scholarly journals The effect of geometric imperfections on the mechanical response of isotropic closed-cell plate-lattices

2021 ◽  
Author(s):  
Chan Soo Ha ◽  
Meng-Ting Hsieh
Keyword(s):  
Mechanical Response ◽  
Mechanical Performance ◽  
Cell Plate ◽  
Face Centered Cubic ◽  
Geometric Imperfections ◽  
Structural Efficiency ◽  
Closed Cell ◽  
Specific Performance ◽  
Scientists And Engineers ◽  
Face Centered

Cubic+octet plate-lattices, whose unit cell comprises plates aligned along simple-cubic and face-centered-cubic planes of crystal structures, have attracted scientists and engineers because of their isotropic, near-optimal mass-specific performance that reaches theoretical upper bounds on stiffness and strength at low density. While their structural efficiency has been recently examined analytically, numerically and experimentally, their sensitivity to geometric imperfections has remained elusive. Here, using finite element simulations, we present sensitivity of the macroscopic mechanical properties of the plate-lattices to two types of geometric imperfections: namely, periodically distributed defects, characterizing plate waviness and displaced intersections, and randomly dispersed defects, representing missing plates, observed in their additively manufactured samples. Our results show that the randomly dispersed imperfections lead to a greater reduction in the Young’s modulus and yield strength than its counterpart across all relative densities under consideration, while their scaling relations with the relative density remains linear, confirming their structural efficiency attributed to stretching-dominated behavior even with the presence of the imperfections. This study sheds light on previously elusive sensitivity of the plate-lattices to the geometric imperfections and provides understanding of their defect-dependent mechanical performance.

FEM Simulation of Elastic Properties of Closed-Cell Starch Extrudate with Spherical Pores

2011 ◽  
Vol 236-238 ◽  
pp. 2429-2435 ◽  
Author(s):  
Xiao Ping Fan ◽  
Wei Xu ◽  
Jia Hua Zhou ◽  
Hong Xiang
Keyword(s):  
Finite Elements ◽  
Corn Starch ◽  
Cell Model ◽  
Fem Simulation ◽  
Face Centered Cubic ◽  
Finite Elements Analysis ◽  
Closed Cell ◽  
Face Centered ◽  
Set Up ◽  
Accuracy Of Results

Three types of single closed cell model, single-centered cubic, face-centered cubic and body-centered cubic were set up based on the geometric character of corn starch extrudate. The elastic moduli were simulated with finite elements method (FEM). Fitting equation for elasticity modulus and relative density calculated from each type of cell model was developed and validated with that calculated from Ashby-Gibson equation. The accuracy of results from finite elements analysis was comparable to that of Ashby-Gibson equation.

scholarly journals Thermo-mechanical response of single-phase face-centered-cubic AlxCoCrFeNi high-entropy alloy microcrystals

2018 ◽  
Vol 6 (5) ◽  
pp. 300-306 ◽  
Author(s):  
Quan Jiao ◽  
Gi-Dong Sim ◽  
Mageshwari Komarasamy ◽  
Rajiv S. Mishra ◽  
Peter K. Liaw ◽  
...  
Keyword(s):  
Single Phase ◽  
Mechanical Response ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Face Centered

Surface Stress Effects on the Yield Strength in Nanotwinned Polycrystal Face-Centered-Cubic Metallic Nanowires

2014 ◽  
Vol 81 (10) ◽  
Author(s):  
Linli Zhu ◽  
Xiang Guo ◽  
Jian Lu
Keyword(s):  
Yield Strength ◽  
Surface Stress ◽  
Mechanical Performance ◽  
Face Centered Cubic ◽  
Stress Effects ◽  
Size Dependent ◽  
The Wire ◽  
Face Centered ◽  
20 Nm ◽  
Twin Spacing

The influence of surface stress on the yield strength of nanotwinned polycrystal face-centered-cubic (FCC) metallic nanowire is theoretically investigated. The contribution of surface boundaries on the strengthening/softening is analyzed in the framework of continuum mechanics theory by accounting for the surface energy effects. The other strengthening mechanisms originated from the inner boundaries are described by the Taylor model for the nanotwinned polycrystalline metals. The theoretical results demonstrate that the yield strength of nanotwinned polycrystal wires is dependent on the twin spacing, grain size and the geometrical size of the wire. The surface stress effects on the strength perform more and more significantly with decreasing the wire diameter, especially for the diameter smaller than 20 nm. In addition, the dependence of surface stress on the strength is also relevant to the size of microstructures as well as the magnitude and direction of surface stress. These results may be useful in evaluating the size-dependent mechanical performance of nanostructured materials.

scholarly journals The Role of Foaming Agent and Processing Route in Mechanical Performance of Fabricated Aluminum Foams

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Alexandra Byakova ◽  
Iegor Kartuzov ◽  
Svyatoslav Gnyloskurenko ◽  
Takashi Nakamura
Keyword(s):  
Cell Wall ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Cell Structure ◽  
Wall Material ◽  
Processing Route ◽  
Foaming Agent ◽  
Closed Cell ◽  
Al Foams

The results of this study highlight the role of foaming agent and processing route in influencing the contamination of cell wall material by side products, which, in turn, affects the macroscopic mechanical response of closed-cell Al-foams. Several kinds of Al-foams have been produced with pure Al/Al-alloys by the Alporas like melt process, all performed with and without Ca additive and processed either with conventional TiH2foaming agent or CaCO3as an alternative one. Damage behavior of contaminations was believed to affect the micromechanism of foam deformation, favoring either plastic buckling or brittle failure of cell walls. No discrepancy between experimental values of compressive strengths for Al-foams comprising ductile cell wall constituents and those prescribed by theoretical models for closed-cell structure was found while the presence of low ductile and/or brittle eutectic domains and contaminations including particles/layers of Al3Ti, residues of partially reacted TiH2, and Ca bearing compounds, results in reducing the compressive strength to values close to or even below those of open-cell foams of the same relative density.

DEFORMATION OF CLOSED-CELL FOAMS INCORPORATING THE EFFECT OF INNER GAS PRESSURE

2010 ◽  
Vol 02 (03) ◽  
pp. 489-513 ◽  
Author(s):  
ZHI MIN XU ◽  
WEI XU ZHANG ◽  
T. J. WANG
Keyword(s):  
Plastic Deformation ◽  
Yield Surface ◽  
Yield Function ◽  
Gas Pressure ◽  
Uniaxial Tensile ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Closed Cell ◽  
Hydrostatic Stresses ◽  
Face Centered

The objective of this work is to numerically investigate the elastic–plastic deformation of closed-cell foams incorporating the effect of inner gas pressure. Both body-centered cubic (BCC) and face-centered cubic (FCC) arrangements of pores are considered in analysis. It is seen that the inner gas pressure has a significant effect on the plastic deformation of closed-cell foams, which is different for the foams with different microstructures and is discussed in detail. The inner gas pressure results in the asymmetry of uniaxial tensile-compressive stress–strain curves and the nominal Poisson's ratio. It is shown that the inner gas pressure makes the yield surface move to the negative direction of the hydrostatic axis in the plane of equivalent and hydrostatic stresses, and the moving distance is equal to the magnitude of inner gas pressure in the foams. Moreover, a new yield function incorporating the effect of inner gas pressure is developed for closed-cell foams. The material constants in the yield function depend on the microstructures of the foams.

Numerical Analysis of Elastoplastic Behavior of Foams with Ellipsoidal Pores

2011 ◽  
Vol 462-463 ◽  
pp. 301-306 ◽  
Author(s):  
Zhi Min Xu ◽  
Wei Xu Zhang ◽  
Tie Jun Wang
Keyword(s):  
Yield Stress ◽  
Gas Pressure ◽  
Uniaxial Tensile ◽  
Face Centered Cubic ◽  
The Finite Element Method ◽  
Elastoplastic Behavior ◽  
Initial Yield Stress ◽  
Initial Yield ◽  
Closed Cell ◽  
Face Centered

The objective of this work is to numerically investigate the elastoplastic behavior of closed-cell foams. Anisotropic geometry with ellipsoidal pores is considered and the contribution of the inner gas pressure within the cells is incorporated to the model. Based on face centered cubic (FCC) arrangements of pores and the finite element method, macroscopic elastic constants and initial yield stress against the relative density and cell aspect ratio are discussed in this paper. Through a systematic study we find that the initial yield stress is dependent on the loading direction. The inner gas pressure results in the asymmetry of uniaxial tensile-compressive stress-strain curves and significantly affects the initial yield stress of the foams for different loading directions.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

A study of interface sliding at F.C.C.-B.C.C. boundaries in a Cu-Zn alloy

1978 ◽  
Vol 36 (1) ◽  
pp. 422-423
Author(s):  
F. Monchoux ◽  
A. Rocher ◽  
J.L. Martin
Keyword(s):  
Face Centered Cubic ◽  
Creep Tests ◽  
High Voltage Electron Microscopy ◽  
Diffusion Treatment ◽  
Voltage Electron ◽  
The Face ◽  
Face Centered ◽  
Interface Sliding ◽  
Zn Alloy ◽  
Made In

Interphase sliding is an important phenomenon of high temperature plasticity. In order to study the microstructural changes associated with it, as well as its influence on the strain rate dependence on stress and temperature, plane boundaries were obtained by welding together two polycrystals of Cu-Zn alloys having the face centered cubic and body centered cubic structures respectively following the procedure described in (1). These specimens were then deformed in shear along the interface on a creep machine (2) at the same temperature as that of the diffusion treatment so as to avoid any precipitation. The present paper reports observations by conventional and high voltage electron microscopy of the microstructure of both phases, in the vicinity of the phase boundary, after different creep tests corresponding to various deformation conditions.Foils were cut by spark machining out of the bulk samples, 0.2 mm thick. They were then electropolished down to 0.1 mm, after which a hole with thin edges was made in an area including the boundary

Microstructure of Electro-Eroded Cemented Carbide Surfaces

1968 ◽  
Vol 26 ◽  
pp. 284-285
Author(s):  
V. N. Filimonenko ◽  
M. H. Richman ◽  
J. Gurland
Keyword(s):  
Surface Layer ◽  
Cobalt Content ◽  
Cemented Carbides ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Metallographic Examination ◽  
Standard Procedures ◽  
Face Centered ◽  
Diamond Paste ◽  
Plastic Carbon

The high temperatures and pressures that are found in a spark gap during electrical discharging lead to a sharp phase transition and structural transformation in the surface layer of cemented carbides containing WC and cobalt. By means of X-ray diffraction both W2C and a high-temperature monocarbide of tungsten (face-centered cubic) were detected after electro-erosion. The W2C forms as a result of the peritectic reaction, WC → W2C+C. The existence and amount of the phases depend on both the energy of the electro-spark discharge and the cobalt content. In the case of a low-energy discharge (i.e. C=0.01μF, V = 300v), WC(f.c.c.) is generally formed in the surface layer. However, at high energies, (e.g. C=30μF, V = 300v), W2C is formed at the surface in preference to the monocarbide. The phase transformations in the surface layer are retarded by the presence of larger percentages of cobalt.Metallographic examination of the electro-eroded surfaces of cemented carbides was carried out on samples with 5-30% cobalt content. The specimens were first metallographically polished using diamond paste and standard procedures and then subjected to various electrical discharges on a Servomet spark machining device. The samples were then repolished and etched in a 3% NH4OH electrolyte at -0.5 amp/cm2. Two stage plastic-carbon replicas were then made and shadowed with chromium at 27°.

Sign in / Sign up

Export Citation Format

Share Document