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Journal Club November 2007: Surface Effects on Nanomaterials
Nanoscale materials, including thin films, quantum dots, nanowires, nanobelts, etc – are all structurally unique because they have a relatively high ratio of surface area to volume ratio. This increase in surface area to volume ratio is important for nanomaterials because wide and unexpected variations in mechanical and other physical properties, such as thermal, electrical and optical, have been found to scale in some proportion to increase in surface area to volume ratio.
What is difference of testing method?
Well...What is their advantages and disadvantages among tensile test, compressive test and torsion test?
plz describe extensively..
Watching buckyballs shrink
PRL 99, 175503 (2007); Jianyu Huang, Feng Ding, Kun Jiao, Boris I Yakobson
Youtube Movie: http://www.youtube.com/watch?v=NSNlE8AreeM http://www.nature.com/nnano/reshigh/2007/1107/full/nnano.2007.404.html
Fracture Simulation Using Discrete Lattice Models
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I am trying to implement quasi static fracture in a discrete lattice model, with material being viscoelastic. Do i need to use an incremental-iterative method? Please give your suggestions.
Multiaxial behavior of nanoporous single crystal copper: a molecular dynamics study
The stress-strain behavior and incipient yield surface of nanoporous single crystal copper are studied by the molecular dynamics (MD) method. The problem is modeled by a periodic unit cell subject to multi-axial loading. The loading induced defect evolution is explored. The incipient yield surfaces are found to be tension-compression asymmetric. For given void volume fraction, apparent size effects in the yield surface are predicted: the smaller behaves stronger.
Crack formation in thin film during deposition process
Dear Researchers,
I am a research student, "Surface modification of materials" is my research topic. I joined your site to discuss the crack propagation during thin film deposition.
A quesntion of Negative Eigenvalues in Buckling analysis
A simple model was constructed to convince the analytical solution and a numerical results.
For instance, the instability of an Euler column was investigated under uniform pressure with magnitude equal to 1 on the top surface. The FEM calculation (Abaqus) exhibits that the eigenvalue for mode 1 is negative and the minus value cann't be transformed to positive though I have try to variate the mesh size and category as well as calculative measures with Lanczos or subspace.
BTW: the step for this model is applied with Buckle in Linear perturbation
"Crack" versus "Fracture"
It seems that within the field of fracture mechanics, some authors use "fracture" to refer to the mechanism of creating new surfaces within a body by breaking the material bonds and reserve the word "crack" for the sharp-tipped discontinuity that results from fracture of a brittle material. But it does not appear that this distinction is followed consistently throughout the literature, and perhaps different research areas within the fracture mechanics field use the two words in different ways.
Questions on ferroelectrics: why tetragonal ferroelectric ceramics are difficult to pole while rhombohedral ceramics easy to?
It may be well known to researchers on ferroelectrics that tetragonal ferroelectric ceramics, such as BaTiO3, Ti-rich lead titanate zirconate (PZT), are difficult to pole even using a high DC field with long holding time. While the rhombohedral PZT or PZT near the morphotropic phase boundary (MPB) are easy to pole, especially the latter. Why?