P.A.J. VAN DEN BOGERT, R. DE BORST, G.T. LUITEN and J. ZEILMAKER
A marked characteristic of rubber‐like materials is the nearly incompressible behaviour. This type of behaviour is best modelled by mixed finite elements with separate…
Abstract
A marked characteristic of rubber‐like materials is the nearly incompressible behaviour. This type of behaviour is best modelled by mixed finite elements with separate interpolation functions for the displacements and the pressure. In this contribution the performance of three‐dimensional elements is investigated using a two‐tiered strategy. First, the ability of some linear and quadratic three‐dimensional elements to deform correctly under nearly isochoric conditions is estimated using the well‐known constraint‐counting method, in which the ratio of the number of degrees‐of‐freedom over the number of kinematic constraints present in the finite element mesh is determined. Next, the performance of the elements is assessed by numerical simulations for three cuboidal rubber blocks with different shape factors. The results turn out to be quite sensitive with respect to the ratio of the number of degrees‐of‐freedom over the number of kinematic constraints, since too many pressure degrees‐of‐freedom make the element overstiff, while too few pressure degrees‐of‐freedom may cause the occurrence of spurious kinematic modes. This observation appears to be not only valid for the global structural behaviour, but also with respect to the specific parts in the structure, where the above‐mentioned ratio is different from the global number, e.g., in corners of the structure.
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C.H. Liu, G. Hofstetter and H.A. Mang
The paper starts with a review of constitutive equations forrubber‐like materials, formulated in the invariants of the rightCauchy—Green deformation tensor. A general framework…
Abstract
The paper starts with a review of constitutive equations for rubber‐like materials, formulated in the invariants of the right Cauchy—Green deformation tensor. A general framework for the derivation of the stress tensor and the tangent moduli for invariant‐based models, for both the reference and the current configuration, is presented. The free energy of incompressible rubber‐like materials is extended to a compressible formulation by adding the volumetric part of the free energy. In order to overcome numerical problems encountered with displacement‐based finite element formulations for nearly incompressible materials, three‐dimensional finite elements, based on a penalty‐type formulation, are proposed. They are characterized by applying reduced integration to the volumetric parts of the tangent stiffness matrix and the pressure‐related parts of the internal force vector only. Moreover, hybrid finite elements are proposed. They are based on a three‐field variational principle, characterized by treating the displacements, the dilatation and the hydrostatic pressure as independent variables. Subsequently, this formulation is reduced to a generalized displacement formulation. In the numerical study these formulations are evaluated. The results obtained are compared with numerical results available in the literature. In addition, the proposed formulations are applied to 3D finite element analysis of an automobile tyre. The computed results are compared with experimental data.
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Stefan Doll, Karl Schweizerhof, Ralf Hauptmann and Christof Freischläger
As known from nearly incompressible elasticity, selective reduced integration (SRI) is a simple and effective method of overcoming the volumetric locking problem in 2D and 3D…
Abstract
As known from nearly incompressible elasticity, selective reduced integration (SRI) is a simple and effective method of overcoming the volumetric locking problem in 2D and 3D solid elements. This method of finite elastoviscoplasticity is discussed as are its well‐known limitations. In this context, an isochoric‐volumetric decoupled material behavior is assumed and thus the additive deviatoric‐volumetric decoupling of the consistent algorithmic moduli tensor is essential. By means of several numerical examples, the performance of elements using selective reduced integration is demonstrated and compared to the performance of other elements such as the enhanced assumed strain elements. It is shown that a minor modification, with little numerical effort, leads to rather robust element behaviour. The application of this process to so‐called solid‐shell elements for thin‐walled structures is also discussed.
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An important characteristic of many soil models is a volume change during plastic flow. In computations, this plastic volume change is expressed via a kinematic constraint on the…
Abstract
An important characteristic of many soil models is a volume change during plastic flow. In computations, this plastic volume change is expressed via a kinematic constraint on the possible deformations. Due to this constraint the plane‐strain three‐noded triangular element exhibits locking when plastic deformations occur, under dilatant, contractant and isochoric conditions. It is demonstrated that using the method of enhanced assumed strains by Simol this locking cannot be remedied. For six‐noded wedges and four‐noded and five‐noded pyramids the same conclusion is obtained.
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M. Kaliske and H. Rothert
Derives a formulation for spatial stress tensors and spatial material tensors of hyperelastic material. Looks at a class of materials with the strain energy function decomposed…
Abstract
Derives a formulation for spatial stress tensors and spatial material tensors of hyperelastic material. Looks at a class of materials with the strain energy function decomposed into a volumetric and a deviatoric part. Separate terms formulate the strain energy with respect to the invariants of the left Cauchy‐Green tensor. Stress and material tensors, which play a crucial role in the solution process of the finite element formulation, are derived solely in the current configuration. Applies the described framework to several different constitutive models based on phenomenologically and physically motivated material descriptions. Proposes a formulation for the finite element implementation of van der Waals material. Compares numerical results with experimental investigations given in the literature. For three‐dimensional finite element computations standard elements and mixed elements, based on a three‐field variational principle where displacements, the hydrostatic pressure and the dilatations are independent variables, are used.
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Heleen van Dijk, Ellen van Kleef, Helen Owen and Lynn J. Frewer
The aim of this study is to identify and explore consumer preferences and information needs regarding the simultaneous communication of risks and benefits associated with food…
Abstract
Purpose
The aim of this study is to identify and explore consumer preferences and information needs regarding the simultaneous communication of risks and benefits associated with food consumption. The focus is on the net health impact of risks and benefits on life expectancy, quality of life, and disability adjusted life years (DALYs).
Design/methodology/approach
Focus groups were conducted in four countries (Iceland, The Netherlands, Portugal, UK). All sessions were audio‐taped, transcribed and content analyzed.
Findings
Current risk‐benefit communication is perceived as “asymmetrical”, confusing, and often distrusted. Participants expressed a preference for more balanced and scientifically derived information. Information about the net health impact on both life expectancy and quality of life was found to be meaningful for food decision making. DALYs were thought too complicated.
Research limitations/implications
Findings confirm the importance of incorporating consumers' viewpoints when developing communications about risk and benefits. The results provide insights into potential issues related to the communication of risk and benefit information. The limitations of the qualitative approach adopted in this study suggest that further research utilizing nationally representative samples is needed, which may explore additional metrics to communicate net health effects to consumers.
Originality/value
Common measures for assessing both risks and benefits are expected to facilitate the communication of the results of risk‐benefit assessment as part of risk analysis. However, research incorporating consumers' perspectives on this issue is scarce. A better understanding of how consumers perceive these measures may promote the development of more effective integrated risk benefit communication.
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Kgomotso Lebelo, Muthoni Masinde, Ntsoaki Malebo and Mokgaotsa Jonas Mochane
This paper aims to report on the bibliometric research trends on the application of machine learning/intelligent systems in the prediction of food contamination and the…
Abstract
Purpose
This paper aims to report on the bibliometric research trends on the application of machine learning/intelligent systems in the prediction of food contamination and the surveillance of foodborne diseases.
Design/methodology/approach
In this study, Web of Science (WoS) core collection database was used to retrieve publications from the year 1996–2021. Document types were classified according to country of origin, journals, citation and key research areas. The bibliometric parameters were analyzed using VOSviewer version 1.6.15 to visualize the international collaboration networks, citation density and link strength.
Findings
A total of 516 articles across 6 document types were extracted with an average h-index of 51 from 10,570 citations. The leading journal in publications was Science of the Total Environment (3.6%) by Elsevier and the International Journal of Food Microbiology (2.5%). The United States of America (USA) (24%) followed by the People's Republic of China (17.2%) were the most influential countries in terms of publications. The top-cited articles in this study focused on themes such as contamination from packaging materials and on the strategies for preventing chemical contaminants in the food chain.
Originality/value
This report is significant because the public health field requires innovative strategies in forecasting foodborne disease outbreaks to advance effective interventions. Therefore, more collaboration need to be fostered, especially in developing nations regarding food safety research.