Didier Boucher

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

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.

Analysis of a radiating thin‐shell sonar transducer using the finite‐element 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 magnetostrictive transducers by the ATILA finite element code

New magnetostrictive rare‐earth‐iron alloys offer an attractive opportunity for the design of high‐power low‐frequency transducers [F. Claeyssen, J. Acoust. Soc. Am. Suppl. 1 81, S89 (1987)]. In order to optimize the design of this particular class of transducers, a model based on a new variational principle has been derived following a classical finite element method approach. This model describes the three‐dimensional dynamic behavior of heterogeneous electrochemically coupled structures. Due to the reduced‐scalar‐potential formulation of the magnetic field, the model has been relatively easily implemented within the ATILA finite element code. In this paper, a general view of the method is given and first computation results on test structures are presented.

Tonpilz type piezoelectric transducer capable of operating alternately as wideband receiver and emitter

A Tonpilz type piezoelectric transducer which can be used alternately as a wide-band receiver and an emitter includes a stack of pairs of piezoelectric segments separated by electrodes, the stack being placed between a horn and a countermass. An emitter is connected by a conductor to one of the two electrodes for each segment pair. One pair of segments next to the countermass is separated from the others by an insulator. The two electrodes to either side of the one pair are connected in parallel to a receiver and, through two diodes connected in opposition, to a grounded common conductor.

An analytical evaluation of the heating of low‐frequency sonar projectors

Heating has become a critical issue for low‐frequency projectors for sonar and oceanography due to their high dissipated power density and long excitation time. An analysis of the transducer heating requires a description of the heat conduction in the structure and of the heat exchanges with the surrounding medium. To solve this problem for the steady‐state case, an analytical model of the heat transfer in the projector, based on thermoelectrical analogies, is proposed. The model is applied to the analysis of heat transfer in two geometries of low‐frequency projectors: a double‐ended longitudinal vibrator and a class IV flextensional transducer. In each case, temperature and heat fluxes are calculated and compared to numerical results from a finite element analysis.

Process to increase the power of the low frequency electro acoustic transducers and corresponding transducers

An electroacoustic transducer according to the invention comprises a stacking of annular plates (13) made of piezoelectric ceramics alternating with annular electrodes (14) and pressed by an axial prestressing stem (15). The contact faces between each plate and the adjacent ones are made of two flat parts (16a, 16b) whose surface is smaller than the maximum cross section, due to the chamfers (19a, 19b, 20a, 20b) which truncate the edges of each plate. One application is the construction of low frequency sonar transmitters. Referenced elements refer to FIG. 3.

Process and transducer for emitting wide band and low frequency acoustic waves in unlimited immersion depths

The present invention relates to a process and transducer for emitting wideand and low frequency acoustic waves in unlimited immersion depth. The invention is applied to tranducers comprising at least one electro-acoustic motor (1) causing any wall 3 of the said waves to vibrate, and a hollow shell 5 enclosing the said motor 1, and delimiting with the said vibrating wall 3 among others, a cavity 7, characterised in that: at least one opening 5, causing cavity 7 to communicate with ambient medium 4, is made in said shell 5; in at least part of the volume of the said cavity 7, at least one flexible bladder 7, is installed; this bladder 8 is filled with a fluid 9 more compressible than fluid 4.

Method and apparatus for emitting high power acoustic waves using transducers

A transducer includes at least one cylindrical driving assembly and at least one headmass coupled to an end of the cylindrical driving assembly. The headmass has an external ring that surrounds a core. The core is made from a core material that is less dense than the material from which the external ring is made. The headmass is dimensioned to occupy a predetermined volume so as to transmit waves within a predetermined frequency range. As a result, the transducer provides higher power waves, yet occupies the same volume as the transducers of the prior art.

A 300 Hz Janus-Helmholtz transducer for ocean acoustic tomography

Ocean acoustic tomography has need for low frequency and high efficiency transducers, in order to reach ranges greater than 500 km with large bandwidth and great depth capability. The characteristics of the Janus-Helmholtz transducer, designed by DCN Ingenierie Sud, widely answer these contradictory requirements. However, as acoustic tomography requires lower frequencies (a working frequency band around 400 Hz is expected), several Janus-Helmholtz transducers with a lower first resonance frequency have been modelled with the finite-element code ATILA. In addition, for other applications, a larger projector with a first resonance frequency at 160 Hz has been defined. Some new insights of the transducer response interpretation are also given.<<ETX>>

Analysis of a magnetostrictive Tonpilz transducer

A rare‐earth iron Tonpilz transducer has been developed in a compact size, low‐frequency, high‐power design. The main reason for this first transducer choice is that its behavior is rather well understood, the rods being used on their longitudinal mode. The active elements of the Tonpilz are four rods of random oriented TbO.3DyO.7 Fel.8 alloy. They are magnetically coupled through a laminated flux return path. Force‐cooled coils provide the dynamic magnetic field as well as the polarizing bias. Data on electrical impedance, transmitting current response, transmitting voltage response, effective coupling coefficient, efficiency, and linearity versus the bias are presented. The in‐air and in‐water measurements are compared with the results predicted by a plane wave model taking into account leakage flux, reluctance of the return path, eddy current losses in the rods and in the return path, and mechanical damping. The material constants of the magnetostrictive alloy used in the model are measured independent...