Journal of Theoretical and Applied Vibration and Acoustics
Volume:8 Issue: 1, Winter & Spring 2022

Predicting the vibration behavior of microsystems is of great importance. In this study, the vibration behavior of a microsensor modeled as a two-layer microplate is investigated. The effect of size has been investigated through the modified couple stress theory. The first natural frequency is extracted using the penalty approach. Boundary conditions are modeled using linear or torsional springs. Finally, changes in the natural frequency of the microsystem are presented according to different values ​​of the microplate parameters such as the thickness of the silicon layer and material of the second layer. The results show that the natural frequency decreases as the thickness of the second layer increases. In addition, despite the different first natural frequencies for different parameters, the natural frequency diagram shows the same behavior in terms of system parameters under various boundary conditions. Finally, the effect of the thicknesses ratio   and material length scale parameters ratio  on the natural frequency is investigated.   Predicting the vibration behavior of microsystems is of great importance. In this study, the vibration behavior of a microsensor modeled as a two-layer microplate is investigated. The effect of size has been investigated through the modified couple stress theory. The first natural frequency is extracted using the penalty approach. Boundary conditions are modeled using linear or torsional springs. Finally, changes in the natural frequency of the microsystem are presented according to different values ​​of the microplate parameters such as the thickness of the silicon layer and material of the second layer. The results show that the natural frequency decreases as the thickness of the second layer increases. In addition, despite the different first natural frequencies for different parameters, the natural frequency diagram shows the same behavior in terms of system parameters under various boundary conditions. Finally, the effect of the thicknesses ratio   and material length scale parameters ratio  on the natural frequency is investigated.

The primary objective of this research is to identify the physical and geometrical properties of the joint-affected region in under-platform dampers and minimize errors caused by the selection of the contact surface type by updating the connection properties. Additionally, an optimized model is proposed for selecting the type of finite elements to reduce execution time using system simulation in finite element software. The experimental test has been done on the three-dimensional model of two blades with the under-platform damper in a free-free manner, and the behavior of the joint-affected region has been optimized according to the results extracted from the experimental test. Three types of affected regions, rectangular and ellipsoidal, and two pieces shapes, are considered in five different dimensions to obtain the best model and dimensions of the affected surface. The results demonstrate that the ellipsoidal model yields simulation results that are closer to the experimental test results with lower error. Moreover, reducing the dimensions of the affected surface to the center of the effect provides more accurate results. These findings have significant implications for improving the performance of under-platform dampers and reducing vibrations in mechanical structures.

In recent times, there has been a growing interest in harnessing environmental energy resources, particularly mechanical vibrations, to power low-energy electrical devices like wireless sensors. Among these energy sources, the movement of the human body stands out. This paper delves into the realm of piezoelectric energy harvesting using the mechanical energy generated by foot acceleration during movement. The energy harvesting mechanism revolves around a nonlinear piezoelectric harvester, featuring a cantilever beam equipped with two piezoelectric patches on opposite sides and supported by curved surfaces. To model the foot's motion, we apply measured foot acceleration as a base excitation to the harvester. Subsequently, we develop a finite element model within the Ansys environment, encompassing the entire system comprising the cantilever beam, piezoelectric patches, supports, and electrical resistance. The culmination of our work involves designing, fabricating, and testing a model. The experimental results are then compared with those obtained from the finite element model. Remarkably, a strong correlation is evident between the measured data and the outcomes generated by the finite element analysis.