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Article
Publication date: 1 August 1999

Jaroslav Mackerle

This paper gives a bibliographical review of the finite element methods (FEMs) applied to the analysis of ceramics and glass materials. The bibliography at the end of the paper…

2604

Abstract

This paper gives a bibliographical review of the finite element methods (FEMs) applied to the analysis of ceramics and glass materials. The bibliography at the end of the paper contains references to papers, conference proceedings and theses/dissertations on the subject that were published between 1977‐1998. The following topics are included: ceramics – material and mechanical properties in general, ceramic coatings and joining problems, ceramic composites, ferrites, piezoceramics, ceramic tools and machining, material processing simulations, fracture mechanics and damage, applications of ceramic/composites in engineering; glass – material and mechanical properties in general, glass fiber composites, material processing simulations, fracture mechanics and damage, and applications of glasses in engineering.

Details

Engineering Computations, vol. 16 no. 5
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 February 1995

B.C. Trent and L.G. Margolin

We have developed a general constitutive theory that estimates the effective elastic moduli of a cemented granular material by applying statistical mechanical averaging to a…

Abstract

We have developed a general constitutive theory that estimates the effective elastic moduli of a cemented granular material by applying statistical mechanical averaging to a purely micromechanical model. We have also constructed a distinct element model of a cemented granular material, based on the same micromechanical model, which accounts for the elastic forces due to bonding between pairs of spherical particles, and which allows for the possibility of anisotropic damage to the bonds. In this paper, we use a model based on the distinct element method (DEM) to validate the predictions of the theory for various prescribed patterns of damage. In particular we impose several anisotropic patterns of damage on the bonds of a randomly generated assembly of particles. We then undertake numerical experiments, sending both p‐waves and s‐waves through the samples and measuring the wave velocities. The predictions of the theory for these velocities agree well with the results of the numerical model for a variety of damage patterns. We discuss the implications of our theory, as well as potential applications.

Details

Engineering Computations, vol. 12 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 1 February 1992

RICHARD J. BATHURST and LEO ROTHENBURG

The development of physically‐correct models of granular behaviour under shear deformations must recognize the discrete nature of the medium and the mechanical properties of the…

Abstract

The development of physically‐correct models of granular behaviour under shear deformations must recognize the discrete nature of the medium and the mechanical properties of the constituent grains at the particle level. Numerical simulation of idealized granular materials offers the researcher the possibility of recovering complete information on these systems that can then guide the development of micromechanical‐based models of granular systems. A numerical technique that has proved useful in meeting this goal is the discrete element method (DEM). The computer implementation of this method to observe microfeatures of idealized granular assemblies was first reported in the published literature by Cundall and Strack. Since that time a number of researchers have used the technique to explore the behaviour of idealized granular systems comprising cohesionless assemblies of discs and assemblies of discs comprising indestructible (bonded) contacts. The paper reviews some of the numerical simulation work that has been carried out by the authors to verify stress‐force‐fabric relationships first proposed by Rothenburg and constitutive stress‐strain laws for dense isotropic assemblies of bonded discs. The numerical technique in each case is the same and involves the solution of the equations of motion of each particle using an explicit time/finite difference algorithm which is the essential feature of the DEM.

Details

Engineering Computations, vol. 9 no. 2
Type: Research Article
ISSN: 0264-4401

Article
Publication date: 29 March 2021

Steffany N. Cerda-Avila, Hugo I. Medellín-Castillo and Theodore Lim

The purpose of this study is to evaluate the capability and performance of analytical models to predict the structural mechanical behaviour of parts fabricated by fused deposition…

Abstract

Purpose

The purpose of this study is to evaluate the capability and performance of analytical models to predict the structural mechanical behaviour of parts fabricated by fused deposition modelling (FDM).

Design/methodology/approach

A total of eight existing and newly proposed analytical models, tailored to satisfy the structural behaviour of FDM parts, are evaluated in terms of their capability to predict the ultimate tensile stress (UTS) and the elastic modulus (E) of parts made of polylactic acid (PLA) by the FDM process. This evaluation is made by comparing the structural properties predicted by these models with the experimental results obtained from tensile tests on FDM specimens fabricated with variable infill percentage, perimeter layers and build orientation.

Findings

Some analytical models are able to predict with high accuracy (prediction errors smaller than 5%) the structural behaviour of FDM and categories of similar additive manufactured parts. The most accurate model is Gibson’s and Ashby, followed by the efficiency model and the two new proposed exponential and variant Duckworth models.

Research limitations/implications

The study has been limited to uniaxial loading conditions along three different build orientations.

Practical implications

The structural properties of FDM parts can be predicted by analytical models based on the process parameters and material properties. Product engineers can use these models during the design for the additive manufacturing process.

Originality/value

Existing methods to estimate the structural properties of FDM parts are based on experimental tests; however, such methods are time-consuming and costly. In this work, the use of analytical models to predict the structural properties of FDM parts is proposed and evaluated.

Details

Rapid Prototyping Journal, vol. 27 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 28 January 2014

Rainer Dudek, Peter Sommer, Andreas Fix, Joerg Trodler, Sven Rzepka and Bernd Michel

Because of the need for electronics use at temperatures beyond 150°C, high temperature resistant interconnection technologies like transient liquid phase (TLP) soldering and…

Abstract

Purpose

Because of the need for electronics use at temperatures beyond 150°C, high temperature resistant interconnection technologies like transient liquid phase (TLP) soldering and silver sintering are being developed which are not only replacements of high-lead solders, but also open new opportunities in terms of temperature resistance and reliability. The paper aims to address the thermo-mechanical reliability issues that have to be considered if the new interconnection technologies will be applied.

Design/methodology/approach

A TLP soldering technique is briefly introduced and new challenges concerning the thermo-mechanical reliability of power devices are worked out by numerical analysis (finite element simulation). They arise as the material properties of the interconnect materials differ substantially from those known for soft solders. The effective material responses of the new materials are determined by localized unit cell models that capture the inhomogeneous structure of the materials.

Findings

It is shown that both the TLP solder layer and the Ag-sinter layer have much less ductility and show less creep than conventional soft solders. The potential failure modes of an assembly made by TLP soldering or Ag sintering change. In particular, the characteristic low cycle fatigue solder failures become unlikely and are replaced either by metallization fatigue, brittle failure of intermetallic compound, components, or interfaces.

Originality/value

A variety of new failure risks, which have been analyzed theoretically, can be avoided only if they are known to the potential user of the new techniques. It is shown that an optimal reliability will be strongly dependent on the actual assembly design.

Details

Soldering & Surface Mount Technology, vol. 26 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 1 August 1998

Jaroslav Mackerle

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder…

4528

Abstract

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder metallurgy and composite material processing are briefly discussed. The range of applications of finite elements on these subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE researchers/users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for 1994‐1996, where 1,370 references are listed. This bibliography is an updating of the paper written by Brannberg and Mackerle which has been published in Engineering Computations, Vol. 11 No. 5, 1994, pp. 413‐55.

Details

Engineering Computations, vol. 15 no. 5
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 23 August 2011

Luis Kosteski, Ignacio Iturrioz, Ruben Galiano Batista and Adrián P. Cisilino

The purpose of this paper is to further develop the truss‐like discrete element method (DEM) in order to make it suitable to deal with damage and fracture problems.

Abstract

Purpose

The purpose of this paper is to further develop the truss‐like discrete element method (DEM) in order to make it suitable to deal with damage and fracture problems.

Design/methodology/approach

Finite and boundary elements are the best developed methods in the field of numerical fracture and damage mechanics. However, these methods are based on a continuum approach, and thus, the modelling of crack nucleation and propagation could be sometimes a cumbersome task. Besides, discrete methods possess the natural ability to introduce discontinuities in a very direct and intuitive way by simply breaking the link between their discrete components. Within this context, the present work extends the capabilities of a truss‐like DEM via the introduction of three novel features: a tri‐linear elasto‐plastic constitutive law; a methodology for crack discretization and the computation of stress intensity factors; and a methodology for the computation of the stress field components from the unixial discrete‐element results.

Findings

Obtained results show the suitability and the performance of the proposed methodologies to solve static and dynamic crack problems (including crack propagation) in brittle and elasto‐plastic materials. Computed results are in good agreement with experimental and numerical results reported in the bibliography.

Research limitations/implications

This paper demonstrates the versatility of the truss‐like DEM to deal with damage mechanics problems. The approach used in this work can be extended to the implementation of time‐dependent damage mechanisms. Besides, the capabilities of the discrete approach could be exploited by coupling the truss‐like DEM to finite and boundary element methods. Coupling strategies would allow using the DEM to model the regions of the problem where crack nucleation and propagation occurs, while finite or boundary elements are used to model the undamaged regions.

Originality/value

The scope of the truss‐like DEM has been extended. New procedures have been introduced to deal with elastoplastic‐crack problems and to improve the post processing of the stress results.

Article
Publication date: 25 February 2014

Shiuh-Chuan Her and Shou-Jan Liu

Carbon nanotubes (CNTs) with exceptional mechanical, thermal and electrical properties are considered to be ideal for reinforcing high-performance structures. The interfacial…

Abstract

Purpose

Carbon nanotubes (CNTs) with exceptional mechanical, thermal and electrical properties are considered to be ideal for reinforcing high-performance structures. The interfacial stresses between the CNTs and surrounding matrix are important phenomena which critically govern the mechanical properties of CNTs-reinforced nanocomposites. A number of methods have been proposed to investigate the stress transfer across the CNT/matrix interface, such as experimental measurement and molecular dynamics (MDs). Experimental tests are difficulty and expensive. MDs simulations, on the other hand, are computationally inefficient. The purpose of this paper is to present a reasonably simplified model. Incorporating the simplified model, the analytical expressions of the interface stresses including the shear stress and longitudinal normal stress are obtained.

Design/methodology/approach

The analytical model consists of two concentric cylinders, namely a single-walled carbon nanotube (SWCNT) cylinder and a matrix cylinder, as the representative volume element (RVE). The interfacial stress analysis is performed using the shear lag model for the axisymmetric RVE. Analytical solutions for the normal stresses in the SWCNT and matrix, and the interfacial shear stress across the SWCNT/matrix interface are obtained. The proposed model has a great ability to theoretical prediction of the stress transfer between the matrix and CNTs.

Findings

In order to demonstrate the simulation capabilities of the proposed model, parametric studies are conducted to investigate the effects of the volume fraction of SWCNT and matrix modulus on the stress transfer. The axial stress in the matrix is decreasing with the increase of the volume fraction and decrease of the matrix modulus. As a result of more loads can be transferred to the SWCNT for a large volume fraction and small matrix modulus. These results show that using a large volume fraction and a small matrix modulus improves the efficiency of the stress transfer from the matrix to the CNTs.

Originality/value

A simple but accurate model using a simplified 2D RVE for characterizing the stress transfer in CNT-reinforced nanocomposites is presented. The predictions from the current method compare favourably with those by existing experimental, analytical and computational studies. The simple and explicit expressions of the interfacial stresses provide valuable analysis tools accessible to practical users.

Details

Engineering Computations, vol. 31 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 8 August 2016

Vladimir Kobelev

The purpose of this paper is to introduce the double-periodic lattice, composed of bending-resistant fibers. The essence of the model is that the filaments are of infinite length…

Abstract

Purpose

The purpose of this paper is to introduce the double-periodic lattice, composed of bending-resistant fibers. The essence of the model is that the filaments are of infinite length and withstand tension and bending. The constitutive equations of the lattice in discrete and differential formulations are derived. Two complementary systems of loads, which cause different deformation two orthogonal families of fibers, occur in the lattice. The fracture behavior of the material containing a semi-infinite crack is investigated. The crack problem reduces to the exactly solvable Riemann-Hilbert problem. The solution demonstrates that the behavior of material cardinally depends upon the tension in the orthogonal family of fibers. If tension in fibers exists, opening of the crack under action of loads in two-dimensional lattice is similar to those in elastic solid. In the absence of tension, contrarily, there is a finite angle between edges at the crack tip.

Design/methodology/approach

The description of stress state in the crack vicinity is reduced to the solution of mixed boundary value problem for simultaneous difference equations. In terms of Fourier images for unknown functions the problem is equivalent to a certain Riemann-Hilbert problem.

Findings

The analytical solution of the problem shows that fracture behavior of the material depends upon the presence of stabilizing tension in fibers, parallel to crack direction. In the presence of tension in parallel fibers fracture character of two-dimensional lattice is similar to behavior of elastic solid. In this case the condition of crack grows can be formulated in terms of critical stress intensity factor. Otherwise, in the absence of stabilizing tension, the crack surfaces form a finite angle at the tip.

Research limitations/implications

Linear behavior of fibers until rupture. Small deflections. Perfect two-dimensional lattice.

Practical implications

The model provides exact analytical estimation of stresses on the crack tip as the function of fibers’ stiffness.

Originality/value

The model is the extension of known lattice models, taking into account the semi-infinite crack in the lattice. This is the first known closed form solution for an infinite lattice model with the crack.

Details

Multidiscipline Modeling in Materials and Structures, vol. 12 no. 2
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 1 August 1996

Ales Svoboda, Hans‐Åke Häggblad and Mats Näsström

Presents a finite element formulation of hot isostatic pressing (HIP) based on a continuum approach using thermal‐elastoviscoplastic constitutive equations with compressibility…

Abstract

Presents a finite element formulation of hot isostatic pressing (HIP) based on a continuum approach using thermal‐elastoviscoplastic constitutive equations with compressibility. The formulation takes into consideration dependence of the viscoplastic part on the porosity. Also takes into account the thermomechanical response, including nonlinear effects in both the thermal and mechanical analyses. Implements the material model in an implicit finite element code. Presents experimental procedures for evaluating the inelastic behaviour of metal powders during densification and experimental data. Chooses the simulation of the dilatometer measurement of a cylindrical component during HIP and manufacturing simulation of a turbine component to near net shape (NNS) as a demonstrator example. Both components are made of a hot isostatically pressed hot‐working martensitic steel. Compares the result of the simulation in the form of the final geometry of the container with the geometry of a real component produced by HIP. Makes a comparison between the calculated and measured deformations during the HIP process for the cylindrical component. Measures the final geometry of the turbine component by means of a computer controlled measuring machine (CMM). Performs the complete process from design and simulation to geometry verification within a computer‐aided concurrent engineering (CACE) system.

Details

Engineering Computations, vol. 13 no. 5
Type: Research Article
ISSN: 0264-4401

Keywords

1 – 10 of 605