@article{62776,
  author       = {{Clausmeyer, Till and Schowtjak, Alexander and Wang, Shuhan and Gitschel, Robin and Hering, Oliver and Pavliuchenko, Pavlo and Lohmar, Johannes and Ostwald, Richard and Hirt, Gerhard and Tekkaya, A. Erman}},
  issn         = {{2351-9789}},
  journal      = {{Procedia Manufacturing}},
  pages        = {{649--655}},
  publisher    = {{Elsevier BV}},
  title        = {{{Prediction of Ductile Damage in the Process Chain of Caliber Rolling and Forward Rod Extrusion}}},
  doi          = {{10.1016/j.promfg.2020.04.201}},
  volume       = {{47}},
  year         = {{2020}},
}

@article{62775,
  author       = {{Schowtjak, Alexander and Wang, Shuhan and Hering, Oliver and Clausmeyer, Till and Lohmar, Johannes and Schulte, Robin and Ostwald, Richard and Hirt, Gerhard and Tekkaya, A. Erman}},
  issn         = {{0944-6524}},
  journal      = {{Production Engineering}},
  number       = {{1}},
  pages        = {{33--41}},
  publisher    = {{Springer Science and Business Media LLC}},
  title        = {{{Prediction and analysis of damage evolution during caliber rolling and subsequent cold forward extrusion}}},
  doi          = {{10.1007/s11740-019-00935-x}},
  volume       = {{14}},
  year         = {{2019}},
}

@article{62779,
  author       = {{Ostwald, Richard and Kuhl, Ellen and Menzel, Andreas}},
  issn         = {{0178-7675}},
  journal      = {{Computational Mechanics}},
  number       = {{3}},
  pages        = {{847--877}},
  publisher    = {{Springer Science and Business Media LLC}},
  title        = {{{On the implementation of finite deformation gradient-enhanced damage models}}},
  doi          = {{10.1007/s00466-019-01684-5}},
  volume       = {{64}},
  year         = {{2019}},
}

@inproceedings{62781,
  author       = {{Ostwald, Richard and Bartel, Thorsten and Menzel, Andreas}},
  booktitle    = {{Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016)}},
  publisher    = {{Institute of Structural Analysis and Antiseismic Research School of Civil Engineering National Technical University of Athens (NTUA) Greece}},
  title        = {{{A THERMODYNAMICALLY CONSISTENT FINITE STRAIN MICRO-SPHERE FRAMEWORK FOR PHASE-TRANSFORMATION}}},
  doi          = {{10.7712/100016.1945.10899}},
  year         = {{2017}},
}

@article{62782,
  abstract     = {{<jats:title>Abstract</jats:title><jats:p>A finite strain micro‐sphere framework for hyperelastic solids elaborated by Carol et al. is extended towards the modelling of phase transformations in order to simulate polycrystalline solids under large deformations such as, e.g., shape memory alloys and shape memory polymers. The implemented phase transformation mechanism is based on statistical physics and is not restricted in terms of the number of solid material phases that can be considered, though we restrict the provided examples to two phases for the sake of conceptual clarity. The specifically chosen non‐quadratic format of the Helmholtz free energy functions considered on the micro‐plane level includes Bain‐type transformation strains for each of the phases considered. Following the Voigt assumption on the micro‐scale, identical total micro‐stretches act in each of the material phases, where a multiplicative decomposition into elastic and transformation‐related contributions is applied. (© 2016 Wiley‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)</jats:p>}},
  author       = {{Ostwald, Richard and Bartel, Thorsten and Menzel, Andreas}},
  issn         = {{1617-7061}},
  journal      = {{PAMM}},
  number       = {{1}},
  pages        = {{381--382}},
  publisher    = {{Wiley}},
  title        = {{{Extending a finite strain hyperelastic micro‐sphere framework towards phase transformations}}},
  doi          = {{10.1002/pamm.201610179}},
  volume       = {{16}},
  year         = {{2016}},
}

@phdthesis{62784,
  abstract     = {{Die vorliegende Arbeit behandelt einen neuartigen Modellierungsrahmen zur Simulation von austenitisch-martensitischen Phasentransformationen in Formgedächtnislegierungen (SMA) und TRIP-Stählen. Das Ziel der Arbeit ist die Entwicklung und Ausarbeitung eines generalisierten Modells, welches das charakteristische makroskopische Verhalten sowohl von SMA als auch von TRIP-Stahl abbildet. Als Basis für die Formulierung dient ein skalarwertiges, thermodynamisch konsistentes, auf statistischer Physik basierendes Modell für die Simulation von SMA. Im Verlauf dieser Arbeit wird das Modell in affine und nicht-affine Microsphere-Formulierungen eingebettet um das polykristalline Materialverhalten abzubilden und um die Simulation dreidimensionaler Randwertprobleme zu ermöglichen. Darüberhinaus wird eine Kopplung an Plastizität vorgestellt, welche zusätzlich die Abbildung des Verhaltens von TRIP-Stahl ermöglicht. Abschließend wird die Implementierung eines dreidimensionalen Phasentransformationsmodells für finite Deformationen mit dem Fokus auf repräsentative Transformationsrichtungen in einem thermo-elastoplastischen Framework gezeigt.}},
  author       = {{Ostwald, Richard}},
  publisher    = {{LibreCat University}},
  title        = {{{Modelling and simulation of phase transformations in elasto-plastic polycrystals}}},
  doi          = {{10.17877/DE290R-155}},
  year         = {{2015}},
}

@article{62783,
  author       = {{Ostwald, Richard and Bartel, Thorsten and Menzel, Andreas}},
  issn         = {{0045-7825}},
  journal      = {{Computer Methods in Applied Mechanics and Engineering}},
  pages        = {{232--265}},
  publisher    = {{Elsevier BV}},
  title        = {{{An energy-barrier-based computational micro-sphere model for phase-transformations interacting with plasticity}}},
  doi          = {{10.1016/j.cma.2015.04.008}},
  volume       = {{293}},
  year         = {{2015}},
}

@article{62785,
  abstract     = {{<jats:title>SUMMARY</jats:title><jats:p>We introduce a material model for the simulation of polycrystalline materials undergoing solid‐to‐solid phase‐transformations. As a basis, we present a scalar‐valued phase‐transformation model where a Helmholtz free energy function depending on volumetric and deviatoric strain measures is assigned to each phase. The analysis of the related overall Gibbs energy density allows for the calculation of energy barriers. With these quantities at hand, we use a statistical‐physics‐based approach to determine the resulting evolution of volume fractions. Though the model facilitates to take into account an arbitrary number of solid phases of the underlying material, we restrict this work to the simulation of phase‐transformations between an austenitic parent phase and a martensitic tension and compression phase. The scalar model is embedded into a computational micro‐sphere formulation in view of the simulation of three‐dimensional boundary value problems. The final modelling approach necessary for macroscopic simulations is accomplished by a finite element formulation, where the local material behaviour at each integration point is governed by the response of the micro‐sphere model.Copyright © 2014 John Wiley &amp; Sons, Ltd.</jats:p>}},
  author       = {{Ostwald, Richard and Bartel, Thorsten and Menzel, Andreas}},
  issn         = {{0029-5981}},
  journal      = {{International Journal for Numerical Methods in Engineering}},
  number       = {{12}},
  pages        = {{851--877}},
  publisher    = {{Wiley}},
  title        = {{{A Gibbs‐energy‐barrier‐based computational micro‐sphere model for the simulation of martensitic phase‐transformations}}},
  doi          = {{10.1002/nme.4601}},
  volume       = {{97}},
  year         = {{2014}},
}

@article{62786,
  author       = {{Ostwald, Richard and Tiffe, Marcel and Bartel, Thorsten and Zabel, Andreas and Menzel, Andreas and Biermann, Dirk}},
  issn         = {{0924-0136}},
  journal      = {{Journal of Materials Processing Technology}},
  number       = {{8}},
  pages        = {{1516--1523}},
  publisher    = {{Elsevier BV}},
  title        = {{{Towards the multi-scale simulation of martensitic phase-transformations: An efficient post-processing approach applied to turning processes}}},
  doi          = {{10.1016/j.jmatprotec.2014.02.022}},
  volume       = {{214}},
  year         = {{2014}},
}

@article{62788,
  abstract     = {{<jats:title>Abstract</jats:title><jats:p>We present a novel approach for the simulation of solid to solid phase‐transformations in polycrystalline materials. To facilitate the utilization of a non‐affine micro‐sphere formulation with volumetric‐deviatoric split, we introduce Helmholtz free energy functions depending on volumetric and deviatoric strain measures for the underlying scalar‐valued phase‐transformation model. As an extension of affine micro‐sphere models [5], the non‐affine micro‐sphere formulation with volumetric‐deviatoric split allows to capture different Young's moduli and Poisson's ratios on the macro‐scale [1]. As a consequence, the temperature‐dependent free energy assigned to each individual phase takes the form of an elliptic paraboloid in volumetric‐deviatoric strain space, where the energy landscape of the overall material is obtained from the contributions of the individual constituents. For the evolution of volume fractions, we use an approach based on statistical physics–taking into account actual Gibbs energy barriers and transformation probabilities [2]. The computation of individual energy barriers between the phases considered is enabled by numerical minimization of parametric intersection curves of elliptic Gibbs energy paraboloids. (© 2012 Wiley‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)</jats:p>}},
  author       = {{Ostwald, Richard and Bartel, Thorsten and Menzel, Andreas}},
  issn         = {{1617-7061}},
  journal      = {{PAMM}},
  number       = {{1}},
  pages        = {{277--278}},
  publisher    = {{Wiley}},
  title        = {{{Simulation of phase‐transformations based on numerical minimization of intersecting Gibbs energy potentials}}},
  doi          = {{10.1002/pamm.201210129}},
  volume       = {{12}},
  year         = {{2012}},
}

@article{62787,
  author       = {{Ostwald, Richard and Bartel, Thorsten and Menzel, Andreas}},
  issn         = {{0927-0256}},
  journal      = {{Computational Materials Science}},
  pages        = {{12--16}},
  publisher    = {{Elsevier BV}},
  title        = {{{Phase-transformations interacting with plasticity – A micro-sphere model applied to TRIP steel}}},
  doi          = {{10.1016/j.commatsci.2012.05.015}},
  volume       = {{64}},
  year         = {{2012}},
}

@article{62790,
  abstract     = {{<jats:title>Abstract</jats:title><jats:p>We present an efficient model for the simulation of solid to solid phase‐transformations in polycrystalline materials. As a basis, we implement a scalar‐valued Gibbs‐energy‐barrier‐based phase‐transformation model making use of statistical physics. In this work, we particularly adopt the model for the simulation of phase‐transformations between an austenitic parent phase and a martensitic tension and compression phase. The incorporation of plasticity phenomena is established by enhancing the Helmholtz free energy functions of the material phases considered, where the plastic driving forces acting in each phase are derived from the overall free energy potential. The coupled model is embedded into a micro‐sphere formulation in order to simulate three‐dimensional boundary value problems—a technique well‐established in the context of computational inelasticity at small strains. It is shown that the model is capable of reflecting experimentally observed behaviour. (© 2011 Wiley‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)</jats:p>}},
  author       = {{Ostwald, Richard and Bartel, Thorsten and Menzel, Andreas}},
  issn         = {{1617-7061}},
  journal      = {{PAMM}},
  number       = {{1}},
  pages        = {{417--418}},
  publisher    = {{Wiley}},
  title        = {{{Interaction of phase‐transformations and plasticity – a multi‐phase micro‐sphere approach}}},
  doi          = {{10.1002/pamm.201110200}},
  volume       = {{11}},
  year         = {{2011}},
}

@article{62789,
  author       = {{Biermann, D. and Menzel, A. and Bartel, T. and Höhne, F. and Holtermann, R. and Ostwald, Richard and Sieben, B. and Tiffe, M. and Zabel, A.}},
  issn         = {{1877-7058}},
  journal      = {{Procedia Engineering}},
  pages        = {{22--27}},
  publisher    = {{Elsevier BV}},
  title        = {{{Experimental and Computational Investigation of Machining Processes for Functionally Graded Materials}}},
  doi          = {{10.1016/j.proeng.2011.11.074}},
  volume       = {{19}},
  year         = {{2011}},
}

@article{62791,
  abstract     = {{<jats:title>Abstract</jats:title><jats:p>We present an efficient model for the simulation of polycrystalline materials undergoing solid to solid phase transformations. As a basis, we use a one‐dimensional, thermodynamically consistent phase‐transformation model. This model is embedded into a micro‐sphere formulation in order to simulate three‐dimensional boundary value problems. To solve the underlying evolution equations, we use a newly developed explicit integration scheme which could be proved to be unconditionally A‐stable. Besides the investigation of homogeneous deformation states, representative finite element examples are discussed. It is shown that the model nicely reflects the overall behaviour.</jats:p>}},
  author       = {{Ostwald, Richard and Bartel, T. and Menzel, A.}},
  issn         = {{0044-2267}},
  journal      = {{ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik}},
  number       = {{7-8}},
  pages        = {{605--622}},
  publisher    = {{Wiley}},
  title        = {{{A computational micro‐sphere model applied to the simulation of phase‐transformations}}},
  doi          = {{10.1002/zamm.200900390}},
  volume       = {{90}},
  year         = {{2010}},
}

@article{62792,
  abstract     = {{<jats:title>Abstract</jats:title><jats:p>We present an efficient model for the simulation of phase‐transformations in polycrystalline materials. As a basis, we use a thermodynamically consistent, one‐dimensional phase‐transformation model, which is embedded into a micro‐sphere formulation in order to be able to simulate three‐dimensional boundary value problems. The underlying evolution equations are solved efficiently using a newly developed explicit integration scheme that has been proved to be unconditionally A‐stable. A numerical example by means of a deformation in simple shear is additionally provided in this contribution. (© 2010 Wiley‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)</jats:p>}},
  author       = {{Ostwald, Richard and Bartel, Thorsten and Menzel, Andreas}},
  issn         = {{1617-7061}},
  journal      = {{PAMM}},
  number       = {{1}},
  pages        = {{315--316}},
  publisher    = {{Wiley}},
  title        = {{{A micro‐sphere approach applied to the modelling of phase‐transformations}}},
  doi          = {{10.1002/pamm.201010150}},
  volume       = {{10}},
  year         = {{2010}},
}

@article{62793,
  author       = {{Unger, J. and Ostwald, Richard and Svendsen, B.}},
  issn         = {{1960-6206}},
  journal      = {{International Journal of Material Forming}},
  number       = {{S1}},
  pages        = {{907--910}},
  publisher    = {{Springer Science and Business Media LLC}},
  title        = {{{Thermodynamic multifield modeling of electromagnetic metal forming}}},
  doi          = {{10.1007/s12289-009-0486-9}},
  volume       = {{2}},
  year         = {{2009}},
}