1aSA – On a Fire Extinguisher with Sound-wind for the Beginning Stage of Fire

Myung-Jin Bae, mjbae@ssu.ac.kr
Myung-Sook Kim, kimm@ssu.ac.kr
Soongil University, 369 Sangdo-ro, Dongjak-gu, 06978 Seoul Korea

Popular version of 1aSA “On a fire extinguisher using sound winds”
Presented 10:30 AM – 12:00 PM., November 28, 2016.
172nd ASA Meeting, Honolulu, U.S.A.
Click here to read the abstract

There are a variety of fire extinguishers available on the market with differing extinguishing methods, including powder-dispersers, fluid-dispersers, gas-dispersers and water-dispersers. There has been little advancement in the technology of fire extinguishers in the past 50 years. Yet, issues may arise when using any of these types of extinguishers during an emergency that hinder its smooth implementation. For example, powder, fluid, or gas can solidify and become stuck inside of containers; or batteries can discharge due to neglected management. This leaves a need for developing a new kind of fire extinguisher that will operated reliably at the beginning stage of fire without risk of faulting. The answer may be the sound fire extinguisher.

The sound fire extinguisher has been in development since the DAPRA, Defense Advanced Research Projects Agency of the United States, publicized the result of its project in 2012, suggesting that a fire can be put out by surrounding it with two large sound speakers. Speakers were enormously large in size then because they needed to create enough sound power to extinguish fire. As a follow-up, in 2015 American graduate students introduced a portable sound extinguisher and demonstrated it with a video posted on YouTube. But it still required heavy equipment, weighing 9 kilograms, was relatively weak in power and had long cables. In August of 2015, we, the Sori Sound Engineering Research Institute (SSERI), introduced an improved device, a sound extinguisher using a sound lens in a speaker to produce more focused power of sound, roughly 10 times stronger in its power than the device presented in the YouTube video.

Our device still exhibited problems, such as its heavy weight over 2.5 kilograms, and its obligatory vicinity to the flame. Here we introduces a further improved sound extinguisher in order to increase the efficiency rate of the device by utilizing the sound-wind. As illustrated in Figures 1 and 2 below, the sound fire extinguishers do not use any water or chemical fluids as do conventional extinguishers, only emitting sound. When the sound extinguisher produces low frequency sound of 100 Hz, its vibration energy touches the flame, scatters its membrane, and blocks the influx of oxygen and subdues the flame.

The first version of the extinguisher, where a sound lens in a speaker produced roughly 10 times more power with focusing, introduced by the research team of SSERI is shown in Figure 1. It was relatively light, weighing only 2.5 kilograms and 1/3 the weight of previous ones, and thus could be carried around with one hand without any connecting cables. It was also small in size measuring 40 centimeters (a little more than 1 feet) in length. With an easy on-off switch, it is trivial to operate up to 1 or 2 meters (about 1 yard) distance from the flame. It can be continuously used for one hour when fully charged.

The further improved version of the sound fire extinguisher is shown in Figure 2. The most important improvement to be found in our new fire extinguisher is the utilization of wind. As we blow out candles using the air from our mouth, similarly the fire can be put out by wind if its speed is over 5 meters/second when it reaches the flame. In order to acquire the power and speed required to put out the fire, we developed a way to increase the speed of wind by using low-powered speakers: a method of magnifying the power of sound wind.

fire extinguisher
Figure 1. The first sound fire extinguisher by SSERI: the mop type.

fire extinguisher
Figure 2. The improved extinguisher by SSERI: the portable type

Wind generally creates white noise, but we covered wind with particular sound frequencies. When wind acquires certain sound frequency, namely, its resonance frequency, its amplitude magnifies it and creates a larger sound-wind. Figure 3 below illustrates the mechanism of a fire extinguisher with sound-wind amplifier. A speaker produces the low frequency sound (100 Hz and below) and creates sound-wind, resonates it by utilizing the horn-effect to magnify and produce 15 times more power. The magnified sound-wind touches the flame and instantly put out the fire.

In summary, with these improvements, the sound-wind extinguisher is fit best for the beginning stage of a fire. It can be used at home, at work, on board in aircrafts, vessels, and cars. In the future, we will continue efforts to further improve the functions of the sound-wind fire extinguisher so that it can be available for a popular use.

fire extinguisher
Figure 3: The mechanism of a sound-wind fire extinguisher

References
[1] DAPRA Demonstration, https://www.youtube.com/watch?v=DanOeC2EpeA
[2] American graduate students (George Mason Univ.), https://www.youtube.com/watch?v=uPVQMZ4ikvM
[3] Park, S.Y., Yeo, K.S., Bae, M.J. “On a Detection of Optimal Frequency for Candle Fire-extinguishing,” ASK, Proceedings of 2015 Fall Conference of ASK, Vol. 34, No. 2(s), pp. 32, No. 13, Nov. 2015.
[4] Ik-Soo Ahn, Hyung-Woo Park, Seong-Geon Bae, Myung-Jin Bae,“ A Study on a sound fire extinguisher using special sound lens,” Acoustical Society of America, Journal of ASA, Vol.139, No.4, pp.2077, April 2016.

*Video file attached: sound-wind extinguisher V2

2pSAa8 – A Study on a Sound Extinguisher Using Sound Lens

Ik-Soo Ahn, aisbestman@naver.com
Hyung-Woo Park pphw@ssu.ac.kr
Myung-Jin Bae, mjbae@ssu.ac.kr
Soongil University
369 Sangdo-ro, Dongjak-gu
Seoul, Korea 06978

Seong-Geon Bae sgbae@kangnam.ac.kr
Kangnam University
111, Gugal-dong, Giheung-gu, Yongin-si
Gyeonggi-do, Korea 16979

Popular version of paper 2pSAa8“A study on a sound fire extinguisher using special sound lens”
Presented Tuesday afternoon, May 24, 2016, 3:10 A in Salon E
171st ASA Meeting, Salt Lake City
Click here to read the abstract

In 2012, DARPA, Defense Advanced Research Projects Agency of the United States, demonstrated that fire can be put out by surrounding it with two large sound speakers. This verified the possibility of a fire extinguisher utilizing sound. Since then, many people have tried to develop a more efficient sound extinguisher, recognizing its future value. For example, in 2015 a couple of American graduate students introduced a portable sound extinguisher and demonstrated it on YouTube, but it was too heavy and too weak with long cables. The basic mechanism for a sound extinguisher can be summarized as follows: When the sound extinguisher produces low frequency sound of 100Hz, its vibration energy touches the flame, scatters its membrane, and then blocks the influx of oxygen, so the flame goes down.

Picture 1 Fire with strong flame

Picture 1 Fire with strong flame

Picture 2 Applying the extinguisher

Picture 2 Applying the extinguisher

Picture 3 The result

Picture 3 The result

Recently, a research team of SSERI, the Sori Sound Engineering Research Institute, introduced an improved device, a “sound-wind extinguisher,” by installing a sound lens in a speaker to produce more focused power of sound, roughly 10 times stronger in its power than the previous one. This sound-wind extinguisher is very light, weighting only about 2 kg, 1/3 of the previous one, and can be carried around with one hand without any connecting cable. It is also small in size measuring 40cm in length. With an easy on-off switch, you can use it anywhere, up to 1~2m distance from the flame.

The most important improvement to be found in our sound extinguisher from the previous one is the installation of a sound lens. If you use the sound in a usual way with a normal speaker, it scatters into the air without displaying any effect on the flame. On the other hand, when the sound lens is used with a speaker, the lens concentrates the sound generated from the speaker into one place and makes it possible to reach the fire more directly. In other words, it amplifies sound to maximize its efficiency without losing the power of sound which might be caused by the interference of the air. air. The team also succeeded in reducing the size and weight of the extinguisher, so that anyone can carry it anywhere at any time, improving its portability with an easy on-off switch. The experimental sound extinguisher is shown in the following pictures and video clip.

The following figure illustrates how and where to install a sound lens inside of the sound extinguisher.
Int Structure

We believe that the sound-wind extinguisher is fit best for the beginning stage of a fire. It can be used at home, at work, on board in aircrafts, vessels, and cars.

References

[1] DAPRA Demonstration, https://www.youtube.com/watch?v=DanOeC2EpeA

[2] American graduate students (George Mason Univ.), https://www.youtube.com/watch?v=uPVQMZ4ikvM

[3] Ahn, I.S., Bae, M.J. “On a Compact Extinguisher Using Sound Lens,” KICS, Proceedings of 2016 Conference of KICS, Vol. 32, No. 1, pp. 10C-13-1~2. Jan. 20-22, 2016.

[4] Lee, E.Y., Bae, M.J. “On a Focused Transducer for Fire-extinguishing,” ASK, Proceedings of 2015 Fall Conference of ASK, Vol. 34, No.2(s), pp. 35, No. 13, 2015.

[5] Park, S.Y., Yeo, K.S., Bae, M.J. “On a Detection of Optimal Frequency for Candle Fire-extinguishing,” ASK, Proceedings of 2015 Fall Conference of ASK, Vol. 34, No. 2(s), pp. 32, No. 13, 2015.

[6] Yeo, K.S., Park, S.Y., Bae, M.J. “On an Extinguisher with Sound and Wind,” ASK, Proceedings of 2015 KSCSPC, Vol. 32, No. 1, pp. 170-171, Aug. 14, 2015.

3aSA7 – Characterizing defects with nonlinear acoustics

Pierre-Yves Le Bas, pylb@lanl.gov1,  Brian E. Anderson1,2, Marcel Remillieux1, Lukasz Pieczonka3, TJ Ulrich1

1Geophysics group EES-17, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
2Department of Physics and Astronomy, Brigham Young University, N377 Eyring Science Center, Provo, UT 84601, USA
3AGH University of Science and Technology, Krakow, Poland

Popular version of paper 3aSA7, “Elasticity Nonlinear Diagnostic method for crack detection and depth estimation”
Presented Wednesday morning, November 4, 2015, 10:20 AM, Daytona room
170th ASA Meeting, Jacksonville

One common problem in industry is to detect and characterize defects, especially at an early stage. Indeed, small cracks are difficult to detect with current techniques and, as a result, it is customary to replace parts after an estimated lifetime instead of keeping them in service until they are effectively approaching failure. Being able to detect early stage damage before it becomes structurally dangerous is a challenging problem of great economic importance. This is where nonlinear acoustics can help. Nonlinear acoustics is extremely sensitive to tiny cracks and thus early damage. The principle of nonlinear acoustics is easily understood if you consider a bell. If the bell is intact, it will ring with an agreeable tone determine by the geometry of the bell. If the bell is cracked, one will hear a dissonant sound, which is due to nonlinear phenomena. Thus, if an object is struck it is possible to determine, by listening to the tone(s) produced, whether or not it is damaged. Here the same principle is used but in a more quantitative way and, usually, at ultrasonic frequencies. Ideally, one would also like to know where the damage is and what its orientation is. Indeed, a crack growing thru an object could be more important to detect as it could lead to the object splitting in half, but in other circumstances, chipping might be more important, so knowing the orientation of a crack is critical in the health assessment of a part.

To localize and characterize a defect, time reversal is a useful technique. Time reversal is a technique that can be used to localize vibration in a known direction, i.e., a sample can be made to vibrate perpendicularly to the surface of the object or parallel to it, which are referred to as out-of-plane and in-plane motions, respectively. The movie below shows how time reversal is used to focus energy: a source broadcasts a wave from the back of a plate and signals are recorded on the edges using other transducers. The signals from this initial phase are then flipped in time and broadcast from all the edge receivers. Time reversal then dictates that these waves focus at the initial source location.

 

1

-video file missing-

Time reversal can also be more that the simple example in the video. Making use of the reciprocity principle, i.e., that a signal traveling from A to B is identical to the same signal traveling from B to A, the source in the back of the plate can be replaced by a receiver and the initial broadcast can be done from the side, meaning TR can focus energy anywhere a signal can be recorded; and with a laser as receiver, this means anywhere on the surface of an object.

In addition, the dominant vibration direction, e.g., in-plane or out-of plane, of the focus can be specified by recording specific directions of motion of the initial signals. If during the first step of the time reversal process, the receiver is set to record in-plane vibration, the focus will be primarily in that in-plane direction; similarly if the receiver records the out-of-plane vibration in the first step of the process, the focus will be essentially in the out-of-plane direction. This is important as the nonlinear response of a crack depends on the orientation of the vibration that makes it vibrate. To fully characterize a sample in terms of crack presence and orientation TR is used to focus energy at defined locations and at each point the nonlinear response is quantified.  This can be done for any orientation of the focused wave. To cover all possibilities, three scans are usually done in three orthogonal directions.

Figure 2 shows three scans on x, y and z directions of the same sample composed of a glass plate glued on an aluminum plate. The sample has 2 defects, one delamination due to a lack of glue between the 2 plates (in the (x,y) plane) at the top of the scan area and one crack perpendicular to the surface in the glass plate in the (x,z) plane in the middle of the scan area.

2 - Nonlinear acoustics

Figure 2. Nonlinear component of the time reversal focus at each point of a scan grid with wave focused in the x, y and z direction (from left to right)

As can be seen on those scans, the delamination in the (x,y) plane is visible only when the wave is focused in the Z direction while the crack in the (x,z) plane is visible only in the Y scan. This means that cracks have a strong nonlinear behavior when excited in a direction perpendicular to their main orientation. So by scanning with three different orientations of the focused vibration one should be able to recreate the orientation of a crack.

Another feature of the time reversal focus is that its spatial extent is about a wavelength of the focus wave. Which means the higher the frequency, the smaller the spot size, i.e., the area of the focused energy. One can then think that the higher the frequency the better the resolution and thus higher frequency is always best. However, the extent of the focus is also the depth that this technique can probe; so lower frequency means a deeper investigation and thus a more complete characterization of the sample. Therefore there is a tradeoff between depth of investigation and resolution. However, by doing several scans at different frequencies, one can extract additional information about a crack. For example, Figure 3 shows 2 scans done on a metallic sample with the only difference being the frequency of the focused wave.

3 - Nonlinear acoustics

Figure 3. From left to right: Nonlinear component of the time reversal focus at each point of a scan grid at 200kHz and 100kHz and photography of the sample from its side.

At 200kHz, it looks like there is only a thin crack while at 100kHz the extent of this crack is larger toward the bottom of the scan and more than double so there is more than just a resolution issue. At 200kHz the depth of investigation is about 5mm; at 100kHz it is about 10mm. Looking on the side of the sample in the right panel of figure 3, the crack is seen to be perpendicular to the surface for about 6mm and then dip severely. At 200kHz, the scan is only sensitive to the part perpendicular to the surface while at 100kHz, the scan will also show the dipping part. So doing several scans at different frequencies can give some information on the depth profile of the crack.

In conclusion, using time reversal to focus energy in several directions and at different frequencies and studying the nonlinear component of this focus can lead to a characterization of a crack, its orientation and depth profile, something that is currently only available using techniques, like X-ray CT, which are not as easily deployable as ultrasonic ones.

3aSA11 – Hollow vs. Foam-filled racket: Feel-good vibrations

Kritika Vayur – kuv126@psu.edu
Dr. Daniel A. Russell – dar119@psu.edu

Pennsylvania State University
201 Applied Science Building
State College, PA, 16802

Popular version of paper 3aSA11, “Vibrational analysis of hollow and foam-filled graphite tennis rackets”
Presented Wednesday morning, May 20, 2015, 11:15 AM in room Kings 3
169th ASA Meeting, Pittsburgh
Read the abstract by clicking here.

Tennis Rackets and Injuries
The typical modern tennis racket has a light-weight, hollow graphite frame with a large head. Though these rackets are easier to swing, there seems to be an increase in the number of players experiencing injuries commonly known as “tennis elbow”. Recently, even notable professional players such as Rafael Nadal, Victoria Azarenka, and Novak Djokovic have withdrawn from tournaments because of wrist, elbow or shoulder injuries.

A recent new solid foam-filled graphite racket design claims to reduce the risk of injury. Previous testing has suggested that these foam-filled rackets are less stiff and damp the vibrations more than hollow rackets, thus reducing the risk of injury and shock delivered to the arm of the player [1]. Figure 1 shows cross-sections of the handles of hollow and foam-filled versions of the same model racket.

The preliminary study reported in this paper was an attempt to identify the vibrational characteristics that might explain why foam-filled rackets improve feel and reduce risk of injury.
Figure 1: Cross-section of the handle of a foam-filled racket (left) and a hollow racket (right).
Figure 1: Cross-section of the handle of a foam-filled racket (left) and a hollow racket (right).

Damping Rates
The first vibrational characteristic we set out to identify was the damping associated with first few bending and torsional vibrations of the racket frame. A higher damping rate means the unwanted vibration dies away faster and results in a less painful vibration delivered to the hand, wrist, and arm. Previous research on handheld sports equipment (baseball and softball bats and field hockey sticks) has demonstrated that bats and sticks with higher damping feel better and minimize painful sting [2,3,4].

We measured the damping rates of 20 different tennis rackets, by suspending the racket from the handle with rubber bands, striking the racket frame in the head region, and measuring the resulting vibration at the handle using an accelerometer. Damping rates were obtained from the frequency response of the racket using a frequency analyzer. We note that suspending the racket from rubber bands is a free boundary condition, but other research has shown that this free boundary condition more closely reproduces the vibrational behavior of a hand-held racket than does a clamped-handle condition [5,6].

Measured damping rates for the first bending mode, shown in Fig. 2, indicate no difference between the damping and decay rates for hollow and foam-filled graphite rackets. Similar results were obtained for other bending and torsional modes. This result suggests that the benefit of or preference for foam-filled rackets is not due to a higher damping that could cause unwanted vibrations to decay more quickly.

Vayur_Fig2
Figure 2: Damping rates of the first bending mode for 20 rackets, hollow (open circles) and foam-filled (solid squares). A higher damping rate means the vibration will have a lower amplitude and will decay more quickly.

Vibrational Mode Shapes and Frequencies
Experimental modal analysis is a common method to determine how the racket vibrates with various mode shapes at its resonance frequencies [7]. In this experiment, two rackets were tested, a hollow and a foam-filled racket of the same make and model. Both rackets were freely suspended by rubber bands, as shown in Fig. 3. An accelerometer, fixed at one location, measured the vibrational response to a force hammer impact at each of approximately 180 locations around the frame and strings of the racket. The resulting Frequency Response Functions for each impact location were post-processed with a modal analysis software to extract vibrational mode shapes and resonance frequencies. An example of the vibrational mode shapes for hollow graphite tennis racket may be found on Dr. Russell’s website.

Figure 3: Modal analysis set up for a freely suspended racket.
Figure 3: Modal analysis set up for a freely suspended racket.

Figure 4 compares the first and third bending modes and the first torsional mode for a hollow and foam-filled racket. The only difference between the two rackets is that one was hollow and the other was foam-filled. In the figure, the pink and green regions represent motion in opposite directions, and the white regions indicate regions, called nodes, where no vibration occurs. The sweet spot of a tennis racket is often identified as being at the center of the nodal line of the first bending mode shape in the head region [8]. An impact from an incoming ball at this location results in zero vibration at the handle, and therefore a better “feel” for the player. The data in Fig. 4 shows that there are very few differences between the mode shapes of the hollow and foam-filled rackets. The frequencies at which the mode shapes for the foam-filled rackets occur are slightly higher than those of the hollow rackets, but the difference in shapes are negligible between the two types.

Vayur_Fig4
Figure 4: Contour maps representing the out-of-plane vibration amplitude for the first bending (left), first torsional (middle), and third bending (right) modes for a hollow (top) and a foam-filled racket (bottom) of the same make and model.

Conclusions
This preliminary study shows that damping rates for this particular design of foam-filled rackets are not higher than those of hollow rackets. The modal analysis gives a closer, yet non-conclusive, look at the intrinsic properties of the hollow and foam-filled rackets. The benefit of using this racket design is perhaps related to a larger impact shock, but additional testing is needed to discover this conjecture.

Bibliography
[1] Ferrara, L., & Cohen, A. (2013). A mechanical study on tennis racquets to investigate design factors that contribute to reduced stress and improved vibrational dampening. Procedia Engineering, 60, 397-402.
[2] Russell D.A. (2012). Vibration damping mechanisms for the reduction of sting in baseball bats. In 164th meeting of the Acoustical Society of America, Kansas City, MO, Oct 22-26. Journal of Acoustical Society of America, 132(3) Pt.2, 1893.
[3] Russell, D.A. (2012). Flexural vibration and the perception of sting in hand-held sports implements. In Proceedings of InterNoise 2012, August 19-22, New York City, NY.
[4] Russell, D.A. (2006). Bending modes, damping, and the sensation of string in
baseball bats. In Proceedings 6th IOMAC Conference, 1, 11-16.
[5] Banwell, G.H., Roberts, J.R., & Halkon, B.J. (2014). Understanding the dynamics behavior of a tennis racket under play conditions. Experimental Mechanics, 54, 527-537.
[6] Kotze, J., Mitchell, S.R., & Rothberg, S.J. (2000).The role of the racket in high-speed tennis serves. Sports Engineering, 3, 67-84.
[7] Schwarz, B.J., & Richardson, M.H. (1999). Experimental modal analysis. CSI Reliability Week, 35(1), 1-12.
[8] Cross, R. (2004). Center of percussion of hand-held implements. American Journal of Physics, 72, 622-630.