Finite element modelling of macro fiber composite with interdigitated electrode for engineering applications
Smart structures with Macro fiber composite (MFC) piezoelectric actuators have been increasingly applied in engineering. A simple but elaborate finite element model of the smart structures not only can predict vibration dynamics, but also can reduce challenges and computational expense in engineering application. Therefore, a simplified FEM developed to model MFC with interdigitated electrodes (IDEs) is proposed in this paper. A new scheme of FEM for IDEs in MFC is presented. With assuming the poling direction is along the same direction and voltage-progressive electrodes configuration in FEM, the piezoelectric elements employ an equivalent periodic tensile/compressive strain and constant electric potential in the poling direction. Numerical tests of free strain and blocking force and experimental methods are both employed to verify the FEM in this paper. A cantilever aluminum beam with a single MFC actuator is presented. The natural frequencies, vertical deflection and Modal Assurance Criterion (MAC) based on the resonant frequencies show the fidelity of the EF model agree well with experimental measurement. This work presented provides a novel FEM to model MFC for engineering applications such as vibration actuation.
A Morphing Concept Based on Unsymmetric Composite Laminates and Piezoceramic MFC Actuators
Bi-stable unsymmetric composite laminates controlled with the piezoelectric MFC actuators are considered as a possible morphing structure. The use of piezoelectric actuators to effect snap-through behavior in bi-stable unsymmetric laminates is studied two ways. First, an experimental actuator-laminate structure is discussed along with efforts to model the shapes and behavior of the structure using the Rayleigh-Ritz technique. The modeling shows promise: the shapes were closely predicted, but the snap-through voltage was under predicted. In the second part of the paper, the capability to model actuator-laminate structures was expanded to include finite-element modeling using the finite-element package ABAQUS. Two finite-element models of simple problems were developed and compared with Rayleigh-Ritz solutions. Agreement between the finite-element and the Rayleigh-Ritz solutions was generally good: the predicted shapes were very similar, but the finite-element solutions were able to capture behavior not seen in the Rayleigh-Ritz solutions.
Prediction of a representative point for rail temperature measurement by considering longitudinal deformation
Monitoring rail temperature is very important for determining the safe running speed of trains and to prevent buckling. In general, the maximum variation of the internal rail temperature can be >7 ℃ depending on the point of measurement. However, there is as yet no sufficient information about how to predict the measurement point to represent the thermal deformation due to temperature distribution. In this study, the authors report a new point, called the representative measurement point, at which the rail temperature can be measured. This point considers the average deformation of the rail through structural analysis by adopting experimental and actual rail temperature data. The authors designed and installed a measurement system similar to an actual rail environment. Using the system, various data were acquired (internal/surface rail temperature and weather data) for 10 months. On the basis of these data, an analysis was done to calculate the average deformation point through thermal analysis. Finally, the representative measurement point was proposed as the position at which the average deformation point converges regardless of weather or seasons. The authors believe that the method described herein is advantageous in that it could be used in a high-accuracy temperature-monitoring system and for predicting thermal deformation and buckling.