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Mini-symposium:”Elastic defects and structures. Modeling and experiments”

Hold Date
2019-12-20 13:00〜2019-12-20 16:20
Seminar Room W1-D-625, West Zone 1, Ito campus, Kyushu University

Mini-symposium:”Elastic defects and structures. Modeling and experiments”

Sponsored by
Italian Embassy’s program: ”Japan meets Italian Scientists”
JSPS kakenhi 19H05131 in the framework of the ”Materials science on mille-feuille structure” project.
 Date  December 20, 2019
 Venue  Seminar Room W1-D-625, West Zone 1, Ito campus, Kyushu University
 Ito Campus map  

 13:00 - 14:00
 Speaker : Marco Morandotti (Technical University of Turin, IT)
 Title : Variational models for dislocations: dynamics and upscaling
     In this seminar, I will present a semi-discrete model for screw dislocation in an elastic solid undergoing anti-plane deformations. An amenable variational setting is proposed to study equilibrium configuration by energy minimisation principles. The dissipative dynamics of screw dislocations is studied rigorously as the gradient flow of the renormalised energy. Finally, I will address upscaling problems in one and two dimensions, showing how plasticity can be recovered when the number of dislocations grows to infinity.

 14:00 - 14:40
 Speaker : Masatoshi Mitsuhara (Kyushu University)
 Title : Microscopic observation of formation process of kink bands in Mg-Zn-Y alloy with LPSO phase
  The formation process of the kink bands in Mg-6%Zn-9%Y alloy was investigated in detail by in-situ analysis by SEM, and it succeeded in capturing the microstruc-tural change with no surface relief which should be called as the incipient kink bands (IKBs). Using TEM, it clearly founded that the IKBs involve the terminated-subgrain-boundaries which consists of edge dislocation arrays.
Authors: Masatoshi Mitsuhara (Kyushu University,), Shigeto Yamasaki (Kyushu University), Hideharu Nakashima (Kyushu University), Koji Hagihara (Osaka Uni-versity), Toshiyuki Fujii (Tokyo Institute of Technology).

 14:40 - 15:00 break

 15:00 - 15:40
 Speaker : Pierluigi Cesana (Kyushu University)
 Title : Mathematical models and ideas for disclinations
     We present some recent results on the modeling of rotational mismatches and frustrations at the level of a crystal lattice. We introduce an energy functional defined over a triangular lattice accounting for nearest-neighbor interactions. We design special rotational type boundary value problems on the lattice so that the minimizers necessarily exhibit non-homogeneous rotations. We are interested in the asymptotics of the energy minima and minimizers as the lattice spacing van-ishes which we compute exactly with Gamma-convergence. We perform some nu-merical calculations for the discrete model and show that both the shape of the solutions as well as the values of the energies are in agreement with classical re-sults for positive and negative disclinations. This is a collaboration with P. van Meurs (Kanazawa).

 15:40 - 16:20
 Speaker : Kenji Kajiwara (Kyushu University)
 Title : Log-aesthetic Curves in Industrial Design as Similarity Geometric Analogue of Euler’s Elasticae
     We consider the log-aesthetic curves (LAC) which is the family of the planar curves developed in the industrial design as the shape elements with built-in aes-thetic character. We show that LAC can be formulated by the traveling wave solu-tions of the integrable deformation equation of the planar curves in the similarity geometry, as well as the variational principle with respect to the ”fairing energy”. This implies that LAC can be regarded as the similarity geometric analogue of the Euler’s elasticae. Based on this observation, we extend LAC to the space curves and surfaces.

Organizers  Pierluigi Cesana (Kyushu University), cesana(at)
 Marco Morandotti (Technical University of Turin, IT)