Review of State of Art of Smart Structures and Integrated Systems

Actuators, transducers and motors based on giant magnetostrictive materials

This thesis contains the complete end-to-end simulation, development, implementation, and calibration of the wide bandwidth, low-Q, Kiwi-SAS synthetic aperture sonar (SAS). Through the use of a very stable towfish, a new novel wide bandwidth transducer design, and autofocus procedures, high-resolution diffraction limited imagery is produced. As a complete system calibration was performed, this diffraction limited imagery is not only geometrically calibrated, it is also calibrated for target cross-section or target strength estimation. Is is important to note that the diffraction limited images are formed without access to any form of inertial measurement information. Previous investigations applying the synthetic aperture technique to sonar have developed processors based on exact, but inefficient, spatial-temporal domain time-delay and sum beamforming algorithms, or they have performed equivalent operations in the frequency domain using fast-correlation techniques (via the fast Fourier transform (FFT)). In this thesis, the algorithms used in the generation of synthetic aperture radar (SAR) images are derived in their wide bandwidth forms and it is shown that these more efficient algorithms can be used to form diffraction limited SAS images. Several new algorithms are developed; accelerated chirp scaling algorithm represents an efficient method for processing synthetic aperture data, while modified phase gradient autofocus and a low-Q autofocus routine based on prominent point processing are used to focus both simulated and real target data that has been corrupted by known and unknown motion or medium propagation errors.

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Synthetic aperture imaging algorithms : with application to wide bandwidth sonar

The invention utilizes harmonics of certain clamped ultrasound transducers to generate ultrasound within the liquid of an ultrasonic tank and in a frequency range of between about 100 khz to 350 khz (i.e., “microsonic” frequencies). The application of microsonic frequencies to liquid preferably occurs simultaneously with a sweeping of the microsonic frequency within the transducer's harmonic bandwidth to reduce or eliminate (a) standing waves within the liquid, (b) other resonances, (c) high energy cavitation implosion, and (d) non-uniform sound fields, each of which is undesirable for cleaning and/or processing of semiconductor wafers and other delicate parts. The invention can also drive ultrasonic transducers such that the frequency of applied energy has a sweep rate within the ultrasonic bandwidth of the transducers; and that sweep rate is also varied so that the sweep rate is substantially non-constant during operation. This reduces or eliminates resonances which are created by transducers operating with a single sweep rate. An ultrasound generator of the invention sometimes utilizes amplitude modulation (AM), and the AM frequency is swept over time so as to reduce resonances. AM control is preferably provided by selecting a portion of the rectified power line frequency. In applications which utilize multiple generators, multiple transducers, and one or more tanks, simultaneously, the invention synchronizes the operation of the generators to a common FM signal to reduce beat frequencies between generators. Each such generator can also be adjusted, through AM, to control the process characteristics within the associated tank. Two or more transducers are sometimes used by the invention, in combination, to broaden the overall bandwidth of acoustical energy applied to the liquid around the primary frequency or one of the harmonics. The bandwidths of the transducers are made to overlap such that an attached generator can drive the transducers, in combination, to deliver ultrasound to the liquid in a broader bandwidth. In a single chamber ultrasound system, two or more generators, each operating or optimized to generate a different range of frequencies, are connected to a multiplexer; and the desired frequency range is selected, and hence the right generator, according to the cavitation implosion energy that is desired within the tank chemistry.

Apparatus and methods for cleaning and/or processing delicate parts

This paper addresses the modeling of strains and forces generated by magnetostrictive transducers in response to applied magnetic fields. The magnetostrictive effect is modeled by considering both the rotation of magnetic moments in response to the field and the elastic vibrations in the transducer. The former is modeled with the Jiles-Atherton model of ferromagnetic hysteresis in combination with a quartic magnetostriction law. The latter is modeled through force balancing which yields a PDE system with magnetostrictive inputs and boundary conditions given by the specific transducer design. The solution to this system provides both rod displacements and forces. The calculated forces are used to quantify the magnetomechanical effect in the transducer core, i.e., the stress-induced magnetization changes. This is done by considering a “law of approach” to the anhysteretic magnetization. The resulting model provides a representation of the bidirectional coupling between the magnetic and elastic states. It is...

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A Coupled Structural-Magnetic Strain and Stress Model for Magnetostrictive Transducers.

A detailed modal analysis of several axisymmetrical or fully three‐dimensional Tonpilz transducers is carried out, both with a plane wave approach and with the finite element method. It allows identification and classification of the modes in a broad frequency range (longitudinal modes of the ceramic stack, flexural modes of the head mass, and longitudinal modes of the stress rod) and demonstrates that the motion of the ceramic part of the structure remains essentially of plane wave type. Following this conclusion, a mixed finite element–plane wave method is proposed and described, which gives fairly good results and uses the computational resources efficiently. Moreover, it is likely to be applied to other types of projectors.

In‐air analysis of piezoelectric Tonpilz transducers in a wide frequency band using a mixed finite element–plane wave method

The design of efficient low‐frequency flextensional sonar transducers is a present challenge which is made difficult by a partial lack of general accurate mathematical models. Thus the application of the finite‐element method to this problem is a promising approach which has been worked recently. To test the ability of the finite‐element code atila [Decarpigny et al., J. Acoust. Soc. Am. 78, 1499–1507 (1985)] to predict the in‐air and in‐water dynamic behavior of such structures, an axisymmetrical thin‐shell transducer was built, and its acoustical behavior was experimentally and numerically analyzed. This paper first presents the modal analysis of this projector, using different finite‐element meshes as well as a mixed finite‐element–plane‐wave model and the comparison of numerical displacement field values to holographic measurements. Second, it describes an in‐water harmonic analysis in which the model of the infinite fluid domain is reduced to a portion of the acoustic nearfield, limited by a spherica...

Analysis of a radiating thin‐shell sonar transducer using the finite‐element method

GD.E RBDoSuMch -eDrC AN Toulon, DCN, Le Bruse, F-83140 Six Fours Les Plages, France The physical parameters which are relevant to the design and construction of magnetostrictive transducers are discussed through the analysis of a lumped parameter model (LPM). Numerical modeling of the magnetostrictive coupling, including a plane wave method (PWM) and the finite element method (FEM) which has been implemented in the ATILA code is presented. A process to determine all the magneto-elastic constants for use in the models is described. A complete magneto-elastic matrix of a Terfenol-D alloy is given. A test characterization device is analyzed using this matrix with the three types of model. The good agreement between measurements and modeling is a validation for both the models and the characterization method.

Modeling and Characterization of the Magnetostrictive Coupling

An electro-acoustic transducer according to the invention is of the Tonpilz type comprising a stack of piezo-electric plates placed between a horn and a countermass, and electrodes inserted between the plates. Some of the electrodes are connected to a common excitation or output conductor through phase-shifting circuits which allow the electric voltage of a proportion of these electrodes to be dephased. A logic unit allows the phase-shifting of the electrodes to be distributed within the stack according to several different groupings in dependence upon frequency. One application of the invention is to the construction of long-range power sonars.

Electrio-acoustic transducers

The invention relates to processes and electro-acoustic transducers for transmitting low-frequency acoustic waves in a liquid. An electro-acoustic transducer according to the invention is a transducer of the double-tonpilz type, comprising two electro-acoustic drivers (1a, 1b) in line on both sides with a central counter-mass (2) and between two horns (3a, 3b). This mechanical assembly is located in a rigid box (4) which is fitted with side holes (5) and which delimits a cavity (7) housing elastic tubes (6) closed at their both ends and filled with gas so that the Helmholtz resonant frequency of the cavity (7) is close and preferably lower than the fundamental frequency of the axial vibrations of the vibrating assembly. An application of the invention is the construction of low-frequency transmitting transducers of the double-tonpilz type with a wide pass-band.

Didier Boucher

Papers

In‐air analysis of piezoelectric Tonpilz transducers in a wide frequency band using a mixed finite element–plane wave method

Analysis of a radiating thin‐shell sonar transducer using the finite‐element method

Modeling and Characterization of the Magnetostrictive Coupling

Electrio-acoustic transducers

Process and electro-acoustic transducers for transmitting low-frequency acoustic waves in a liquid