Marc Lethiecq

Learn More
High-intensity and high-frequency ultrasound was tested for its ability to accelerate meat ageing and increase beef tenderness. Samples (≈50g) of semimembranosus muscles from 8 cull cows were assigned to ultrasonic treatment (2.6MHz; 10W/cm(2); 2 ×15s) either pre-rigor (day 0, pH 6.2) or post-rigor (day 1, pH 5.4). When applied pre-rigor, ultrasound induced(More)
A new hybrid finite-difference (FD) and pseudospectral (PS) method adapted to the modeling of piezoelectric transducers (PZTs) is presented. The time-dependent equations of propagation are solved using the PS method while the electric field induced in the piezoelectric material is determined through a FD representation. The purpose of this combination is to(More)
A model is proposed to predict the electroelastic moduli of 0-3 connectivity piezo-composites from which parameters such as longitudinal wave velocity and thickness mode coupling factor can be deduced. The composite, a polymer loaded with ceramic particles, is represented by a unit cell, and a matrix manipulation is shown to be a practical way to perform a(More)
The design of transducers requires a clear understanding of their electromechanical behavior. This involves precise linear modeling as well as characterization. With the development of novel techniques such as harmonic imaging as well as high-power applications, nonlinear aspects must also be taken into account. In this study, harmonic generation in the(More)
The objective of this study is to understand the role of residual stress in piezoelectric layers in order to predict the performance of integrated structures. This is of particular importance in thick or thin film technology. Considering a bulk piezoelectric material, the Christoffel equation for a piezoelectric material is modified to take into account a(More)
A screen-printed PZT thick film with a final thickness of about 40 microm was deposited on a porous PZT substrate to obtain an integrated structure for ultrasonic transducer applications. This process makes it possible to decrease the number of steps in the fabrication of high-frequency, single-element transducers. The porous PZT substrates allow high(More)
The goal of this work was to develop an extended ultrasound transducer model that would optimize the trade-off between accuracy of the calculation and computational time. The derivations are presented for a generalized transducer model, that is center frequency, pulse duration and physical dimensions are all normalized. The paper presents a computationally(More)
Approximate formulas including losses to predict the electrical impedance of a thin unloaded piezoelectric plate around antiresonant frequencies of the thickness modes have been derived. To do so, a total loss factor is defined that includes both mechanical and electrical losses. Complex electrical impedance measurements on a lead metaniobate and four(More)
The transient analysis of piezoelectric transducers is often performed using finite-element or finite-difference time-domain methods, which efficiently calculate the vibration of the structure but whose numerical dispersion prevents the modeling of waves propagating over large distances. A second analytical or numerical simulation is therefore often(More)