Abstract

The present study deals with the nonlinear free vibration analysis of sandwich plates containing electrorheological (ER) fluid as the core layer. Since yield stress of the ER fluid is relatively low, the fluid widely operates in the post-yield region in which the shear stress and shear strain relation is no longer linear. This study employs an equivalent linearized complex shear modulus to quantify the storage and loss moduli of the fluid in different levels of shear strain amplitude and electric field intensity. Also, Classical Plate Theory (CPT) along with von Kármán kinematic formulations are incorporated to extract governing equations of motion of the ER based sandwich plates, in a finite element formulation. The nonlinear governing equations of motion of the structure are solved using a displacement control strategy to evaluate the resonant frequencies and corresponding loss factors of the sandwich plate. Then, the primary attention is focused on the effect of post-yield characteristics of ER fluid on the nonlinear dynamic behavior of the ER based sandwich structure. Furthermore, the effect of applied electric field, boundary conditions and plate parameters such as core layer thickness on the natural frequencies and damping of the structure are comprehensively investigated.

摘要

本研究涉及包含电流变 (ER) 流体作为核心层的夹层板的非线性自由振动分析。由于 ER 流体的屈服应力相对较低，因此该流体在剪切应力和剪切应变关系不再呈线性的后屈服区域广泛运行。本研究采用等效线性化复数剪切模量来量化流体在不同剪切应变幅度和电场强度水平下的储能和损耗模量。此外，经典板理论 (CPT) 与 von Kármán 运动学公式相结合，以在有限元公式中提取基于 ER 的夹层板的运动控制方程。使用位移控制策略求解结构的非线性运动控制方程，以评估夹层板的共振频率和相应的损耗因子。然后，主要关注电流变流体的屈服后特性对电流变夹层结构非线性动力学行为的影响。此外，还综合研究了外加电场、边界条件和核心层厚度等板材参数对结构固有频率和阻尼的影响。