scholarly journals MODELING OF PLASTIC DEFORMATION OF POROUS POWDER MATERIALS

2003 ◽  
Vol 8 (4) ◽  
pp. 351-360
Author(s):  
G. Zayats ◽  
R. Kusin ◽  
V. Kapcevich
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Unit Cell ◽  
Powder Materials ◽  
Porous Powder ◽  
Technological Parameters ◽  
Technological Characteristics ◽  
Unit Cells ◽  
Powder Particles ◽  
Good Agreement

In the present study the model of plastic deformation of porous powder materials (PPM) is described and numerically simulated. This model enables prediction of change of fundamental technological parameters of PPM in plastic deformation conditions, i.e. porosity, pore size, specific surface and mechanical properties. Porous media is described by unit cells consisting of eight powder particles. The parameters of unit cell (the distance between the centers of particles, the angles of the array and the dimensions of interparticle connections) form the model of porous material and define its technological characteristics. The model takes into account the effect of deforming anisotropy on PPM properties. Calculations are performed in nonorthogonal coordinates connected with unit cell. In the case of uniaxial straining obtained numerical results have shown good agreement with the experimental results.

Electron microscopy study of shock synthesis of silicides

1993 ◽  
Vol 51 ◽  
pp. 1162-1163
Author(s):  
Kenneth S. Vecchio
Keyword(s):  
Shock Wave ◽  
Plastic Deformation ◽  
Close Contact ◽  
Microscopy Study ◽  
High Energy ◽  
Electron Microscopy Study ◽  
Powder Materials ◽  
Porous Powder ◽  
Wave Effects ◽  
Wave Passage

Shock-induced reactions (or shock synthesis) have been studied since the 1960’s but are still poorly understood, partly due to the fact that the reaction kinetics are very fast making experimental analysis of the reaction difficult. Shock synthesis is closely related to combustion synthesis, and occurs in the same systems that undergo exothermic gasless combustion reactions. The thermite reaction (Fe2O3 + 2Al -> 2Fe + Al2O3) is prototypical of this class of reactions. The effects of shock-wave passage through porous (powder) materials are complex, because intense and non-uniform plastic deformation is coupled with the shock-wave effects. Thus, the particle interiors experience primarily the effects of shock waves, while the surfaces undergo intense plastic deformation which can often result in interfacial melting. Shock synthesis of compounds from powders is triggered by the extraordinarily high energy deposition rate at the surfaces of the powders, forcing them in close contact, activating them by introducing defects, and heating them close to or even above their melting temperatures.

scholarly journals Dual Graded Lattice Structures: Generation Framework and Mechanical Properties Characterization

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1528
Author(s):  
Khaled G. Mostafa ◽  
Guilherme A. Momesso ◽  
Xiuhui Li ◽  
David S. Nobes ◽  
Ahmed J. Qureshi
Keyword(s):  
Mechanical Properties ◽  
Relative Density ◽  
Lattice Structure ◽  
Cell Types ◽  
Functionally Graded ◽  
Unit Cell ◽  
Lattice Structures ◽  
Unit Cells ◽  
Mechanical Properties Characterization ◽  
Graded Lattice

Additive manufacturing (AM) enables the production of complex structured parts with tailored properties. Instead of manufacturing parts as fully solid, they can be infilled with lattice structures to optimize mechanical, thermal, and other functional properties. A lattice structure is formed by the repetition of a particular unit cell based on a defined pattern. The unit cell’s geometry, relative density, and size dictate the lattice structure’s properties. Where certain domains of the part require denser infill compared to other domains, the functionally graded lattice structure allows for further part optimization. This manuscript consists of two main sections. In the first section, we discussed the dual graded lattice structure (DGLS) generation framework. This framework can grade both the size and the relative density or porosity of standard and custom unit cells simultaneously as a function of the structure spatial coordinates. Popular benchmark parts from different fields were used to test the framework’s efficiency against different unit cell types and grading equations. In the second part, we investigated the effect of lattice structure dual grading on mechanical properties. It was found that combining both relative density and size grading fine-tunes the compressive strength, modulus of elasticity, absorbed energy, and fracture behavior of the lattice structure.

scholarly journals Experimental Characterization of 2 × 2 Electronically Reconfigurable 1 Bit Unit Cells for a Beamforming Transmitarray at X Band

2021 ◽  
Vol 21 (2) ◽  
pp. 153-160
Author(s):  
Biswarup Rana ◽  
In-Gon Lee ◽  
Ic-Pyo Hong
Keyword(s):  
Phase Shifter ◽  
Unit Cell ◽  
Experimental Characterization ◽  
Waveguide Transition ◽  
Transmitted Waves ◽  
X Band ◽  
Unit Cells ◽  
New Type ◽  
Good Agreement

This paper proposes a reconfigurable unit cell for a transmitarray operating at the X band. The unit cell consists of an active patch, a passive patch, and a phase shifter. The active patch has two PIN diodes that change the phase of 180° of the transmitted waves. The passive and active patches both have circular slots to enhance the bandwidth of the transmitted wave. We also propose a new type of experimental characterization technique to measure the performance of the unit cells at the X band without fabricating the entire transmitarray. Instead of a 1 unit cell as described in the literature, we propose 2 × 2 unit cells to measure the performance of unit cells using the X band waveguide. The waveguide consists of a WR-90 section and a rectangular to square waveguide transition section that can be fit to our proposed structure. A good agreement between simulated and measured results was found.

scholarly journals Effect of Strain Heterogeneities on Microstructure, Texture, Hardness, and H-Activation of High-Pressure Torsion Mg Consolidated from Different Powders

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1335 ◽  
Author(s):  
Subrata Panda ◽  
Laszlo Toth ◽  
Jianxin Zou ◽  
Thierry Grosdidier
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Local Strain ◽  
Powder Materials ◽  
Deformation Characteristics ◽  
Hydrogen Activation ◽  
Activation Kinetics ◽  
Different Types ◽  
Powder Particles

Severe plastic deformation techniques, such as high-pressure torsion (HPT), have been increasingly applied on powder materials to consolidate bulk nanostructured materials. In this context, the aim of the present study is to compare the plastic deformation characteristics during HPT of two distinct Mg-based powder precursors: (i) atomized micro-sized powder and (ii) condensed and passivated nanopowder. Dynamic recrystallization could take place during HPT consolidation of the atomized powder particles while the oxide pinning of the grain boundaries restricted it for the condensed powder. Consequently, there have been substantial differences in the development of the microstructure, texture, local strain heterogeneities, and hardness in the two types of consolidated products. Different types of local strain heterogeneities were also revealed in the consolidated products. The associated diversity in microstructure within the same consolidated product has been demonstrated to have an effect on the hydrogen activation kinetics to form hydrides for these Mg-based materials that could be suitable for solid state H-storage applications.

scholarly journals Сrystalline microcone coatings on titanium sponge.

2020 ◽  
Vol 11 (3-2020) ◽  
pp. 185-189
Author(s):  
K. V. Stepanova ◽  
◽  
A. M. Shulga ◽  
N. M. Yakovleva ◽  
A. N. Kokatev ◽  
...  
Keyword(s):  
Crystalline Structure ◽  
Titanium Sponge ◽  
Powder Materials ◽  
Porous Powder ◽  
Base Diameter ◽  
X Ray ◽  
Nanoscale Structures ◽  
Sensor Devices ◽  
Powder Particles ◽  
First Time

For the first time it was shown how to obtain microcone-shaped TiO2structures by means of anodizing of porous powder materials made of titanium sponge. It was established that during anodizing in 10 %Н2SO4+ 0,15 % HF electrolyte along with the growth of the X-ray amorphous nanoporous TiO2film a set of microcones with anatase crystalline structure is formed on the surface of titanium sponge powder particles. Microcones (height is up to 7m, base diameter is up to 5m) consist of multilayer nanoscale structures. Such structures are promising for the manufacture of new nanomaterials for catalytic and sensor devices.

scholarly journals ON THE DEVELOPMENT OF A UNIVERSAL CALCULATION METHOD FOR ASSESSING THE DEGRADATION OF RECYCLED METAL POWDER MATERIALS, DEPENDING ON THE CYCLICITY OF USE IN THE SELECTIVE LASER MELTING PROCESS

2020 ◽  
pp. 3-11
Author(s):  
A.G. Evgenov ◽  
◽  
S.V. Shurtakov ◽  
S.M. Prager ◽  
R.Yu. Malinin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Metal Powder ◽  
Cross Section ◽  
Calculation Method ◽  
Melting Process ◽  
Powder Materials ◽  
Laser Melting ◽  
Technological Characteristics ◽  
Frequency Of Use ◽  
Synthesized Materials

This article analyses foreign articles on the influence of the frequency of use on the level of impurities, technological characteristics of the powder in the SLM (DMLS) process and on the mechanical properties of the synthesized materials. A solution to the problem of developing a universal calculation method for evaluating degradation in the SLM process of recycled metal powder materials has been proposed. The algorithm includes the automatic correlation of the contamination factors with the corresponding exposure mode elements of each type of cross-section (contour, upskin, downskin, core) during measurement of the longitude of the laser path or the exposure duration of all elements that form the cross-section of a part.

Variations of In-Plane Mechanical Properties of Cellular Structures With Different Hierarchical Organizations

2020 ◽  
Author(s):  
Souvik Chakraborty ◽  
Dylan Hebert ◽  
Tanvir Rahman Faisal
Keyword(s):  
Mechanical Properties ◽  
Cell Wall ◽  
Hierarchical Structure ◽  
Unit Cell ◽  
Cellular Structures ◽  
Initial Shape ◽  
Unit Cells ◽  
Cell Topology ◽  
Homogeneous Cell ◽  
Hierarchical Organizations

Abstract Inspired by the nature, this study analyzes in-plane compressive responses of different modes of hierarchical architected structures with varying topologies. Architected cellular structures with two different unit cell topologies — square and kagome are considered, both having a relative density of 0.25. Each unit cell topology is designed with three different configurations. The base structure is the primitive one with solid homogeneous cell wall. The nested hierarchical structure is derived from the primitive one with cellular structuring in the cell wall. The third and final one is the fractal-like hierarchical structure, where same unit cells appear on different length scales. 3D printed structures were subjected to uniaxial compression to characterize their in-plane mechanical properties. The compressive stress-strain behaviors reveal that all the structures demonstrate the classical behavior of cellular structures followed by significant recovery of their initial shape upon load withdrawal. The energy absorptions demonstrated by the plateau regions before densification are not only governed by their structural topologies, but also largely governed by the configurations of hierarchical organizations. Hence, this study suggests the application specific design of hierarchical architected structures for defined loading conditions.

scholarly journals Mechanical properties of a hybrid auxetic metamaterial and metastructure system

2021 ◽  
pp. 073168442110095
Author(s):  
Wenjiao Zhang ◽  
Shuyuan Zhao ◽  
Rujie Sun ◽  
Fabrizio Scarpa ◽  
Jinwu Wang
Keyword(s):  
Mechanical Properties ◽  
Finite Elements ◽  
Internal Pressure ◽  
Flexible Electronics ◽  
Mechanical Performance ◽  
Unit Cell ◽  
Geometric Parameters ◽  
Mechanical Behaviors ◽  
Unit Cells ◽  
The One

We propose in this work an innovative hybrid auxetic metamaterial with a centersymmetric unit cell and tessellation topology similar to the one provided by the missing rib configuration. The tessellation proposed is applied to different core unit cells (star shape, cross-chiral shape with same dimensions, and reentrant). The effects of the geometric parameters of the cells on the in-plane mechanical properties of this hybrid auxetic metamaterial system are investigated via finite elements (FEMs). Representative unit cells (RUCs) with optimal mechanical behaviors are identified; those configurations exhibit the larger negative Poisson’s ratios and enhanced specific moduli. Designs related to two groups of auxetic metastructures with cylindric and cubic shapes are then developed based on the optimized RUCs along x and y directions. The equivalent mechanical performance of these metastructures under internal pressure is evaluated from a numerical standpoint. Auxetic cylindrical metastructures can be tailored by adjusting the number of the optimized RUCs along the circumferential and longitudinal directions, together with the geometric parameters of the optimized RUC itself. These hybrid auxetic metamaterials and metastructures provide the potential for multifunctional applications in biomechanics, flexible electronics, and aerospace.

Bayesian removal of noise for increased sensitivity in vector pattern recognition lattice imaging of interfaces

1993 ◽  
Vol 51 ◽  
pp. 994-995
Author(s):  
L. Fei ◽  
P. Fraundorf
Keyword(s):  
Pattern Recognition ◽  
Perfect Crystal ◽  
Unit Cell ◽  
Ion Milling ◽  
Beam Radiation ◽  
Major Interest ◽  
Unit Cells ◽  
Mapping Process ◽  
Increased Sensitivity ◽  
Electron Microscopes

Interface structure is of major interest in microscopy. With high resolution transmission electron microscopes (TEMs) and scanning probe microscopes, it is possible to reveal structure of interfaces in unit cells, in some cases with atomic resolution. A. Ourmazd et al. proposed quantifying such observations by using vector pattern recognition to map chemical composition changes across the interface in TEM images with unit cell resolution. The sensitivity of the mapping process, however, is limited by the repeatability of unit cell images of perfect crystal, and hence by the amount of delocalized noise, e.g. due to ion milling or beam radiation damage. Bayesian removal of noise, based on statistical inference, can be used to reduce the amount of non-periodic noise in images after acquisition. The basic principle of Bayesian phase-model background subtraction, according to our previous study, is that the optimum (rms error minimizing strategy) Fourier phases of the noise can be obtained provided the amplitudes of the noise is given, while the noise amplitude can often be estimated from the image itself.

Sign in / Sign up

Export Citation Format

Share Document