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International electronics conference
Toronto, Canada, 6-8 October 1969
International
Electronics Conference
The Conference, sponsored by the Canadian Region of the Institute of Electrical and Electronics Engineers, is a regular event taking place every second year. The Conference is combined with an Exposition of electronic equipment and is the largest conference in Canada dealing with electronics, with the total registration of well over 10,000. The technical program comprises over 100 papers treating a wide variety of electronics subjects. At the 1967 conference, a session on Ultrasonics was introduced with five papers: ‘UltrasonicsGeneral Review’, T. S. Hutchison, RMC, ‘Recent developments in piezoelectric transducer materials,’ S. R. Burlage, Clevite Corp, ‘Instrumentation for Ultrasonic studies in solids.’ 0. M. M. Mitchell. Bell Telenhone Laboratories. ?Laser modulation by acoustic waves,’ A. J. De Maria, United Aircraft Research Laboratories and Ultrasonics and the physics of normal and superconducting metals,’ J. M. Perz, University of Toronto. A session of five review papers dealing with ultrasonics was included in the 1989 program. Two papers were on high intensity sound and ultrasound. The first paper, by A. J. Last, Ontario Research Foundation, dealt with a variety of high intensity sources operating in gases and in liquids, some of them developed by the author and his group. Large whistles up to 1OOkwof acoustic energy, pulsating combustion sources and electro-acoustic horns were described in detail. Of sources operating in liquids, focused beam generators deserve special attention. They make it possible to generate very high intensities at some distance from the radiating surface. Professor R. C. McMaster, who is a well known authority on applications of high intensity ultrasound, gave an amazing array of examples in various fields of engineering and industry: civil, ceramics and metallurgical .engineering in particular. In metal working operations the ultrasonically assisted metal deformation is of great interest and is under intensive investigation. Incidentally, at the first International Symposium on high intensity ultrasonics to be held in Graz, Austria, the emphasis will be on forming and processing of metals and plastics. Professor McMaster is also known to everybody using ultrasonics as a nondestructive technique, as the editor of the classic two volume set of books on Nondestructive Testing, American Society for Nondestructive Testing (1959) and we hear the second edition of this work is in preparation.
Ultrasonic inspection methods were the subject of the paper Material Evaluation by Ultrasonics by G. D. Martens, Automation Industries Inc, Sperry Division. After dealing with inspection concepts, including the delta configuration, the advances in the equipment were described. Gating, ultrasonic multiplexing, multi-channel instrumentation and C-Scan recording were explained. Ultrasonic Holography was the subject of the paper by E. Marom, Bendix Research Laboratories. Dr Marom, who is well known for his contribution in acoustic# holography, first outlined the theory of light and acoustical holography and then discussed various detection configurations used in ultrasonic holography in particular. Acoustic holograms have been generated by point-by-point scanning of a detector in both air and water. Fast hologram generators can be obtained by either electronic or light scanning, utilizing a TV monitor to display the holograms. The possibility of real-time spatial modulation of a laser beam was discusses.. Finally, an underwater imaging system based on holographic principles was described. Numerous holograms mainly from the authors laboratory were shown. The last paper dealt with Physical Measurements with Lasers-Ultrasonics by A. A. Gundjian and S. Sizgoric, McGill University, Montreal. The paper gave a review of the different experimental methods utilizing the interaction of laser radiation with ultrasonic structure in order to obtain information about the acoustic and electro-mechanical properties of materials. Methods for determining the velocity and attenuation of ultrasonic and hypersonic waves in transparent materials were described. Laser beam can be used also in the study of the propagation characteristics of ultrasonic surface waves. Further, measurements of small mechanical deformations can be made either by modulation of the laser frequency by perturbation of the resonant cavity length, or by the use of an external Michelson-type interferometer where mechanical deformations modulate in amplitude the resulting, superposted laser beam. Two page abstracts of papers are available in the PreConference Digest (IEEE Cat 89C40-Reg 7). W. J. Bratina
San Diego, California, 4-7 November 1969
78th Meeting of the Acoustical Society of America
An attendance .__ of 1012 gathered at San Diego to hear a record number of 427 papers including special sessions on interaction of light with sound and urban noise. Probably the session of greatest interest to readers of Ultrasonics was one containing a group of five papers on ultrasonic cavitation. CAVITATION Robert E. Apfel of the Acoustics Research Laboratory, Harvard discussed the role of vapour-cavity dynamics in cavitation threshold determinations (Paper 6Ml). Following his work on nucleation of cavities from cracks on motes (solid impurities) Apfel has now shown by numerical solutions of a nondimensional equation that a small spherical cavity will only grow in a few cycles to many times its initial radius if a certain threshold value of acoustic pressure amplitude is exceeded. Viscosity as well as surface tension is shown to play an important role. 126
ULTRASONICS April 1970
H. Scott Fogler of the University of Michigan (Paper 6M2) presented some studies of the stability and collapse of spherical cavities in visco-elastic fluids. Taking a linear rheological model for the liquid, a non-linear integro-differential equation of motion for the cavity was obtained. Analytical solutions were derived for limiting values of the parameters, and numerical results for other values. One of the more interesting results of this work is the finding that elasticity in the liquid can significantly retard the collapse of a void and produce prolonged oscillatory motion whenever the relaxation time is moderately large in comparison with the Rayleigh collapse time. F. A. Angona of Mobil Research and Development Corporation described measurements (Paper 6M3) of the threshold of cavitation in water at ambient pressures from 1 to 15atm. A 3OkHz beam was focused by an aluminum parabolic reflector to a small volume in the interior of the pressure chamber, thus minimizing wall effects and erosion damage. The
International
Electronics Conference
The Conference, sponsored by the Canadian Region of the Institute of Electrical and Electronics Engineers, is a regular event taking place every second year. The Conference is combined with an Exposition of electronic equipment and is the largest conference in Canada dealing with electronics, with the total registration of well over 10,000. The technical program comprises over 100 papers treating a wide variety of electronics subjects. At the 1967 conference, a session on Ultrasonics was introduced with five papers: ‘UltrasonicsGeneral Review’, T. S. Hutchison, RMC, ‘Recent developments in piezoelectric transducer materials,’ S. R. Burlage, Clevite Corp, ‘Instrumentation for Ultrasonic studies in solids.’ 0. M. M. Mitchell. Bell Telenhone Laboratories. ?Laser modulation by acoustic waves,’ A. J. De Maria, United Aircraft Research Laboratories and Ultrasonics and the physics of normal and superconducting metals,’ J. M. Perz, University of Toronto. A session of five review papers dealing with ultrasonics was included in the 1989 program. Two papers were on high intensity sound and ultrasound. The first paper, by A. J. Last, Ontario Research Foundation, dealt with a variety of high intensity sources operating in gases and in liquids, some of them developed by the author and his group. Large whistles up to 1OOkwof acoustic energy, pulsating combustion sources and electro-acoustic horns were described in detail. Of sources operating in liquids, focused beam generators deserve special attention. They make it possible to generate very high intensities at some distance from the radiating surface. Professor R. C. McMaster, who is a well known authority on applications of high intensity ultrasound, gave an amazing array of examples in various fields of engineering and industry: civil, ceramics and metallurgical .engineering in particular. In metal working operations the ultrasonically assisted metal deformation is of great interest and is under intensive investigation. Incidentally, at the first International Symposium on high intensity ultrasonics to be held in Graz, Austria, the emphasis will be on forming and processing of metals and plastics. Professor McMaster is also known to everybody using ultrasonics as a nondestructive technique, as the editor of the classic two volume set of books on Nondestructive Testing, American Society for Nondestructive Testing (1959) and we hear the second edition of this work is in preparation.
Ultrasonic inspection methods were the subject of the paper Material Evaluation by Ultrasonics by G. D. Martens, Automation Industries Inc, Sperry Division. After dealing with inspection concepts, including the delta configuration, the advances in the equipment were described. Gating, ultrasonic multiplexing, multi-channel instrumentation and C-Scan recording were explained. Ultrasonic Holography was the subject of the paper by E. Marom, Bendix Research Laboratories. Dr Marom, who is well known for his contribution in acoustic# holography, first outlined the theory of light and acoustical holography and then discussed various detection configurations used in ultrasonic holography in particular. Acoustic holograms have been generated by point-by-point scanning of a detector in both air and water. Fast hologram generators can be obtained by either electronic or light scanning, utilizing a TV monitor to display the holograms. The possibility of real-time spatial modulation of a laser beam was discusses.. Finally, an underwater imaging system based on holographic principles was described. Numerous holograms mainly from the authors laboratory were shown. The last paper dealt with Physical Measurements with Lasers-Ultrasonics by A. A. Gundjian and S. Sizgoric, McGill University, Montreal. The paper gave a review of the different experimental methods utilizing the interaction of laser radiation with ultrasonic structure in order to obtain information about the acoustic and electro-mechanical properties of materials. Methods for determining the velocity and attenuation of ultrasonic and hypersonic waves in transparent materials were described. Laser beam can be used also in the study of the propagation characteristics of ultrasonic surface waves. Further, measurements of small mechanical deformations can be made either by modulation of the laser frequency by perturbation of the resonant cavity length, or by the use of an external Michelson-type interferometer where mechanical deformations modulate in amplitude the resulting, superposted laser beam. Two page abstracts of papers are available in the PreConference Digest (IEEE Cat 89C40-Reg 7). W. J. Bratina
San Diego, California, 4-7 November 1969
78th Meeting of the Acoustical Society of America
An attendance .__ of 1012 gathered at San Diego to hear a record number of 427 papers including special sessions on interaction of light with sound and urban noise. Probably the session of greatest interest to readers of Ultrasonics was one containing a group of five papers on ultrasonic cavitation. CAVITATION Robert E. Apfel of the Acoustics Research Laboratory, Harvard discussed the role of vapour-cavity dynamics in cavitation threshold determinations (Paper 6Ml). Following his work on nucleation of cavities from cracks on motes (solid impurities) Apfel has now shown by numerical solutions of a nondimensional equation that a small spherical cavity will only grow in a few cycles to many times its initial radius if a certain threshold value of acoustic pressure amplitude is exceeded. Viscosity as well as surface tension is shown to play an important role. 126
ULTRASONICS April 1970
H. Scott Fogler of the University of Michigan (Paper 6M2) presented some studies of the stability and collapse of spherical cavities in visco-elastic fluids. Taking a linear rheological model for the liquid, a non-linear integro-differential equation of motion for the cavity was obtained. Analytical solutions were derived for limiting values of the parameters, and numerical results for other values. One of the more interesting results of this work is the finding that elasticity in the liquid can significantly retard the collapse of a void and produce prolonged oscillatory motion whenever the relaxation time is moderately large in comparison with the Rayleigh collapse time. F. A. Angona of Mobil Research and Development Corporation described measurements (Paper 6M3) of the threshold of cavitation in water at ambient pressures from 1 to 15atm. A 3OkHz beam was focused by an aluminum parabolic reflector to a small volume in the interior of the pressure chamber, thus minimizing wall effects and erosion damage. The