Novel multidirectional negative stiffness mechanical metamaterials

2019 ◽  
Vol 29 (1) ◽  
pp. 015037 ◽  
Author(s):  
Xiaojun Tan ◽  
Bing Wang ◽  
Shaowei Zhu ◽  
Shuai Chen ◽  
Kaili Yao ◽  
...  
Author(s):  
K. K. Dudek ◽  
R. Gatt ◽  
M. R. Dudek ◽  
J. N. Grima

This work discusses the concept of allowing the control of the stiffness of a particular class of re-entrant auxetic magneto-mechanical metamaterials through the introduction of magnets to the system. It is shown, through experimental testing backed up by a theoretical model, that the appropriate insertion of magnets in such a system will alter its stiffness, possibly even making it exhibit ‘negative stiffness’. This leads to a completely different behaviour of the structure in terms of stability. It is also reported that the investigated mechanical metamaterials may exhibit both negative stiffness and negative Poisson's ratio at the same time. Moreover, it is shown that the effect which magnets have on the stiffness of the system may be fine-tuned upon replacing magnets with electromagnets. Such systems have the potential to be used in a wide range of practical applications such as vibration damping devices where achieving a negative stiffness is of fundamental importance.


Author(s):  
Ankur Dwivedi ◽  
Arnab Banerjee ◽  
Bishakh Bhattacharya

Abstract Dynamics of periodic materials and structures have a profound historic background starting from Newton’s first effort to find sound propagation in the air to Rayleigh’s exploration of continuous periodic structures. This field of interest has received another surge from the early 21st century. Elastic mechanical metamaterials are the exemplars of periodic structures that exhibit interesting frequency-dependent properties like negative Young’s modulus, negative mass and negative Poisson’s ratio in a specific frequency band due to additional feature of local resonance. In this research, we present the modeling of piezo-embedded negative stiffness metamaterials by considering a shunted inductor energy harvesting circuit. For a chain of a finite number of metamaterial units, the coupled equation of motion of the system is deduced using generalized Bloch’s theorem. Successively, the backward substitution method is applied to compute harvested power and the transmissibility of the system. Additionally, through the extensive non-dimensional study of this system, the proposed metamaterial band structure is investigated to perceive locally resonant mechanical and electromechanical bandgaps. The results explicate that the insertion of the piezoelectric material in the resonating unit provides better tun-ability for vibration attenuation and harvested energy.


2020 ◽  
Vol 31 (8) ◽  
pp. 1076-1090 ◽  
Author(s):  
Ankur Dwivedi ◽  
Arnab Banerjee ◽  
Bishakh Bhattacharya

Mechanical metamaterials are uniquely engineered form of periodically arranged unit cells that exhibit interesting frequency-dependent physical properties like negative effective mass, Young’s modulus and Poisson’s ratio. These extreme engineering properties are beyond the natural properties of a material, which can modulate the propagation of wave. In this article, a mechanical realization of one of these uncommon properties called negative stiffness is emulated through analytical simulation. Wave propagation in metamaterials is contingent on frequency, which in turn results in transmission and attenuation bands. Simultaneous vibration control and energy harvesting can be executed by embedding energy harvesting smart material within the resonating units of the metamaterial. However, this needs careful design studies to outline the range of parameters. In this work, first, the band structure of a piezo-embedded negative stiffness metamaterial is studied using generalized Bloch’s theorem. Subsequently, harvested power along with the transmissibility is computed for a chain of finite number of metamaterial units by using backward substitution method. The results of the parametric studies elucidate that piezo-embedded negative stiffness metamaterial can enhance the performance in terms of vibration attenuation and harvested energy.


2021 ◽  
Author(s):  
Natsuki Tsushima ◽  
Ryo Higuchi ◽  
Hitoshi Arizono ◽  
Masato Tamayama

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