@article{65266,
  abstract     = {{<jats:title>ABSTRACT</jats:title>
                  <jats:p>This work is concerned with the modeling of a cold‐box sand, a composition of sand grains and a resin binder. To this end, experiments are performed, which show the following characteristics: localization phenomena in the form of a shear band, softening behavior in the force‐displacement curve, and asymmetric behavior for compression and tension. To model this complex material behavior, a micromorphic continuum is used. In the present contribution, we focus on the linear‐elastic regime and demonstrate the identifiability of micromorphic material parameters under deliberately induced inhomogeneous deformation states. In addition to the degrees of freedom of a classical continuum, the micromorphic model has additional degrees of freedom, introduced here in a phenomenological sense to represent kinematically enriched deformation modes associated with the granular microstructure. Accordingly, the micromorphic fields are not interpreted as a separate physical scale (e.g., “binder” vs. “grains”), but as an effective continuum description at the specimen scale. This contribution addresses parameter identification for a micromorphic model of cold‐box sand, with a clear separation between homogeneous deformation states governing classical elastic parameters and inhomogeneous states required to activate and identify micromorphic length‐scale parameters. The main challenge lies in identifying the micro material parameters. To determine these, the corresponding gradient terms in the constitutive formulation must be triggered via properly tuned experiments. Micro‐parameter identification is demonstrated using synthetic data generated from a boundary‐value problem with inhomogeneous displacement fields. The chosen benchmark enables controlled activation of gradient terms and thereby renders optimization‐based identification of micromorphic parameters feasible. The synthetic example is deliberately chosen to assess feasibility and identifiability under controlled conditions, thereby isolating micromorphic identifiability aspects from experimental uncertainties. The novelty of the contribution lies in explicitly linking micromorphic parameter identifiability to kinematic inhomogeneity, and in demonstrating this link within a tractable forward– inverse setting for a linear‐elastic micromorphic continuum.</jats:p>}},
  author       = {{Börger, Alexander and Mahnken, Rolf and Caylak, Ismail and Ostwald, Richard}},
  issn         = {{1617-7061}},
  journal      = {{Proceedings in Applied Mathematics and Mechanics}},
  number       = {{2}},
  publisher    = {{Wiley}},
  title        = {{{Aspects of Parameter Identification for a Micromorphic Continuum applied to a Cold‐Box Sand}}},
  doi          = {{10.1002/pamm.70093}},
  volume       = {{26}},
  year         = {{2026}},
}

@article{65491,
  abstract     = {{<jats:title>Abstract</jats:title>
                  <jats:p>The micropolar continuum is a special case of a micromorphic material model and has additional degrees of freedom in the form of microrotations compared to the classical continuum. With the micropolar model, size effects can be considered and the boundary value problem can be regularized when localization effects occur. In order to map the microrotations, an additional strain measure and an additional stress are introduced. For simulation of plasticity, it is possible to define one yield function, and thus one plastic multiplier as well as one equivalent plastic strain occur. This approach is known as the single-surface plasticity approach. The macro- and micro-stresses are coupled in a common flow function. On the other hand, there is the so-called double-surface plasticity when one yield function, one plastic multiplier, and one equivalent plastic strain, respectively, are introduced for each of the macro- and micro-variables. The coupling of the macro- and micro-variables is established by a possible coupling of both yield functions. The purpose of this paper is to compare both approaches and to identify similarities and differences.</jats:p>}},
  author       = {{Börger, Alexander and Mahnken, Rolf}},
  issn         = {{0939-1533}},
  journal      = {{Archive of Applied Mechanics}},
  number       = {{5}},
  publisher    = {{Springer Science and Business Media LLC}},
  title        = {{{Single-surface and double-surface plasticity for micropolar continuum}}},
  doi          = {{10.1007/s00419-026-03049-w}},
  volume       = {{96}},
  year         = {{2026}},
}