In case of elasto-plastic problem it is mentioned that unloading of an integration point should be started along the elastic moduli when the solution gives a negetive increment of the plastic strain at the integration point. If anyone could elaborate it a little more, it will be really helpful.
I am working with shape memory alloys (nitinol), and am in that respect investigating fracture behaviour of NiTi, using, among other things, simulations in ABAQUS. ABAQUS doesn't have a material model that include plasticity unless you pay for it. I am wondering if anyone have implemented either of the following models as a UMAT, and if you are willing to share the code with me.
The models I am interested in are:
Dear AllI has question about these stresses.1.Are deviatoric stress generate plastic deformation?2. Are hydrostatic stress generate plastic deformation?3.What is the advantage of transferring strain tenser orientation to the principle coordinate axes? 4. What is the difference between rupture and fracture stress?
Help!!! How to calculate the consistency parameter by consistency condition (potential function) of plasitc flowSubmitted by michael_chn on Wed, 2009-10-21 21:10.
I have read a "Manual for LS-DYNA Wood Material Model 143"(website: http://www.tfhrc.gov/safety/pubs/04097/sec150.htm#toc_1_5_1 and http://www.tfhrc.gov/safety/pubs/04097/append_e.htm).
I have two question:
1. how to calculate the consistency parameter (formula (180)) by potential function, I'm quite not understant how the formula (19), (20), (25), and (26) came out. Could anyone explain it to me or tell me what material I should get and read?
Recently, I am trying to build a plastic contact model to describe teh relationship between the plastic deformation and the contact force, which is a crucial point in my work that dealing with the grasp force in robotics. So, anybody has some ideas about this? Actually, I am attempting to find a analytic model.
A post-doc position is available now for one who has recently obtained (or about to get) his/her PhD on computational
geomechanics or computational mechanics. The successful candidate is expected to have strong background of mechanics
and extensive experience on computer programming (e.g., coding in FEM and/or DEM), and is able to work independently.
He/she who has previously worked on multi-scale modeling of material behavior will be particularly welcome to apply. The
initial contract is one year and is extendable to multiple years subject to his/her performance and availability of funding.
(in Journal of the Mechanics and Physics of Solids)
Nonsingular, stressed, dislocation (wall) profiles are shown to be 1-d equilibria of a non-equilibrium theory of Field Dislocation Mechanics (FDM). It is also shown that such equilibrium profiles corresponding to a given level of load cannot generally serve as a traveling wave profile of the governing equation for other values of nearby constant load; however, one case of soft loading with a special form of the dislocation velocity law is demonstrated to have no ‘Peierls barrier’ in this sense. The analysis is facilitated by the formulation of a 1-d, scalar, time-dependent, Hamilton-Jacobi equation as an exact special case of the full 3-d FDM theory accounting for non-convex elastic energy, small, Nye-tensor dependent core energy, and possibly an energy contribution based on incompatible slip. Relevant nonlinear stability questions, including that of nucleation, are formulated in a non-equilibrium setting. Elementary averaging ideas show a singular perturbation structure in the evolution of the (unsymmetric) macroscopic plastic distortion, thus pointing to the possibility of predicting generally rate-insensitive slow response constrained to a tensorial ‘yield’ surface, while allowing fast excursions off it, even though only simple kinetic assumptions are employed in the microscopic FDM theory. The emergent small viscosity on averaging that serves as the small parameter for the perturbation structure is a robust, almost-geometric consequence of large gradients of slip in the dislocation core and the persistent presence of a large number of dislocations in the averaging volume. In the simplest approximation, the macroscopic yield criterion displays anisotropy based on the microscopic dislocation line and Burgers vector distribution, a dependence on the Laplacian of the incompatible slip tensor and a nonlocal term related to a Stokes-Helmholtz-curl projection of an ‘internal stress’ derived from the incompatible slip energy.
I came upon a recent paper called "Deformation gradients for continuum mechanical analysis of atomistic simulations" by Jonathan A. Zimmerman , Douglas J. Bammann, and Huajian Gao, International Journal of Solids and Structures 46 (2009) 238–253 where the authors conclude with
I am doing numerical simulation using ABAQUS 6.7. I faced some problem to apply load that will be used as the forced displacement in one face of our model.I used user subroutine for appling load.But, i don't know how to apply forced displacement means the command of forced displacement.
Could you please help me regarding this problem.
My name is Aurelio Tronci and I am a PhD student at the University of Cagliari (Italy). My research topics are related to friction stir welding (FSW). The work done so far has focused on the application of the DOE technique in order to investigate the influence of welding parameters on the microstructural and mechanical properties of aluminum alloys (AA 2198 T3-T8) joints. At the moment I am interested in the development of a thermo-mechanical model of FSW with CFD, but I find it really difficult to find material constants (Sellars and Tegart law) for all the alloys I have to test. Any kind of help in this sense would be very useful!
INELASTICITY OF MATERIALS- An Engineering Approach and a Practical Guide
(Texas A&M University, USA)
(Indian Institute of Technology, Madras, India)
With the advent of a host of new materials ranging from shape memory alloys to biomaterials to multiphase alloys, acquiring the capacity to model inelastic behavior and to choose the right model in a commercial analysis software has become a pressing need for practicing engineers. Even with the traditional materials, there is a continued emphasis on optimizing and extending their full range of capability in the applications. This textbook builds upon the existing knowledge of elasticity and thermodynamics, and allows the reader to gain confidence in extending one's skills in understanding and analyzing problems in inelasticity. By reading this textbook and working through the assigned exercises, the reader will gain a level of comfort and competence in developing and using inelasticity models. Thus, the book serves as a valuable book for practicing engineers and senior-level undergraduate/graduate-level students in the mechanical, civil, aeronautical, metallurgical and other disciplines.
Article on web
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.
So, what is the reason of change of elastic modulus with plastic deformation? Any References??
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.
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. Abaqus uses a non-associative plastic flow rule definition in the shear yield space but doesn't provide any valid explanation for the equation of the flow potential used.
Nano Letters 9, 2295 (2009), 10.1021/nl9004805, http://www.rsc.org/chemistryworld/News/2009/May/26050903.asp, http://www.nytimes.com/2009/07/07/science/07obsalt.html, http://www.sciencenews.org/view/generic/id/45132/title/Salt_stretches_in..., http://www.sandia.gov/LabNews/090605.html, http://www.newscientist.com/article/dn17374-salt-crystals-reveal-surpris..., http://www.youtube.com/watch?v=OGcFCD8E7o8
I am currently running a Quasi-Static compression simulation in Abaqus Explicit using the Johnson-Cook Plasticity option. As the strain gets beyond the elastic range, the stress-strain response begins to oscillate +- 5 MPa around the expected curve. Does anyone know why this is happening and/or how to repair the problem?
D. Barrett Hardin
Dear Mechanical Engineers,
It's my pleasure to be one of your group. I have a question in Abaqus Explicit and all my friends recommended me to as iMechanica as the explicit Abaqus is more popular to you than us as civil engineers.
Does anyone knows where I can find any paper discuss the existence of potential functinoal for materials that violate the maximum plastic dissipation principle (due to non-convex yield function and/or non-associately fluw rule)?
this is Probal from university of western ontario (UWO). I am working on three roller flow forming process and i have to model the deformation specially in the splined area. could you please give me any idea or give any link so that i can have an idea what to do.
thank you probal
In joint material interface between elastic and elastic-plastic material, how can we show the continuity of displacement theoretically?It must be continuous and compatible of deformation in practical case.Could anyone help me to understand this answer?
"Defects and Microstructure at the Nanoscale and Beyond," Mini-symposium at USNCCM-10, July 16-19, 2009Submitted by Robin Selinger on Mon, 2009-01-05 22:01.
There will be a mini-symposium entitled "Defects and Microstructure at the Nanoscale and Beyond," at the USNCCM-10 conference in Columbus, OH, July 16 -19, 2009. This topic is of keen interest to the I-Mechanica community and we hope many of you will join us there. Our goal is to bring together researchers from the mechanics, materials, and physics communities to cross-fertilize research on defect-mediated processes in microstructural evolution, with a focus on both hard and soft materials.
ı am looking for relationship between shore D and shore A.Not a curve i need chart.I would be appreciated if you send me this diagram.I have some hypolon and PU roll .I am using shoremeter to see the hardness .
if you have you may send email@example.com
have a nice day
Recently, we do some work about the dynamic strain aging. In order to investigate the function of solute clouds and precipitates in DSA, we do some experiments. The solution treated LY12 alloys are tested on MTS at low temperature (173K), and the Portevin-Le Chatelier phenomenon disappeared as we expected. But, we need more information about the change of microstructure under the low temperature, what is more the micro-optical observation should be finished in a very short time when we consider the effect of natural aging. Obviously the TEM can not meet our needs.
A postdoctoral position at Sandia National Labs in Livermore, CA is available for an applied mechanics engineer with a strong background in computational constitutive model development. The work will support our current projects in the areas of continuum plasticity and failure modeling. The applicant will also be expected to implement models into Sandia computer codes for high-performance computing simulations. In addition, the candidate will collaborate with structural analysts to apply these advanced models to Sandia applications.