Blog posts
Change in Elastic Modulus with Plastic Deformation
Article on web
http://www.eng-tips.com/faqs.cfm?fid=1441
The physical basis of material
properties like Young's modulus can be understood by examining
materials on the atomic scale. There are two main things that influence
the value of the modulus:
1.) The atomic microstructure
2.) The interatomic bonds.
A post-doc position available for molecular dynamics modeling of nanoparticle growth
A post-doc researcher position is available from Sept 2009. Please contact Prof. John Wen at the Univerity of Waterloo. (jzwen [at] uwaterloo.ca (jzwen[at]uwaterloo[dot]ca))
Simple calculation, Interesting result -- van der Waal interaction of DWCNT
It is well known that the wall-to-wall interactions play a great part in the deformation of MWCNTs. At the first glance, I thought the pressures, duing to van der Waal interaction, on the inner tube and out tube should be proportional to their radii inversely, because this interaction is a kind of action and reaction. BUT actually it is not the case, as illuminated in our paper published in APL, although this two pressures are both functions of the radii, they are not inversely proportional to the radii.
Can we creat a new kind of "boundary condition" to LBM for solve the mulpiple coupled fields problems
As we know, lattice boltzmann method is one method to solve the fluid problems. and the primary work to use this method is give the corrected "boundary conditon"__pressure conditions and velocity conditions.
To general problems, the PC and VC for 2D/3D problems has been obtained by some scientists(eg.D3Q19,D2q9 ...model).
But to the lowest scale problems, the "force" fields is complexed and the traditional PC/VC is not suit for this kind of problems.
My opinion:
Calibration of rate independent phenomenological plasticity models
I have a question regarding the experimental determination of rate independent phenomenological elaso plastic constitutive model.
Since the models are rate independent, does the strain rate in the experiments used to calibrate the model parametes have any influence on the model. I am talking about this in context to the Cap plasticity model used in Abaqus. One has to run a certain number of powder compaction experiments to calibrate the model.
Plastic potentials/ Flow rules
I have a fundamental question regarding flow rules of finite plasticity models especially those used in soil mechanics. In most of the papers and books, I have seen the usage of an associated flow rule with the plastic potential similar to the yield surface. However, I am unable to understand the means of obtaining a non-associative flow rule. I am using Abaqus with cap plasticity model (modified Drucker Prager Cap model) to simulate powder compaction process.
A novel "multiscale stochastic finite element method" on solid mechanics
Research on multiscale stochastic modeling is becoming big. In this article "A Green-function-based multiscale method for uncertainty quantification of finite body random heterogeneous materials" doi:10.1016/j.compstruc.2009.05.009 , one of the first multiscale stochastic methods is developed for solid mechanics applications.....
Inorganic islands on a highly stretchable polyimide substrate
For a flexible electronic device integrating inorganic materials on a polymer substrate, the polymer can deform substantially, but the inorganic materials usually fracture at small strains. This paper describes an approach to make such a device highly stretchable. A polyimide substrate is first coated with a thin layer of an elastomer, on top of which SiNx islands are fabricated. When the substrate is stretched to a large strain, the SiNx islands remain intact. Calculations confirm that the elastomer reduces the strain in the S