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.
Low-Computational-Cost Technique for Modeling Macro Fiber Composite Piezoelectric Actuators Using Finite Element Method
The large number of interdigitated electrodes (IDEs) in a macro fiber composite (MFC) piezoelectric actuator dictates using a very fine finite element (FE) mesh that requires extremely large computational costs, especially with a large number of actuators. The situation becomes infeasible if repeated finite element simulations are required, as in control tasks. In this paper, an efficient technique is proposed for modeling MFC using a finite element method. The proposed technique replaces the MFC actuator with an equivalent simple monolithic piezoceramic actuator using two electrodes only, which dramatically reduces the computational costs. The proposed technique was proven theoretically since it generates the same electric field, strain, and displacement as the physical MFC. Then, it was validated with the detailed FE model using the actual number of IDEs, as well as with experimental tests using triaxial rosette strain gauges. The computational costs for the simplified model compared with the detailed model were dramatically reduced by about 74% for memory usage, 99% for result file size, and 98.6% for computational time. Furthermore, the experimental results successfully verified the proposed technique with good consistency. To show the effectiveness of the proposed technique, it was used to simulate a morphing wing covered almost entirely by MFCs with low computational cost.
New approach to vision-based BGA package inspection
Ball grid array (BGA) techniques have developed very fast due to the advantages of more I/O ports, small size, and so on. In this paper, a vision-based algorithm for BGA package inspection is proposed to accurately estimate center and diameters of solder-balls of BGA packages, so that defects of BGA packages, such as missing or extra balls, oversize or undersize balls, over-height or under-height balls, and pitch can be detected for ensuring the quality of BGA packages.