报告人：Prof. Michael Zaiser，埃尔朗根-纽伦堡大学，材料科学系系主任

报告时间：2019.9.25 13:00-14:00

报告地点：HE楼207室

Abstract:Constitutive equations for plasticity are normally formulated as deterministic relations between state variables (including possible internal variables) and their rates. However, real material microstructures are often heterogeneous and disordered, and the dynamics of materials on the microstructure level is therefore only predictable to a very limited extent. While averaging over sufficiently large volumes may remedy this problem, there are many situations where average descriptions prove inadequate because either the (microscale) system is smaller than the RVE, or conversely the RVE is larger than the (macroscopic) system.

Stochastic plasticity models are a means of incorporating microstructural disorder into constitutive equations for plastic deformation. In such models, local material properties are considered as random fields whose evolution is described by stochastic processes. We give several examples illustrating this approach. We first consider crystal plasticity, where stochasticity is related to the microscopically random nature of the dislocation arrangement, and then plasticity of amorphous materials where it stems from the random arrangement of atoms. We show that in both cases plastic flow is characterized by scale-free avalanche phenomena that share common universal characteristics. We then proceed to analyse the effect of microscopic material heterogeneity on strain localization and failure, and discuss possible implications for strain localization phenomena in irradiated materials.

Research experiences:

1990—1993 PhD student, Max-Planck Institute for Metals Research (A. Seeger)

1994—1997 Postdoc at JRC-EC Ispra, Italy, and MechanicsofMaterialsLaboratory,Universityof Thessaloniki (Prof.E.C.Aifantis).

1998—2001 DFGAdvancedFellowship.

2001—2007 Lecturer and Reader, SchoolofEngineeringandElectronics,TheUniversityofEdinburgh

2008—2012 ChairProfessorofMechanicsofMaterials,TheUniversityof Edinburgh.

2009—2012 Head, Institute for Materials and Processes, University of Edinburgh

Since 2012 Chair ProfessorofMaterialsSimulation,FAU Erlangen-Nürnberg

2019 – Head, Department of Materials Science,FAU Erlangen- Nürnberg

Main research fields:

lDislocation theory and dislocation simulation

lFailure and microstructure evolution of foams and networks

lDeformation and failure of materials with amorphous or disordered microstructures

Publications:

> 180 Publications, of which 2 in Science, 1 in Nature Physics, 1 in Nature Communications, 8 in Physical Review Letters

Citationstatistics:~5300citations,h=36(GoogleScholarCitations);~3800 citations,h=31(Scopus).