PFM investigation of stress induced ferroelastic switching in piezoelectric bulk ceramics

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Crack propagation is critical for the assessment of the strength of rocks. Linear Elastic Fracture Mechanics (LEFM) theory is commonly used to describe its propagation. However, the variation of the fracture energy, its key parameter, is generally poorly understood as its experimental measurements are influenced by temperature, stress biaxiality, and rupture velocity. This indicates other dissipative processes may occur in the vicinity of the crack. We conduct Modified Ring Tests (MRT) on Carrara marble to

The characteristic functionality of ferroelectric materials is due to the symmetry of their crystalline structure. As such, ferroelectrics lend themselves to design approaches that manipulate this structural symmetry by introducing extrinsic strain. Using ...

Deviations from conventional hydraulic fracturing simulators’ predictions are sometimes observed in the field and laboratory. This questions the basic assumptions adopted in linear hydraulic fracture mechanics (LHFM): a linear elastic solid and a simplified fluid flow in the fracture. Some rocks encountered in the domain of hydraulic fracturing show a strong non-linear behavior with the existence of a process zone, and fluid flow in small rough apertures also presents a departure from the Poiseuille law. By

We have successfully demonstrated the fabrication of self-actuating multilayer NEMS resonators including cantilevers and double clamped beams. Resonant sensors are widely used as precision mass sensors for the detection and quantification of small concentration of analyte molecules in a gaseous solution or bacteria from biological sample which requires extremely high mass sensitivity and responsivity of the resonant sensor. Nanofabrication techniques have enabled the use of ultrathin layers for the fabricat

Steel tubular truss are lightweight, aesthetical and used in many different applications. These structures are sensitive to fatigue and specific verification methods have been developed for them, in particular by CIDECT [2001]. Due to assembly and welding, these structures contain large internal self-balanced stresses. Since tensile residual stresses tend to open cracks, they have a detrimental influence on the fatigue crack propagating under cyclic traffic loadings. Different studies on the behaviour of tu

Recent investigations of the tensile fracture behaviour of representative glassy and semicrystalline impact-resistant polymers are reviewed, with emphasis on the microdeformation behaviour as revealed by electron microscopy of sections from bulk specimens, where the crack-tip damage zone has been embedded and/or stained under load, and on thin films deformed in situ. The insight that such techniques have provided into the toughening mechanisms is discussed.

A unified approach for analysis of polarization fatigue and size effects on ferroelectric switching in relationship with injection and entrapment of charge at the interfacial layer of the ferroelectric film is developed. The proposed model suggests that an enhancement of the entrapped charge relaxation at the interfaces has a positive impact on both the polarization fatigue and size effects. This concept is implemented experimentally by introducing a thin conductive oxide (RuO2) layer into the top interface

The structure of the antiphase domain boundaries of strontium titanate SrTiO3 that exist at temperatures below the antiferrodistortive transition, is analyzed. It is found that some boundaries are similar to Neel domain walls, as an additional component of the order parameter develops within them. We show quantitatively that at low temperatures, typically below similar to 40 K, such boundaries become unstable with respect to the development of a ferroelectric polarization. This ferroelectric transition migh

The mechanical response of piezoelectric cantilever beams actuated by sol-gel- derived lead zirconium titanate (PZT) thin film is reported. Small multilayered beams are used to analyse the converse piezoelectric effect and to measure the mechanical deflection of the beams with a standard interferometry method. Interferometric displacement measurements, electrical measurements and finite- element simulations are reported to determine the piezoelectric coefficient d(31) of the PZT thin film.

We fabricated and characterized a micromotor driven by a piezoelectric PZT (PbZrxTi1-xO3) thin films. Sputter and sol-gel techniques have been applied for the deposition of the PZT films onto a silicon stator membrane, which was 20 to 30 µm thick and had a diameter of 4 mm. The amplitudes of the membrane deflections are as large as 800 nm/V at the first resonance (26 kHz), and 60 nm/V at 1 Hz. The operation of the motor was obtained at 1 to 3 Vrms, with speeds of up to 200 rpm at 1.1 Vrms and torques of 35

PFM investigation of stress induced ferroelastic switching in piezoelectric bulk ceramics

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Fracture energy variations of rocks: a mechanical investigation

Long-range symmetry breaking in embedded ferroelectrics

Propagation of a Radial Fluid-driven Fracture in Nonlinear Solid --around the tip of a fluid-driven fracture: process zone vs deviated fluid flow

Design and Fabrication of Multilayer Piezoelectric NEMS Resonators

Alternative stress definition and residual stress effects in fatigue design of welded tubular structures

Microdeformation in heterogeneous polymers revealed by electron microscopy

Charge relaxation at the interfaces of low-voltage ferroelectric film capacitors: Fatigue endurance and size effects

Prediction of a low-temperature ferroelectric instability in antiphase domain boundaries of strontium titanate

Piezoelectric cantilever beams actuated by PZT sol-gel thin film

Micromachined PZT thin film actuators for micromotors