scholarly journals Stiffer, Stronger and Centrosymmetrical Class of Pentamodal Mechanical Metamaterials

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3470 ◽  
Author(s):  
Yan Huang ◽  
Xiaozhe Zhang ◽  
Muamer Kadic ◽  
Gongying Liang
Keyword(s):  
Finite Element Method ◽  
Size Dependence ◽  
Load Factor ◽  
The Finite Element Method ◽  
New Class ◽  
Scalability Analysis ◽  
Mechanical Metamaterials ◽  
Unit Cells ◽  
Anisotropic Structures ◽  
Infinite Case

Pentamode metamaterials have been used as a crucial element to achieve elastical unfeelability cloaking devices. They are seen as potentially fragile and not simple for integration in anisotropic structures due to a non-centrosymmetric crystalline structure. Here, we introduce a new class of pentamode metamaterial with centrosymmetry, which shows better performances regarding stiffness, toughness, stability and size dependence. The phonon band structure is calculated based on the finite element method, and the pentamodal properties are evaluated by analyzing the single band gap and the ratio of bulk and shear modulus. The Poisson’s ratio becomes isotropic and close to 0.5 in the limit of small double-cone connections. Stability and scalability analysis results show that the critical load factor of this structure is obviously higher than the classical pentamode structure under the same static elastic properties, and the Young’s modulus gradually converges to a stable value (the infinite case) with an increasing number of unit cells.

scholarly journals Bio-Inspired Active Skins for Surface Morphing

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yujin Park ◽  
Gianmarco Vella ◽  
Kenneth J. Loh
Keyword(s):  
Deformation Mechanism ◽  
Unit Cell ◽  
Material Behavior ◽  
Two Dimensional ◽  
New Class ◽  
Mechanical Metamaterials ◽  
Unique Material ◽  
Out Of Plane ◽  
Unit Cells ◽  
Significant Attention

AbstractMechanical metamaterials that leverage precise geometrical designs and imperfections to induce unique material behavior have garnered significant attention. This study proposes a Bio-Inspired Active Skin (BIAS) as a new class of instability-induced morphable structures, where selective out-of-plane material deformations can be pre-programmed during design and activated by in-plane strains. The deformation mechanism of a unit cell geometrical design is analyzed to identify how the introduction of hinge-like notches or instabilities, versus their pristine counterparts, can pave way for controlling bulk BIAS behavior. Two-dimensional arrays of repeating unit cells were fabricated, with notches implemented at key locations throughout the structure, to harvest the instability-induced surface features for applications such as camouflage, surface morphing, and soft robotic grippers.

Compressive Strength Prediction of Quad-Diametral Lattice Structures

2020 ◽  
Vol 847 ◽  
pp. 69-74
Author(s):  
Karel Raz ◽  
Zdenek Chval ◽  
Frantisek Sedlacek
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
Finite Element ◽  
Plastic Material ◽  
Lattice Structures ◽  
The Finite Element Method ◽  
Compressive Test ◽  
Unit Cells ◽  
Special Space ◽  
Element Method

Additive manufacturing is rapidly developing technology in all areas of industry. It is reducing the delivering time of each prototype from the manufacturer to the final user. This paper deals with mechanical properties of lattice structures. They are produced by additive technologies from the plastic material. Lattice structures are special space-filling unit cells, which can fill gaps in parts. They have good ratio between overall weight and strength. Nowadays are these structures commonly used, but their mechanical properties are not well described. This makes the design process difficult. Mechanical compressive test and virtual evaluation by the finite element method was performed. It was done for three different Quad-Diametral structures (Quad-Diametral, Quad-Diametral-Line and Quad-Diametral-Cross). Results from both testing approaches (real measurement and finite element method) are deeply described in this paper. It was shown, that the Quad-Diametral-Cross lattice cell has higher mechanical properties comparing to others. Increasing of the stiffness was 121% only with weight higher by 43%. The plastic material Ultimaker PLA (polyactic acid) was used as reference material in this research.

scholarly journals Large characteristic lengths in 3D chiral elastic metamaterials

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Tobias Frenzel ◽  
Vincent Hahn ◽  
Patrick Ziemke ◽  
Jonathan Ludwig Günter Schneider ◽  
Yi Chen ◽  
...  
Keyword(s):  
Size Dependence ◽  
Characteristic Length ◽  
Axial Strain ◽  
Three Dimensional ◽  
Small Sample ◽  
Micropolar Continuum ◽  
Chiral Metamaterials ◽  
Mechanical Metamaterials ◽  
Unit Cells ◽  
Elastic Metamaterials

AbstractThree-dimensional (3D) chiral mechanical metamaterials enable behaviors not accessible in ordinary materials. In particular, a coupling between displacements and rotations can occur, which is symmetry-forbidden without chirality. In this work, we solve three open challenges of chiral metamaterials. First, we provide a simple analytical model, which we use to rationalize the design of the chiral characteristic length. Second, using rapid multi-photon multi-focus 3D laser microprinting, we manufacture samples with more than 105 micrometer-sized 3D chiral unit cells. This number surpasses previous work by more than two orders of magnitude. Third, using analytical and numerical modeling, we realize chiral characteristic lengths of the order of ten unit cells, changing the sample-size dependence qualitatively and quantitatively. In the small-sample limit, the twist per axial strain is initially proportional to the sample side length, reaching a maximum at the characteristic length. In the thermodynamic limit, the twist per axial strain is proportional to the square of the characteristic length. We show that chiral micropolar continuum elasticity can reproduce this behavior.

Computation of load factors in bolted connections

2008 ◽  
Vol 223 (4) ◽  
pp. 795-808 ◽  
Author(s):  
R E Cornwell
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Design Parameters ◽  
Load Factor ◽  
The Finite Element Method ◽  
Bolted Connections ◽  
Joint Design ◽  
Load Factors ◽  
Joint Load ◽  
Element Method

An accurate computation of the joint load factors is critical for the safe design of bolted connections. This study provides a four-step procedure for the direct computation of the joint load factors for a variety of bolt diameters, joint thicknesses, individual plate thicknesses, and plate material combinations. The finite element method was used to calculate the bolt and plate deformations necessary to directly compute the load factor for 4424 unique combinations of the four joint design parameters. The procedure developed in this study provides accurate estimates of the joint load factor over the entire range of the four joint design parameters. All 4424 joint designs originally analysed with the finite element method were recomputed using the proposed procedure. The root mean square error was found to be 0.58 per cent with a correlation coefficient between the load factors computed by using the original finite element analyses and the proposed procedure to be 0.9998.

Simulation of tuning graphene plasmonic behaviors by ferroelectric domains for self-driven infrared photodetector applications

Nanoscale ◽  
2019 ◽  
Vol 11 (43) ◽  
pp. 20868-20875 ◽  
Author(s):  
Junxiong Guo ◽  
Yu Liu ◽  
Yuan Lin ◽  
Yu Tian ◽  
Jinxing Zhang ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Interfacial Effect ◽  
Infrared Photodetector ◽  
The Finite Element Method ◽  
Ferroelectric Domains ◽  
Element Method

We propose a graphene plasmonic infrared photodetector tuned by ferroelectric domains and investigate the interfacial effect using the finite element method.

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