scholarly journals Idealized 3D Auxetic Mechanical Metamaterial: An Analytical, Numerical, and Experimental Study

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 993
Author(s):  
Naeim Ghavidelnia ◽  
Mahdi Bodaghi ◽  
Reza Hedayati
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Poisson’S Ratio ◽  
Element Model ◽  
Industrial Applications ◽  
Poisson's Ratio ◽  
Geometrical Parameters ◽  
Mechanical Metamaterials ◽  
Strength And Stiffness ◽  
The One

Mechanical metamaterials are man-made rationally-designed structures that present unprecedented mechanical properties not found in nature. One of the most well-known mechanical metamaterials is auxetics, which demonstrates negative Poisson’s ratio (NPR) behavior that is very beneficial in several industrial applications. In this study, a specific type of auxetic metamaterial structure namely idealized 3D re-entrant structure is studied analytically, numerically, and experimentally. The noted structure is constructed of three types of struts—one loaded purely axially and two loaded simultaneously flexurally and axially, which are inclined and are spatially defined by angles θ and φ. Analytical relationships for elastic modulus, yield stress, and Poisson’s ratio of the 3D re-entrant unit cell are derived based on two well-known beam theories namely Euler–Bernoulli and Timoshenko. Moreover, two finite element approaches one based on beam elements and one based on volumetric elements are implemented. Furthermore, several specimens are additively manufactured (3D printed) and tested under compression. The analytical results had good agreement with the experimental results on the one hand and the volumetric finite element model results on the other hand. Moreover, the effect of various geometrical parameters on the mechanical properties of the structure was studied, and the results demonstrated that angle θ (related to tension-dominated struts) has the highest influence on the sign of Poisson’s ratio and its extent, while angle φ (related to compression-dominated struts) has the lowest influence on the Poisson’s ratio. Nevertheless, the compression-dominated struts (defined by angle φ) provide strength and stiffness for the structure. The results also demonstrated that the structure could have zero Poisson’s ratio for a specific range of θ and φ angles. Finally, a lightened 3D re-entrant structure is introduced, and its results are compared to those of the idealized 3D re-entrant structure.

scholarly journals 3D auxetic mechanical metamaterials: an analytical, numerical, and experimental study

2020 ◽  
Author(s):  
Naeim Ghavidelnia ◽  
Reza Hedayati ◽  
Bodaghi
Keyword(s):  
Mechanical Properties ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Geometrical Parameters ◽  
Beam Elements ◽  
Mechanical Metamaterials ◽  
Strength And Stiffness ◽  
Beam Theories ◽  
Good Agreement ◽  
Numerical Approaches

Metamaterials are man-made rationally-designed structures that present unprecedented mechanical properties not found in nature. One of the most common metamaterials are Auxetics which demonstrate negative Poisson’s ratio (NPR) behavior that is very beneficial for biomedical and engineering applications. In this study, a specific type of auxetic metamaterial structure namely idealized 3D re-entrant structure is studied analytically, numerically, and experimentally. The noted structure is constructed of three types of struts: one loaded purely axially, and two loaded simultaneously flexurally and axially which are inclined and are spatially defined by angles θ and φ). Analytical relationships for elastic modulus, yield stress, and Poisson’s ratio of the 3D re-entrant unit cell based on two well-known beam theories namely Euler-Bernoulli and Timoshenko theories are derived. Moreover, two numerical approaches one based on beam elements and the other based on volumetric elements are implemented. Moreover, several specimens are additively manufactured and tested under compression. The analytical results had good agreement with volumetric numerical model and experimental results. Moreover, the effect of various geometrical parameters on the mechanical properties of the structure was studied and the results demonstrated that angle θ (related to tension-dominated struts) has the most effect on the sign of the Poisson’s ratio and its extent, while angle φ (related to compression-dominated struts) has minimal effect on Poisson’s ratio. However, the struts corresponding to φ angle provide strength and stiffness for the structure. The results also demonstrated that the structure could have zero Poison’s ratio for a specific range of θ and φ angles. Finally, a lightened re-entrant structure is introduced and its results are compared to those of the idealized 3D re-entrant structure.

scholarly journals An Isotropic Auxetic Structural Network With Limited Shear Stiffness

2011 ◽  
Author(s):  
Alessandro Spadoni
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Poisson’S Ratio ◽  
Shear Stiffness ◽  
Element Model ◽  
Mirror Image ◽  
Poisson's Ratio ◽  
Structural Components ◽  
Sandwich Construction ◽  
Structural Network

The chiral lattice is a unique structural network not symmetric to its mirror image, and with a negative Poisson’s ratio. Previous investigations have considered this structural network for the design of superior structural components with sandwich construction, but these were limited by the in-plane Poisson’s ratio predicted to be exactly −1. This paper presents estimates of the mechanical properties of the chiral lattice obtained from a multi-cell finite-element model. It is shown that the chiral lattice has a shear stiffness bound by that of the triangular lattice and it is very compliant to direct stresses. The minimum in-plane poisson’s ratio is estimated to be ≈ −0.94.

Young's Modulus and Poisson's Ratio Estimation Based on PSO Constriction Factor Method Parameters Evaluation

2019 ◽  
Vol 9 (2) ◽  
pp. 33-46
Author(s):  
George Lucas Dias ◽  
Ricardo Rodrigues Magalhães ◽  
Danton Diego Ferreira ◽  
Bruno Henrique Groenner Barbosa
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Young’S Modulus ◽  
Cantilever Beam ◽  
Poisson’S Ratio ◽  
Inverse Analysis ◽  
Young's Modulus ◽  
Poisson's Ratio ◽  
Factor Method ◽  
Constriction Factor

The knowledge of materials' mechanical properties in design during product development phases is necessary to identify components and assembly problems. These are problems such as mechanical stresses and deformations which normally cause plastic deformation, early fatigue or even fracture. This article is aimed to use particle swarm optimization (PSO) and finite element inverse analysis to determine Young's Modulus and Poisson's ratio from a cantilever beam, manufactured in ASTM A36 steel, subjected to a load of 19.6 N applied to its free end. The cantilever beam was modeled and simulated using a commercial FEA software. Constriction Factor Method (PSO variation) was used and its parameters were analyzed in order to improve errors. PSO results indicated Young's Modulus and Poisson's ratio errors of around 1.9% and 0.4%, respectively, when compared to the original material properties. Improvement in the data convergence and a reduction in the number of PSO iterations was observed. This shows the potentiality of using PSO along with Finite Element Inverse Analysis for mechanical properties evaluation.

FINITE ELEMENT ANALYSIS OF MECHANICAL DEFORMATION OF CHONDROCYTE TO 2D SUBSTRATE AND 3D SCAFFOLD

2015 ◽  
Vol 15 (05) ◽  
pp. 1550077 ◽  
Author(s):  
JINJU CHEN ◽  
D. L. BADER ◽  
D. A. LEE ◽  
M. M. KNIGHT
Keyword(s):  
Mechanical Properties ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Poisson’S Ratio ◽  
Glass Plate ◽  
Mechanical Deformation ◽  
Poisson's Ratio ◽  
3D Scaffold ◽  
Element Analysis ◽  
Cell Functions

The mechanical properties of cells are important in regulation of many aspects of cell functions. The cell may respond differently to a 2D plate and a 3D scaffold. In this study, the finite element analysis (FEA) was adopted to investigate mechanical deformation of chondrocyte on a 2D glass plate and chondrocyte seeded in a 3D scaffold. The elastic properties of the cell differ in these two different compression tests. This is because that the cell sensed different environment (2D plate and 3D construct) which can alter its structure and mechanical properties. It reveals how the apparent Poisson's ratio of a cell changes with the applied strain depends on its mechanical environment (e.g., the elastic moduli and Poisson's ratios of the scaffold and extracellular matrix) which regulates cell mechanics. In addition, the elastic modulus of the nucleus also plays a significant role in the determination of the Poisson's ratio of the cell for the cells seeded scaffold. It also reveals the intrinsic Poisson's ratio of the cell cannot be obtained by extrapolating the measured apparent Poisson's ratio to zero strain, particularly when scaffold's Poisson's ratio is quite different from the cell.

scholarly journals Robust topological designs for extreme metamaterial micro-structures

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tanmoy Chatterjee ◽  
Souvik Chakraborty ◽  
Somdatta Goswami ◽  
Sondipon Adhikari ◽  
Michael I. Friswell
Keyword(s):  
Mechanical Properties ◽  
Topology Optimization ◽  
Elastic Modulus ◽  
Robust Design ◽  
Poisson’S Ratio ◽  
Mechanical Performance ◽  
Poisson's Ratio ◽  
Mechanical Metamaterials ◽  
Homogenization Approach ◽  
Micro Structures

AbstractWe demonstrate that the consideration of material uncertainty can dramatically impact the optimal topological micro-structural configuration of mechanical metamaterials. The robust optimization problem is formulated in such a way that it facilitates the emergence of extreme mechanical properties of metamaterials. The algorithm is based on the bi-directional evolutionary topology optimization and energy-based homogenization approach. To simulate additive manufacturing uncertainty, combinations of spatial variation of the elastic modulus and/or, parametric variation of the Poisson’s ratio at the unit cell level are considered. Computationally parallel Monte Carlo simulations are performed to quantify the effect of input material uncertainty to the mechanical properties of interest. Results are shown for four configurations of extreme mechanical properties: (1) maximum bulk modulus (2) maximum shear modulus (3) minimum negative Poisson’s ratio (auxetic metamaterial) and (4) maximum equivalent elastic modulus. The study illustrates the importance of considering uncertainty for topology optimization of metamaterials with extreme mechanical performance. The results reveal that robust design leads to improvement in terms of (1) optimal mean performance (2) least sensitive design, and (3) elastic properties of the metamaterials compared to the corresponding deterministic design. Many interesting topological patterns have been obtained for guiding the extreme material robust design.

scholarly journals Modelling of Nanoindentation of TiAlN and TiN Thin Film Coatings for Automotive Bearing

2019 ◽  
Vol 8 (3) ◽  
pp. 7194-7199
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
Finite Element ◽  
Yield Strength ◽  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Poisson's Ratio ◽  
The Finite Element Method ◽  
Element Method

Bearings are critical components for the transmission of motion in machines. Automotive components, especially bearings, will wear out over a certain period of time because they are constantly subjected to high levels of stress and friction. Studies have proven that coatings can extend the lifespan of bearings. Hence, it is necessary to conduct studies on coatings for bearings, particularly the mechanical and wear properties of the coating material. This detailed study focused on the mechanical properties of single-coatings of TiN and TiAIN using the finite element method (FEM). The mechanical properties that can be obtained from nano-indentation experiments are confined to just the Young’s modulus and hardness. Therefore, nanoindentation simulations were conducted together with the finite element method to obtain more comprehensive mechanical properties such as the yield strength and Poisson’s ratio. In addition, various coating materials could be examined by means of these nanoindentation simulations, as well the effects of those parameters that could not be controlled experimentally, such as the geometry of the indenter and the bonding between the coating and the substrate. The simulations were carried out using the ANSYS Mechanical APDL software. The mechanical properties such as the Young’s modulus, yield strength, Poisson’s ratio and tangent modulus were 370 GPa, 19 GPa, 0.21 and 10 GPa, respectively for the TiAlN coating and 460 GPa, 14 GPa, 0.25 and 8 GPa, respectively for the TiN coating. The difference between the mechanical properties obtained from the simulations and experiments was less than 5 %.

scholarly journals Finite Element Study on the Effect of Geometrical Parameters on the Mechanical Behavior of 3D Reentrant Auxetic Honeycombs.

2022 ◽  
pp. 1-7
Author(s):  
Sai Adithya Vanga ◽  
Aravind Rajan Ayagara ◽  
Rohan Gooty ◽  
Taha Hussain ◽  
Moulshree Srivastava
Keyword(s):  
Finite Element ◽  
Energy Absorption ◽  
Poisson’S Ratio ◽  
Bulk Material ◽  
Three Dimensional ◽  
Unit Cell ◽  
Poisson's Ratio ◽  
Geometrical Parameters ◽  
Self Healing ◽  
Strain Behavior

Auxetic materials are a special case of cellular materials, which exhibit a negative Poisson’s ratio. This in fact is the reason behind their peculiar behavior i.e. lateral shrinkage under longitudinal compression and vice versa. Since these materials do not obey the laws of “normal” materials and go beyond common sense, they are still an emerging class which can be put to use for various purposes like self-locking reinforcing fibers in composites, controlled release media, self-healing films, piezoelectric sensors, and also be used in biomedical engineering. Their stress-strain behavior, Poisson’s ratio and impact energy absorption are controlled by bulk material as well as the unit cell geometry. Among many forms of auxetic structures available, we have chosen a three-dimensional reentrant auxetic honeycomb unit cell. The unit cell geometrical parameters were taken from literature. In this study, we try to understand the effects of strut angle through finite element simulations while keeping the bulk material, unit cell size, strut thickness and number of repetitions constant. A total of three different angles were tested, based on which we conclude that as angle increases, the Poisson’s ratio increases and Energy absorption is maximum at 30 deg.

Prediction of Elastic Constants of Carbon Fabric/Polyurethane Composites

2016 ◽  
Vol 258 ◽  
pp. 233-236 ◽  
Author(s):  
Shun Fa Hwang ◽  
Hsuan Ting Liu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Young’S Modulus ◽  
Elastic Constants ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Element Model ◽  
Curing Temperature ◽  
Poisson's Ratio ◽  
Fiber Fabric

The purpose of this work is to study a new composite material consisting of polyurethane (PU) resin and carbon fiber fabric. This PU resin is superior in impact, viscosity, low curing temperature, and short curing time. If this resin is combined with fiber fabric by vacuum assisted resin transfer method, the fabrication time will be short. Since it is a braided composite, it’s important to have a model to predict the elastic constants for different braid angels. To predict the elastic constants including Young’s modulus, shear modulus, and Poisson’s ratio, a finite element model is established. In this model a braided layer is treated as two uni-directional layers. Then, the elastic constants of this composite with different braid angels are estimated. After that, the composites with different braid angels are fabricated and tested to obtain the elastic constants, and the comparison with the finite element results is made. The results indicate that the agreement is very good for the Young’s modulus. For the Poisson’s ratio, the difference between the prediction and the measurement is reasonable. From the comparison, it can be concluded that the finite element model is good. Then, this model is used to predict all in-plane elastic constants for arbitrary braid angles.

scholarly journals Computational Approach in Formulating Mechanical Characteristics of 3D Star Honeycomb Auxetic Structure

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Mozafar Shokri Rad ◽  
Zaini Ahmad ◽  
Amran Alias
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Element Model ◽  
Honeycomb Structure ◽  
Geometrical Parameters ◽  
Theoretical Formulation ◽  
Design Guideline ◽  
Structural Cell ◽  
Auxetic Materials ◽  
Structural Applications

Auxetic materials exhibit a unique characteristic due to the altered microstructure. Different structures have been used to model these materials. This paper treats a development of finite element model and theoretical formulation of 3D star honeycomb structure of these materials. Various shape parameters of the structural cell were evaluated with respect to the basic mechanical properties of the cell. Finite element and analytical approach for various geometrical parameters were numerically used to formulate the characteristics of the material. The study aims at quantifying mechanical properties for any domain in which auxetic material is of interest for variations in geometrical parameters. It is evident that mechanical properties of the material could be controlled by changing the base wall angle of the configuration. The primary outcome of the study is a design guideline for the use of 3D star honeycomb auxetic cellular structure in structural applications.

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