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Article
Publication date: 10 June 2019

Bingqi Li, Zhenyu Zhang, Xiaogang Wang and Xiaonan Liu

The behavior of joints has a significant effect on the stability of water conveyance tunnel. The purpose of this paper is to study the contact and friction at the joint of…

Abstract

Purpose

The behavior of joints has a significant effect on the stability of water conveyance tunnel. The purpose of this paper is to study the contact and friction at the joint of the tunneling segment lining and establish its contact friction model. At the same time, the stress and deformation characteristics at the joint of the segment under hydrostatic load are analyzed.

Design/methodology/approach

In this study, the contact and friction in a bolted joint are examined using shear testing. The feasibility of the proposed model is verified by a numerical simulation of tests and a theoretical analysis. Accordingly, the effect of joints on the lining is explored under internal hydrostatic loading.

Findings

The results show that the openings of tunnel segments in joints gradually expand from the positions of the inner and outer edges to the location of the bolt. Moreover, the stress concentration zone is formed at the bolt. Under hydraulic loading, the opening displacement at the joint increases as the water pressure increases; nevertheless, it does not exceed engineering requirements. When the water pressure of the tunnel lining joint reaches 0.5 MPa, the opening of the joint slowly increases. When the water pressure exceeds 0.7 MPa, the opening of the joint rapidly and significantly increases.

Originality/value

Contact and friction in a bolted joint were examined using shear testing. A cohesive zone model of bolted joints was proposed based on test results. The influence of joint behavior on the stability of water conveyance tunnel was studied.

Details

Engineering Computations, vol. 36 no. 5
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 28 August 2007

Gordon Geißler, Michael Kaliske, Michael Nase and Wolfgang Grellmann

The purpose of this paper is to evaluate current simulation capabilities for thin film delamination on the basis of real test data as well as a contribution to its…

Abstract

Purpose

The purpose of this paper is to evaluate current simulation capabilities for thin film delamination on the basis of real test data as well as a contribution to its extension in order to partly substitute experimental investigations.

Design/methodology/approach

The proposed model consists of a formulation that describes the behaviour of the bulk material and an approach that introduces the film's delamination capability. An implicit finite element framework with a cohesive zone implementation is used and described in detail. The numerical results on the basis of the a priori identified material parameters are related to the experimental work. In order to capture the obvious peel speed dependency of these delamination processes, a viscoelastic cohesive formulation is introduced and compared with a pure separation rate dependent cohesive material in the second part of this contribution.

Findings

The performed numerical simulations show a good approximation of the experimental peel process. The extension in order to take time‐dependent effects into account is required for the simulation of such problems. In contrast with the pure rate‐dependent model, the presented consistent formulation of the cohesive part is able to cover the whole range of observed material phenomena.

Research limitations/implications

Owing to the absence of suitable experimental single mode investigations of the sealed layer, the used cohesive material parameters are identified in relation to the pre‐existing experimental results. Furthermore, the resultant peel force has a constant value due to the assumed homogeneous cohesive material and therefore gives only a mean approximation of the experimental values at this stage of the investigation.

Originality/value

The numerical representation of such a thin film delamination process in relation to real experimental results shows the additional capabilities and the usability of the implicit finite element method with a cohesive zone implementation in a clear and illustrative way. The first proposed cohesive extension based on a rheological model shows the capability to cover the full range of time‐dependent interface layer behaviour.

Details

Engineering Computations, vol. 24 no. 6
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 12 August 2014

A. Pirondi, G. Giuliese and F. Moroni

In this work, the cohesive zone model (CZM) developed by some of the authors to simulate the propagation of fatigue defects in two dimensions is extended in order to…

Abstract

Purpose

In this work, the cohesive zone model (CZM) developed by some of the authors to simulate the propagation of fatigue defects in two dimensions is extended in order to simulate the propagation of defects in 3D. The paper aims to discuss this issue.

Design/methodology/approach

The procedure has been implemented in the finite element (FE) solver (Abaqus) by programming the appropriate software-embedded subroutines. Part of the procedure is devoted to the calculation of the rate of energy release per unit, G, necessary to know the growth of the defect.

Findings

The model was tested on different joint geometries, with different load conditions (pure mode I, mode II pure, mixed mode I/II) and the results of the analysis were compared with analytical solutions or virtual crack closure technique (VCCT).

Originality/value

The possibility to simulate the growth of a crack without any re-meshing requirements and the relatively easy possibility to manipulate the constitutive law of the cohesive elements makes the CZM attractive also for the fatigue crack growth simulation. However, differently from VCCT, three-dimensional fatigue de-bonding/delamination with CZM is not yet state-of-art in FE softwares.

Details

International Journal of Structural Integrity, vol. 5 no. 3
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 10 May 2013

Peter Filipp Fuchs, Klaus Fellner and Gerald Pinter

The purpose of this paper is to analyse, in a finite element simulation, the failure of a multilayer printed circuit board (PCB), exposed to an impact load, to better…

Abstract

Purpose

The purpose of this paper is to analyse, in a finite element simulation, the failure of a multilayer printed circuit board (PCB), exposed to an impact load, to better evaluate the reliability and lifetime. Thereby the focus was set on failures in the outermost epoxy layer.

Design/methodology/approach

The fracture behaviour of the affected material was characterized. The parameters of a cohesive zone law were determined by performing a double cantilever beam test and a corresponding simulation. The cohesive zone law was used in an enriched finite element local simulation model to predict the crack initiation and crack propagation. Using the determined location of the initial crack, the energy release rate at the crack tip was calculated, allowing an evaluation of the local loading situation.

Findings

A good concurrence between the simulated and the experimentally observed failure pattern was observed. Calculating the energy release rate of two example PCBs, the significant influence of the chosen type on the local failure behaviour was proven.

Originality/value

The work presented in this paper allows for the simulation and evaluation of failure in the outermost epoxy layers of printed circuit boards due to impact loads.

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Article
Publication date: 12 July 2013

Kyungmok Kim, Jean Geringer and Bernard Forest

The purpose of this paper is to describe finite element modelling for fracture and fatigue behaviour of zirconia toughened alumina microstructures.

Abstract

Purpose

The purpose of this paper is to describe finite element modelling for fracture and fatigue behaviour of zirconia toughened alumina microstructures.

Design/methodology/approach

A two‐dimensional finite element model is developed with an actual Al2O3‐10 vol% ZrO2 microstructure. A bilinear, time‐independent cohesive zone law is implemented for describing fracture behaviour of grain boundaries. Simulation conditions are similar to those found at contact between a head and a cup of hip prosthesis. Residual stresses arisen from the mismatch of thermal coefficient between grains are determined. Then, effects of a micro‐void and contact stress magnitude are investigated with models containing residual stresses. For the purpose of simulating fatigue behaviour, cyclic loadings are applied to the models.

Findings

Results show that crack density is gradually increased with increasing magnitude of contact stress or number of fatigue cycles. It is also identified that a micro‐void brings about the increase of crack density rate.

Social implications

This paper is the first step for predicting the lifetime of ceramic implants. The social implications would appear in the next few years about health issues.

Originality/value

This proposed finite element method allows describing fracture and fatigue behaviours of alumina‐zirconia microstructures for hip prosthesis, provided that a microstructure image is available.

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Article
Publication date: 1 February 2001

T.I. Zohdi and P. Wriggers

A model for the decohesion of aggregates of suspended particulate material in a binding matrix is developed. In the model cohesive zones which envelop each particle…

Abstract

A model for the decohesion of aggregates of suspended particulate material in a binding matrix is developed. In the model cohesive zones which envelop each particle individually are introduced at the particulate/binder interface. During progressive loading, the deterioration of the cohesive zones is initiated if constraints placed on the microstress fields are violated. In order for the material behavior to be energetically admissible, the deterioration of the material at a point is in the form of a reduction of the elasticity tensor’s eigenvalues at that point. The material within the cohesive zones deteriorates until the constraints are met. In order to isolate and study the effects of interfacial deterioration, outside of the cohesive zones, the material is unaltered. Mathematical properties of the model, as well as physical restrictions, are discussed. Numerical simulations are performed employing the finite element method to illustrate the approach in three‐dimensional applications.

Details

Engineering Computations, vol. 18 no. 1/2
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 4 July 2016

Wei Zhou, Wei Yuan, Gang Ma and Xiao-Lin Chang

The purpose of this paper is to propose a novel combined finite-discrete element method (FDEM), based on the cohesive zone model, for simulating rockslide problems at the…

Abstract

Purpose

The purpose of this paper is to propose a novel combined finite-discrete element method (FDEM), based on the cohesive zone model, for simulating rockslide problems at the laboratory scale.

Design/methodology/approach

The combined FDEM is realized using ABAQUS/Explicit. The rock mass is represented as a collection of elastic bulk elements glued by cohesive elements with zero thickness. To reproduce the tensile and shear micro-fractures in rock material, the Mohr-Coulomb model with tension cut-off is employed as the damage initiation criterion of cohesive elements. Three simulated laboratory tests are considered to verify the capability of combined FDEM in reproducing the mechanical behavior of rock masses. Three slope models with different joint inclinations are taken to illustrate the application of the combined FDEM to rockslide simulation.

Findings

The results show that the joint inclination is an important factor for inducing the progressive failure behavior. With a low joint inclination, the slope failure process is observed to be a collapse mode. As the joint inclination becomes higher, the failure mode changes to sliding and the steady time of rock blocks is shortened. Moreover, the runout distance and post-failure slope angle decrease as the joint inclination increases.

Originality/value

These studies indicate that the combined FDEM performed within ABAQUS can simulate slope stability problems for research purposes and is useful for studying the slope failure mechanism comprehensively.

Details

Engineering Computations, vol. 33 no. 5
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 4 January 2011

Luca Lampani

The purpose of this paper is to assess a numerical tool to simulate and predict the onset and the propagation of the delaminations in a composite structure.

Abstract

Purpose

The purpose of this paper is to assess a numerical tool to simulate and predict the onset and the propagation of the delaminations in a composite structure.

Design/methodology/approach

The approach to the work is done through the cohesive zone model technique applied to the finite element method.

Findings

Double cantilever beam, end notched flexure and mixed mode bending tests have been performed and correlated to benchmark cases, in order to validate the procedure. Numerical test campaign on specimens of the skirts with delaminations has been performed to analyze the behaviour under compressive load and the buckling.

Originality/value

This tool is applied to the study of the behaviour of some components in carbon/epoxy composite of a space structure in which one or more delaminations are eventually present following impact damage or manufacturing process. The components in particular are the booster's skirts of a small class launcher, subjected to a compressive load.

Details

Engineering Computations, vol. 28 no. 1
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 9 April 2018

Sunil Bhat and S. Narayanan

Behavior of mode I crack tip in fiber metal laminate (FML) differs from that in homogeneous or plain specimen made of metal used in the laminate due to the load transfer…

Abstract

Purpose

Behavior of mode I crack tip in fiber metal laminate (FML) differs from that in homogeneous or plain specimen made of metal used in the laminate due to the load transfer effect in the laminate caused by property mismatch between dissimilar material layers. The purpose of this paper is to present a finite element investigation on the characteristics of crack tip in monotonically loaded and residually stressed FML.

Design/methodology/approach

Crack tip characteristics are assessed by: the sizes of various zones that form at the tip; and crack tip energy release rates. The same are found by modeling two types of Glare laminates under monotonic tension with different crack orientations in SSY regime – Type I and Type II. Residual stresses are externally introduced in the models. Delaminations are modeled by cohesive elements. Crack tip zone sizes are measured from finite element solutions. Values of J integrals are computed over cyclic paths near the crack tips. Identically cracked and loaded plain aluminum alloy specimens are also modeled for comparison.

Findings

The sizes of crack tip zones in Glare laminates are found to be different than those in plain specimens. Process zone is observed to form at crack tip in Type I laminate whereas it does not develop in Type II laminate, the reverse being true in plain specimens. Values of J integrals near crack tips are also found to deviate from those in plain specimens, higher in Type I laminate due to crack tip stress amplification and lower in Type II laminate due to stress reduction. Crack orientation decides the amplification or shielding effect in the laminate.

Research limitations/implications

There is scope for validating the numerical results reported in the paper by theoretical models.

Practical implications

The method to quantify crack tip shielding and amplification is presented that shall be useful in checking the structural integrity/safety of the laminate during actual service conditions.

Originality/value

Shielding and amplification effects are explicitly described and illustrated in the paper. Suitability of using J integrals over paths crossing non-homogeneous and property mismatched material layers is tested. Use of cohesive zone method that is readily applicable in finite element procedures and is relatively simple, fast and reasonably accurate is also demonstrated.

Details

International Journal of Structural Integrity, vol. 9 no. 2
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 23 February 2012

L. Peng, X. Gong, K. Wong and L. Guillaumat

The parameters of cohesive elements have to be chosen correctly in the simulation of composite delamination by finite element method: such as interface strength, interface…

Abstract

The parameters of cohesive elements have to be chosen correctly in the simulation of composite delamination by finite element method: such as interface strength, interface stiffness and shape of cohesive law. The purpose of this work is to investigate their influence on the accuracy of the results obtained. A three-dimensional cohesive-zone model has been established using Ls-dyna to simulate Double-Cantilever-Beam mode I (DCB) and Edge-Notched-Flexure mode II (ENF) tests. The influence of these parameters of cohesive element on the maximum load and the slope of load-displacement curve have been discussed by comparing experimental and numerical results. Four traction-separation laws: bilinear, linear-parabolic, exponential and trapezoidal were considered associated with a large variation of the interface strength and of the initial interface stiffness.

Details

World Journal of Engineering, vol. 9 no. 2
Type: Research Article
ISSN: 1708-5284

Keywords

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