Researchers in power ultrasonics know of the frequent reference to the 1927 Wood and Loomis paper as the seminal publication of a new field of ultrasound. The story behind the discovery of "power ultrasonics" is a fascinating chapter of acoustics. The modern ultrasonics era arose from Professor Langevin's 1917 invention of the quartz sandwich transducer for underwater sound transmission in submarine detection. Intense ultrasound's physical effects had not gone unnoticed in the first decade of modern ultrasonics. Langevin's tests with quartz plate transducers had resulted in killing fish in the beam of
sound. Professor Van Dyke had observed in 1924 the searing of skin when a resonant quartz bar was touched, theexplosive atomization of water drops from the end of the rod and friction alleviation between a metal surface and the vibrating quartz. Nevertheless, no steps were taken to investigate these early observations more fully. Among observers of Langevin's work was Professor R. W. Wood, an American physicist from Johns Hopkins University. Already famous for his work in optics and spectroscopy, and for his classic book "Physical Optics," he was also known as a brilliant lecturer and a writer of popular fiction and verse. With U.S. entry into WW I, Professor Wood was commissioned an Army Major and assigned to the Bureau of Inventions in Paris, where he devoted particular attention to the work of Langevin. Wood later noted how the
contact with Langevin had made a strong impression: "It was my good fortune during the war to be associated for a brief time with Prof. Langevin during his remarkable developments. At the arsenal at Toulon I witnessed many of the experiments with the high power generators. One was mounted in a large wooden tank filled with sea water, and when the Poulsen arc was started and the frequency adjusted for resonance the narrow beam of supersonic waves shot across the tank causing the formation of millions of minute air bubbles and killing small fish which occasionally swam into the beam. If the hand was held in the water near the plate an almost insupportabale pain was felt, which gave one the impression that the bones were being heated." Another wartime meeting that proved essential to the invention of power ultrasonics occurred when Professor Wood met Alfred E. Loomis at the Aberdeen Proving Grounds. Loomis, a successful lawyer, was directing
Aberdeen research as an Army Major and invented, during this time, the "Loomis chronograph" for measuring the velocities of shells. After the war, Wood pursued other areas of war research and returned to his work in optics and spectroscopy, with his interests in ultrasonics remained dormant for several years. Loomis, following the war, entered investment banking, amassing a personal fortune during the 1920s. However, his interest returned increasingly to scientific research and, in 1924, Loomis renewed the wartime acquaintance with Wood and offered to collaborate and underwrite any joint research ventures. In 1926, Wood told Loomis of Langevin's experiments and suggested the subject offered a wide field for research in physics, chemistry, and biology. Langevin placed a high power General Electric vacuum-tube oscillator and a quartz
plate transducer immersed in an oil-filled dish, experiments began in Loomis's garage in Tuxedo Park, New York. As research expanded, Loomis purchased a nearby mansion, converting it into his well-known Tuxedo Park Laboratory. The huge vacuum tubes, a large bank of oil condensers and an oversize variable condenser and step-up induction coil made the ultrasonic apparatus an imposing affair. Vibrations of 200-500 kHz were transmitted through the oil bath into glass vessels or rods immersed in the bath, achieving a range of spectacular effects that included: radiation pressures of sufficient magnitude to support 150 g and to raise a pronounced mound of oil above the transducer.intense searing of the skin by the vibrating glass rod and the burning of wood chips and the etching and drilling of glass pressed against the tips of vibrating glass rods; heating of liquids and solids and the formations of emulsions and fogs; biological effects including rupturing of red blood cells, killing of cellular organisms, and harmful to lethal effects on fish, frogs, and mice; observations of chemical reactions and crystallization and flocculation of particles suspended in a liquid. These pioneering results could be taken as a present-day litany of ultrasonic achievements. Wood and Loomis also made observations of the modal patterns of rods, tubes, and plates and gave some of the first experimental data on phase velocity in rods and disks. Another first occurred when they made an ultrasonic horn by drawing down a glass tube to a tapered point to concentrate the energy at the point of application.
Publication of these results started avenues of work being exploited to the present day. Professor Wood did not continue work in ultrasonics, but returned to optics and spectroscopy. Aside from a 1939 "supersonics" monograph, in a scientific career spanning a half-century, this was to represent his involvement with ultrasonics. Loomis continued with other collaborators in research on the chemical effects of ultrasound while maintaining his interest in precision time measurement and other scientific areas. Backed by a private fortune, he was a 20th century patron of the sciences. In the years ahead, Loomis played an important role in founding other major laboratories and in stimulating World War II radar research.
Rudolph Koenig produced Ultrasonic vibrations trying to find the highest pitch a human can hear. Using tuning forks he was able to create frequencies between 4 khz and 90 khz. Mr. Galton first created the Ultrasonic whistle in 1883 which was able to create incremental graduations of ultrasonic pitch having an upper limit of 25 khz. Ultrasonics began moving out of the realm of theoretical contemplation to reall applications in Toulon France in 1917 with the attempts of Prof. Langevin to counter the U-boat threats to France using Quartz crystals which inadvertently created bubbles due to cavitation causing little fish to be killed and the bones of hands to feel that they were being heated. This effect was called the piezo effect which was discovered 35 years earlier. The ideal structure turned out to be what`s called a piezo sandwich whereby the piezo crystals are sandwiched between two plates of steel with the overall assemly needing to resonate at the resonant frequency of the driving power supply. During WW-2, sonar came into being which is another term for ultrasonics and the very same power supply and transducers can be used for welding and other industrial processes. Radar employs the same sound and electronic theories but is another branch of the frequency spectrum as it is in the upper khz and lower mhz frequencies. Currently there are hundreds of ultrasonic applications.
See Graff, K. F., "A History of Ultrasonics," Chapter 1 of "Physical
Acoustics," Vol. 15, Mason and Thurston, editors, Academic Press, 1981 for an extended account.
Below is simulation of ultrasonic power supply circuit in development.
Not shown are 2 oscilloscopes, 1 Frequency counter, 1 function generator, several muti-testers, a tiny cnc mill for prototypes, a small milling machine, a 4 ft universal Lathe, Saw & welding equipment used to produce horns, fixtures and soon the machines themselves. The power supply design self taught process is nearing a conclusion.
DESIGN & Fabrication of ULTRASONIC horns (acoustical impedance matching apparatus), high production Fixtures comprising pneumatic actuation and plastic welder conversions all at COMPETITIVE RATES.
Titanium & Aluminum wedge horns designed/built/tested by me.
An ultrasonic welder converted to ultrasonic grinding.
Solid modelling can be done at reasonable rates.
A CNC controlled plasma cutter can be built at reasonable costs.
An ultrasonic water treatment device for sale 450 $
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