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Jeong, Sinwoo,Cho, Jae Yong,Sung, Tae Hyun,Yoo, Hong Hee IOP 2017 Smart materials & structures Vol.26 No.3
<P>Conventional vibration-based piezoelectric energy harvesters (PEHs) have advantages including the ubiquity of their energy source and their ease of manufacturing. However, they have a critical disadvantage as well: they can produce a reasonable amount of power only if the excitation frequency is concentrated near a natural frequency of the PEH. Because the excitation frequency is often spread and/or variable, it is very difficult to successfully design a conventional PEH. In this paper, we propose a new cantilevered PEH whose design includes an attached mass and a segmented piezoelectric layer. By choosing a proper size and location for the attached mass, the gap between the first and second natural frequencies of the PEH can be decreased in order to broaden the effective excitation frequency range and thus to allow reasonable power generation. Especially, the output power performance improves significantly around the second natural frequency of the PEH since the voltage cancellation effect can be made very weak by segmenting the piezoelectric layer at an appropriate location. To investigate the power performance of the new PEH, herein a reduced-order electromechanical analysis model is proposed and the accuracy of this model is validated experimentally. The effects of variable load resistance and piezoelectric layer segmentation location upon the power performance of the new PEH are investigated by means of the reduced-order analysis model.</P>
Flexibility modeling of a beam undergoing large deflection using the assumed mode method
Jeong, Sinwoo,Yoo, Hong Hee Pergamon Press 2017 International journal of mechanical sciences Vol.133 No.-
<P><B>Abstract</B></P> <P>We propose a new nonlinear modeling method to conduct the static or dynamic analysis of a flexible beam undergoing large deflection in this paper. In the proposed modeling method, we employ the in-extensible beam assumption which simplifies the expressions of strain energy and geometric constraints among deformation variables. Deformation variables are approximated using modal coordinates and quasi-comparison functions. Governing equations are derived based on the extended Hamilton's principle and used to solve various kinds of nonlinear static and dynamic analysis problems. The accuracy of the proposed modeling method is validated by comparing numerical results to those obtained with a commercial nonlinear finite element code. The efficiency and solution convergence robustness of the proposed modeling method are also compared.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A nonlinear modeling method for a beam undergoing large deflection is proposed. </LI> <LI> The assumed mode method is employed for the nonlinear modeling method. </LI> <LI> Various numerical examples for beams undergoing large deflection are solved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>(a) Circular-path guided compliant mechanism and (b) deformed shapes of the flexible link versus β</P> <P>[DISPLAY OMISSION]</P>