The Experts below are selected from a list of 29967 Experts worldwide ranked by ideXlab platform
Christian Miehe - One of the best experts on this subject based on the ideXlab platform.
-
a phase field model for chemo mechanical induced fracture in lithium ion battery electrode particles
International Journal for Numerical Methods in Engineering, 2016Co-Authors: Christian Miehe, Lisa Marie Schänzel, Husnu Dal, Arun RainaAbstract:© 2016 John Wiley & Sons, Ltd. Capacity fade in conventional Li-ion battery systems due to chemo-mechanical degradation during charge-discharge cycles is the bottleneck in high-performance battery design. Stresses generated by diffusion-mechanical coupling in Li-ion intercalation and deintercalation cycles, accompanied by swelling and shrinking at finite strains, cause micro-cracks, which finally disturb the electrical conductivity and isolate the electrode particles. This leads to battery capacity fade. As a first attempt towards a reliable description of this complex phenomenon, we propose a novel finite strain theory for chemo-elasticity coupled with phase-field modeling of fracture, which regularizes a sharp crack topology. We apply a rigorous geometric approach to the diffusive crack modeling based on the introduction of a global evolution equation of regularized crack surface, governed by the crack phase field. The irreversible evolution of the crack phase field is modeled through a novel critical stress-based growth function. A Modular Concept is outlined for linking of the diffusive crack modeling to the complex chemo-elastic material response of the bulk material. Here, we incorporate standard as well as gradient-extended Cahn-Hilliard-type diffusion for the Li-ions, where the latter accounts for a possible phase segregation. From the viewpoint of the methodology, the separation of modules for the crack evolution and the bulk response provides a highly attractive and transparent structure of the multi-physics problem. This structure is exploited on the numerical side by constructing a robust finite element method, based on an algorithmic decoupling of updates for the crack phase field and the state variables of the chemo-mechanical bulk response. We demonstrate the performance of the proposed coupled multi-field formulation by an analysis of representative boundary value problems.
-
Phase field modeling of fracture in multi-physics problems. Part III. Crack driving forces in hydro-poro-elasticity and hydraulic fracturing of fluid-saturated porous media
Computer Methods in Applied Mechanics and Engineering, 2016Co-Authors: Christian Miehe, Steffen MautheAbstract:The prediction of fluid- and moisture-driven crack propagation in deforming porous media has achieved increasing interest in recent years, in particular with regard to the modeling of hydraulic fracturing, the so-called "fracking". Here, the challenge is to link at least three modeling ingredients for (i) the behavior of the solid skeleton and fluid bulk phases and their interaction, (ii) the crack propagation on not a priori known paths and (iii) the extra fluid flow within developed cracks. To this end, a macroscopic framework is proposed for a continuum phase field modeling of fracture in porous media. It provides a rigorous geometric approach to a diffusive crack modeling based on the introduction of a constitutive balance equation for a regularized crack surface and its Modular linkage to a Darcy-Biot-type bulk response of hydro-poro-elasticity. The approach overcomes difficulties associated with the computational realization of sharp crack discontinuities, in particular when it comes to complex crack topologies including branching. A Modular Concept is outlined for linking of the diffusive crack modeling with the hydro-poro-elastic response of the porous bulk material. This includes a generalization of crack driving forces from energetic definitions towards threshold-based criteria in terms of the effective stress related to the solid skeleton of a fluid-saturated porous medium. Furthermore, a Poiseuille-type constitutive continuum modeling of the extra fluid flow in developed cracks is suggested based on a deformation-dependent permeability, that is scaled by a characteristic length. This proposed Modular model structure is exploited in the numerical implementation by constructing a robust finite element method, based on an algorithmic decoupling of updates for the crack phase field and the state variables of the hydro-poro-elastic bulk response. We demonstrate the performance of the phase field formulation of fracture for a spectrum of model problems of hydraulic fracture. A slight modification of the framework allows the simulation of drying-caused crack patterns in partially saturated capillar-porous media.
-
Phase field modeling of fracture in multi-physics problems. Part I. Balance of crack surface and failure criteria for brittle crack propagation in thermo-elastic solids
Computer Methods in Applied Mechanics and Engineering, 2015Co-Authors: Christian Miehe, Lisa Marie Schänzel, Heike UlmerAbstract:This work presents a generalization of recently developed continuum phase field models for brittle fracture towards fully coupled thermo-mechanical and multi-physics problems at large strains. It outlines a rigorous geometric approach to the diffusive crack modeling based on the introduction of a balance of regularized crack surface, governed by a crack phase field. The regularized crack surface functional is based on a crack surface density function, that describes the macroscopic crack surface in the bulk material per unit of the reference volume. The approach overcomes difficulties associated with the computational realization of sharp crack discontinuities, in particular when it comes to complex crack topologies. The formulation proposed is essentially a gradient damage theory, however, equipped with critical ingredients rooted in fracture mechanics. A Modular Concept is outlined for the linking of the diffusive crack modeling with complex multi-field response of the bulk material, where focus is put on the model problem of finite thermo-elasticity. This concerns a generalization of crack driving forces from the energetic definitions towards stress-based criteria, the constitutive modeling of heat conduction across cracks and convective heat exchanges at crack faces based on additional constitutive functions. This is achieved by approximating surface load integrals of the sharp crack approach by distinct volume integrals. We demonstrate the performance of the phase field formulation of fracture at large strains by means of representative numerical examples.
Claudia Schutze - One of the best experts on this subject based on the ideXlab platform.
-
diagnostic monitoring to identify preferential near surface structures for co2 degassing into the atmosphere tools for investigations at different spatial scales validated at a natural analogue site
International Journal of Greenhouse Gas Control, 2013Co-Authors: Claudia Schutze, Peter Dietrich, U SauerAbstract:Abstract Diagnostic monitoring tools applied at different scales are required to reliably detect and assess CO 2 leakages from storage formations in the shallow subsurface, as well as playing an important role in helping to establish a risk assessment strategy at carbon dioxide capture and storage facilities. These tools incorporate method developments and applications that will enable large spatial areas to be consistently covered in sufficient spatial and temporal resolutions. The use of remote sensing (open-path Fourier-transform infrared (OP-FTIR) spectroscopy) in combination with regional measurements (geophysics and chamber based soil CO 2 flux measurement) and local in situ measurements (Direct Push technology) enables a more reliable validation of risk, using a joint data interpretation approach. A promising tool currently in development for large-scale leakage detection and monitoring is Fourier transform infrared (FTIR) spectroscopy, which is used to determine spatial atmospheric CO 2 distribution in the near-surface atmosphere. Sufficient geophysical techniques for meso-scale monitoring include geoelectrical and self potential (SP) surveys. These methods are useful for characterizing fluid flow and transport processes in permeable near-surface sedimentary layers and can yield important information concerning CO 2 affected subsurface structures. The paper presents promising results achieved from measurements taken at a natural analogue site in the Czech Republic and indicates that the hierarchical monitoring approach represents a successful multidisciplinary Modular Concept to monitor physical and chemical processes taking place during CO 2 migration and seepage. The application of FTIR spectroscopy in combination with soil gas surveys and geoelectrical investigations results in a comprehensive site characterization, including the atmospheric and near-surface CO 2 distribution as well as subsurface structural features. Our data illustrate a correlation of higher CO 2 concentration in the atmosphere with increased CO 2 soil flux rates and soil CO 2 concentrations. These soil gas anomalies coincide with structural units characterized by a distinct negative SP anomaly and a zone of decreased resistivity in the ERT result.
-
diagnostic monitoring to identify preferential near surface structures for co2 degassing into the atmosphere tools for investigations at different spatial scales validated at a natural analogue site
International Journal of Greenhouse Gas Control, 2013Co-Authors: Claudia Schutze, Pete Dietrich, U SaueAbstract:Abstract Diagnostic monitoring tools applied at different scales are required to reliably detect and assess CO 2 leakages from storage formations in the shallow subsurface, as well as playing an important role in helping to establish a risk assessment strategy at carbon dioxide capture and storage facilities. These tools incorporate method developments and applications that will enable large spatial areas to be consistently covered in sufficient spatial and temporal resolutions. The use of remote sensing (open-path Fourier-transform infrared (OP-FTIR) spectroscopy) in combination with regional measurements (geophysics and chamber based soil CO 2 flux measurement) and local in situ measurements (Direct Push technology) enables a more reliable validation of risk, using a joint data interpretation approach. A promising tool currently in development for large-scale leakage detection and monitoring is Fourier transform infrared (FTIR) spectroscopy, which is used to determine spatial atmospheric CO 2 distribution in the near-surface atmosphere. Sufficient geophysical techniques for meso-scale monitoring include geoelectrical and self potential (SP) surveys. These methods are useful for characterizing fluid flow and transport processes in permeable near-surface sedimentary layers and can yield important information concerning CO 2 affected subsurface structures. The paper presents promising results achieved from measurements taken at a natural analogue site in the Czech Republic and indicates that the hierarchical monitoring approach represents a successful multidisciplinary Modular Concept to monitor physical and chemical processes taking place during CO 2 migration and seepage. The application of FTIR spectroscopy in combination with soil gas surveys and geoelectrical investigations results in a comprehensive site characterization, including the atmospheric and near-surface CO 2 distribution as well as subsurface structural features. Our data illustrate a correlation of higher CO 2 concentration in the atmosphere with increased CO 2 soil flux rates and soil CO 2 concentrations. These soil gas anomalies coincide with structural units characterized by a distinct negative SP anomaly and a zone of decreased resistivity in the ERT result.
Lisa Marie Schänzel - One of the best experts on this subject based on the ideXlab platform.
-
a phase field model for chemo mechanical induced fracture in lithium ion battery electrode particles
International Journal for Numerical Methods in Engineering, 2016Co-Authors: Christian Miehe, Lisa Marie Schänzel, Husnu Dal, Arun RainaAbstract:© 2016 John Wiley & Sons, Ltd. Capacity fade in conventional Li-ion battery systems due to chemo-mechanical degradation during charge-discharge cycles is the bottleneck in high-performance battery design. Stresses generated by diffusion-mechanical coupling in Li-ion intercalation and deintercalation cycles, accompanied by swelling and shrinking at finite strains, cause micro-cracks, which finally disturb the electrical conductivity and isolate the electrode particles. This leads to battery capacity fade. As a first attempt towards a reliable description of this complex phenomenon, we propose a novel finite strain theory for chemo-elasticity coupled with phase-field modeling of fracture, which regularizes a sharp crack topology. We apply a rigorous geometric approach to the diffusive crack modeling based on the introduction of a global evolution equation of regularized crack surface, governed by the crack phase field. The irreversible evolution of the crack phase field is modeled through a novel critical stress-based growth function. A Modular Concept is outlined for linking of the diffusive crack modeling to the complex chemo-elastic material response of the bulk material. Here, we incorporate standard as well as gradient-extended Cahn-Hilliard-type diffusion for the Li-ions, where the latter accounts for a possible phase segregation. From the viewpoint of the methodology, the separation of modules for the crack evolution and the bulk response provides a highly attractive and transparent structure of the multi-physics problem. This structure is exploited on the numerical side by constructing a robust finite element method, based on an algorithmic decoupling of updates for the crack phase field and the state variables of the chemo-mechanical bulk response. We demonstrate the performance of the proposed coupled multi-field formulation by an analysis of representative boundary value problems.
-
Phase field modeling of fracture in multi-physics problems. Part I. Balance of crack surface and failure criteria for brittle crack propagation in thermo-elastic solids
Computer Methods in Applied Mechanics and Engineering, 2015Co-Authors: Christian Miehe, Lisa Marie Schänzel, Heike UlmerAbstract:This work presents a generalization of recently developed continuum phase field models for brittle fracture towards fully coupled thermo-mechanical and multi-physics problems at large strains. It outlines a rigorous geometric approach to the diffusive crack modeling based on the introduction of a balance of regularized crack surface, governed by a crack phase field. The regularized crack surface functional is based on a crack surface density function, that describes the macroscopic crack surface in the bulk material per unit of the reference volume. The approach overcomes difficulties associated with the computational realization of sharp crack discontinuities, in particular when it comes to complex crack topologies. The formulation proposed is essentially a gradient damage theory, however, equipped with critical ingredients rooted in fracture mechanics. A Modular Concept is outlined for the linking of the diffusive crack modeling with complex multi-field response of the bulk material, where focus is put on the model problem of finite thermo-elasticity. This concerns a generalization of crack driving forces from the energetic definitions towards stress-based criteria, the constitutive modeling of heat conduction across cracks and convective heat exchanges at crack faces based on additional constitutive functions. This is achieved by approximating surface load integrals of the sharp crack approach by distinct volume integrals. We demonstrate the performance of the phase field formulation of fracture at large strains by means of representative numerical examples.
Reymond Clavel - One of the best experts on this subject based on the ideXlab platform.
-
Concept of Modular flexure based mechanisms for ultra high precision robot design
Mechanical Sciences, 2011Co-Authors: Murielle Richard, Reymond ClavelAbstract:Abstract. This paper introduces a new Concept of Modular flexure-based mechanisms to design industrial ultra-high precision robots, which aims at significantly reducing both the complexity of their design and their development time. This Modular Concept can be considered as a robotic Lego, where a finite number of building bricks is used to quickly build a high-precision robot. The core of the Concept is the transformation of a 3-D design problem into several 2-D ones, which are simpler and well-mastered. This paper will first briefly present the theoretical bases of this methodology and the requirements of both types of building bricks: the active and the passive bricks. The section dedicated to the design of the active bricks will detail the current research directions, mainly the maximisation of the strokes and the development of an actuation sub-brick. As for the passive bricks, some examples will be presented, and a discussion regarding the establishment of a mechanical solution catalogue will conclude the section. Last, this Modular Concept will be illustrated with a practical example, consisting in the design of a 5-degree of freedom ultra-high precision robot.
-
a new Concept of Modular kinematics to design ultra high precision flexure based robots
International Symposium on Robotics, 2010Co-Authors: Murielle Richard, Reymond ClavelAbstract:This work deals with the kinematic Conception and the mechanical design of ultra-high precision robots, which are at present costly to develop, both in time and money. The aim of this paper is thus to introduce a new Modular Concept of kinematics which allows to significantly reduce the time-to-market and a new double-stage flexure-based pivot. Regarding the Modular Concept of kinematics, this ‘robotic Lego’ consists in a finite number of building bricks allowing to rapidly design a high precision machine and to easily modify its mobility. The realised mock-up of a 4-DOF (Degrees of Freedom) robot, transformable into a 5-DOF one, validates this Concept and the mechanical design of its bricks. Flexure hinges are used to achieve the aimed sub-micrometer precision; however, existing flexure-based rotary joints are not able to fulfil the requirements of some applications, as they present a too low angular stroke and a parasitic motion of their centre of rotation. Thus, this paper also introduces a new double-stage pivot based on blades working in torsion; experiments performed on a prototype allow to validate its principle and the simulation model used for its development.
Heike Ulmer - One of the best experts on this subject based on the ideXlab platform.
-
Phase field modeling of fracture in multi-physics problems. Part I. Balance of crack surface and failure criteria for brittle crack propagation in thermo-elastic solids
Computer Methods in Applied Mechanics and Engineering, 2015Co-Authors: Christian Miehe, Lisa Marie Schänzel, Heike UlmerAbstract:This work presents a generalization of recently developed continuum phase field models for brittle fracture towards fully coupled thermo-mechanical and multi-physics problems at large strains. It outlines a rigorous geometric approach to the diffusive crack modeling based on the introduction of a balance of regularized crack surface, governed by a crack phase field. The regularized crack surface functional is based on a crack surface density function, that describes the macroscopic crack surface in the bulk material per unit of the reference volume. The approach overcomes difficulties associated with the computational realization of sharp crack discontinuities, in particular when it comes to complex crack topologies. The formulation proposed is essentially a gradient damage theory, however, equipped with critical ingredients rooted in fracture mechanics. A Modular Concept is outlined for the linking of the diffusive crack modeling with complex multi-field response of the bulk material, where focus is put on the model problem of finite thermo-elasticity. This concerns a generalization of crack driving forces from the energetic definitions towards stress-based criteria, the constitutive modeling of heat conduction across cracks and convective heat exchanges at crack faces based on additional constitutive functions. This is achieved by approximating surface load integrals of the sharp crack approach by distinct volume integrals. We demonstrate the performance of the phase field formulation of fracture at large strains by means of representative numerical examples.