16th, 2011
Even within the Brazilian context, in which the oldest university is 90 years old,
Unicamp can be considered a young institution (only 43 years old) but has
already a strong tradition in education, in research and services to society.
School of
Agricultural
Engineering
(FEAGRI)
-31 thousand
undergraduate students
(66 courses)
-16 thousand graduate
students (135 Programs)
- 10% of the master’s
and doctoral thesis in
the country.
-1.733 faculty members
-15 % of all research
done in Brazilian
universities
NDT Research Group
Researches and Students Group
• 1 associated professor,
• 1 assistant professor,
• 2 postdoctoral,
• 2 PhD students,
• 2 master students,
• 1 technique
• 12 undergraduate students.
INTRODUCTION
One of reasons for the low yield of a tree is the presence of hole. Some
species of commercial or strategic value present holes caused by the
action of fungi and bacteria or by natural causes. If this hollow is large it is
economically unfeasible to extract timber for the timber sector.
INTRODUCTION
One the other hand some companies in the business of furniture
designs are interested in the use of parts of trunk that have the
hollow
OBJECTIVE
Evaluate the change in velocity of ultrasound wave propagation in the presence of holes of known size and
determining a model describing this behavior to generate images.
• Wood piece - Pequiá (Aspidosperma desmanthum);
MATERIAL
• Wood piece - Pequiá (Aspidosperma desmanthum);
MATERIAL
Density is approximately:
•790 kg m-3 in the air dry condition (humidity around 13%)
•1210 kg m-3 in the saturated condition.
• Wood piece - Pequiá (Aspidosperma desmanthum);
MATERIAL
Evaluate the change in velocity
of ultrasound wave propagation
in the presence of holes and
determining a model describing
this behavior.
390 mm x 390 mm x 50 mm
Healthy and massive
• Wood piece - Pequiá (Aspidosperma desmanthum);
• Ultrasound equipment (USLab, AGRICEF, Brasil);
• Exponential Transducer of 45 kHz;
MATERIAL
Scheme of the production of artificial circular hole with the percentage increase in size as compared to the healthy and massive part
METHODOLOGY
30 mm
• CNC machine – SENAI - Itatiba-SP;
• Circular holes: 5%, 10%, 15%, 20%, 25%, 35%, ande 55%
METHODOLOGY
RESULTS AND DISCUSSION
0,0
100,0
200,0
300,0
400,0
500,0
600,0
0 10 20 30 40 50 60
Tim
e o
f w
ave
pro
pag
atio
n
(s)
Hole percentages (%)
X6
X5
X7
X4
X8
Time behavior as a function of the position of measurement in X direction for the hole.
RESULTS AND DISCUSSION
RESULTS AND DISCUSSION
0,0
100,0
200,0
300,0
400,0
500,0
600,0
0 10 20 30 40 50 60
Tim
e o
f w
ave
pro
pag
atio
n
(s)
Hole percentages (%)
X6
X5
X7
X4
X8
The more displaced from the center of the hollow, the smaller the increased of wave
travel, because there is a shorter way to deviate from the hollow
RESULTS AND DISCUSSION
In order to verify if the wave changes in its course when faced with the presence of hollow, for each strip of the grid and for each percentage increase in the hole, it was measured the expected length path wave, which corresponds to the smallest perimeter around the produced hollow. This calculation was performed using photos taken at the time of the test, which were reproduced in the AutoCad, and using this software, the lengths path around the hollow could be determined accurately.
Expected wave path length (X6)
In order to verify if the wave changes in its
course when faced with the presence of hollow,
for each strip of the grid and for each percentage
increase in the hole, it was measured the
expected length path wave, which corresponds to
the smallest perimeter around the produced
hollow. This calculation was performed using
photos taken at the time of the test, which were
reproduced in the AutoCad, and using this
software, the lengths path around the hollow
could be determined accurately.
Hollow
RESULTS AND DISCUSSION
Hole (%) Velocity (m.s-1) Path Length (mm)
0 1670 390
5 1604 426
10 1600 427
15 1480 447
20 1470 449
25 1470 449
35 1240 486
55 762 563
Velocity and path length calculated for the center strip of the grid (X6, Y6).
120% 70%
The velocity variations were 120% and path length 70%
RESULTS AND DISCUSSION
Hole (%) Velocity (m.s-1) Path Length (mm)
0 1670 390
5 1604 426
10 1600 427
15 1480 447
20 1470 449
25 1470 449
35 1240 486
55 762 563
The increase of the time wave propagation in the presence of the hollow in
the piece were caused by the change of wave path and not by its passage
through the inner void produced
RESULTS AND DISCUSSION
Correlations between the variation of velocity of ultrasonic wave propagation
and the path of ultrasonic wave for the wood of Pequiá
Path = -0.1619*Vel + 686.52 R = 0.89
300
350
400
450
500
550
600
650
500 1000 1500 2000
Pat
h o
f u
ltra
son
ic w
ave
s p
rop
agat
ion
(m
m)
Velocity of ultrasonic waves propagation (m.s-1)
• Wood piece - Pequiá (Aspidosperma desmanthum);
Based a model generate
images
Ø 670 mm and 100 mm thickness
RESULTS AND DISCUSSION
RESULTS AND DISCUSSION
30 mm
• CNC machine – SENAI - Itatiba-SP;
• Circular holes: 5%, 15%, 25%, 35%, 45%, 55%, 65%, 75%, 85%
and 90%.
RESULTS AND DISCUSSION
METHODOLOGY
RESULTS AND DISCUSSION
0 %
5 %
Pequiá Photo Generated image
Pequiá Photo Generated image
RESULTS AND DISCUSSION
15 %
25 %
Pequiá Photo Generated image
Pequiá Photo Generated image
RESULTS AND DISCUSSION
35 %
45 %
Pequiá Photo Generated image
Pequiá Photo Generated image
RESULTS AND DISCUSSION
55 %
65 %
Pequiá Photo Generated image
Pequiá Photo Generated image
RESULTS AND DISCUSSION
75 %
85 %
Pequiá Photo Generated image
Pequiá Photo Generated image
Pequiá Photo Generated image
2 1
RESULTS AND DISCUSSION
90 %
Despite some distortion in the hollow shape represented by the image, and
also in the case of the pieces with 85% and 90% of hollow the image
indicate the advancing of hollow to the edges, in general the image
represents adequately the existence, size and positioning the hollow.
NEXT STEPS
In the continuity of this research the diffraction grid also was used
(not focused in this presentation), which presented better results,
showing more accuracy to detect the small holes, and less
interferences distortions in the hollow shape and in the edges.
• The results showed that the velocity of ultrasound wave
propagation is affected by the presence of hollow and, the
velocity reduction is caused by the change of the wave path,
which tends to shift the void and go to the material.
• The variation of velocity with the increase of the dimension
of the hollow can be represented by a linear model.
• Although the generated images present some failures,
caused by interference of the method used by the adopted
software, the actual condition of the piece was adequately
represented. This result indicating the possibility of using the
Brazilian equipment and the simple methodology of
ultrasound wave propagation in this kind of evaluation.
CONCLUSIONS
ACKNOWLEDGMENTS