The Experts below are selected from a list of 78 Experts worldwide ranked by ideXlab platform
Andreas Menzel - One of the best experts on this subject based on the ideXlab platform.
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A Gradient-Enhanced Continuum Damage Model for Residually Stressed Fibre-Reinforced Materials at Finite Strains
Biomedical Technology, 2014Co-Authors: Tobias Waffenschmidt, César Polindara, Andreas MenzelAbstract:The modelling of damage effects in Materials constitutes a major challenge in various engineering-related disciplines. However, the assumption of purely local continuum damage formulations may lead to ill-posed boundary value problems and—with regard to numerical methods such as the finite element method—to mesh-dependent solutions, a vanishing localised damage zone upon mesh refinement, and hence physically questionable results. In order to circumvent these deficiencies, we present a non-local gradient-enhanced damage model at finite strains. We additively compose the hyperelastic constitutive response at local Material point level of an isotropic matrix and of an anisotropic Fibre-Reinforced Material. The inelastic constitutive response is characterised by a scalar [1– d]-damage model, where we assume only the anisotropic elastic part to damage. Furthermore, we enhance the local free energy by a gradient-term. This term essentially contains the gradient of the non-local damage variable which we introduce as an additional global field variable. In order to guarantee the equivalence between the local and non-local damage variable, we incorporate a penalisation term within the free energy. Based on the principle of minimum total potential energy, we obtain a coupled system of variational equations. The associated non-linear system of equations is symmetric and can conveniently be solved by standard incremental-iterative Newton-Raphson schemes or arc-length-based solution methods. As a further key aspect, we incorporate residual stresses by means of a multiplicative composition of the deformation gradient. As a three-dimensional finite element example, we study the Material degradation of a Fibre-Reinforced tube subjected to internal pressure. This highlights the mesh-objective and constitutive properties of the model and illustratively underlines the capabilities of the formulation with regard to biomechanical application such as the simulation of arteries.
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A gradient-enhanced large-deformation continuum damage model for Fibre-Reinforced Materials
Computer Methods in Applied Mechanics and Engineering, 2013Co-Authors: Tobias Waffenschmidt, César Polindara, Andreas Menzel, Sergio BlancoAbstract:A non-local gradient-based damage formulation within a geometrically non-linear setting is presented. The hyperelastic constitutive response at local Material point level is governed by a strain energy which is additively composed of an isotropic matrix and of an anisotropic Fibre-Reinforced Material, respectively. The inelastic constitutive response is governed by a scalar [1–d]-type damage formulation, where only the anisotropic elastic part is assumed to be affected by the damage. Following the concept in Dimitrijevic and Hackl [28], the local free energy function is enhanced by a gradient-term. This term essentially contains the gradient of the non-local damage variable which, itself, is introduced as an additional independent variable. In order to guarantee the equivalence between the local and non-local damage variable, a penalisation term is incorporated within the free energy function. Based on the principle of minimum total potential energy, a coupled system of Euler–Lagrange equations, i.e., the balance of linear momentum and the balance of the non-local damage field, is obtained and solved in weak form. The resulting coupled, highly non-linear system of equations is symmetric and can conveniently be solved by a standard incremental-iterative Newton–Raphson-type solution scheme. Several three-dimensional displacement- and force-driven boundary value problems—partially motivated by biomechanical application—highlight the mesh-objective characteristics and constitutive properties of the model and illustratively underline the capabilities of the formulation proposed.
Tobias Waffenschmidt - One of the best experts on this subject based on the ideXlab platform.
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A Gradient-Enhanced Continuum Damage Model for Residually Stressed Fibre-Reinforced Materials at Finite Strains
Biomedical Technology, 2014Co-Authors: Tobias Waffenschmidt, César Polindara, Andreas MenzelAbstract:The modelling of damage effects in Materials constitutes a major challenge in various engineering-related disciplines. However, the assumption of purely local continuum damage formulations may lead to ill-posed boundary value problems and—with regard to numerical methods such as the finite element method—to mesh-dependent solutions, a vanishing localised damage zone upon mesh refinement, and hence physically questionable results. In order to circumvent these deficiencies, we present a non-local gradient-enhanced damage model at finite strains. We additively compose the hyperelastic constitutive response at local Material point level of an isotropic matrix and of an anisotropic Fibre-Reinforced Material. The inelastic constitutive response is characterised by a scalar [1– d]-damage model, where we assume only the anisotropic elastic part to damage. Furthermore, we enhance the local free energy by a gradient-term. This term essentially contains the gradient of the non-local damage variable which we introduce as an additional global field variable. In order to guarantee the equivalence between the local and non-local damage variable, we incorporate a penalisation term within the free energy. Based on the principle of minimum total potential energy, we obtain a coupled system of variational equations. The associated non-linear system of equations is symmetric and can conveniently be solved by standard incremental-iterative Newton-Raphson schemes or arc-length-based solution methods. As a further key aspect, we incorporate residual stresses by means of a multiplicative composition of the deformation gradient. As a three-dimensional finite element example, we study the Material degradation of a Fibre-Reinforced tube subjected to internal pressure. This highlights the mesh-objective and constitutive properties of the model and illustratively underlines the capabilities of the formulation with regard to biomechanical application such as the simulation of arteries.
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A gradient-enhanced large-deformation continuum damage model for Fibre-Reinforced Materials
Computer Methods in Applied Mechanics and Engineering, 2013Co-Authors: Tobias Waffenschmidt, César Polindara, Andreas Menzel, Sergio BlancoAbstract:A non-local gradient-based damage formulation within a geometrically non-linear setting is presented. The hyperelastic constitutive response at local Material point level is governed by a strain energy which is additively composed of an isotropic matrix and of an anisotropic Fibre-Reinforced Material, respectively. The inelastic constitutive response is governed by a scalar [1–d]-type damage formulation, where only the anisotropic elastic part is assumed to be affected by the damage. Following the concept in Dimitrijevic and Hackl [28], the local free energy function is enhanced by a gradient-term. This term essentially contains the gradient of the non-local damage variable which, itself, is introduced as an additional independent variable. In order to guarantee the equivalence between the local and non-local damage variable, a penalisation term is incorporated within the free energy function. Based on the principle of minimum total potential energy, a coupled system of Euler–Lagrange equations, i.e., the balance of linear momentum and the balance of the non-local damage field, is obtained and solved in weak form. The resulting coupled, highly non-linear system of equations is symmetric and can conveniently be solved by a standard incremental-iterative Newton–Raphson-type solution scheme. Several three-dimensional displacement- and force-driven boundary value problems—partially motivated by biomechanical application—highlight the mesh-objective characteristics and constitutive properties of the model and illustratively underline the capabilities of the formulation proposed.
George Jeronimidis - One of the best experts on this subject based on the ideXlab platform.
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Has biomimetics arrived in architecture?
Bioinspiration and Biomimetics, 2012Co-Authors: Petra Gruber, George JeronimidisAbstract:Architecture and construction are highly interdisciplinary fields, integrating many professions and many disciplines on different levels of scale and complexity. Studies of natural systems have at all times been inspirational for design. Investigating the overlaps between biology and architecture we find that a biological paradigm inspires the current frontier of research and innovation in many sectors. Using biology's categories to analyse the field we discover many 'signs of life' in architecture projects, and many researchers are actively involved with ways to implement more and more aspects of life into buildings without calling themselves biomimeticists. Meanwhile the architectural landscape has adopted biomimetics, bionics, biologically inspired design or biomimicry as valid strategies. However, it still lacks a showcase of innovative products or real breakthrough in the form of a 'really biomimetic building'. This implies the interpretation of biomimetics as an architectural style, defining the entirety of a building, best reflected in the overall form. Architecture is developed in different layers and has to meet often contradictory requirements that make information transfer difficult. Too many possibilities and levels of information are interconnected to identify simple straightforward questions and answers. In addition, other challenges have to be met for the adoption of principles from biology in architecture and there is still a difficulty in the gathering of information. Finding phenomena that lend themselves as role models is a challenge for architects and designers in spite of various attempts at generating databases and knowledge transfer systems. Whenever designers stumble across an interesting phenomenon, the relevant information is often available only in a generic manner or, even worse, limited to a narrow view angle related to a specific interest. In order to get hold of transferable information, research from another perspective in life sciences is needed, so that interdisciplinary collaboration can provide the platform essential for successful developments, as illustrated in the present collection of papers. In spite of all of the participating research groups working with a biomimetic focus, the translations and inspirations discussed in the papers are located mostly on the level of generic abstract principles, sometimes also referred to as 'deep principles'. Examples include composite Materials aspects, anisotropy and heterogeneity, when we talk about Materials and systems, and morphological differentiation and adaptation when we consider form generation processes. Tom Wiscombe designs visionary buildings that explore the potentials of architectural surfaces to be shifted from two-dimensionality to one or three dimensionality by introducing de-lamination, winding, fusing, blending and embedding of building systems. The use of non-mineral Materials and suggestion of the logic of healing and weaving are directly taken from biological Material processing. Functionally graded Materials and the introduction of microparticles and biochemical systems shall further extend the possibilities to create future environments. Jan Knippers, Thomas Speck and Achim Menges have initiated a successful interdisciplinary collaboration between architecture, computational design, engineering and biology. They interpret architecture and biological evolution as nondeterministic processes, sharing parallels but fundamental differences at the same time. Those differences are the basis for the investigation of new technologies. The ICD/ITKE Research Pavillion 2010 stands as an example for a homogenous construction using a single textured Material, parametric differentiation and shaping of large elastic deformations, using digital simulation, planning and production processes. The development of the so-called Flectofin(®) lamellas for shading of facades is based on the kinematics of the Strelitzia reginae flower, and again exploits an effect usually unwelcomed in engineering-torsional buckling-together with the use of fibre reinforced Material. The introduction of such a system into a large scale building facade is presented with the thematic pavilion at EXPO 2012 in Korea, designed and engineered by SOMA Architects, Vienna and Knippers Helbig Advanced Engineering, Stuttgart, New York. These large scale implementations of principles derived from nature show the potential for the application of biomimetics in architectural design. Achim Menges' paper is a concise discussion of morphogenetic computational design, presenting form generation in contrast to the traditional form definition and form finding strategies in architectural design. Computational design allows for radically new approaches in the use, processing and generation of information that is translated into architectural form via new technologies. The generative design process is limited by phylogenetic and physical constraints. According to Menges, the challenge of this approach lies in resolving the complexity arising from the interrelation and reciprocal effects of Material systems and dynamic environments. Evolutionary design exploration is introduced as a method together with a detailed description of case studies exploring the design of form-performance relations of overall building morphologies and urban block morphologies. Taken together, the presented papers show a promising development towards the implementation of biomimetics in the design of future built environments. References Wiscombe T 2012 Beyond assemblies: systems convergence and multi-Materiality Bioinspir. Biomim. 7 015001 Knippers J and Speck T 2012 Design and construction principles in nature and architecture Bioinspir. Biomim. 7 015002 Menges A 2012 Biomimetic design processes in architecture: morphogenetic and evolutionary computational design Bioinspir. Biomim. 7 015003.
César Polindara - One of the best experts on this subject based on the ideXlab platform.
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A Gradient-Enhanced Continuum Damage Model for Residually Stressed Fibre-Reinforced Materials at Finite Strains
Biomedical Technology, 2014Co-Authors: Tobias Waffenschmidt, César Polindara, Andreas MenzelAbstract:The modelling of damage effects in Materials constitutes a major challenge in various engineering-related disciplines. However, the assumption of purely local continuum damage formulations may lead to ill-posed boundary value problems and—with regard to numerical methods such as the finite element method—to mesh-dependent solutions, a vanishing localised damage zone upon mesh refinement, and hence physically questionable results. In order to circumvent these deficiencies, we present a non-local gradient-enhanced damage model at finite strains. We additively compose the hyperelastic constitutive response at local Material point level of an isotropic matrix and of an anisotropic Fibre-Reinforced Material. The inelastic constitutive response is characterised by a scalar [1– d]-damage model, where we assume only the anisotropic elastic part to damage. Furthermore, we enhance the local free energy by a gradient-term. This term essentially contains the gradient of the non-local damage variable which we introduce as an additional global field variable. In order to guarantee the equivalence between the local and non-local damage variable, we incorporate a penalisation term within the free energy. Based on the principle of minimum total potential energy, we obtain a coupled system of variational equations. The associated non-linear system of equations is symmetric and can conveniently be solved by standard incremental-iterative Newton-Raphson schemes or arc-length-based solution methods. As a further key aspect, we incorporate residual stresses by means of a multiplicative composition of the deformation gradient. As a three-dimensional finite element example, we study the Material degradation of a Fibre-Reinforced tube subjected to internal pressure. This highlights the mesh-objective and constitutive properties of the model and illustratively underlines the capabilities of the formulation with regard to biomechanical application such as the simulation of arteries.
-
A gradient-enhanced large-deformation continuum damage model for Fibre-Reinforced Materials
Computer Methods in Applied Mechanics and Engineering, 2013Co-Authors: Tobias Waffenschmidt, César Polindara, Andreas Menzel, Sergio BlancoAbstract:A non-local gradient-based damage formulation within a geometrically non-linear setting is presented. The hyperelastic constitutive response at local Material point level is governed by a strain energy which is additively composed of an isotropic matrix and of an anisotropic Fibre-Reinforced Material, respectively. The inelastic constitutive response is governed by a scalar [1–d]-type damage formulation, where only the anisotropic elastic part is assumed to be affected by the damage. Following the concept in Dimitrijevic and Hackl [28], the local free energy function is enhanced by a gradient-term. This term essentially contains the gradient of the non-local damage variable which, itself, is introduced as an additional independent variable. In order to guarantee the equivalence between the local and non-local damage variable, a penalisation term is incorporated within the free energy function. Based on the principle of minimum total potential energy, a coupled system of Euler–Lagrange equations, i.e., the balance of linear momentum and the balance of the non-local damage field, is obtained and solved in weak form. The resulting coupled, highly non-linear system of equations is symmetric and can conveniently be solved by a standard incremental-iterative Newton–Raphson-type solution scheme. Several three-dimensional displacement- and force-driven boundary value problems—partially motivated by biomechanical application—highlight the mesh-objective characteristics and constitutive properties of the model and illustratively underline the capabilities of the formulation proposed.
Petra Gruber - One of the best experts on this subject based on the ideXlab platform.
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Has biomimetics arrived in architecture?
Bioinspiration and Biomimetics, 2012Co-Authors: Petra Gruber, George JeronimidisAbstract:Architecture and construction are highly interdisciplinary fields, integrating many professions and many disciplines on different levels of scale and complexity. Studies of natural systems have at all times been inspirational for design. Investigating the overlaps between biology and architecture we find that a biological paradigm inspires the current frontier of research and innovation in many sectors. Using biology's categories to analyse the field we discover many 'signs of life' in architecture projects, and many researchers are actively involved with ways to implement more and more aspects of life into buildings without calling themselves biomimeticists. Meanwhile the architectural landscape has adopted biomimetics, bionics, biologically inspired design or biomimicry as valid strategies. However, it still lacks a showcase of innovative products or real breakthrough in the form of a 'really biomimetic building'. This implies the interpretation of biomimetics as an architectural style, defining the entirety of a building, best reflected in the overall form. Architecture is developed in different layers and has to meet often contradictory requirements that make information transfer difficult. Too many possibilities and levels of information are interconnected to identify simple straightforward questions and answers. In addition, other challenges have to be met for the adoption of principles from biology in architecture and there is still a difficulty in the gathering of information. Finding phenomena that lend themselves as role models is a challenge for architects and designers in spite of various attempts at generating databases and knowledge transfer systems. Whenever designers stumble across an interesting phenomenon, the relevant information is often available only in a generic manner or, even worse, limited to a narrow view angle related to a specific interest. In order to get hold of transferable information, research from another perspective in life sciences is needed, so that interdisciplinary collaboration can provide the platform essential for successful developments, as illustrated in the present collection of papers. In spite of all of the participating research groups working with a biomimetic focus, the translations and inspirations discussed in the papers are located mostly on the level of generic abstract principles, sometimes also referred to as 'deep principles'. Examples include composite Materials aspects, anisotropy and heterogeneity, when we talk about Materials and systems, and morphological differentiation and adaptation when we consider form generation processes. Tom Wiscombe designs visionary buildings that explore the potentials of architectural surfaces to be shifted from two-dimensionality to one or three dimensionality by introducing de-lamination, winding, fusing, blending and embedding of building systems. The use of non-mineral Materials and suggestion of the logic of healing and weaving are directly taken from biological Material processing. Functionally graded Materials and the introduction of microparticles and biochemical systems shall further extend the possibilities to create future environments. Jan Knippers, Thomas Speck and Achim Menges have initiated a successful interdisciplinary collaboration between architecture, computational design, engineering and biology. They interpret architecture and biological evolution as nondeterministic processes, sharing parallels but fundamental differences at the same time. Those differences are the basis for the investigation of new technologies. The ICD/ITKE Research Pavillion 2010 stands as an example for a homogenous construction using a single textured Material, parametric differentiation and shaping of large elastic deformations, using digital simulation, planning and production processes. The development of the so-called Flectofin(®) lamellas for shading of facades is based on the kinematics of the Strelitzia reginae flower, and again exploits an effect usually unwelcomed in engineering-torsional buckling-together with the use of fibre reinforced Material. The introduction of such a system into a large scale building facade is presented with the thematic pavilion at EXPO 2012 in Korea, designed and engineered by SOMA Architects, Vienna and Knippers Helbig Advanced Engineering, Stuttgart, New York. These large scale implementations of principles derived from nature show the potential for the application of biomimetics in architectural design. Achim Menges' paper is a concise discussion of morphogenetic computational design, presenting form generation in contrast to the traditional form definition and form finding strategies in architectural design. Computational design allows for radically new approaches in the use, processing and generation of information that is translated into architectural form via new technologies. The generative design process is limited by phylogenetic and physical constraints. According to Menges, the challenge of this approach lies in resolving the complexity arising from the interrelation and reciprocal effects of Material systems and dynamic environments. Evolutionary design exploration is introduced as a method together with a detailed description of case studies exploring the design of form-performance relations of overall building morphologies and urban block morphologies. Taken together, the presented papers show a promising development towards the implementation of biomimetics in the design of future built environments. References Wiscombe T 2012 Beyond assemblies: systems convergence and multi-Materiality Bioinspir. Biomim. 7 015001 Knippers J and Speck T 2012 Design and construction principles in nature and architecture Bioinspir. Biomim. 7 015002 Menges A 2012 Biomimetic design processes in architecture: morphogenetic and evolutionary computational design Bioinspir. Biomim. 7 015003.