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Thermodynamic and rate variational formulation of models for inhomogeneous gradient materials with microstructure and application to phase field modeling

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Acta Mechanica Sinica 2015年第2期31卷 162-172页

作者： Svyatoslav Gladkov bob svendsen Material Mechanics RWTH Aachen Aachen Germany Microstructure Physics and Alloy Design Max-Planck-Institut fur Eisenforschung DusseldorfGermany

In this work,thermodynamic models for the energetics and kinetics of inhomogeneous gradient materials with microstructure are formulated in the context of continuum thermodynamics and material *** simplicity,attention is restricted to isothermal *** materials of interest here are characterized by（1） first- and secondorder gradients of the deformation field and（2） a kinematic microstructure field and its gradient（e.g.,in the sense of director,micromorphic or Cosserat microstructure）.Material inhomogeneity takes the form of multiple phases and chemical constituents,modeled here with the help of corresponding phase *** requirements together with the dissipation principle result in the reduced model field and constitutive *** cases of these include the wellknown Cahn-Hilliard and Ginzburg-Landau *** the last part of the work,initial boundary value problems for this class of materials are formulated with the help of rate variational methods.

关键词： Continuum thermodynamics Material inhomogeneity Conservative Non-conservative phase fields

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EFFECT OF SURFACE ENERGY ON DISLOCATION-INDUCED FIELD IN HALF-SPACE WITH APPLICATION TO THIN FILM-SUBSTRATE SYSTEMS

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Acta Mechanica Solida Sinica 2009年第5期22卷 436-442页

作者： Ganyun Huang bob svendsen Zhixing Lu Institute of Mechanics Dortmund University of Technology 44221 Dortmund Germany Sehool of Mechanical Engineering Tianjin University Tianjin 300072 China Department of Mechanical Engineering University of Colorado at Boulder Colorado USA

In this work the elastic field of an edge dislocation in a half-space with the effect of surface energy has been obtained. The elastic field is then used to study the image force on the dislocation, the critical thickness for dislocation generation in epitaxial thin films with strain mismatch and the yielding strength of thin films on substrates. The results show that the image forces on the dislocation deviate from the conventional solutions when the distance of the dislocation from the free surface is smaller than several times of the characteristic length. Also due to the effect of surface energy, the critical thickness for dislocation generation is smaller than that predicted by the conventional elastic solutions and the extent of the deviation depends on the magnitude of mismatch strain. In contrast, the effect of surface energy on the yielding strength for many practical thin films can be neglected except for some soft ones where the characteristic length is comparable to the thickness.

关键词： thin film surface energy effect dislocation half-space critical thickness yielding strength

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An artificial neural network for surrogate modeling of stress fields in viscoplastic polycrystalline materials

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npj Computational Materials 2023年第1期9卷 1981-1990页

作者： Mohammad S.Khorrami Jaber R.Mianroodi Nima H.Siboni Pawan Goyal bob svendsen Peter Benner Dierk Raabe Microstructure Physics and Alloy Design Max-Planck-Institut für EisenforschungDüsseldorfGermany Ergodic Labs Lohmühlenstraße 6512435 BerlinGermany Computational Methods in Systems and Control Theory Max Planck Institute for Dynamics of Complex Technical SystemsMagdeburgGermany Material Mechanics RWTH Aachen UniversityAachenGermany

The purpose of this work is the development of a trained artificial neural network for surrogate modeling of the mechanical response of elasto-viscoplastic grain *** this end,a U-Net-based convolutional neural network(CNN)is trained using results for the von Mises stress field from the numerical solution of initial-boundary-value problems(IBVPs)for mechanical equilibrium in such microstructures subject to quasi-static uniaxial *** resulting trained CNN(tCNN)accurately reproduces the von Mises stress field about 500 times faster than numerical solutions of the corresponding IBVP based on spectral *** of the tCNN to test cases based on microstructure morphologies and boundary conditions not contained in the training dataset is also investigated and discussed.

关键词： methods boundary faster

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Effect of surface energy on the dislocation-half-space interaction and the implications in thin films on substrates

Effect of surface energy on the dislocation-half-space inter...

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损伤、断裂与微纳米力学学术研讨会

作者： bob svendsen Institute of Mechanics Dortmund University of Technology

In this paper,the elastic field of an edge dislocation in a half-space with the effect of surface energy is *** elastic field is then used to study the image force on the dislocation, the critical thickness for dislocation generation in epitaxial thin films with strain mismatch and the yielding strength of thin films on *** results show that the image forces on the dislocation deviate from the conventional solutions when the distance of the dislocation from the free surface is smaller than several times of the characteristic *** due to the effect of surface energy,the critical thickness for dislocation generation is smaller than predicted by the conventional elastic solutions and the extent of the deviation depends on the magnitude of mismatch *** contrast,the effect of surface energy on the yielding strength for many practical thin films can be neglected except for some soft ones where the characteristic length is comparable to the thickness.

关键词： Thin film Surface energy effect Dislocation Critical thickness Yielding strength

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Modeling and simulation of microstructure in metallic systems based on multi-physics approaches

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npj Computational Materials 2022年第1期8卷 867-881页

作者： Jaber Rezaei Mianroodi Pratheek Shanthraj Chuanlai Liu Samad Vakili Sharan Roongta Nima Hamidi Siboni Nathan Perchikov Yang Bai bob svendsen Franz Roters Dierk Raabe Martin Diehl Microstructure Physics and Alloy Design Max-Planck-Institut für Eisenforschung40237DüsseldorfGermany Ergodic Labs Lohmühlenstraße12435BerlinGermany The Department of Materials The University of ManchesterManchesterM139PLUK Material Mechanics RWTH Aachen University52062AachenGermany Department of Computer Science KU LeuvenCelestijnenlaan 200A3001LeuvenBelgium Department of Materials Engineering KU LeuvenKasteelpark Arenberg 443001LeuvenBelgium

The complex interplay between chemistry,microstructure,and behavior of many engineering materials has been investigated predominantly by experimental *** to the increase in computer power,advances in computational modeling methods have resulted in a level of sophistication which is comparable to that of *** the continuum level,one class of such models is based on continuum thermodynamics,phase-field methods,and crystal plasticity,facilitating the account of multiple physical mechanisms (multi-physics) and their interaction during microstructure *** paper reviews the status of simulation approaches and software packages in this field and gives an outlook towards promising research directions.

关键词： computer microstructure metallic

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Model of Mismatched Contact for the Dislocation Generation During Coalescence of Grains

Model of Mismatched Contact for the Dislocation Generation D...

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The 16th Annual Conference of Hong Kong Society of Theoretical and Applied Mechanics 2012、The 1st Mainland-Hong Kong Youth Forum on Mechanics 2012、The 8th Shanghai-Hong Kong Forum on Mechanics and Its Application 2012

作者： Gan-Yun Huang bob svendsen Department of Mechanics Tianjin University Chair of Material Mechanics RWTH Aachen University

The presence of dislocations in crystals may be either detrimental or beneficial to their ***,study on dislocation generation during crystal growth has always attracted much *** has been observed by Mei et al.(2007) that dislocations generate during the coalescence of islands in epitaxial growth of thin ***,dislocations also generate in the crystal growth by oriented attachment,see,e.g.,Lee Perm and Banfield(1998).However,the mechanisms underlying have seldom been *** coalescence of either islands or the grains is usually driven by the reduction of surface energy and may involve misorientation at the contacting interface(Freund and Chason 2001,Suh et al 2004),we investigate the dislocation generation in mismatched ***,we assume the coalescence of grains can be characterized by adhesive contact with strain *** generate as a result of the relaxation of the mismatched *** energetic approach is proposed to tackle the problem. Namely,we compare the energy of dislocation-free mismatched contact with that in the mismatched contact with a dislocation *** the latter is smaller,then dislocation generation will be energetically *** such an approach,numerical calculation has been conducted. Results demonstrate that dislocation generation depends strongly on the size of the grains and the mismatched *** implications for crystal growth will be discussed.

关键词： Model of Mismatched Contact for the Dislocation Generation During Coalescence of Grains

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