报告题目：Micromechanical modeling for ductile porous materials by variationalmethods
报 告 人：Long Cheng
Main subject of the presentation: the first objective is to develop and implement extended limit analysis in the context of ductile porous geomaterials whose matrix obeys to a perfectly non associated plastic laws. This has been observed through a large number of experimentation that many plastic constitutive laws of engineering materials, particularly those of geomaterials, are non-associated. The corresponding analytical modeling is achieved by using the extended limit analysis based on the Bipotential theory for which a trial stress field and a trial velocity field should be considered. Materials admitting a bipotential are called Implicit Standard Materials (ISM) because the constitutive law is a subnormality law but the relation between the dual variables is implicit. In the second part, we propose from the micromechanical point of view an analytical model by using the linear comparison composite method to study the elasto-plastic response of porous materials especially subjected to cyclic loading with isotropic and linear kinematic hardening at finite strains. To this end, we use an approximate but numerically efficient decoupled homogenization strategy between the elastic and plastic parts. The resulting effective back stress in the porous solid, similar to the macroscopic stress and plastic strain depend on the porosity, the void shape and orientation as a result of the homogenization process. Subsequently, a complete set of equations is defined to describe the evolution of the microstructure, i.e., void volume fraction (porosity), (ellipsoidal) void shape and orientation both in the elastic and the plastic regimes.
Sept. 2017 – Present Associate Professor.
Laboratory GeoRessources, École nationale supérieure de géologie, University of Lorraine, Nancy, France .
Feb. 2017 –Jul. 2017Postdoctoral Research Associate.
Laboratory LEM3, Arts et Métiers ParisTech, Metz, France .
Sept. 2015 –Dec. 2016Postdoctoral Research Associate.
Laboratory of Solid Mechanics, École polytechnique, Palaiseau, France .
Apr. 2014 –Aug. 2015Postdoctoral Research Associate and teaching assistant.
Institute Jean Le Rond d’Alembert, University Pierre and Marie CURIE,Paris, France.
2009 – 2013 Master, Ph.D, teaching assistant in Mechanics, Lille Laboratoryof Mechanics, University of Lille 1, France.
2005 – 2009 Bachelor in Physical oceanography, Ocean University of China, College of Oceanic and Atmospheric Sciences , Qingdao, China.
Three important publications
- L. Cheng, Y. Jia, A. Oueslati, G. de Saxcé, D. Kondo. A bipotential-based limit analysis and homogenization of ductile porous materials with non-associated Drucker-Pragermatrix, Journal of the Mechanics and Physics of Solids, 77, 1-26, 2015.
- L. Cheng, K. Danas, A. Constantinescu, D. Kondo. A homogenization model for porousductile solids under cyclic loads comprising a matrix with isotropic and linear kinematichardening International Journal of Solids and Structures, 121, 174-190, 2017.
- L. Cheng, G. de Saxcé, D. Kondo. A stress-based variational macroscopic model forductile porous materials, International Journal of Plasticity, 55, 133-151, 2014.
Geomechanics, Continuum mechanics, Constitutive law, Calculations of elastic structures,Mechanical behavior of materials, Analysis of static and dynamic structures by FEM,Numerical method, etc.
Micromechanics, Analytical and numerical homogenization and damage, Fracture mechanics, Modeling of multiphysical phenomenon, etc.