scholarly journals Extreme Mechanical Properties of Regular Tensegrity Unit Cells in 3D Lattice Metamaterials

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4845
Author(s):  
Anna Al Sabouni-Zawadzka
Keyword(s):  
Mechanical Properties ◽  
Continuum Model ◽  
Soft Mode ◽  
Point Of View ◽  
Unit Cells ◽  
Deformation Modes

The study focuses on the identification of extreme mechanical properties of 3D lattice metamaterials based on regular tensegrity modules: 4-strut simplex, 3-strut simplex, expanded octahedron, truncated tetrahedron and X-module. The basis of the analysis is a continuum model which is used to find the equivalent elasticity matrices of the unit cells. For each examined tensegrity module a line of extreme properties is determined, which indicates the occurrence of the soft mode of deformation. Moreover, the eigenvectors corresponding to soft and stiff deformation modes are calculated and presented graphically. The obtained results are promising from the point of view of future creation of tensegrity lattices and metamaterials with extreme mechanical properties. One of the analysed materials is identified as quasi bimode, two as quasi trimodes, another one as a trimode and one more as a unimode.

Development of Combined Machining Modes, Investigation of Mechanical Properties and Structure of Deformed Semi-Finished Products from Alloy 01417

2020 ◽  
Vol 992 ◽  
pp. 498-503
Author(s):  
S. Sidelnikov ◽  
D. Voroshilov ◽  
M. Motkov ◽  
M. Voroshilova ◽  
V. Bespalov
Keyword(s):  
Mechanical Properties ◽  
Rare Earth Metals ◽  
Electrophysical Properties ◽  
Intermediate Annealing ◽  
Plastic Properties ◽  
Bar Rolling ◽  
Annealing Temperatures ◽  
Continuous Ingot ◽  
The Wire ◽  
Deformation Modes

The article presents the results of studies on the production of wire with a diameter of 0.5 mm from aluminum alloy 01417 with a content of rare-earth metals (REM) in the amount of 7-9% for aircraft construction needs. The deformation modes, the experimental technique and equipment for the implementation of the proposed technology described. The wire was obtained by drawing and bar rolling with subsequent drawing from a rod with a diameter of 5 mm, obtained previously using the process of combined rolling-extruding (CRE) from a continuous ingot with a diameter of 12 mm, cast in an electromagnetic mold (EMM). The wire obtained by the presented technology was subjected to 4 different heat treatment modes with annealing temperatures from 350 to 500 °C and holding time of 1 h in the furnace to achieve mechanical and electrophysical properties corresponding to TS 1-809-1038-2018. The level of strength and plastic properties obtained in the course of research required only one intermediate annealing. The microstructure of the wire was investigated and the modes were revealed that made it possible to obtain the required level of mechanical properties and electrical resistivity, satisfying TS 1-809-1038-2018.

scholarly journals Towards Recognition of Scale Effects in a Solid Model of Lattices with Tensegrity-Inspired Microstructure

Solids ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 50-59
Author(s):  
Wojciech Gilewski ◽  
Anna Al Sabouni-Zawadzka
Keyword(s):  
Mechanical Properties ◽  
Continuum Model ◽  
Scale Effects ◽  
Theory Of Elasticity ◽  
Solid Model ◽  
Gradient Theory ◽  
General Description ◽  
Normal Forces ◽  
Second Gradient ◽  
Proposed Model

This paper is dedicated to the extended solid (continuum) model of tensegrity structures or lattices. Tensegrity is defined as a pin-joined truss structure with an infinitesimal mechanism stabilized by a set of self-equilibrated normal forces. The proposed model is inspired by the continuum model that matches the first gradient theory of elasticity. The extension leads to the second- or higher-order gradient formulation. General description is supplemented with examples in 2D and 3D spaces. A detailed form of material coefficients related to the first and second deformation gradients is presented. Substitute mechanical properties of the lattice are dependent on the cable-to-strut stiffness ratio and self-stress. Scale effect as well as coupling of the first and second gradient terms are identified. The extended solid model can be used for the evaluation of unusual mechanical properties of tensegrity lattices.

Rheology of hydrocarbon gels

1950 ◽  
Vol 200 (1061) ◽  
pp. 183-188 ◽  
Keyword(s):  
Mechanical Properties ◽  
Experimental Measurement ◽  
Theoretical Basis ◽  
Continuous Media ◽  
Point Of View ◽  
Coarse Grained ◽  
Testing Instrument ◽  
Fine Grained ◽  
Mineral Oils ◽  
Space And Time

Hydrocarbon gels contain a number of materials, such as rubber, greases, saponified mineral oils, etc., of great interest for various engineering purposes. Specific requirements in mechanical properties have been met by producing gels in appropriately chosen patterns of constituent components of visible, colloidal, molecular and atomic sizes, ranging from coarse-grained aggregates, represented by sponges, foams, emulsions, etc.; to fine-grained and apparently homogeneous ones, represented by optically clear compounds. The engineer who has to deal with the whole range of such materials will adopt a macroscopic point of view, based on an apparent continuity of all the material structures and of the distributions in space and time of the displacements and forces occurring under mechanical actions. It has been possible to determine these distributions in the framework of a comprehensive scheme in which the fundamental principles of the mechanics of continuous media provide the theoretical basis, and a testing instrument of new design, termed Rheogoniometer, the means of experimental measurement (Weissenberg 1931, 1934, 1946, 1947, 1948).

scholarly journals Development of PLA Fibers as an Antimicrobial Agent with Enhanced Infection Resistance using Electrospinning/Plasma Technology

2020 ◽  
Author(s):  
Abdelrahman Mahmoud ◽  
Mohammed Naser ◽  
Mahmoud Abdelrasool ◽  
Khalid Jama ◽  
Mohamed Hussein ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Three Dimensional ◽  
Plasma Technology ◽  
Energy Increase ◽  
The Past ◽  
Unit Cells ◽  
Infection Resistance ◽  
Dimensional Shape ◽  
Fiber Dimensions ◽  
Three Dimensional Shape

Humans are vulnerable and easily prone to all kind of injuries, diseases, and traumas that can be damaging to their tissues (including its building unit, cells), bones, or even organs. Therefore, they would need assistance in healing or re-growing once again. Medical scaffolds have emerged over the past decades as one of the most important concepts in the tissue-engineering field as they enable and aide the re-growth of tissues and their successors. An optimal medical scaffold should be addressing the following factors: biocompatibility, biodegradability, mechanical properties, scaffold architecture/porosity, precise three-dimensional shape and manufacturing technology. There are several materials utilized in the fabrication of medical scaffolds, but one of the most extensively studied polymers is polylactic acid (PLA). PLA is biodegradable thermoplastic aliphatic polyester that is derived from naturally produced lactic acid. PLA is characterized with its excellent mechanical properties, biodegradability, promising eco-friendly, and excellent biocompatibility. PLA can be fabricated into nanofibers for medical scaffolds used through many techniques; electrospinning is one of the widely used methods for such fabrication. Electrospinning is a favorable technique because in the preparation of scaffolds, some parameters such as fiber dimensions, morphology, and porosity are easily controlled. A problem that is associated with medical scaffolds, such as inflammation and infection, was reported in many cases resulting in a degradation of tissues. Therefore, a surface modification was thought of as a needed solution which mostly focuses on an incorporation of extra functionalities responsible for the surface free energy increase (wettability). Therefore, plasma technique was a favorable solution for the surface treatment and modification. Plasma treatment enables the formation of free radicals. These radicals can be easily utilized for grafting process. Subsequently, ascorbic acid (ASA) could be incorporated as anti-inflammatory and anti-infection agent on the plasma pretreated surface of scaffolds.

Mechanical Properties of Fired-Clay Brick Masonry Models in Moist and Dry Conditions

2014 ◽  
Vol 624 ◽  
pp. 307-312 ◽  
Author(s):  
Cristina Gentilini ◽  
Elisa Franzoni ◽  
Gabriela Graziani ◽  
Simone Bandini
Keyword(s):  
Mechanical Properties ◽  
Mechanical Performance ◽  
Point Of View ◽  
Shear Behaviour ◽  
Masonry Buildings ◽  
Masonry Structures ◽  
Clay Brick ◽  
Clay Bricks ◽  
Dry Conditions ◽  
Rising Damp

Rising damp is one of the main issues affecting masonry buildings. However, its consequences on the mechanical performance of masonry structures are not so largely explored. In this paper, the compressive and shear behaviour of masonry triplets, manufactured with solid fired-clay bricks and cement-based mortar, is investigated in dry and moist conditions. The results are interpreted on the basis of the features of the single materials, from both a mechanical and microstructural point of view.

THREE-DIMENSIONAL COSSERAT CONTINUUM MODELING OF FRACTURED ROCK MASSES

2010 ◽  
Vol 02 (03n04) ◽  
pp. 217-234
Author(s):  
IOANNIS STEFANOU ◽  
JEAN SULEM
Keyword(s):  
Mechanical Properties ◽  
Discrete System ◽  
Degrees Of Freedom ◽  
Fractured Rock ◽  
Three Dimensional ◽  
Cosserat Continuum ◽  
Point Of View ◽  
Rock Masses ◽  
Homogenization Technique ◽  
Rock Structure

The behavior of rock masses is influenced by the existence of discontinuities, which divide the rock in joint blocks making it an inhomogeneous anisotropic material. From the mechanical point of view, the geometrical and mechanical properties of the rock discontinuities define the mechanical properties of the rock structure. In the present paper we consider a rock mass with three joint sets of different dip angle, dip direction, spacing and mechanical properties. The dynamic behavior of the discrete system is then described by a continuum model, which is derived by homogenization. The homogenization technique applied here is called generalized differential expansion homogenization technique and has its roots in Germain's (1973) formulation for micromorphic continua. The main advantage of the method is the avoidance of the averaging of the kinematic quotients and the derivation of a continuum that maps exactly the degrees of freedom of the discrete system through a one-to-one correspondence of the kinematic measures. The derivation of the equivalent continuum is based on the identification for any virtual kinematic field of the power of the internal forces and of the kinetic energy of the continuum with the corresponding quantities of the discrete system. The result is an anisotropic three-dimensional Cosserat continuum.

Behaviors of Xiashu Loess in the Lower Reaches of China’s Yangtze River under Triaxial Compression and the Microscopic Explanations

2016 ◽  
Vol 858 ◽  
pp. 91-97
Author(s):  
Jun Hua Xiao ◽  
Wen Qi Zheng
Keyword(s):  
Mechanical Properties ◽  
Yangtze River ◽  
Shear Failure ◽  
Triaxial Compression ◽  
Processing Technique ◽  
Point Of View ◽  
Image Processing Technique ◽  
Test Results ◽  
Compression Tests ◽  
Triaxial Compression Tests

To investigate the macroscopic mechanical properties of undisturbed structural Xiashu loess in the lower reaches of China’s Yangtze River under triaxial compression, and obtain the intrinsic explanations for the macroscopic mechanical properties from the microscopic point of view, in laboratory, triaxial compression tests were carried out, microstructure images of sheared samples were collected by scanning electron microscope (SEM), and quantitative parameters of microstructure (mainly about particle or pore size, distribution, and alignment) were extracted by digital image processing technique. Based on the test results, the deviator stress-strain relationships of both undisturbed and remoulded Xiashu loess, the structural strength, and the microstructural evolution mechanism about the formation of shear failure zone of Xiashu loess under triaxial compression were analyzed.

Roughness and fractality of fracture surfaces as indicators of mechanical quantities of porous solids

Open Physics ◽  
2011 ◽  
Vol 9 (6) ◽  
Author(s):  
Tomáš Ficker ◽  
Dalibor Martišek
Keyword(s):  
Mechanical Properties ◽  
Fractal Dimension ◽  
Fractal Dimensions ◽  
Point Of View ◽  
Porous Solids ◽  
Surface Parameter ◽  
Cement Pastes ◽  
Fracture Surfaces ◽  
Profile Parameter ◽  
3D Profile

AbstractThe 3D profile surface parameter H q and fractal dimension D were tested as indicators of mechanical properties inferred from fracture surfaces of porous solids. High porous hydrated cement pastes were used as prototypes of porous materials. Both the profile parameter H q and the fractal dimension D showed capability to assess compressive strength from the fracture surfaces of hydrated pastes. From a practical point of view the 3D profile parameter H q seems to be more convenient as an indicator of mechanical properties, as its values suffer much less from statistical scatter than those of fractal dimensions.

Entropy of Nanostructures

2017 ◽  
pp. 600-614
Author(s):  
Ottorino Ori ◽  
Franco Cataldo ◽  
Mihai V. Putz
Keyword(s):  
Mechanical Properties ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Defect Formation ◽  
Vacancy Concentration ◽  
Structural Evolution ◽  
Point Of View ◽  
Structural Defects ◽  
Formation Mechanisms ◽  
Topological Invariants

Recent advances in graphene studies deal with the influence of structural defects on graphene chemical, electrical, magnetic and mechanical properties. Here the complex mechanisms leading to the formation of clusters of vacancies in 2D honeycomb HD lattices are described by a pure topological point of view, aiming to correlate the variation of specific topological invariants, sensible to vacancy concentration, to the structural evolution of the defective networks driven by the topo-thermodynamical Gibbs free energy. Interesting predictions on defect formation mechanisms add details on the topological mechanisms featured by the graphenic structures with defects. Future roles of bondonic particles in defective HD materials are also envisaged.

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