Primary objective of the work is to design, fabrication and testing of a 3-dimensional Mechanical vibration test bed.
Vibration testing of engineering prototype devices in mechanical and industrial laboratories is essential to understand the
response of the envisioned model under physical excitation conditions. Typically, two sorts of vibration sources are
available in physical environment, acoustical and mechanical. Traditionally, test bed to simulate unidirectional acoustic
or mechanical vibration is used in engineering laboratories. However, a device may encounter multiple uncoupled and/or
coupled loading conditions. Hence, a comprehensive test bed in essential that can simulate all possible sorts of vibration
conditions. In this article, an electrodynamic vibration exciter is presented which is capable of simulating 3-dimensional
uncoupled (unidirectional) and coupled excitation, in mechanical environments. The proposed model consists of three
electromagnetic shakers (for mechanical excitation). A robust electrical control circuit is designed to regulate the
components of the test bed through a self-developed Graphical User Interface. Finally, performance of the test bed is
tested and validated using commercially available piezoelectric sensors.
In this work, predictive model for a bio-inspired broadband frequency sensor is developed. Broadband frequency sensing is essential in many domains of science and technology. One great example of such sensor is human cochlea, where it senses a frequency band of 20 Hz to 20 KHz. Developing broadband sensor adopting the physics of human cochlea has found tremendous interest in recent years. Although few experimental studies have been reported, a true predictive model to design such sensors is missing. A predictive model is utmost necessary for accurate design of selective broadband sensors that are capable of sensing very selective band of frequencies. Hence, in this study, we proposed a novel predictive model for the cochlea-inspired broadband sensor, aiming to select the frequency band and model parameters predictively. Tapered plate geometry is considered mimicking the real shape of the basilar membrane in the human cochlea. The predictive model is intended to develop flexible enough that can be employed in a wide variety of scientific domains. To do that, the predictive model is developed in such a way that, it can not only handle homogeneous but also any functionally graded model parameters. Additionally, the predictive model is capable of managing various types of boundary conditions. It has been found that, using the homogeneous model parameters, it is possible to sense a specific frequency band from a specific portion (B) of the model length (L). It is also possible to alter the attributes of ‘B’ using functionally graded model parameters, which confirms the predictive frequency selection ability of the developed model.
This article presents the possibility of energy scavenging (ES) utilizing the physics of acousto-elastic metamaterial (AEMM) and use them in a dual mode (Acoustic Filter and Energy Harvester), simultaneously. Concurrent wave filtering and energy harvesting mechanism is previously presented using local resonance phenomenon in phononic crystal, however energy harvesting capabilities of AEMM is not reported extensively. Traditionally acoustic metamaterials are used in filtering acoustic waves by trapping or guiding the acoustic energy, whereas this work presents that the trapped dynamic energy inside the soft constituent (matrix) of metamaterials can be significantly harvested by strategically embedding piezoelectric wafers in the matrix. With unit cell model, we asserted that at lower acoustic frequencies maximum power in the micro Watts (~36μW) range can be generated, which is significantly higher than the existing harvesters of same kind. Efficient energy scavengers at low acoustic frequencies are almost absent due to large required size relevant to the acoustic wavelength. In this work we propose sub wave length scale energy scavengers utilizing the coupled physics of local, structural and matrix resonances. Upon validation of the argument through analytical, numerical and experimental studies, a broadband energy scavenger (ES) with multi-cell model is designed with varying geometrical properties.
To recover the hearing deficiency, cochlea implantation is essential if the inner ear is damaged. Existing implantable cochlea is an electronic device, usually placed outside the ear to receive sound from environment, convert into electric impulses and send to auditory nerve bypassing the damaged cochlea. However, due to growing demand researchers are interested in fabricating artificial mechanical cochlea to overcome the limitations of electronic cochlea. Only a hand full number of research have been published in last couple of years showing fabrication of basilar membrane mimicking the cochlear operations. Basilar membrane plays the most important role in a human cochlea by responding only on sonic frequencies using its varying material properties from basal to apical end. Only few sonic frequencies have been sensed with the proposed models; however no process was discussed on how the frequency selectivity of the models can be improved to sense the entire sonic frequency range. Thus, we argue that a predictive model is the missing-link and is the utmost necessity. Hence, in this study, we intend to develop a multi-scale predictive model for basilar membrane such that sensing potential of the artificial cochlea can be designed and tuned predictively by altering the model parameters.
A novel metamaterial using split ring resonator is envisioned. Unlike traditional metamaterials, multiple, uniquely designed split rings and elliptical full rings, embedded in polymer matrix are proposed. Purpose of such metamaterial is not only creating simultaneous negative effective mass density and negative bulk modulus but also use them to control structural vibration. Eigen-frequency analyses are performed to find multiple resonant frequencies and corresponding multiple acoustic band gaps. The dispersion equation of the periodic media is solved numerically using finite element method. The acoustic wave modes corresponding to both low and high frequency phonons are obtained. The proposed media was considered to be a periodic media consists of periodic array of unit cells, each cell containing specific geometry of split rings. Each unit cell is made of a metal sphere enclosed in metal circular ring. A pairs of circular split rings are placed symmetrically at the center of the unit cell. In addition to circular split rings, another set of elliptical split rings are also positioned to enclose the aforementioned assembly. To understand the effect of elliptical split rings on band gaps, split rings are then replaced by full rings and dispersion of similar acoustic wave modes are compared.