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Article
Publication date: 16 November 2018

Robert Fleischhauer, Jens U. Hartig, Peer Haller and Michael Kaliske

The purpose of this study is the numerical investigation of densification and molding processes of wood. Providing theoretical and numerical approaches with respect to a…

Abstract

Purpose

The purpose of this study is the numerical investigation of densification and molding processes of wood. Providing theoretical and numerical approaches with respect to a consistent multi-physical finite element method framework are further goals of this research.

Design/methodology/approach

Constitutive phenomenological descriptions of the thermo-mechanical and moisture-dependent material characteristics of wood are introduced. Special focus is given to a consistent hygro-thermo-mechanical modeling at finite deformations to capture the realistic material behavior of wood, especially when it is subjected to densification and molding processes.

Findings

Realistic theoretical formulations of different hygro-thermo-mechanical processes are provided. A successful numerical modeling is demonstrated for beech wood by validation at experimental findings.

Originality/value

The constitutive laws and numerical findings are new, as they govern a multi-physical large deformation framework and are applied to the advanced technology of densification and molding of wood.

Details

Engineering Computations, vol. 36 no. 1
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 4 June 2021

Jike Han, Bo Yin, Michael Kaliske and Kenjiro Tarada

This study aims to develop a new analysis approach devised by incorporating a gradient-enhanced microplane damage model (GeMpDM) into isogeometric analysis (IGA), which…

Abstract

Purpose

This study aims to develop a new analysis approach devised by incorporating a gradient-enhanced microplane damage model (GeMpDM) into isogeometric analysis (IGA), which shows computational stability and capability in accurately predicting crack propagations in structures with complex geometries.

Design/methodology/approach

For the non-local microplane damage modeling, the maximum modified von-Mises equivalent strain among all microplanes is regularized as a representative quantity. This characterization implies that only one additional governing equation is considered, which improves computational efficiency dramatically. By combined use of GeMpDM and IGA, quasi-static and dynamic numerical analyses are conducted to demonstrate the capability in predicting crack paths of complex geometries in comparison to FEM and experimental results.

Findings

The implicit scheme with the adopted damage model shows favorable numerical stability and the numerical results exhibit appropriate convergence characteristics concerning the mesh size. The damage evolution is successfully controlled by a tension-compression damage factor. Thanks to the advanced geometric design capability of IGA, the details of crack patterns can be predicted reliably, which are somewhat difficult to be acquired by FEM. Additionally, the damage distribution obtained in the dynamic analysis is in close agreement with experimental results.

Originality/value

The paper originally incorporates GeMpDM into IGA. Especially, only one non-local variable is considered besides the displacement field, which improves the computational efficiency and favorable convergence characteristics within the IGA framework. Also, enjoying the geometric design ability of IGA, the proposed analysis method is capable of accurately predicting crack paths reflecting the complex geometries of target structures.

Details

Engineering Computations, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 5 May 2015

Clemens Gebhardt and Michael Kaliske

The purpose of this paper is to propose a path-finding algorithm to solve problems with an arbitrary load-displacement relationship which results from geometrical and…

Abstract

Purpose

The purpose of this paper is to propose a path-finding algorithm to solve problems with an arbitrary load-displacement relationship which results from geometrical and material nonlinear models to simulate e.g. timber structures realistically.

Design/methodology/approach

A method using combined load and displacement control for the Newton method along with path-characterising measures and sub-incremention is introduced. A path-related stiffness measure is used to identify the situation when it is necessary to select the displacement control and chose the best degree of freedom as a parameter instead of the load factor. The nonlinearity index extracts information about the convergence behaviour during one incremental step. Together with the reduction of the load increments it avoids leaving the equilibrium path.

Findings

The method is discussed based on numerical examples with highly nonlinear behaviour. It is capable to solve systems with decreasing load capacity and snap-back effects.

Originality/value

The algorithm combines load and displacement control and adaptively choses the method and the corresponding degree of freedom and cares for reliable path following.

Details

Engineering Computations, vol. 32 no. 3
Type: Research Article
ISSN: 0264-4401

Keywords

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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

Keywords

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Article
Publication date: 13 June 2016

Marko Bozic, Robert Fleischhauer and Michael Kaliske

The purpose of this paper is to investigate of interphasial effects, including temperature dependency, within fiber reinforced polymers on the overall composite behavior…

Abstract

Purpose

The purpose of this paper is to investigate of interphasial effects, including temperature dependency, within fiber reinforced polymers on the overall composite behavior. Providing theoretical and numerical approaches in terms of a consistent thermomechanical finite element method framework are further goals of this research.

Design/methodology/approach

Starting points for achieving the aims of this research are the partial differential equations describing the evolution of the displacements and temperature within a continuum mechanical setting. Based on the continuous formulation of a thermomechanical equilibrium, constitutive equations are derived, accounting for the modeling of fiber reinforced thermosets and thermoplastics, respectively. The numerical solutions of different initial boundary value problems are obtained by a consistent implementation of the proposed formulations into a finite element framework.

Findings

The successful theoretical formulation and numerical modeling of the thermoinelastic matrix materials as well as the thermomechanical treatment of the composite interphase (IP) are demonstrated for an epoxy/glass system. The influence of the IP on the overall composite behavior is successfully investigated and concluded as a further aspect.

Originality/value

A thermomechanical material model, suitable for finite thermoinelasticity of thermosets and thermoplastics is introduced and implemented into a novel kinematic framework in context of the inelastic deformation evolution. The gradually changing material properties between the matrix and the fiber of a composite are continuously formulated and numerically processed, in order to achieve an efficient and realistic approach to model fiber reinforced composites.

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Article
Publication date: 11 October 2011

Zhenggang Zhu and Michael Kaliske

The purpose of this paper is to present a numerical model of coupled heat, moisture transfer and their effects on the mechanical deformations of wood during the drying process.

Abstract

Purpose

The purpose of this paper is to present a numerical model of coupled heat, moisture transfer and their effects on the mechanical deformations of wood during the drying process.

Design/methodology/approach

Coupling among heat, moisture, and mechanical deformations is solved consecutively by use of sparse solver of MATLAB. The weighted residual of the equilibrium equations of drying process of wood, based on finite element method, is investigated. The stress and plastic strain increments can be solved with Newton's method.

Findings

The numerical model is applied to a plain strain problem of a long wood board taken from the outer region of the wood log. Numerical simulation reveals the stress reversal during the drying process. The mechanical deformations and the principle stresses of a three‐dimensional wood board in consideration of the orthotropic properties are presented.

Originality/value

Plane strain and plane stress are analysed. The tangential modulus is derived. The transformation of the stress and strain tensors between the local coordinate system resulting from the cylindrical properties of wood and the global one is evaluated. Selection of element type for temperature, moisture content and displacement is discussed.

Details

Engineering Computations, vol. 28 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

Content available
Article
Publication date: 1 January 2013

Abstract

Details

Engineering Computations, vol. 30 no. 1
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 11 June 2018

Patricia Raposo, Michael Andrade, José Correia, Maria E. Salavessa, Cristina Reis, Carlos Oliveira and Abilio M.P. de Jesus

The case-study building of this work is the Medieval Inn of Gralheira (“Pousada Medieval da Gralheira”) located in Vila Pouca de Aguiar, Portugal. This building is an…

Abstract

Purpose

The case-study building of this work is the Medieval Inn of Gralheira (“Pousada Medieval da Gralheira”) located in Vila Pouca de Aguiar, Portugal. This building is an example of the structures of that time, located in Trás-os-Montes, Portugal. A large amount of the built heritage suffers from advanced degradation, making the recovery, increasing the complexity of the rehabilitation and restoration intervention and implying a highly specialized interdisciplinary component. Therefore, the purpose of this paper is to carry out a study of the building in order to perform an analysis of its wood floor and assess its structural behaviour and conservation status. This work also presents some examples of intervention methods and rehabilitation techniques used to solve problems in the masonry structure and wood structures.

Design/methodology/approach

In this work, a numerical model of a wood pavement of a medieval building is presented, which was developed and calibrated with values obtained in an experimental campaign of wood specimens extracted from the floor structure and the deformation measured in situ. This model aims to analyse and predict the behaviour of the structure in terms of serviceability limit states. Rehabilitation and reinforcing techniques are described, for specific damages, complemented with a critical comparative analysis to define the most appropriate rehabilitation measures for each situation.

Findings

In this work, for the numerical model of the medieval building under consideration, the support of the beams in the walls between 50 per cent embedded and simply supported (hinge supports) was used. Since the beams have some restriction imposed by the wall, they have a delivery about 20 cm in the wall. The consideration of the delivery between beam and columns as simply supported (hinge supports) is a reasonable approximation. There is a difference between the values of deformation obtained in the numerical model and in situ due to the support conditions and also due to the consideration of the pavement loads as a distributed load, which does not correspond entirely to reality, since the pavement confers rigidity to the floor, behaving like a diaphragm. The presented intervention techniques are not applicable in all structures because each building has different characteristics, in terms of materials and construction. The pathologies occur due to many sources and each case is unique, and must be carefully studied before taking decisions about the rehabilitation methods to use.

Originality/value

This work presents a numerical model of wood pavement of a medieval building developed according to some experimental values obtained in an experimental campaign using wood specimens extracted from original beams and based on in situ measurements. This study is part of master thesis of Michael Andrade, an original research work.

Details

International Journal of Structural Integrity, vol. 9 no. 3
Type: Research Article
ISSN: 1757-9864

Keywords

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