Numerical Evaluation of Micro- to Macroscopic Mechanical Behavior of Plastic Foam

2007 ◽  
Vol 340-341 ◽  
pp. 1025-1030
Author(s):  
Isamu Riku ◽  
Koji Mimura
Keyword(s):  
Mechanical Behavior ◽  
Strain Hardening ◽  
Loading Condition ◽  
Volume Fraction ◽  
Plastic Foam ◽  
Uniform Compression ◽  
Initial Volume ◽  
Initial Volume Fraction ◽  
Characteristic Value ◽  
Initial Modulus

In this study, we employ the two-dimensional homogenization model based on molecular chain network theory to investigate the micro- to macroscopic mechanical behavior of plastic foam under macroscopic uniform compression. A parametric study is performed to quantify the effect of a characteristic value of matrix, distribution and initial volume fraction of voids, and the macroscopic triaxiality of loading condition on the deformation behavior of the foam. The results suggest that the onset of localized shear band at the ligament between voids together with the microscopic buckling of the ligament leads to the macroscopic yield of the foam. The initial modulus and the macroscopic yield stress of the foam have no dependence on the characteristic value of matrix. Furthermore, as the microscopic buckling of the ligament is promoted in case of high initial volume fraction of voids and high triaxiality loading condition, the macroscopic yield point appears at early deformation stage. After the macroscopic yield, macroscopic strain hardening appears in the macroscopic response and a remarkable strain hardening is shown in case of high initial volume fraction of voids and high triaxiality loading condition due to the considerable increase of the density of the foam in these cases.

Initiation of underwater granular avalanches: Influence of the initial volume fraction

2008 ◽  
Vol 20 (11) ◽  
pp. 111701 ◽  
Author(s):  
M. Pailha ◽  
M. Nicolas ◽  
O. Pouliquen
Keyword(s):  
Volume Fraction ◽  
Initial Volume ◽  
Initial Volume Fraction

Compressive Yield Stress of Cement Paste

1994 ◽  
Vol 370 ◽  
Author(s):  
Kelly T. Miller ◽  
Wei Shi ◽  
Leslie J. Struble ◽  
Charles F. Zukoski
Keyword(s):  
Yield Stress ◽  
Calcium Aluminate ◽  
General Property ◽  
Volume Fraction ◽  
Initial Structure ◽  
Compressive Behavior ◽  
Initial Volume ◽  
Initial Volume Fraction ◽  
Compressive Yield Stress ◽  
Aluminate Cement

AbstractCompressive yield stresses have been measured for pastes (0.35 ≤ w/c ≤ 0.50) of portland cement, calcium aluminate cement, and weakly and strongly flocculated alumina (Φ0 = 0.20) using the centrifuge sediment height technique. Equilibrium sediment heights are reached quickly, allowing all measurements to be taken during the cement's induction period. The compressive behavior showed little dependence on the compressive history. Compressive yield stress was, however, dependent upon initial volume fraction, decreasing as the initial volume fraction increases. This behavior was observed in both the cements and alumina suspensions, implying that strong dependencies on initial structure may be a general property of the compressive behavior of flocculated suspensions.

Initiation of Submarine Granular Avalanches: Role of the Initial Volume Fraction

2008 ◽  
Author(s):  
Mickaël Pailha ◽  
Olivier Pouliquen ◽  
Maxime Nicolas ◽  
Albert Co ◽  
Gary L. Leal ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Initial Volume ◽  
Initial Volume Fraction

scholarly journals Granular collapse in a fluid: Role of the initial volume fraction

2011 ◽  
Vol 23 (7) ◽  
pp. 073301 ◽  
Author(s):  
L. Rondon ◽  
O. Pouliquen ◽  
P. Aussillous
Keyword(s):  
Volume Fraction ◽  
Initial Volume ◽  
Initial Volume Fraction ◽  
Granular Collapse

scholarly journals EFFECT OF γ′-PHASE PARTICLES ON THE MECHANICAL BEHAVIOR AND DEFORMATION MECHANISM OF (CoCrFeNi)94Ti2Al4 HIGH ENTROPY ALLOY SINGLE CRYSTALS

2021 ◽  
pp. 84-90
Author(s):  
A. A. Saraeva ◽  
Keyword(s):  
Mechanical Behavior ◽  
Strain Hardening ◽  
Single Crystals ◽  
Yield Point ◽  
Volume Fraction ◽  
High Entropy Alloy ◽  
Strong Temperature Dependence ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Hardening Coefficient

Recently, the interest of researchers has focused on a new FCC class (FCC – face-centered cubic lattice) high-entropy alloys (HEA), due to their unique properties – high values of the strain hardening coefficient, good plasticity, and ductile fracture at low test temperatures. Such a combination of properties in an FCC of HEA is achieved by mixing five or more elements in equal atomic proportions. Due to the strong temperature dependence of stresses at the σ0.1(T) yield point, these alloys have low σ0.1 values at temperatures above room temperature, which hinders their practical application. A precipitation hardening is an effective way to achieve high strength and is successfully used for hardening HEA FCC. The paper studied the influence of ageing at 923 K for 4 hours and at 1073 K for 18 and 30 hours on the mechanical behavior of single crystals of (CoCrFeNi)94Ti2Al4 (at.%) HEA FCC oriented along the [001] direction under tension. Ageing at 923 K for 4 hours and at 1073 K for 18 and 30 hours leads to the precipitation of γ′-phase particles, the size and volume fraction of which depend on the ageing temperature and time. The γ′-phase particles precipitation leads to an increase in stresses at the yield point from 47 MPa (ageing at 923 K, 4 hours) to 226 MPa (ageing at 1073 K, 30 hours) relative to quenched crystals at 296 K. The study identified the dependence of the strain hardening coefficient, plasticity, and the maximum stress level before fracture on heat treatment. The author discussed the reasons for the growth of stresses at the yield point and the strain hardening coefficient upon precipitation of γ′-phase particles.

A two-phase flow description of the initiation of underwater granular avalanches

2009 ◽  
Vol 633 ◽  
pp. 115-135 ◽  
Author(s):  
MICKAËL PAILHA ◽  
OLIVIER POULIQUEN
Keyword(s):  
Critical State ◽  
Two Phase Flow ◽  
Volume Fraction ◽  
State Theory ◽  
Phase Flow ◽  
Two Phase ◽  
Initial Volume ◽  
Initial Volume Fraction ◽  
Critical State Theory

A theoretical model based on a depth-averaged version of two-phase flow equations is developed to describe the initiation of underwater granular avalanches. The rheology of the granular phase is based on a shear-rate-dependent critical state theory, which combines a critical state theory proposed by Roux & Radjai (1998), and a rheological model recently proposed for immersed granular flows. Using those phenomenological constitutive equations, the model is able to describe both the dilatancy effects experienced by the granular skeleton during the initial deformations and the rheology of wet granular media when the flow is fully developed. Numerical solutions of the two-phase flow model are computed in the case of a uniform layer of granular material fully immersed in a liquid and suddenly inclined from horizontal. The predictions are quantitatively compared with experiments by Pailha, Nicolas & Pouliquen (2008), who have studied the role of the initial volume fraction on the dynamics of underwater granular avalanches. Once the rheology is calibrated using steady-state regimes, the model correctly predicts the complex transient dynamics observed in the experiments and the crucial role of the initial volume fraction. Quantitative predictions are obtained for the triggering time of the avalanche, for the acceleration of the layer and for the pore pressure.

MICROSTRUCTURE AND MECHANICAL BEHAVIOR OF AMORPHOUS Al–Cu–Ti METAL FOAMS SYNTHESIZED BY SPARK PLASMA SINTERING

2017 ◽  
Vol 24 (Supp02) ◽  
pp. 1850022
Author(s):  
MAOYUAN LI ◽  
LIN LU ◽  
ZHEN DAI ◽  
YIQIANG HONG ◽  
WEIWEI CHEN ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Intermetallic Compounds ◽  
Spark Plasma Sintering ◽  
Elevated Temperatures ◽  
Volume Fraction ◽  
Metal Foams ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Xrd Patterns

Amorphous Al–Cu–Ti metal foams were prepared by spark plasma sintering (SPS) process with the diameter of 10[Formula: see text]mm. The SPS process was conducted at the pressure of 200 and 300[Formula: see text]MPa with the temperature of 653–723[Formula: see text]K, respectively. NaCl was used as the space-holder, forming almost separated pores with the porosity of 65 vol%. The microstructure and mechanical behavior of the amorphous Al–Cu–Ti metal foams were systematically investigated. The results show that the crystallinity increased at elevated temperatures. The effect of pressure and holding time on the crystallization was almost negligible. The intermetallic compounds, i.e. Al–Ti, Al–Cu and Al–Cu–Ti were identified from X-ray diffraction (XRD) patterns. It was found that weak adhesion and brittle intermetallic compounds reduced the mechanical properties, while lower volume fraction and smaller size of NaCl powders improved the mechanical properties.

Influence of Omega-Phase Precipitation Hardening on the Static and Dynamic Properties of Metastable Beta Ti-Nb-Zr and Ti-Nb-Ta Alloys

2013 ◽  
Vol 738-739 ◽  
pp. 189-194 ◽  
Author(s):  
Vladimir Brailovski ◽  
Sergey Prokoshkin ◽  
Karine Inaekyan ◽  
Sergey Dubinskiy
Keyword(s):  
Mechanical Behavior ◽  
Volume Fraction ◽  
Thermomechanical Processing ◽  
Subgrain Size ◽  
Dynamic Properties ◽  
Aging Treatment ◽  
Stress Generation ◽  
Phase Precipitation ◽  
Superelastic Behavior ◽  
Temperature Scanning

The influence of thermomechanical processing on the Ti-21.8Nb-6Zr (TNZ) and Ti-19.7Nb-5.8Ta (TNT) (at%) alloys’ structure, phase composition, mechanical and functional properties is studied. Both alloys possess polygonized dislocation substructure (average subgrain size  100 nm), and manifest superelastic behavior at room temperature and recovery stress generation during constant-strain temperature scanning experiments. After aging treatment, both alloys were -phase precipitation hardened, but their mechanical behavior was impacted differently -- it was detrimental for TNZ and beneficial for TNT. The different impact of aging heat treatment on the mechanical behavior of these alloys is explained by the differences in the -phase nucleation rate, precipitates’ size, shape, volume fraction and distribution, and by their effect on the alloys’ critical stresses and transformation temperatures.

scholarly journals Iron-chromium-carbon-vanadium white cast irons: Microstructure and properties

2014 ◽  
Vol 68 (4) ◽  
pp. 413-427 ◽  
Author(s):  
Mirjana Filipovic
Keyword(s):  
Fracture Toughness ◽  
Strain Hardening ◽  
Volume Fraction ◽  
Dynamic Fracture Toughness ◽  
M23c6 Carbide ◽  
Cast Irons ◽  
Repeated Impact ◽  
Secondary Carbides ◽  
The Matrix ◽  
Microstructure Parameters

The as-cast microstructure of Fe-Cr-C-V white irons consists of M7C3 and vanadium rich M6C5 carbides in austenitic matrix. Vanadium changed the microstructure parameters of phase present in the structure of these alloys, including volume fraction, size and morphology. The degree of martensitic transformation also depended on the content of vanadium in the alloy. The volume fraction of the carbide phase, carbide size and distribution has an important influence on the wear resistance of Fe-Cr-C-V white irons under low-stress abrasion conditions. However, the dynamic fracture toughness of Fe-Cr-C-V irons is determined mainly by the properties of the matrix. The austenite is more effective in this respect than martensite. Since the austenite in these alloys contained very fine M23C6 carbide particles, higher fracture toughness was attributed to a strengthening of the austenite during fracture. Besides, the secondary carbides which precipitate in the matrix regions also influence the abrasion behaviour. By increasing the matrix strength through a dispersion hardening effect, the fine secondary carbides can increase the mechanical support of the carbides. Deformation and appropriate strain hardening occur in the retained austenite of Fe-Cr-C-V alloys under repeated impact loading. The particles of precipitated M23C6 secondary carbides disturb dislocations movement and contribute to increase the effects of strain hardening in Fe-Cr-C-V white irons.

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