Theoretical and experimental study of the electroacoustic behavior of lithium niobate under an initial mechanical stress.

Recently, a second-order formalism of piezoelectric structures under an external mechanical stress was developed. Because the yield strength of lithium niobate was unknown, this study was not able to describe and evaluate realistic benefits of a prestress load on electromechanical properties. Therefore, in this study, experimental determination of the yield strength of lithium niobate sample is performed and shows that this limit is close to 110 MPa.

Relations between single-domain and multidomain piezoelastic properties in single crystals.

This paper presents a new method to compute the piezoelastic properties of multidomain single crystals from the single-domain constants. Based on a quasi static assumption, a PMN-chiPT multidomain is defined as a periodic medium with a lattice composed of layers of two domains in a twin structure. Such a structure is assumed to have charged domain walls that imply specific lattice media and boundary conditions.

Modeling of ultrasonic wave propagation in integrated piezoelectric structures under residual stress.

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 uniform residual stress on a given cross section.

A non-invasive method of tendon force measurement.

The ability to measure the forces exerted in vivo on tendons and, consequently, the forces produced by muscles on tendons, offers a unique opportunity to investigate questions in disciplines as varied as physiology, biomechanics, orthopaedics and neuroscience. Until now, tendon loads could be assessed directly only by means of invasive sensors implanted within or attached to these collagenous structures. This study shows that the forces acting on tendons can be measured, in a non-invasive way, from the analysis of the propagation of an acoustic wave.