Professor Bjoern Kiefer, TU Dortmund, Institute of Mechanics, Germany

Continuum Modeling of Magnetostriction on Different Length Scales
When Mar 13, 2015
from 02:00 PM to 03:00 PM
Where LR7, IEB Building, Engineering Science
Contact Name
Contact Phone 01865-273925
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Active and multifunctional materials have drawn considerable interest in recent years, as they show
great potential for enabling novel sensing, actuation, transduction, energy harvesting and biomimetic
applications, to be employed in aerospace, the automotive industry, microelectronics, the biomedical
and other fields. In addition to the exploration, synthesis and characterization of new material systems,
the accurate modeling and simulation of their constitutive response is of key importance in the
endeavor of leading the application design beyond purely conceptual ideas.
Here, we focus on the modeling of active materials exhibiting magneto-mechanical coupling, e.g. giant
magnetostrictives and magnetic shape memory alloys. From a modeling standpoint, great challenges
stem from the complex coupled, nonlinear, and inelastic nature of the response exhibited by these
materials. The macroscopic behavior is thereby driven by microstructural changes, such as phase
transformations or twin-boundary and magnetic domain wall motion. The presented work is concerned
with capturing these various magneto-mechanical mechanisms causing changes in deformation and
magnetization on different length scales via continuum thermodynamics based modeling.

Bjoern Kiefer

Figure 1: Prediction of magnetic-field-biased pseudoelasticity in the magnetic shape memory alloy
Ni2MnGa [3] based on the energy minimizing evolution of laminated microstructure.
Three particular modeling approaches are discussed and illustrated with numerical examples. First,
as an extension of classical computational inelasticity, a macroscopic model for magnetic shape memory
behavior is presented. Secondly, a general macroscopic variational-based modeling and simulation
framework for dissipative magnetostriction, is introduced, and some details on its algorithmic treatment
are given. The third part of the lecture discusses approaches to the meso-scale modeling of
microstructure evolution in magnetizable solids based on concepts of energy relaxation, particularly
in the context of extensions to the constrained theory of magnetoelasticity proposed by DeSimone and
James. Finally, the extendibility of these general concepts—e.g. to the phase field modeling of domain
evolution or to finite deformation theories for magnetoactive polymers—is briefly addressed.
[1] B. Kiefer and D. C. Lagoudas, Modeling the Coupled Strain and Magnetization Response of Magnetic
Shape Memory Alloys under Magnetomechanical Loading, Journal of Intelligent Material Systems and
Structures Vol. 20, 143–170, 2009.
[2] C. Miehe, B. Kiefer and D. Rosato, An Incremental Variational Formulation of Dissipative Magnetostriction
at the Macroscopic Continuum Level, International Journal of Solids and Structures Vol. 48,
1846–1866, 2011.
[3] B. Kiefer, K. Buckmann, T. Bartel, Numerical Energy Relaxation to Model Microstructure Evolution
in Functional Magnetic Materials, GAMM-Mitteilungen Vol. 21(1), 171–195, 2015.