The 14th IFToMM World Congress, Taipei, Taiwan, October 25-30, 2015
DOI Number: 10.6567/IFToMM.14TH.WC.OS4.023
High Speed Fracture Behavior of Glass Container by Underwater Shockwave
by Explosive and Large Current Impulse Energy
Seidai Honda1, a, Yoshifumi Ohbuchi1, Shinjiro Kawabe2, Hidetoshi Sakamoto1, b
1
2
Graduate School of Science and Technology, Kumamoto University, Kumamoto, Japan
Kumamoto Prefectural College of Technology, Kumamoto, Japan
a
[email protected] , [email protected]
Abstract: Recently, almost countries are promoting the
reproduction and the use of consumer goods；aluminum
cans, PET bottles, and so on. On the other hand, the
reproduction of the glass containers is not as active
excluding use as a returnable bottle, because the recycle
cost is high. The glass containers are fractured by the small
fragment called “Cullet” for reproduction. The cullet is
melted and molded again as glassware. The surface area is
enlarged by making the bottle cullet, and it is possible to
melt these efficiently. As a result, it becomes possible to
shorten the time to melt the glass bottle and reduce a
consumption of the fuel oil. The reasons with not active
recycling of the glass bottle are that large-scale crushing
equipment is required and it takes a lot of time and cost.
This study proposed a new recycling technique for
fracturing the glass bottle by using an underwater
shockwave by explosive and large electric pulse.
In the proposed technique, the bottle cleaning process
before the crushing can be skipped because this propose
system execute in water. As a result, the recycling cost can
be decreased.
Keywords: Electric pulse, Underwater shockwave,
Glass bottle, Glass cullet, Bottle recycle, High speed
fracture
I. Introduction
In this research, we carried out the crushing glass bottle
by underwater shockwave in order in order to examine the
optimal conditions for miniaturization.
We used two methods to generate underwater shockwave,
one method is generated by detonating explosives, and
another method is generated by detonating by large electric
pulse energy of metal wire.
In recent years, it has shifted to use of underwater shock
wave by electric pulse energy from the reason that the
electric pulse energy is safer than the explosive energy.
The purposes of this study are as follows.
(1) The underwater shockwave was visualized by the high
speed camera with a flashlight
(2) The shock wave pressures produced by the explosive
and the electric pulse were measured and the optimum
crushing conditions were discussed.
(3) In order to calculate the electric energy which was
turned on electricity in the metal wire, the electric current
and the voltage in the metal wire were measured.
Here, the “Cullet” generation process is visualized by
high speed camera methods. Furthermore, the pressure
variation under underwater shockwave which is caused by
these energies was measured.
II.
Shockwave propagation and fracture behavior
A.
Experiment by using an explosive
i.
Experimental method
The scheme of experimental apparatus is shown in Fig. 1.
In this experiment, a glass bottle and explosive were set at
a tank filled with water, and a glass bottle is crushed by the
underwater shockwave. The explosive used was PETN
(explosive rate: 6300 [m/s]), and electric detonator was
used as igniter. In order to visualize the bottle fracture
behaviors caused by underwater shockwave, the fracture
process was taken by using the High Speed Camera with a
flashlight.
The procedure of an experiment is shown below.
1. The inside of a tank is filled with water
2. Fix a glass bottle and an explosive
3. Put them into the tank
4. Ignition by the electric detonator
5. Collection of cullet
6. Drying of cullet
7. Classified by particle size
The specimen is shown in Fig. 2. The specimen is used
commercial beer bottle(500ml). Specification of beer
bottle is shown in Table 1.
Fig. 1 Scheme of experimental apparatus
ii.
Experimental conditions
Experimental conditions are shown in Table 2. Two kinds
of explosive shapes, string type (DF) and ball type (SEP)
were used. 200 [mm] explosive (DF) contains PETN
2.0 [g]. The distances of glass bottle and explosive were set
at 60 [mm] on all the conditions. In ball type explosive
(SEP), the effect of explosive set height was studied.
Table 1 Specification of beer bottle
Weight
Height(h)
Diameter(d)
upper part
81g
down part
125g
bottom part
63g
whole
475g
250mm
72mm
Table 2 Experimental conditions
A
B
C-1
C-2
Explosive
form
Explosive
quantity
Distance
[mm]
Inside of a
bottle
Installation
height of SEP
C-3
DF
DF
SEP
SEP
SEP
200
mm
200
mm
3.0g
3.0g
3.0g
60
60
60
60
60
Air
Water
Water
Water
Water
-
-
Middle
Top
bottom
B.
Experiment by using electric pulse
i.
Experimental method
The scheme of experimental apparatus is shown in Fig. 2.
In this experiment, a glass bottle and metal wire were set at
a tank filled with water. By high current pass through the
metal wire, the wire carries out instantaneous heating, and
explodes, therefore underwater shockwave occurs. And a
glass bottle is crushed by the underwater shockwave. The
fracture process is also visualized by the high speed camera
with a flashlight.
Table 3 Experimental conditions
D
E
F-1
Type of metal
Cu
Al
Al
Diameter [mm]
0.5
0.5
0.8
Distance [mm]
60
60
60
Inside of a bottle
ii.
Experimental conditions
Experimental conditions are shown in Table 3. In the case
of metal wire having low electrical resistivity can be
obtained higher current value. Then, it is thought that
strong underwater shockwave is produced. So, we chose
two types of metal as a metal wire, Aluminum (electrical
resistivity: 2.65 × 10-8 [Ωm]) and Copper (electrical
resistivity: 1.68 × 10-8 [Ωm]). And, in order to compare the
effect of metal wire’s diameter, we prepare three kinds of
aluminum wire having different diameter, 0.5 [mm],
0.8 [mm] and 1.0 [mm].
Air
Water
Water
C. Results and discussion
Fig. 3.1 (a) ~ (d) and Fig. 3.2 (a) ~ (d) show the framing
photographs of glass bottle fracture process by underwater
shockwave.
The cullet size distributions in each condition are shown
in Fig. 4.
Over 4.75 [mm] cullet of conditions A (string type
explosive, bottle inside is Air) is 50%, and that of
conditions B (string type explosive, and bottle inside is
water) is 80%. Comparing these cullet distributions, it is
found that the cullet sizes of inside-air bottle are smaller
than that of inside-water. This is explained by the fact
which the inside-air bottle is easy to deform compared with
inside-water bottle because while air is compressibility,
water is incompressibility. From the Fig. 3.1 (c) and 3.2 (c),
when underwater shock wave collide on bottle surface, the
bottle is crushed to pieces in inside–air bottle, but, the
fracture progresses in inside-water bottle with keeping the
bottle shape.
Comparing the condition B (string type explosive) and
conditions C-1 (ball type explosive), the weight
distribution rate of over 4.75 [mm] cullet in condition C is
less than that of B. In the case of ball type explosive, the
cullet size becomes to be smaller than that of string type
explosive. While the string type explosive gives the
uniform stress to the bottle surface, the ball type explosive
force propagates concentrically around the explosive.
Consequently, the cullet of bottle part close by the ball type
explosive become small.
(a)
Fig. 2 Scheme of experimental apparatus
Air
F-2
Al
1.0
60
(c)
(b)
(d)
Fig. 3.1 Fracture process by explosive (condition A)
(a) 67μs, (b) 122μs, (c) 2980μs and (d) 22516μs
(a)
(c)
fracture behavior for a while from the shockwave
generated, furthermore, after light became weaker, it was
too dark to observe the process of destruction.
The cullet size distributions in each condition are shown
in Fig. 6.
(b)
(d)
Fig. 6 Distributions of cullet size
Fig. 3.2 fracture process by explosive (condition B)
(a) 51μs, (b) 134μs, (c) 2937μs and (d) 22501μs
Fig. 4 Distributions of cullet size
Fig. 5 (a) ~ (d) shows the time-lapse photographs of glass
bottle fracture process by underwater shockwave.
(a)
(c)
(b)
(d)
Fig.5 Recording results (condition F - 1)
(a) 0μs, (b) 5562μs, (c) 8127μs and (d) 21114μs
In the case of aluminum, it was not able to be observed
fracture behavior for a while from the shockwave
generated, because strong light was emitted when high
current was impressed. Then, we make aperture of camera
narrow at the condition F-2, but, we also couldn’t observe
Comparing the condition D (Copper) and conditions E
(Aluminum), Over 4.75 [mm] cullet of conditions D is
90%, and that of conditions E is 80%. Metal wire having
low electrical resistivity can be obtained higher current
value, but, cullet sizes of the case of aluminum are smaller
than that of copper. It is thought that this result is due to the
thermite reaction of aluminum and water.
Comparing the condition F-1 (Diameter is 0.8 [mm]) and,
F-2 (Diameter is 1.0 [mm]), the weight distribution rate of
over 4.75 [mm] cullet in condition F-2 is less than that of
F-1.
III. Measurement of underwater shockwave pressure
A. Underwater shockwave by an explosive
i.
Experimental method
In this experiment, the pressure sensor and the explosive
were set in the pressure container which was filled with
water shown in Fig. 7. The explosive used was PETN, and
electric detonator was used as igniter.
First, the pressure container is filled with water. Next, a
pressure sensor and an explosive are set in the support
frame. The support frame is stored in the pressure
container.
In order to measure underwater shockwave pressure, one
tourmaline sensor was used. When the tourmaline receives
pressure, the voltage is generated by piezoelectric effect.
By measuring this voltage with an oscilloscope, the
underwater shock wave pressure can be obtained.
ii.
Experimental conditions
In this experiment, the shape and quantity of explosive
were shown in Table 4 and the distance between the
pressure sensor and the explosive was changed as shown in
Table 5.
Shape
String type
Table 4 Explosive conditions
Explosive
Explosive
length
Quantity
200 [mm]
2.0 [g]
Blasting
depth
1000 [mm]
[mm] distance between the explosive and the sensor,
respectively.
20
pressure (MPa)
distance
350mm
500mm
650mm
800mm
10
0
0
Fig. 7 Experimental equipment (explosive)
1400
B. Underwater shockwave by a high current pulse
i.
Experimental method
The frame of which a metallic wire and the pressure
sensor are set is stored in the small tank filled with the
water shown in Fig. 8. After that the electrobe is connected
and the high power current discharged to the metal wire.
The underwater shockwave pressure and the actually
discharged current are measured. The pressure sensor used
the same sensor as the experiment of the explosive.
1500
The result of the underwater shock wave by the electric
pulse is shown in Fig. 10. Fig. 10 (a) and (b) show the
result of the 0.5 [mm] and 0.8 [mm] diameter in metal wire,
respectively. In the case of the 1.0 [mm] diameter in metal
wire, since an intense noise occurred when the electric
current discharged, it was not able to measure. Comparing
the pressure by explosive and electric pulse at the
350 [mm] distance, the pressure 15~18 [MPa] was
obtained.
30
Aluminium 0.5mm
(a)
pressure (MPa)
350
Table 5 Experimental conditions (explosive)
Distance between explosive and sensor [mm]
500
650
800
950
1100
1250
500
1000
time (μs)
Fig. 9 Effect of distance (explosive)
distance
250mm
350mm
450mm
20
10
0
0
100
200 300 400
time (μs)
500
600
30
Fig. 8 Experimental equipment (electric pulse)
ii.
Experimental conditions
The kind and length of the metal wire were same. The
distance from the pressure sensor to the wire and the
diameter of metal wire are shown in Table 6. The kind of
metal wire was aluminum.
Table 6 Experimental conditions (electric pulse)
Diameter of metal wire [mm]
0.5
0.8
1.0
Distance metal wire – sensor [mm]
250
350
450
C. Results and discussion
The result of the underwater shock wave by an explosive
is shown in Fig. 9. Fig. 9 shows the result at the 350-800
pressure (MPa)
(b)
Aluminium 0.8mm
distance
250mm
350mm
450mm
20
10
0
0
100
200 300 400
time (μs)
500
600
Fig. 10 Effect of distance (electric pulse)
The detonation velocity and the effective shock wave
impulse were calculated from these results. Each result
is shown in Fig. 11 and Fig. 12, respectively. The effective
shockwave impulse was calculated from time to receive the
pressure of 3.5 [MPa] or more. The pressure 3.5 [MPa] is
allowable crushing stress of glass bottle. Each result of the
detonation velocity is about 1500 [m/s]. However the
effective shockwave impulse turned out that the value of
detonation velocity (m/s)
the electric pulse is approximately a half compared with
the explosive.
was 5 [kΩ]. And this experiment was carried out in the air.
2000
ii.
Experimental conditions
Experimental conditions were shown in Table 7. In this
experiment, there were six conditions (a) ~ (f): 2 kinds of
metal wire, 4 lengths and 3 diameters of the metal wire
were used.
1000
Table 7 Experimental conditions
Metal wire
Aluminium 0.5mm
Diameter
[mm]
200
0.5
0.8
1.0
100
300
200
0.5
Aluminium 0.8mm
(a)
(b)
(c)
(d)
(e)
(f)
PETN 250mm
0
0
200
400
distance (mm)
600
Fig. 11 Detonation velocity
3
Aluminium 0.5mm
impulse (N・s)
Length
[mm]
Al
Cu
0.5
Aluminium 0.8mm
2
PETN 250mm
1
0
0
200
400
distance (mm)
600
Fig. 12 Effective shockwave impulse
IV. Measurement of high electric voltage and current
i.
Experimental method
The condenser bank is equipped with a Rogowskii coil
and the electric current in the metal wire was measured by
it. A voltage divider was turned out to measure the voltage
which applied with the metal wire. A schematic diagram of
the voltage divider was shown in Fig. 13.
Fig. 13 Electric device
It is expected that the maximum voltage applied with the
metal wire is approximately 40 [kV]. Thereby, the values
of two resistances were calculated by the Ohm’s law. One
resistance“R1”was 50 [MΩ] and the other resistance “ R2 ”
iii.
Results and discussions
A part of the results are shown in Fig. 14: the
experimental conditions were (a), (b), (c) and (f).
In the case of diameter of 0.5 [mm], the electric energy
was measured twice not depended on Al or Cu.
And larger electric energy was obtained by the metal wire
of Al than Cu.
And more, larger electric energy was obtained by the
diameter of 0.8 [mm] than 0.5 [mm]. But smaller electric
energy was obtained by the diameter of 1.0 [mm] than 0.8
[mm]
V.
Conclusions
The shock wave propagation, glass fracture behaviors by
shockwave and shockwave pressure change produced by
the explosive and the electric pulse energy were observed
and measured. By these behaviors of the shockwave
propagation and pressure change, the optimum crushing
conditions (“Cullet” generation system) for glass container
recycling was discussed. The results obtained are as
follows.
(1) The appearance of the shock wave propagation wave
and glass containers fracture behaviors were clarified by
taking the high-speed photograph and high-speed video
system.
(2) The cullet size distributions depend on various
conditions such as the bottle inside conditions, distance
from the explosive to the glass bottle, explosive shapes and
explosive setting positions, etc.
(3) The difference of the shock wave impulse characteristic
between the explosive and the electric pulse is considered
as one of the major factors which cannot make small cullet
by using the electric pulse.
(4) The difference of the shock wave impulse
characteristic between the explosive and the electric pulse
is considered as one of the major factors which cannot
make small cullet by using the electric pulse.
(5) In the case of electric pulse, larger electric energy was
obtained by the diameter of 0.8 mm than 0.5 mm. But
smaller electric energy was obtained by the diameter of 1.0
mm than 0.8 mm
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