Support and join the UIA [New 2004 Logo all rights reserved to UIA]

INDEX

    Applications List.

    Keywords (Applications) Index - moved from Page 3 on 12 Feb 00.

    Probe-type Ultrasonic Processing Equipment.

    Brain Storming - bright ideas, pipe dreams, pie-in-the-sky?

On Ultrasonics Page A (this page - created 19 Apr 01)

  ULTRASONIC PROCESSING

    Power vs.Intensity.

    AL-1C - "CONDENSED GUIDE TO ULTRASONIC PROCESSING"
        (A Layperson's Explanation of a Complex Letterhead)
            {moved from the main ultrasonics page on 05 Jan 2002}.

    AL-1P - "A POPULARIZED GUIDE TO ULTRASONIC PROCESSING".
        (A Non-Technical Explanation of a Complicated Letterhead).

    Failure Modes in Horns.

    Ultrasonic Soldering, Galvanizing, etc.

On Ultrasonics Page 1 (the next page - created 12 Feb 00):

    AL-1V - "A POPULARIZED GUIDE TO ULTRASONIC CAVITATION"
        (A Non-Technical Explanation of "Cold Boiling").

    TUBULAR HORNS (Radial Radiators).

    CARE of TIPS (Radiating Faces).

    ULTRASONIC DEGASSING.

On Ultrasonics Page 1A (rearranged 12 Feb 00):

    AL-4 - AMPLITUDE MEASUREMENT.

    Free Bubbling.

    Bubble Entrapment.

    Extenders.

    Call for Contributions for Book.

On Ultrasonics Page 2:

    More on Cavitation.

    AL-2 - "ULTRASONICS AND FINE PARTICLES -
       BENEFICIATION OF SLURRIES AND FINE-PARTICLE SUSPENSIONS
       [CERAMICS, COAL & ORES, COATINGS, COLUMN PACKINGS,
        SINTERING, SLIPS].

On Ultrasonics Page 3:

    AM-1 - "ULTRASONIC STERILIZATION and DISINFECTION".

    UM-1 - "ULTRASONICS, HEARING, and HEALTH".

    Ultrasonics and Living Organisms.

    What's New?

On Ultrasonics Page 4:

    Foaming and Aerosoling - moved 28 May 02 from Page 1A.

    Ultrasonic Propulsion (Propulsive Force) - Moving Material.

    Ultrasonic Fountains - Atomization, Nebulization, Humidification,
        Misting, Particle Creation and Sizing.

    Ultrasonics and Nuclear Fusion.

    Quick Links for Ultrasonic Probe Manufacturers (moved 10 Jul 2002).

On the Ultrasonic Cleaning Page:

    ULTRASONIC CLEANING {in process}.

    Immersible Transducers.

    What's New?

On the ULTRASONICS GLOSSARY page:

    ULTRASONICS GLOSSARY {in process}.

ULTRASONICS BIBLIOGRAPHY
    Ultrasonic Bibliography Page 1 - Reference Books on Acoustics,
        Vibration, and Sound.
    Ultrasonic Bibliography Page 2 - Sonochemistry.
    Ultrasonic Bibliography Page 3 - Selected Articles.

CALL FOR CONTRIBUTIONS:  I am writing a book on "High-Intensity Ultrasonic Technology and Applications" (intended for Marcel Dekker's "Mechanical Engineering Series", edited by Profs. Lynn L. Faulkner and S. Bradford Menkes).  This book will focus on the practical application of power (high intensity) ultrasonics, the use of ultrasonic energy to change materials.  Contributions are welcome.

THE CAVITATION BUBBLE

[image from University of Washington, Applied Physics Laboratory (Lawrence Crum, Ph.D.)
- bubble diameter approximately 1mm]

---

ULTRASONIC PROCESSING

(Moved from the main ultrasonics page on 05 Jan 2002)

---

Power vs. Intensity

Any truly satisfactory ultrasonic liquid processor or cell disruptor must provide controlled amplitude under all varying load conditions within specifications.  It does so by regulating the power output to maintain the frequency against any imposed load, usually by adjusting the voltage impressed on the piezo-electric crystals (or the magnetic coil for a magnetostrictive device).  Think of the horn or probe tip as a piston, operating in a liquid cylinder.  This is not as illogical as it may seem at first glance; at the frequncies involved (generally 20KHz and higher), the molecules of the liquid do not have time to restore fully after each stroke, thus generating the extremes of pressure and vacuum that are inherent in this process.  The energetics are thus virtually identical to a problem in simple hydraulics; the larger the piston (radiating face) diameter, the longer the stroke (amplitude), the faster the stroke rate (frequency), the higher the static head (pressure), the more resistant and cold the liquid (viscosity), the higher the power required to move the radiating face.  Similarly, the faster and the further you move the tip, the higher the energy you impart to the cavitation bubble and the greater the intensity of the energy released in the implosion of that bubble.

Thus, power drawn is dependant on the geometry of the radiator/liquid arrangements and intensity is related only to amplitude (excursion) of the radiating face.  The amount of power required to provide and maintain that intensity thus is a multi-variable parameter.

Further, liquids, especially water, are a "neurotic" load.  Many variables affect the efficiency of cavitation and thus the power drawn.  As the load increases on the generator, the vibrating body reacts by decelerating, slowing in frequency; it "bogs down".  The generator (a well-regulated one, anyway) responds with more voltage, accelerating the motion of the radiating masses and thus increasing frequency.  Once the system reaches its voltage limit, amplitude can not be increased further.  In addition (from "Cleaning"), once cavitation bubbles "blanket" the radiating face, an increase in amplitude will produce no more cavitation; "blanketing" is a limiting phenomenon in the cavitation field in which the density of the bubble cloud is so great that no further cavitation can take place when additional energy is introduced (analgous to the phenomenon at the temperature of thermal boiling, above which no further change of state occurs).  The "blanketing threshold" is that intensity of cavitation at which the blanketing phenomenon occurs; for practical purposes, the blanketing threshold may be considered a relative term based on the efficiency of conversion from increased radiated energy to increased cavitation.

It is my intention to expand upon this in an update of my seminal articles, "Power vs. Intensity" and "Application of Ultrasonic Processors (Power vs. Intensity in Sonication)" of 1984 and previous.

It should be noted here (as it is elsewhere on these pages) that higher frequencies yield smaller cavitation bubbles and thus give better penetration into fine holes and crevices and do less damage to components, but have less shock front energy (intensity).  The trade-off is that processing time may have to be increased for full cleaning or other processing of items at higher frequencies.  Similarly, lower frequencies give better cleaning of heavy, bulky objects (more "bang for the buck"), but may cause greater cavitational erosion of the workpiece surface.

AL-1C

APPLICATIONS MONOGRAPH

4-97

Ultrasonic processing applies intense, high-frequency sound to liquids, producing intimate mixing and powerful chemical and physical reactions.  The process ("cavitation") is, in effect, "cold boiling" and results from the creation and collapse of countless microbubbles in the liquid, producing shock waves.  The technique is used to accelerate reactions, treat wastes, ores, and minerals, disperse fine particles and suspend slurries, disrupt biological cells and tissues, homogenize and emulsify, and clean surfaces and porous materials.  This work entails "blasting" liquids, usually water, with powerful sound energy, unlike sonar, imaging, measuring, or non-destructive testing, in which the subject is not altered by the sound energy.  Most such work is done at very high frequencies, far above human hearing.  Processing, on the other hand, works at frequencies just above human hearing, 20 to 40kHz (20,000 to 40,000 cycles per second).  In ultrasonic processing, sound is used to change materials.  Some of the more significant applications:

SONOCHEMISTRY - exposing of fresh material surface to enhance reactions and even to generate new species hitherto unobtainable by classic means such as heat, electricity, light, and catalysis.

REACTION ACCELERATION - cavitation accelerates both chemical and physical reactions, such as those of surfactancy and detergency, which is why it is a preferred cleaning technique, as noted below.

BENEFICIATION OF ORES AND MINERALS - improving flotation and extraction of ores and minerals such as coal.

FINE PARTICLE DISPERSION - dispersing iron oxide for coating data processing media; enhancing analysis of particle size distribution and characterization; improving fine ceramic slurries used as insulation for electronic capacitors and to make luxury table china; making more wear-resistant sintered carbide tools; fluidization.

DISRUPTION - breaking open biological tissues and cells to extract enzymes and DNA, prepare vaccines, study intercellular components.

HOMOGENIZATION - making more uniform mixtures of liquids or liquid suspensions for CPI, biotechnology, processing of paper pulp.

EMULSIFICATION - processing foods, pharmaceuticals, and cosmetics (oil and water DO mix!); incorporating water into more efficient, cool-burning, yet stable, motor fuels; creating non-flammable jet fuels.

POLLUTION ABATEMENT - recovering oil from soils, decomposing PCBs, degrading toxic wastes, reacting pollutants.

DISSOLUTION - dissolving solids in solvents; speeding quality control of pharmaceuticals, flavors and fragrances, sheet and pelletized plastic materials.

DEGASSING - removing gases from solutions without heat or vacuum; quality control (TOD) of wines, spirits, and carbonated beverages.

CLEANING OF SURFACES AND POROUS MATERIALS - stripping away oxides and other films, emulsifying oil coatings, suspending particulates, enhancing detergency, and degreasing without hydrocarbon solvents.

For more information, please contact S. Berliner, III.

© Copyright S. Berliner, III 1991/1997 (all rights reserved) Updated: 26 May 97, 01:15

Ultrasonic processing is unlike underwater sonar, fetal imaging, thickness or level measuring, or non-destructive testing, in which the subject is not altered by the sound energy.  Most such work is done at very high frequencies, far above human hearing.  Processing, on the other hand, works at frequencies just above human hearing, 20 to 40kHz (20,000 to 40,000 cycles per second).  Just for example, ordinary alternating (A.C.) house current pulses 60 times a second in the U.S. or 50 times a second in Europe and Japan.  In ultrasonic processing, sound actually changes materials.

Some of the more significant applications:

SONOCHEMISTRY - cleaning the surface of a material to get stronger reactions with other chemicals touching that surface and even generating new kinds of chemicals which couldn't previously be made by heating, electricity, light, and chemical reaction.

REACTION ACCELERATION - cavitation makes both chemical and physical reactions, such as the cleaning power of soaps or detergents, occur faster.

BENEFICIATION OF ORES AND MINERALS - improving the removal of ores and minerals such as coal from the rock in which they are found.

FINE PARTICLE DISPERSION - evenly separating (dispersing) tiny bits of iron oxide (rust) used to coat computer and audio/video tapes and disks; giving better analysis of fine particles floating in liquids; improving the fine ceramic particles used to make insulation for electronic capacitors and to make luxury table china; making more wear-resistant sintered carbide tools; and making better fluidized beds (quicksands).

DISRUPTION - breaking open biological tissues and cells to get out enzymes and DNA for study, to prepare vaccines, and to study the materials inside cells.

HOMOGENIZATION - mixing liquids or fine particles suspended in liquids for chmeical processing, biotechnology, and processing of paper pulp, like mixing milk and cream.

EMULSIFICATION - processing foods, pharmaceuticals, and cosmetics (oil and water DO mix!); adding water to motor fuels to make them burn more efficiently and coolly. <[P> POLLUTION ABATEMENT - getting spilled oil from the soil, decomposing dangerous chemicals, degrading toxic waste, getting rid of pollutants.

DISSOLUTION - dissolving solids in solvents; improving quality control of pharmaceuticals, flavors and fragrances, plastics.

DEGASSING - removing air and other gases from solutions without heat or vacuum; quality control of wines, spirits, and carbonated beverages (soda).

CLEANING OF SURFACES AND POROUS MATERIALS - removing rust, tarnish, oil, grease, and other contaminants, without solvents, and making soaps and detergents work better.

For more information, please contact S. Berliner, III.

© Copyright S. Berliner, III 1997 (all rights reserved) Updated: 09 July 1997, 09:15

As has been noted elsewhere on this site, horns are longitudinal bells, carefully designed and crafted to resonate primarily in the axial mode.  That is the critical word, though, "primarily".  As with any elastic body, when it shrinks in one (or two) dimension(s), it must expand in the other(s).  The analogy of a child's sausage balloon is most apt; squeeze the big end and the small end shoots (extends) 'way out.  In more technical terms, use the analogy of a differential piston; a small excursion of the larger diameter will result in a greater excursion of the smaller diameter ("compounding").  Mass must be conserved.  This is how the horn acts as a mechanical amplifier.  Excerpting from the horn segment of the Convertor-Stack-Horn Layout drawing and the terminology of the succeeding drawing, both on the main Ultrasonic page, we can see the concepts more graphically:

(Illustration by and © S. Berliner, III 1999 - all rights reserved)
[Click on thumbnailed picture for larger image]

At nodes (centers), the most critical place is the STEP, the transition from one diameter to another; any notch from damage or from poor design or machining is almost garanteed to cause failure, especially at high amplitudes.

Similary, at antinodes (ends), any flaw in the connecting stud, grit in the joint, non-planar mating of the opposing faces, skewed alignment, etc., will almost certainly cause heating and eventual failure.  In cases of extreme extension (as in ultra-high amplitude Microtips), operating near or at the tensile limit of the material, the slightest discrepancy can cause virtually instantaneous failure.

Such failure is not catastrophic (except financially); the horn or tip or stud merely fractures and falls apart, sometimes almost instantaneously.  Quite often, however, the immediate precursor and warning is a screech of tortured metal, sounding for all the world like the proverbial stuck pig (never having been "blessèd" with the dubious privilege of hearing same, I must use my perfervid imagination).

For a brilliant (literally and figuratively) dissertation on horn design, see Don Culp's Krell Engineering site, replete with horn performance (FEA) animations.

See also CARE of TIPS (Radiating Faces).

In addition, ultrasonic processing probes have been adapted to serve as ultrasonic soldering irons; such difficult materials as aluminum, stainless steel, ceramics, and even glass can be soldered and, because such sufaces can be wetted, disparate materials can be soldered.  {The author well remembers the thrill of first soldering glass.}

By extension, subject to the limitations of temperature, the same operations can be used for silver soldering and galvanizing and related processes.

A completely new field of wave soldering has been developed for soldering printed circuit boards and the like at megahertz frequencies, utilizing Lambda waves (lateral propagation), especialy well suited for through-hole applications, but is beyond the scope of this presentation.

Please note that a far-more detailed explanation of ultrasonic processing, as well as other technical literature, is available at no charge to consultation clients.  However, as what I believe to be a public service, I shall be adding more of my monographs on ultrasonics on this site; watch for them in the index (above).