Exploring the dynamics of hourglass shaped lattice metastructures

Revolutionizing Prosthetic Design with Auxetic Metamaterials and Structures: A Review of Mechanical Properties and Limitations

Prosthetics have come a long way since their inception, and recent advancements in materials science have enabled the development of prosthetic devices with improved functionality and comfort. One promising area of research is the use of auxetic metamaterials in prosthetics. Auxetic materials have a negative Poisson's ratio, which means that they expand laterally when stretched, unlike conventional materials, which contract laterally. This unique property allows for the creation of prosthetic devices that can better conform to the contours of the human body and provide a more natural feel. In this review article, we provide an overview of the current state of the art in the development of prosthetics using auxetic metamaterials. We discuss the mechanical properties of these materials, including their negative Poisson's ratio and other properties that make them suitable for use in prosthetic devices. We also explore the limitations that currently exist in implementing these materials in prosthetic devices, including challenges in manufacturing and cost. Despite these challenges, the future prospects for the development of prosthetic devices using auxetic metamaterials are promising. Continued research and development in this field could lead to the creation of more comfortable, functional, and natural-feeling prosthetic devices. Overall, the use of auxetic metamaterials in prosthetics represents a promising area of research with the potential to improve the lives of millions of people around the world who rely on prosthetic devices.

On the Possibility of Using 3D Printed Polymer Models for Modal Tests on Shaking Tables: Linking Material Properties Investigations, Field Experiments, Shaking Table Tests, and FEM Modeling

In this article, the possibility and the pertinence of using 3D printed polymeric materials for models in modal tests on shaking tables were recognized. Four stages of the research have been linked: The material properties investigation, the field experiment on the modal properties of the reinforced concrete chimney (a prototype), the shaking table tests on the modal properties of the 3D printed polymer model of the chimney, scaled according to the similarity criteria, and the numerical calculations of the FE model of the 3D printed mockup. First, the investigation of the properties of 3D printed polymer materials revealed that the direction of lamination had no significant effect on the modulus of elasticity of the material. This is a great benefit, especially when printing models of tall structures, such as chimneys, which for technical reasons could only be printed in a spiral manner with the horizontal direction of lamination. The investigation also proved that the yield strength depended on the direction of the lamination of the specimens. Next, the natural frequencies of the chimney, assessed through the field experiment and the shaking table tests were compared and showed good compatibility. This is a substantial argument demonstrating the pertinence of using 3D printed polymer materials to create models for shaking table tests. Finally, the finite element model of the 3D printed polymer mockup was completed. Modal properties obtained numerically and obtained from the shaking table test also indicated good agreement. The presented study may be supportive in answering the question of whether traditional models (made of the same material as prototypes) used in shaking table tests are still the best solution, or whether innovative 3D printed polymer models can be a better choice, in regard to the assessment of the modal properties and the dynamic performance of structures.

Vibration mitigation of an MDoF system subjected to stochastic loading by means of hysteretic nonlinear locally resonant metamaterials

In this paper, we intend to mitigate absolute accelerations and displacements in the low-frequency regime of multiple-degrees-of-freedom fuel storage tanks subjected to stochastic seismic excitations. Therefore, we propose to optimize a finite locally resonant metafoundation equipped with massive resonators and fully nonlinear hysteretic devices. The optimization process takes into account the stochastic nature of seismic records in the stationary frequency domain; the records are modelled with the power spectral density S₀ and modified with a Kanai–Tajimi filter. Moreover, the massive superstructure of a fuel storage tank is also considered in the optimization procedure. To optimize the nonlinear behaviour of dampers, we use a Bouc–Wen hysteretic model; the relevant nonlinear differential equations are reduced to a system of linear equations through the stochastic equivalent linearization technique. The optimized system is successively verified against natural seismic records by means of nonlinear transient time history analyses. Finally, we determine the dispersion relations for the relevant periodic metafoundation.