Large welded structures, including ships and offshore structures, are normally in operation under cyclic fatigue loadings. These structures include many geometric as well as material discontinuities due to weld joints, and the fatigue strength at these hot spots is of critical importance for the structural performance. In the past, various Non-Destructive Evaluation (NDE) techniques have been d...

This paper presents a new design for a linear ultrasonic micromotor for precision positioning developed by Physik Instrumente (PI). The stator of the ultrasonic motor consists of a rectangular piezoceramic plate. Two sliders, bonded to a spring which presses them against the stator, move along guides integrated in the stator. These motors are characterized by their extremely simple construction...

Piezoelectric wafer active sensors (PWAS) used in structural health monitoring (SHM) applications are able to detect structural damage using Lamb waves. PWAS are small, lightweight, unobtrusive and inexpensive. PWAS achieve direct transduction between electric and elastic wave energies. PWAS are essential elements in the Lamb-wave SHM with pitch-catch, pulse-echo, phased array system and electr...

The feasibility of harnessing electric energy using piezoelectric inserts in a sport sneaker has been demonstrated. Continuing in that spirit, this thesis compares regulation schemes for conditioning the electric energy harnessed by a piezoceramic source imbedded in a shoe insole. Two off-line, dc-dc direct converter hybrids (buck and forward) are proposed and implemented to improve the convers...

The class V cymbal is a flextensional transducer commonly used in low-power ultrasonic applications. The resonance frequency of the transducer can be tailored by the choice of end-cap and driver materials, and the dimensions of the end-caps. The cymbal transducer has one significant limitation which restricts the operational vibration amplitude of the device. This is the limit imposed by the me...

In order to get, at the ultrasonic receiver input, a clear echo pulse, it is very important to apply on the transducer a short high amplitude pulse (hundreds of volts). The pulse frequency is low enough to allow the reception and processing of the informations received from the analysed material between two adjacent pulses, but high enough to ensure an integral control of the material. The piez...

The use of porosity to modify the functional properties of piezoelectric ceramics is well known in the scientific literature as well as by the industry, and porous ceramic can be seen as a 2-phase composite. In the present work, examples are given of applications where controlled porosity is exploited in order to optimise the dielectric, piezoelectric and acoustic properties of the piezoceramic...