ENERGY ABSORPTION OF HONEYCOMB RANDOMLY FILLED WITH INCLUSIONS SUBJECTED TO IN-PLANE IMPACT

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1343-1348
Author(s):  
HIROAKI NAKAMOTO ◽  
TADAHARU ADACHI ◽  
WAKAKO ARAKI
Keyword(s):  
Lower Energy ◽  
Volume Fraction ◽  
Shear Bands ◽  
Average Stress ◽  
The Finite Element Method ◽  
Absorbed Energy ◽  
Cell Region ◽  
Honeycomb Structures ◽  
Random Arrangement ◽  
Deformation Processes

The in-plane impact behaviors of honeycomb structures with some cells randomly filled with stiff inclusions were analyzed by using the finite element method (FEM). The effect of the random arrangement of inclusions on the deformation processes of the honeycomb structures was considered. During these deformation processes, the growth of shear bands was disturbed by the inclusions and the cell region surrounded by inclusions did not deform. The average stress increased and densification strain decreased with increasing volume fraction of inclusions. A honeycomb with volume fraction of inclusions of 0.5 could not be deformed. Below 0.5, the average stress steeply increased and densification strain approached zero. Some models for less than a volume fraction of inclusions of 0.25 had higher absorbed energy than the model with no inclusions and others had lower energy. Above 0.25, the absorbed energy decreased and linearly reached zero at a volume fraction of inclusions of 0.5.

The Compressive Response of Idealized Cermetlike Materials

2015 ◽  
Vol 82 (4) ◽  
Author(s):  
Eral Bele ◽  
Vikram S. Deshpande
Keyword(s):  
Granular Media ◽  
Volume Fraction ◽  
Solder Matrix ◽  
Shear Bands ◽  
High Volume ◽  
Large Strains ◽  
Compressive Response ◽  
Hard Particles ◽  
Random Arrangement ◽  
Inclusion Volume

Metals reinforced with a high volume fraction of hard particles, e.g., cermets, have properties that are more akin to those of granular media than conventional composites. Here, the mechanical properties and deformation mechanisms of this class of materials are investigated through the fabrication and testing of idealized cermets, comprising steel spheres in a Sn/Pb solder matrix. These materials have a similar contrast in the properties of constituent phases compared to commercial cermets; however, the simpler microstructure allows an easier interpretation of their properties. A combination of X-ray tomography and multiaxial strain measurements revealed that deformation at large strains occurs by the development of shear bands similar to granular media, with the material dilating under hydrostatic pressure within these shear bands. Predictions of finite element models with a random arrangement of inclusions were in excellent agreement with the experimental results of idealized cermets. These calculations showed that at large inclusion volume fractions, composites with a random arrangement of inclusions are significantly stronger compared to their periodic counterparts, due to the development of a network of force chains through the percolated particles.

Transient Vibroacoustic Analysis of Functionally Graded Plates

2021 ◽  
pp. 1-36
Author(s):  
Avnish Mahendra Pandey ◽  
K. V. Nagendra Gopal
Keyword(s):  
Volume Fraction ◽  
Free Field ◽  
Shear Deformation Theory ◽  
Structural Response ◽  
Functionally Graded ◽  
Functionally Graded Plates ◽  
The Finite Element Method ◽  
Time Marching ◽  
The Time Domain ◽  
Vibroacoustic Response

Abstract This paper presents the vibroacoustic response of pure functionally graded plates under transient loading of mechanical nature. The functionally graded plate is modelled using the conventional first-order shear deformation theory to incorporate the effects of transverse shear and rotary inertia. The mid-surface variables are determined using the finite element method. Transient structural response is determined using Newmark Beta time marching scheme and the acoustic pressure in the free field is obtained using the time-domain Rayleigh integral. The effective material properties of the FG plate and the transient response of both the structural and acoustic fields have been computed in MATLAB. The influence of the volume fraction index, thickness ratio and boundary conditions of pure FG plate on its transient vibroacoustic response is investigated by a detailed parametric study.

Hot Deformation and Dynamic Recrystallization in Titanium Aluminide

2018 ◽  
Vol 941 ◽  
pp. 1391-1396 ◽  
Author(s):  
Nitish Bibhanshu ◽  
Satyam Suwas
Keyword(s):  
Shear Band ◽  
Dynamic Recrystallization ◽  
Titanium Aluminide ◽  
Volume Fraction ◽  
Shear Bands ◽  
Hot Workability ◽  
Compression Tests ◽  
Electron Backscattered Diffraction ◽  
Gamma Titanium Aluminide ◽  
Z Contrast

The hot workability of gamma titanium aluminide alloy, Ti-48Al-2V-2Nb, was assessed in the cast condition through a series of compression tests conducted over a range of temperatures (1000 to 1175 °C) and at the strain rate of 10 S-1. The mechanism of dynamics recrystallization has been investigated from SEM Z-contrast images and from the Electron backscattered diffraction EBSD as well. It has been observed that volume fraction of the recrystallized grains increases with increasing the deformation temperature. The major volume fraction of the recrystallized grains was observed in the shear band which was forming at an angle 45 ̊ with respect to the compression direction. The mechanism of breaking of the laths and the region of the dynamic recrystallization were also investigated from the SEM Z-contrast image and EBSD. The dynamic recrystallization occurred in the region of the broken laths and shear bands. The breaking of the laths was because of the kinking of the lamellae. The shear band, kinked lamellae and dynamic recrystallized region where all investigated simultaneously.

A Theoretical Formula for the Validity Limits of the Dipole Approximation for a Dielectric Mixture

2014 ◽  
Vol 906 ◽  
pp. 72-80
Author(s):  
Chang He Yang ◽  
Ding Long Cao ◽  
Lin Song Guo
Keyword(s):  
Finite Element Method ◽  
Numerical Solutions ◽  
Volume Fraction ◽  
Dipole Approximation ◽  
Empirical Method ◽  
Theoretical Formula ◽  
The Finite Element Method ◽  
Dielectric Mixture ◽  
Good Agreement ◽  
Dielectric Mismatch

A newly criterion for the validity limits of the dipole approximation for a dielectric mixture was presented, based on the comparison between the dipole approximation and the numerical solutions by the finite-element method (FEM). In terms of this criterion and the dipole-enhanced model, a simple theoretical formula for the validity limits was derived. This formula includes three variables: the dielectric mismatch, the volume fraction of particles and the precision. Its calculated results have a good agreement with the limits determined by the empirical method in the range of our interest, which indicates the theoretical formula is creditable. Using this formula, we can approximate the precision of the dipole approximation for an arbitrary dielectric mixture. And we found that the dipole approximation is acceptable with the precision equal to 30% when the dielectric mismatch is less than 2.3 (εi/ εe2.3) for the almost touching spheres.

Correlation between the Enhanced Plasticity of Glassy Matrix Composites and the Volume Fraction, Size and Intrinsic Mechanical Property of Reinforcements

2014 ◽  
Vol 783-786 ◽  
pp. 1967-1970
Author(s):  
Z.H. Chu ◽  
Hidemi Kato ◽  
Guo Qiang Xie ◽  
D.R. Yan ◽  
Guang Yin Yuan
Keyword(s):  
Mechanical Properties ◽  
Metallic Glasses ◽  
Volume Fraction ◽  
Shear Bands ◽  
Ex Situ ◽  
Glassy Matrix ◽  
Matrix Composites ◽  
Micro Scale ◽  
Fraction Size

In recent years, bulk metallic glasses (BMGs) have received considerable attention due to their unique mechanical properties. However, the deformation of BMGs is highly localized in a few shear bands so that many of them exhibit poor plasticity. As such, more and more researchers have focused on improving the plasticity by in-situ or ex-situ introducing of nanoor micro-scale crystalline phases into the metallic glassy matrix in order to formation of multiple shear bands.

Numerical Modeling of Deformation Processes in Rock Pillars

2014 ◽  
Vol 682 ◽  
pp. 202-205 ◽  
Author(s):  
V.V. Aksenov ◽  
S.V. Lavrikov ◽  
Alexander F. Revuzhenko
Keyword(s):  
Mathematical Model ◽  
Finite Element Method ◽  
Rock Mass ◽  
Deformation Process ◽  
The Finite Element Method ◽  
Sequential Development ◽  
Deformation Processes ◽  
Rock Pillars ◽  
The Mathematical Model ◽  
Loss Of Strength

The mathematical model of rock mass in the context of its internal structure, anisotropy, loss of strength, elastic energy accumulation and release is considered. The numerical solution to the problem of quasistatic deformation in a rock mass pillar is obtained by the finite element method. The sequential development of softening and residual strength zones is considered. It is shown that if the softening modulus is strong enough then the deformation process becomes unstable.

scholarly journals Computational Homogenization of Cement-Based Porous Piezoelectric Composites with Random Structure

2019 ◽  
Vol 69 (2) ◽  
pp. 77-88
Author(s):  
Novák Pavol ◽  
Bishay Peter ◽  
Žmindák Milan
Keyword(s):  
Volume Fraction ◽  
Particle Volume Fraction ◽  
Ceramic Composites ◽  
Cement Matrix ◽  
Random Structure ◽  
The Finite Element Method ◽  
Particle Volume ◽  
Piezoelectric Composites ◽  
Pore Volume Fraction ◽  
Composite Properties

AbstractThe finite element method (FEM) is used to characterize the effective thermo-electromechanical material properties of cement-based piezoelectric ceramic composites in this paper. The micromechanics representative volume element (RVE) approach is used with distribution of piezoelectric particles in the porous cement matrix. The effects of the piezoelectric particle volume fraction and pore volume fraction on the effective composite properties are determined using sets of different boundary conditions. Microscale homogenization is carried out through the analysis of particles which are randomly distributed in a homogenized matrix.

scholarly journals NUMERICAL SIMULATION ANDCONSTRUCTAL DESIGN APPLIED TO THE STUDY OF ELASTIC BUCKLING IN THIN STEEL PLATES WITH OBLONG PERFORATIONS

2018 ◽  
Vol 8 (20) ◽  
Author(s):  
Emilio Gabriel Gonçalves Folzke ◽  
Thiago Da Silveira ◽  
João Paulo Silva Lima ◽  
Luiz Alberto Oliveira Rocha ◽  
Elizaldo Domingues Dos Santos ◽  
...  
Keyword(s):  
Critical Load ◽  
Volume Fraction ◽  
Design Method ◽  
Steel Plates ◽  
Constructal Theory ◽  
Elastic Buckling ◽  
The Finite Element Method ◽  
Perforated Plates ◽  
Constructal Design ◽  
Thin Steel

ABSTRACTBuckling is an instability phenomenon that can happen when a slender plate is subjected to axial compression loads. In addition, perforated plates are often necessary in the engineering field. Throughout this article, the Constructal Design Method, which is based on the Constructal Theory, has been used to evaluate the influence of the hole on thin steel plates under elastic buckling. For that, the different types of holes analyzed were both transversal and longitudinal oblong. They were all placed in the center of the plate. The geometry of the hole varied according to the degree of freedom H0/L0, which relates the dimensions of each type of different hole. The size of the perforation are varied by means the hole volume fraction (f) parameter, that represents the relation between the volume of the hole and the total volume of the plate (without hole). The main goal is to achieve the greatest critical load for the perforated plates. To do so, the ANSYS software, based on the Finite Element Method (FEM), has been used to numerically analyze the elastic buckling in each case. It has been observed the importance of the geometry when seeking superior performances: through a simple fluctuation of the geometry of the hole, once the volume fraction was kept constant, it was possible to achieve a significant increase on the critical loads. Key words: Buckling; Computational Modeling; Critical Load; Constructal Design.

scholarly journals Microstructure-Based Computational Simulation and Experimental Measurement of Stresses in Spheroidized Steels

2007 ◽  
Vol 26-28 ◽  
pp. 1157-1160
Author(s):  
Lei Che ◽  
Masahide Gotoh ◽  
Yoshiaki Horimoto ◽  
Yukio Hirose
Keyword(s):  
Internal Stress ◽  
Volume Fraction ◽  
Computational Simulation ◽  
Carbon Steels ◽  
The Finite Element Method ◽  
Computational Simulations ◽  
Engineering Material ◽  
X Ray ◽  
Cementite Phase ◽  
Stress States

Carbon steel is the most popular engineering material, usually consisted of ferrite and cementite phases. Internal stress state of the steel under thermal or mechanical loading is strongly affected by the amount and morphology in the cementite phase. With this aim, a computational model which applies the finite element method at the microscale was used in present study. Effects of volume fraction and particle size of the spheriodal cementite on the internal stress states in carbon steels under the mechanical and thermal loadings are investigated. To verify the reliability of the computational simulations, the residual stresses in the constituent phases are measured by means of X-ray stress diffraction technique. The computational simulations fit well with the experimental data, and the microstructure-based model is validated.

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