c Birkh¨auser Verlag, Basel, 2004 NoDEA Nonlinear differ. equ. appl. 11 (2004) 151–189 1021–9722/04/020151–39 DOI 10.1007/s00030-003-1052-7 On rate-independent hysteresis models Alexander MIELKE Institut f¨ur Analysis, Dynamik und Modellierung Mathematisches Institut A Universit¨at Stuttgart D–70569 Stuttgart, Germany e-mail:
[email protected] Florian THEIL Mathematics Institute University of Warwick Coventry CV4 7AL, UK e-mail:
[email protected] 1 Introduction This paper deals with a general approach to the modeling of rate-independent processes which may display hysteretic behavior. Such processes play an impor- tant role in many applications like plasticity and phase transformations in elastic solids, electromagnetism, dry friction on surfaces, or in pinning problems in super- conductivity, cf. [Vis94, BrS96]. The evolution equations which govern those processes constitute the limit problems if the influence of inertia and relaxation times vanishes, i.e. the system rests unless the external loading is varied. Only the stick-slip dynamics is present in the Cauchy problem, this means that the evolution equations are necessarily non-autonomous. Although the solutions often exhibit quite singular behavior, the reduced framework offers great advantages. Firstly the amount of modelling can be reduced to its absolute minimum. More importantly, our approach is only based on energy principles. This allows us to treat the Cauchy problem by mainly using variational techniques. This robustness is necessary in order to study problems which come from continuum mechanics, like plasticity, cf. [Mie02, CHM02, Mie03]. There the potential energy 152 Alexander Mielke and Florian Theil NoDEA is invariant under the group of rigid body rotations SO(d) where d ∈{1, 2, 3} is the dimension.