Although deformation processes in submicron-sized metallic crystals are
well documented, the direct observation of deformation mechanisms in
crystals with dimensions below the sub-10-nm range is currently lacking.
Here, through in situ high-resolution transmission electron
microscopy (HRTEM) observations, we show that (1) in sharp contrast to
what happens in bulk materials, in which plasticity is mediated by
dislocation emission from Frank-Read sources and multiplication, partial
dislocations emitted from free surfaces dominate the deformation of
My PhD student Peter Falkingham (who graduated 15 December 2010) has published some interesting papers on Dinosaur Trackways. These might be of interest to those teaching Soil Mechanics, to give some examples that might be more stimulating than foundation design or traditional geotechnical engineering.
The successful candidate will work on the EPSRC funded research project 'Ultimate and permissible limit state behaviour of soil-filled masonry arch bridges', which is being undertaken in collaboration with the University of Salford and various industrial partners (Network Rail, ADEPT, the International Union of Railways and Balfour Beatty Rail). This is an exciting opportunity to help develop the next generation of analysis and assessment techniques for masonry arch bridges, thus helping to ensure a sustainable future for structures that continue to form a vitally important part of the rail and regional road networks of the UK and other countries.
In the last decade, different
cyclic plasticity models, based on the “continuum” approach, have been proposed
in order to account for different mechanical effects (such as ratchetting,
strain range dependence, non-proportional loading and memory effect), [1, 2]. A
disadvantage of this approach is the elevated number of model parameters
introduced in order to correctly predict the material behaviour. The determination
of these parameters, usually difficult and expensive, is one of the reasons why the modern
constitutive models are not widely used in finite element simulations of
Abstracts due Friday, Nov. 19, 2010
APS March Meeting Focus session: "Tribophysics: Friction, Fracture and Deformation Across Length Scales"
March 21 - 25, 2011, Dallas, Texas
Details at http://www.aps.org/meetings/march/scientific/focus2.cfm#12.7.3
Invited speakers: Michael Marder (Univ. of Texas); Julia Greer (Caltech)
Organizers: Robin Selinger (Kent State), Jacqueline Krim (NCSU), Noam Bernstein (NRL)
(Journal of Elasticity, Carlson memorial Volume)
A methodology is devised to utilize the statistical mechanical entropy of an isolated, constrained atomistic system to define the dissipative driving-force and energetic fields in continuum thermomechanics. A thermodynamic model of dislocation mechanics is discussed. One outcome is a definition for the mesoscale back-stress tensor and the symmetric, polar dislocation density-dependent, Cauchy stress tensor from atomistic ingredients.
I am using a VUMAT with isotropic hardening in my three dimensional model. Can someone tell me how is plasticity data passed into this subroutine? In VUMAT for kinematic hardening we define the yield stress and hardening modulus along with E and poisson's ratio in *User Material. I did not find any isotropic hardening VUMAT examples in manual. Do we define the hardening modulus or the yield stress-plastic strain data in isotropic hardening VUMAT? I will be really thankful if anyone can help me.
We tried to simulate simple shear using ABAQUS and compared it with the analytical solution. To our surprise, even though the equivalent stress and strain matched perfectly, the component stress and strain had a large deviation between the semi analytical and ABAQUS methods. The zero components in the analytical model were calculated to be non-zero in the results of ABAQUS. This paradox could not be understood clearly as whether it is a case of software deficiency or conceptual error. A COMPLETE ANALYSIS OF THE PROBLEM IS ATTACHED AS A REPORT.
I have asked for technique support. Their answer was that my strain rate was incorrect for finite deformation. But I do not think so.
A new postdoctoral position in continuum mechanics is available at the Weizmann Institute of Science. Candidates should have a strong background in physics and/or theoretical mechanics, as well as experience with analytical and computational methods for solving partial differential equations. Possible projects include the mechanics of frictional sliding, the mechanics of biomaterials, the mechanics of glassy materials and dislocation-mediated plasticity. Highly motivated candidates are requested to send their CV, publications list and statement of research interests to Dr. Eran Bouchbinder firstname.lastname@example.org
I will be teaching a sophomore level class mechanics of materials class. The class will cover mechanics of basic strength of materials (e.g. beams, pressure vessels), but I also want to teach basic elements of failure mechanics (fracture, fatigue, plasticity, and wear.) I'm looking for a recommendation of an undergrad mechanics textbook that covers the fracture, fatigue, plasticity, and wear. The students will have had a statics and mechanics class and their textbook already covers strength of materials. Thanks.
Good Time to Everybody, I am working on Thermoplasticity, especially thermoviscoplasticity, will be comparing the results of some basic examples problem worked be Simo and Miehe, modelled in Abaqus with the results of a locally developed code. I am new comer in this excellent forum and I am happy to see myself among a nice community of Mechanicians. I regard all those who are conneted in this form and those who helped in connecting this chain of Mechanics.
Continuing on the work from the previous thread posted on
Results are presented on the evolution of subsequent yield surfaces with
finite deformation in a very high work hardening annealed 1100 aluminum
alloy. In Part I [Khan, A.S., Kazmi, R., Stoughton, T., Pandey, A.,
2009a. Evolution of subsequent yield surfaces and elastic constants with
finite plastic deformation. Part 1: a very low work hardening aluminum
alloy (Al-6061–T6511) 25, 1611–1625.] of this paper, similar results are
presented for a very low work hardening aluminum alloy.
This is a review on ductile fracture committed to the Advances in Applied Mechanics (Vol 44). Part of the review has an educational purpose and, as such, is intended for advanced undergraduates and starting graduate students. The other part is an account of recent research conducted in the field.
Though quite long, the review is by no means exhaustive. As noted in the discussion, many valuable contributions to this field have been left out. The focus was laid on micromechanics-based approaches to connect to microstructural aspects in engineering materials.
I will try to post the electronic PDF once I get permission from Elsevier.
hi friends am doin my my project on" FEA of plasticity induced crack closure". my specimen size is 80*80 mm. by using symmetry condition i modelled 1/4th of model in ANSYS. therfore i created 40*40 mm plate. with initial crack length of 4mm.means its MT specimen of 80*80mm with 8 mm crack length, by symmetry condition i modelled 40*40 with 4mm crack lenth.
I am working with abaqus 6.7 software. I wish to simulate uni-axial tension and compression cyclic analysis. My objective is to predict the response of steel subjected to cyclic load and in particular, to predict ratcheting effect. I am also interested to draw S-N curve, stress-strain curve, ratcheting behaviour, etc. from the result of the analysis. I tried to simulate an axi-symmetric model and job submission is successfully completed. But I am not aware of the fact that how the results of analysis can be retrieved to draw the above mentioned curves, please specify how the 'no.of cycle' data can be obtained.
I am working on plastic behaviour of metal. I am using Abaqus 6.7 for simulation of uniaxial ratcheting of steel under cyclic loading. Modelling and job submission/completion has been done successfully. But I cann't understand where the data for Stresses(S) & number of cycle(N) is strored to draw S-N curve. Please suggest.
Concrete is sensitive to strain rate. I want to create a model for a reinforced concrete plane frame. The material model used for concrete is concrete damaged plasticity, and the element type is B21. I want to consider strain rate effects of concrete(strength). The problem is that ABAQUS can not work after considering strain rate effects of concrete when the concrete yields. Can you help me? Thank you in advance.
I am an M.S student, my subject in modelling of high strength concrete column under eecentric loading. I made a model of reinforced
concrete column with in ANSYS by solid65 to represent concrete and link8 for steel.
My model is 200*200*4000 mm, i choose multi., conc.,and elastic linear for concrete, closing crushing for it, for steel bilinear, elastic.
Slenderness ratio (l/d)=20 Although Using large displacement analysis option, model give me very small displacement (less than
I decided to put this post since I am trying to model piles on granular materials with Abaqus and I am having LOADS of problems, some of them due to my lack of understanding in the subject and others becasue there is not enough information around. Some of my problems are:
1- convergence problems: I am using Mohr coulomb for the soil and elasticity for the pile. If the difference between Young's modulus for both materials is to big it does not converge on Abaqus Static. If I do not put a bit of cohesion in my soil it also does not converge.
2- Different failure mode or smaller than it should be.
We are looking for suitable candidates for a PhD research work in Computational Mechanics and numerical simulation, to be carried out at the Department of Mechanical Engineering, University of Aveiro, Portugal, in one of the following areas:
- development of new finite elements for metal forming applications;
- numerical simulation of metal forming (sheet and bulk forming);
- tubular hydroforming numerical simulation;
- structural stability and buckling analysis of reinforced aircraft panels;
- integrated design, modelling and reliability assessment (iDMR) by computational tools.
Candidates are free to contact me using the email: robertt AT ua DOT pt
Would like to hear your expertise/user/non-expert/sceptic comments on XFEM. Here are some of the challenges. Would like to hear your relections.
1. Can XFEM be utilized in characterizing Failure rather than Fracture?
2. What sort of challenges XFEM still have with respect to Fracture Mechanics?
3. How the Fracture mechanics benefit the industry, from the perspective of strcutural integrity?
4. Failue investigations vs. Fracture investigations: benefit to industry?
5. Academist vs Engineer: Perspective on XFEM
If possible, please vindicate your justifications with any relevant literature. Would like to see where and how XFEM is evolving.
I am looking for a way to measure notch tip radius experimentally. Would you give me some ideas about that? is there any relationship between morphology of notched cracked body surface and notch tip radius?
Thank you and Regards,