TY - BOOK

T1 - Modeling strategies for structural phase transformations in shape memory alloys and steels

AU - Fischlschweiger, Michael

N1 - no embargo

PY - 2012

Y1 - 2012

N2 - Athermal structural phase transformations (martensitic phase transformations) as they occur in various materials, e.g., shape memory alloys, steels, polymers, ceramics and proteins are accompanied by macroscopic property changes, i.e., strain evolution, stiffness changes, which make them particularly relevant for structural applications in the field of sensors, actuators, damping elements and in light weight design. It is of high industrial value to develop modeling strategies for predicting the mechanical consequences of these transformations to enable a robust and optimized product development and design. The mechanisms governing martensitic transformation can be viewed from various space and time scales, thus research efforts are confronted with the challenge of multi-scale material modeling. In this work the focus will be put on the theoretical and numerical analysis of athermal structural phase transformations in shape memory alloys and steels. This requires developing tools for bridging the gap between the scales for ensuring an efficient information flow from results obtained at the nanoscale up to the macroscale. The basis of the model formulation in the first part of the thesis is statistical physics, where the focus is on the description of the reversible transformation behavior in shape memory alloys. Contrary to other approaches this concept allows natural phase triggering, where critical thermodynamical driving forces are not required. The second part deals with continuum mechanical modeling of irreversible martensitic transformations. Here the previously developed statistical physics approach serves as a tool identifying the mechanisms necessary to obtain new constitutive equations within a phenomenological non-equilibrium thermodynamical framework. Especially, the -scale transition is introduced as a bridging tool between the meso- and the macrolevel. The thesis concludes with a comparison of modeling and experimental results which show a good agreement and hence confirm the predictive capability of the model. With this work a modeling framework has been laid out capturing the complex phenomena occurring in materials showing martensitic phase transformations thus providing a good tool for material and product design.

AB - Athermal structural phase transformations (martensitic phase transformations) as they occur in various materials, e.g., shape memory alloys, steels, polymers, ceramics and proteins are accompanied by macroscopic property changes, i.e., strain evolution, stiffness changes, which make them particularly relevant for structural applications in the field of sensors, actuators, damping elements and in light weight design. It is of high industrial value to develop modeling strategies for predicting the mechanical consequences of these transformations to enable a robust and optimized product development and design. The mechanisms governing martensitic transformation can be viewed from various space and time scales, thus research efforts are confronted with the challenge of multi-scale material modeling. In this work the focus will be put on the theoretical and numerical analysis of athermal structural phase transformations in shape memory alloys and steels. This requires developing tools for bridging the gap between the scales for ensuring an efficient information flow from results obtained at the nanoscale up to the macroscale. The basis of the model formulation in the first part of the thesis is statistical physics, where the focus is on the description of the reversible transformation behavior in shape memory alloys. Contrary to other approaches this concept allows natural phase triggering, where critical thermodynamical driving forces are not required. The second part deals with continuum mechanical modeling of irreversible martensitic transformations. Here the previously developed statistical physics approach serves as a tool identifying the mechanisms necessary to obtain new constitutive equations within a phenomenological non-equilibrium thermodynamical framework. Especially, the -scale transition is introduced as a bridging tool between the meso- and the macrolevel. The thesis concludes with a comparison of modeling and experimental results which show a good agreement and hence confirm the predictive capability of the model. With this work a modeling framework has been laid out capturing the complex phenomena occurring in materials showing martensitic phase transformations thus providing a good tool for material and product design.

KW - multi-scale material modeling

KW - constitutive modeling

KW - mechanics of phase transformations

KW - Multiskalige Materialmodellierung

KW - Entwicklung von Konstitutivgesetzen

KW - Mechanik der strukturellen Phasentransformationen

M3 - Doctoral Thesis

ER -