A sensor for the direct measurement of curvature based on flexoelectricity

Abstract

A direct curvature sensing measurement based on the flexoelectricity of Ba 0.64 Sr 0.36 TiO 3 (BST) material through electromechanical coupling is proposed and developed in this paper. The curvature sensing was demonstrated in four point bending tests of a beam with bonded BST curvature sensors under different applied loads with low time-harmonic frequencies from 0.5 to 3 Hz. A shear lag concept which describes the efficiency of the loading transfer from the epoxy bonding layer was taken into account in extracting the actual curvature from the sensor measurement. A finite element analysis has been performed to estimate the curvature transfer efficiency and the bonding layer thickness is found to be a critical parameter in determining the curvature transfer. Experimental results showed a good linearity of charge output dependence on curvature inputs in a limited frequency range and showed a curvature sensitivity of 30.78 pC m, in comparison with 32.48 pC m from theoretical predictions. Using the measured curvature, the bending stiffness of the beam was then obtained from the experimentally obtained moment-curvature curve. This work demonstrated that the flexoelectric BST sensor provides a direct curvature measurement instead of using a traditional strain gage sensor through interpolation, and thus offers an important avenue for on-line and in situ structural health monitoring.

Strain Gauges Based 3D Shape Monitoring of Beam Structures Using Finite Width Gauge Model

“…A simple and straightforward way to monitor shape consists in measuring directly the displacement of the material structure by using technologies based on electronics and optics, such as deflection gauge, CCD camera or laser scanner [7,8]. Nevertheless, this type of direct monitoring can be challenging in some cases due to instrumentation constraints and hidden or unreachable areas [9]. Structure shape monitoring can then be achieved indirectly by reconstructing the shape from the structure characteristics, such as strain.…”

Enhanced Ferroelectric Functionality in Flexible Lead Zirconate Titanate Films with In Situ Substrate‐Clamping Compensation

“…Among the flexing methods, four-point stressing produces the most homogeneous strain distribution over a long range, enabling characterization of the functional properties independent of the position of the PFM probe as well as under the larger-scale beam of an X-ray diffraction (XRD) tool. The applied stress (σ) and hence the induced strain (ε) along a beam according to the torque behavior are described as follows: [14,15]…”

A pin-moment model of flexoelectric actuators

“…Resulting from the direct flexoelectric effect and the scaling effect of the mechanical gradient, flexoelectricity provides another potential avenue for sensing application. Yan et al (2013) and co-workers developed a direct curvature measurement sensor by using Ba 0.64 Sr 0.36 TiO 3 (BST) material. A flexoelectric torque sensor based on un-polarised polyvinylidene fluoride (PVDF) that does not require external electric power excitation was proposed by Zhang et al (2015).…”