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Questions related to Abaqus
Is it possible to get the coordinates of all integration points in an element in ABAQUS UMAT?
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I know that it is possible to get the COORDS of one integration point, but my UMAT (based upon mechanism based strain gradient crystal plasticity) requires that I must have the COORDS of other integration points as well in the same element.
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@Mubeen: You have to creat user defined variables to store coordinates of other integration points. The only problem is you can't use these coordinates until next step
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I wish to model the crack on composite beam using ABAQUS software. Can anyone tell me the procedure?
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What we have noticed is that you can model a crack with XFEM as long as you don't have a compressive residual stress in front of the crack. In addition, If your R ratio is negative or you have compressive residual stress the crack closes onto itself and then you face issues with convergence of the solution.
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ABAQUS CAE (finite element program) treats each inclusion and a matrix as an independent part and therefore the mesh of one part (inclusion) is not connected with the mesh of another part. That is why the user needs to enforce displacement continuity conditions on all interfaces between inclusions and the matrix in order to "bind" them into a single model. This process is very inconvenient and time-consuming especially if there are many inclusions. How can I avoid this and make the mesh of one part dependent on the mesh of another part automatically?
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Don't complicate your model with contact definition if it is not needed. This is your case.... Do it as simple as possible.... The way I explained above work with simple input file and without contact....
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I am trying to model a Micropipette Aspiration experiment, which is in fact creeping of a portion of a hyperelastic thin wall spherical membrane into a rigid pipette as a result of applying negative pressure (suction) through the pipette.
I obtained the equibiaxial data from my experiments and accordingly defined the test data in the Material properties section in ABAQUS. The problem is although in reality (experiment), there is up to 50 % nominal areal strain (in the portion of sphere which is sucked into the pipette), my FE model in abaqus/standard (quasi-static solution) would be aborted after experiencing 7% areal strain with unknown errors and warnings such as
I have used almost all possible hyperelastic models in my FE analysis (to find which is the best fit) but they didn’t work out and they all got aborted in the same point of running. Also, I have tried different contact conditions and considering different steps of solution but they didn’t work for me so far.
Does anybody think that I should write any subroutine (UMAT,…) to sort this problem out? If yes, which one? Given that I am new in using ABAQUS, I would be grateful if anybody could kindly send me any file/tutorial in this regard or point me to the correct direction.
For your further consideration, I have also attached a figure of the experiment I am trying to simulate.
Any guide or suggestion would be much appreciated.
Many thanks in advance.
Navid
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Navid,
I've never seen such a message and it's hard to judge what exactly causes the error in this particular case without seeing the model.
But things I would look into are:
1) Boundary conditions. Make sure that nodes are not under-constrained and there is no rigid body motion.
2) Contact definition. You already tried many contact properties but try to read manual and check some more settings concerning the contact. Also try to avoid any initial overclosure and penetration of parts.
3) Time increment. If you choose too large an increment, solution will cut the increment and after five cut backs the analysis will stop. Try decreasing both initial and minimum time increment.
I've never dealt with hyperelastic materials but I believe you can solve this problem without UMAT at first.
Hope it helps.
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My material property like density, conductivity will change with porosity as well as with temperature. I have the data for change of porosity with time. The change of porosity is linear with time.
I have no idea how I can change the properties with time.
Can you give me some idea please?
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Dear Redwan,
In Abaqus all the material properties can be function of temperature and user defined fields. While it is quite easy to define the temperature dependency if you have, for instance, a coupled temperature-displacement simulation or if you impose a temperature field during the simulation imposing a field dependency with time is a bit more difficult.
In the first case you just enter the value change of conductivity at X degrees and Y degrees ant the solver does everything. just be aware that the interpolation between temperatures is linear so if you have a dramatic change in properties you have better to introduce many points. In the second case, just a preliminary consideration. Are you obliged to use time as parameter? Usually is not a physical representative parameter if your material properties evolve in time you have better to find the cause of that and than simulate that physical process and just afterwards try to match with the evolution in time.
If this is not practical for you, I suggest that you have a look to the USDFIELD subroutine in the abaqus manual. With this subroutine you are able to define a field that depends on all the physical parameter of the simulation and also on time. It is not so hard to code it and the manual is well explanatory however it requires a bit of knowledge of fortran.
I hope that helps you
kind regards
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I am a new user of Abaqus. I want to ask whether it's possible or not to perform fatigue life analysis using standard abaqus (without sub-routine). If possible, then how to define their loadings and where can I get their results. I hope that somebody can share their experiences here. Many thanks.
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Hi,
It is possible to perform fatigue analysis using Abaqus. we can do that in load (stress) control for high cycle fatigue and disp (strain) control for low cycle fatigue depending on the kind of problem you are attempting. The material properties can be defined in abaqus. especially in case of low cycle fatigue, you would need plastic deformation properties (isotropic/kinematic or both) which can be incorporated without using any subroutine in abaqus.
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Can anyone help me with a video tutorial, or a step by step guide, or a CAE/INP file of bullet impacting a material. I would like to use this approach, to model penetration of soft tissue using a bed of needles in Abaqus. Currently in Abaqus I have used the surface to surface contact, approach as a starter, and would like to progress to actual penetration.
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Has any one performed in on Ceramics. I am using JHB or JH-2 damge model but it is not penetrating like it used to do in the case of metal (Johnson Cook Damage Model). Can anyone help me on this ?
Erroneous Spatial displacement for coupled Temp-Disp Problem in ABAQUS?
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There are 3 parts in a assembly, Lower mould, Upper mould, a rectangular block placed at center of the blocks. The block is sitting over the lower mould. Upper mould is in just contact with the block. Objective is to find residual stress analysis in the block. There is no external forces. Only thermal loads are acting on the entire system. It is being heated and then cooled rapidly. In coupled temperature displacement, after the analysis I find a spatial displacement of the block in the Z- direction. Uexpan user subroutine is being used for capturing the thermal expansion behaviour of the block. Kindly can anyone suggest solution for it? I have tried *TIE option: result -> the block pulls the lower mould. I have tried Coupling DOF constraint : Result-> simulation runs like a infinite loop. No step increment is taking place.
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Following
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Actually my research area is fault diagnosis of beams. So I want test the modal analysis of cracked composite beam. So, how can I create crack over composite beams?
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Thank you Himayat
I will try in Ansys....
If any doubt arises , then I will ask again..
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I have to model fiber-matrix debonding in polymeric composites using cohesive elements. Can anybody help me?
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you can use XFEM in Abaqus software to crack/debonding in composite materials. Plz follow the link.
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When I was doing numerical simulation by using Abaqus software for a deep drawing process, I got the output result for stress in that tha contour plot colour indication is in grey. What is the indication of that colour? Does it mean failure condition?
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The grey color is the over values of the range (max and min values defined by the user). You can change it in viewport module.If you want you can use the automatic mode and normally the grey colour would be suppressed.
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For every load step, fortran code is complied from beginning, when we link with abaqus. My question is: if, for example, I am solving for a(t) and 't' is time at current load step and I want a(t) value in the next load increment a(t+1), how will I get value of a(t) ? Because for every load increment fortran code run from beginning and I don't know how to call/use, all previously solved/stored value. Can any one help?.
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Hi, What kind of routine you use?
Abaqus provides Solution Dependent variables for various type of user routine (Such as UMAT,UEL,VUMAT,VEUL,........) in order to save data and receive them in next increment. You can save your variable(s) in solution dependent variables which are passed into abaqus for each increment. Also yo can use user-defined output variables using UVARM routine. For more details see Abaqus user subroutine manual.
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In numerical integration of (B^t*D*B) for calculation stiffness matrix, can its value (B^t*D*B) be printed at integration points. Also, is it possible to print value of weight at each integration point which is being taken by abaqus.
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The answer of the first question is Yes. You need to develop a script in the python to be able to. follow the below information:
http://your host/v6.11/books/ker/default.htm
For the second question I don't have any idea.
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I am trying to model a composite cantilever beam using a solid section on ABAQUS. This requires defining elastic material property using engineering constants. Can anyone help me define transverse properties of the material in ABAQUS/CAE?
Thank you.
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did you use anysotropic material ?, in abaqus, for elastic properties, if you use engineering constant instead of anisotropic, you only need to fill the modulus and poissons ratio for all directions. Typically, if you use a UD, transverse shear will be near to in plane shear in 13 direction and to matrix shear properties in 23, in the case of woven fabric, you might refere to similar material from the literature. If you can give me some more details, maybe I can help more.
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Could anybody help me with the analysis of a 2D 3 story single bay frame on Abaqus? I have obtained my pseudo acceleration of a given earthquake and I am trying to apply it on my model so that I can conduct a response spectrum analysis. I am having two problems: after I upload my data on my acceleration spectrum table (acceleration, frequency and damping) and I try to run the analysis I get an error message saying that my frequency needs to be continuously increasing. Given that these are pseudo acceleration graph data I am using, my frequency can not always be increasing..It's a highly non linear graph..I tried overcoming that problem by keeping the values that only indicated the frequency is increasing. When I did that I got no error messages however this is where my second problem appeared. When I go to history output to plot my displacements/ acceleration etc.. the results are blank. As if nothing is applied on the frame. Does this have something to do with my boundary conditions? or with the fact that I manipulated the acceleration spectrum maybe?
This work is for the submission of my masters thesis. Your help would be much appreciated.
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I am not familiar with Abaqus. But, after reading the question, I understood that you are trying to perform time-history analysis.
In response spectrum analysis, we usually use harmonic excitation and sweep the frequency, i.e., we try to increase the frequency in fixed steps. Then we plot the maximum (abs) displacement vs the time period (inverse of frequency).
In time-history analysis, we take any excitation, varying with time. In your case, it is pseudo acceleration. Then the responses are plotted against time.
You may try performing the time-history analysis. Post your experiences, so that it may be helpful to others also.
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For a start, I just want to make a 2D-axisymmetric model.
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How to define/apply fatigue load(sin varing fuction) in Abaqus?
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Dear Rajkumar,
If you are interested to know the life of the component madeup of that material you need to know fatigue life curve and the cyclic stress strain behaviour of the material, . and how to make use of Simulation technique for knowing this fatigue life you can refer some papers from literature or my own paper(http://onlinelibrary.wiley.com/doi/10.1111/j.1460-2695.2011.01589.x/abstract) . and For this problem you need not to apply Cyclic load using ABAQUS
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I could not find any damage model associated with Mohr coulomb plasticity model. When I try other damage models there was an error that those could be used with other plasticity models except Mohr Coulomb plasticity.
Does anyone know how to refer damage associated with Mohr Coulomb model?
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Maybe you use the modified Drucker-Prager/cap Model for simulating plasticity. You can calculate the main shear parameters for the Drucker-Prager Model from your Mohr-Coloumb Model (see ABAQUS guide).
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I have used the Abaqus software for deep drawing process.In that I was not able to get the output for shell thickness (STH) .Can anyone help me to get the output.
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From field output => Volume/Thickness/Coordinates
STH output (section thickness)
then you can plot contour of section thickness in visualization module.
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Rate dependent viscoplastic
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You may need to write user subroutine (UMAT or VUMAT).
take a look at this paper:
"Multiscale modeling of plasticity based on embedding the viscoplastic self-consistent formulation in implicit finite elements "
this is crystal plasticity modelling but involve embedding viscoplatic behavior in UMAT
I hope this can help you
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Could anyone explain or post a video tutorial in modeling of MMC rod in ABAQUS?
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For modeling i assumed particles are in Spherical shape and these particles are inside a cube. and modeled in ABAQUS. now problem is i am unable to mesh it. could u please help me out in this.
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I used the section force command but wondering if there is a visual way to do it.
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I wrote an VUEL. However, there are some problems on it. When you stretch it the element volume increases. You can get the poisson ratio and it's positive 0.33. I want to check the inner calculation process by abaqus itself. Did anyone do this before? Abstract these matrix from abaqus?
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I dont know. But I think that printing mass and stiffness from Abaqus analysis is not require. Also, you cant define element exactly same with standard Abaqus element for explicit or implicit simulation. Best way for checking results is comparing Load_displacement curve and stress_strain curve from your VUEL and Abaqus standard element (I used this method for my UEL, also it suggested by Abaqus).
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I am printing the stiffness matrix from abaqus for C3D8 element and also I have written a code for 8 noded brick element with full gauss integration. But stiffness matrix is not matching. Does C3D8 takes care of shear locking or something else?
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I noticed the same some time ago. This is due to the fact that C3D8 is not an standard brick element with the standar isoparametric shape functions. The element is enriched (I think using formulation of Simo) for shear locking but the modification resulted in a much better bending behavior. Just check how C3D8 captures much better the classic solution for bending of an elastic beam than your own element,
The main problem is that almost no information is given in the manual about the formulation of that elements.
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For a cantilever TWB, U cross section, 10 Hz excitation, I tried using general contact in Abaqus/Explicit (edge to edge contact, normal interaction: hard contact; tangential: rough), modeling with shell elements for 3 seconds of simulation time. It works, but here is the point: Is it a realistic simulation? The crack, located at a flange, is regarded as a very sharp V-notch: with mouth of 0.001 mm (length of the beam: 2000 mm; flange: 100 mm; crack depth: 50 mm).
I would like some opinions. Thank you in advance.
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If you want to see whether and how the crack propagates, then you may try the extended finite element method (XFEM) in ABAQUS. But then two problems are to be solved: First, use 3-dimensional elements instead of shell elements. This might be computationally more expensive. Second, try to transfer the inertia forces of your dynamic simulation into an equivalent static load. If you can do this, then XFEM shows the crack path, if the crack propagates at all.
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I’m trying to install a free Windows Fortran compiler to run Abaqus subroutines. I found a couple of compiler, gcc and open64, but they seem not windows compatible (I couldn't install them). If you have any alternative Fortran compiler, please let me know. In addition, would be helpful an explanation about how to link the compiler to Abaqus (I mean what to write in the environmental variables and so on).
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As a student, you can use the Intel Fortran Compiler (ifort) for free (and ifort definitely works in Abaqus). If you want to use gfortran in windows, you have to install MinGW. But I'm not sure, if gfortran works in Abaqus.
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We have used gasket elements with Abaqus/Standard for a long time. But it is even not possible in Abaqus/Explicit. Does anyone have any idea how can we solve this problem?
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If your gasket model is 2D, use GK3D4LN. If your gasket model is 3D(Hexa mesh), use C3D20RH. 
Why is there alternate layers in visualization when I select section points - top in composite layup?
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Alternate quarter by quarter.
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My mesh is like that attaced.
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At present I am facing a memory problem in ANSYS (APDL) while meshing as well as solving the solution for the model. I know that in Abaqus there are no memory problems while meshing and solving solutions for applied load.
So if I change my analysis from FEA to Abaqus, will it affect my results because I need to validate it? The analysis in FEA will be Tensile and Flexural and the same has to be simulated in Abaqus.
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Hi Ramanathan,
from your question, it appears that the problem you are approaching is a static loading problem including tensile and flexural loading conditions. As far as my experience with ANSYS goes, you should be able to get the solution for this, even if you model is quite complicated. I feel ANSYS offers a simpler and more user friendly environment. If you are using an academic version of ANSYS licensed to your institution, you may face the issue on limited DOF.
I beg pardon if I am underestimating your model's complicacy, but I feel that instead of changing the software you should to take up some simpler model and try out with your loading situations...
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I am using unstructured mesh for analysis. The number of points where I need displacement is high. So, rather than selecting or giving every coordinate individually, I would prefer to input all coordinates at once if possible.
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The path is a good option to extract the data. Additionaly you can simply copy-paste the coordinates of point for e.g. Excel to Abaqus input table when defining the path. Each row should be a string in a form: X,Y,Z.
Could someone give me some advice how to get a reasonable ply contour plot for the solid element composite?
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I'm trying to display the individual ply stresses in a composite OHT model. I am modelling 3D composite damage, therefore I used a composite layup with solid elements. The envelope plot seems fine, but if I display the individual plies, the orientation of the displayed contour surface is not corresponding with the laminate surface. http://abaqus-users.1086179.n5.nabble.com/Composite-Contour-Plot-td17508.html
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You may need to change the coordinate system to display the contour. Try to display in the local (ply) coordinate system.
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Drilling behaviour of natural fiber composite.
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Ur answer is very helpfull to me.thnkx for help.....
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Stress intensity factor in abaqus
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I am trying to penetrate a hyperelastic material with a single needle model and have discovered that I can achieve this using abaqus explicit, but will need to use element deletion.
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Dear Collegue
when you use abaqus explicit with your own routine Vumat
there is an internal variable you can select
When it is set to one, element satisfying a given condition are deleted
Otherwise no.
C deletion flag 1active 0 inactive
if delete than
stateNew(km,10)=1
end
I hope this is sufficient for you
Kind regards
RF
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Is there a rational way to select the penalty contact stiffness values based on the elastic properties of the contacting materials? It would seem reasonable to relate the pressure - overclosure function to the bulk modulus, but how?
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Timo,
the problem with numerical contact is, as others have mentioned, the overclosure. Theory formulations consider a perfect geometry, but when dealing with a discretization you will have a node penetrating the opposite element. This is where the overclosure/contact formulation comes into play. Penalty methods are easier to program, but suffer from numerical instability: the ideal penalty is infinite, but then you don't get a solution (infinite times zero is indetermined), and if you relax the penalty value, you might not capture the mechanics you are looking for.
An approach that has worked for me in the past is to start with a somewhat relaxed penalty value (e.g. equal to the bulk modulus or a small integer fraction of that). Once you get convergence, increase the penalty incrementally and refine your results, starting from the last converged solution. This way you can increase the penalty to values that would otherwise lead to divergence.
Depending on the software you are using, you may consider using a different contact algorithm, e.g. Lagrange multipliers, which are a much more elegant formulation and do not suffer from this instability...
Hope this helps,
Fernando
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Air cavity simulation in ABAQUS
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Good question.. Please share me the best answer might you trust...
Regards…
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I am going to model the polymer matrix composite tube and find out the cutting forces while machining.Can anyone recommend which software show better results?MSC/NASTRAN or ABAQUS?
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HI
believe the MSC / NASTRAN software is more compatible for modeling of composite materials with MSC MARC software integration
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We have a problem finding a suitable damage model for poylmer concrete. The most important characteristics of this concrete is that there are nonlinear elastic-plastic behavior with large volume change at the plateau zone at nearly constant pressure, pronounced hardening under clamping conditions after the plateau zone and very early damage under shear loading conditions without clamping.
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I have some experience with nonlinear damaged beam model. New developed method (FEM) was necessary. Investigated model is clamped-clamped beam.
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I've given the time history in Load-> tools-> Amplitude -> Amp 1. I've given a
small time history for practice. For the gravity step, the model deforms, but for the apply acceleration step, the model doesn't deform even if I give large values.
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Here is the .jnl file
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Plasticity behavior of lamina.
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I don't think so.. Constitutive laws for shell composites normally are restricted to elastic relations. Consider that interlaminar stresses normally cause failure of composites and this is not well accounted for in classical lamination theory.
How can I combine different materials from ABAQUS library and UEL at the same time?
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I want to run a composite material simulation from Abaqus library, linear elastic for a material and a UEL subroutine for the other material?
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You can specify by each section the law for each material
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I need guidance how to calculate J-integral in Abaqus.
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if meshing is done in Hypermesh for your model, then there is input card in HM, which will allow you to input the data table and after analysis it will give you J integral . Also the plots directly
Can anyone recommend software or numerical methodology for modeling pile in liquefied soil?
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I'm working on my thesis that needs numerical modeling and now I am looking for good software for modeling liquefaction in soil, with the capability to consider pile as a structure element in the soil. Abaqus might be a good option but I don't know its performance in modeling soil, especially the liquefaction phenomenon.
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I suggest flac2d or 3d .
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Is it possible to model plastic behavior of fiber reinforced polymer composite in Abaqus (without using subroutines)? As u know, just elastic behavior for lamina can be defined in property module.
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Yes you can if you have the experimental plastic curve of the material you can introduce it in the software with Yield stress/strain
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How do I carry out analysis of RC beam for reversed cyclic load using Abaqus?
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By the addition of many step
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The problem has been solved :)
For who's interested in this topic, we have published a paper in E.S journal with detailed information about the damage evolution in DPM among new approach for obtaining dt,dc. This is a link where you can download the Journal version http://www.sciencedirect.com/science/article/pii/S0141029616312317
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Hi bashar
I was read your paper, i can't find why in your paper you use ac=2800 and at=380
How you get the ac and at ?
Thank you
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All I know is that the journal file should be saved as a python file and then the saved filed can be invoked from Abaqus CAE.
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Dear Alexander,
Python is indeed a very powerful tool to preprocess and post-process your Abaqus simulations. I use Python and some major modules to perform these tasks: Matplotlib for graphics, SQLAlchemy for data management (with SQLite mainly), Scipy for classical numerical algorithms. I made a short tutorial I attached to this answer. If you have more specific questions, I have developed a bigger package dedicated to perform most task automatically.
Regards.
Ludovic
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I am trying to simulate foam using crushable foam in Abaqus under the uniaxial compression. As I understand, I need to insert true stress and plastic strain (from uniaxial compression test) for foam hardening. However, the foam that i am using has poison ratio 0. Can I assume the engineering stress equals to the true stress as there is no change in the Area. I have tried inserting true stress and plastic strain but it gave me a less stiffer compressive stress strain curve as compared to the experimental data. I attached the uniaxial compression test data here. I would really appreciate your advice.
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Did you come right?
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The problem is that I want to define initial strain field for my model and leave the other fields such as displacement Zero. I used the predefined field option in ABAQUS and chose the initial state but the problem is that I want the displacements to be zero.
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You can import a previous file where only the strain levels are written. So you can have a displacement equal to zero but with a strain level from a previous work.
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I am making a coupled temperature-electrical-structural model for spark plasma sintering. I have used Abaqus standard.
The model worked for simple geometry involving only 3 parts (2 punch and die), but it is not converging for my original model which has 2 punch, sample, die, 4 spacers.
The error that I am getting is -
Too many attempts made for this increment
There are few warning messages aswell
1. Displacement increment for contact is too big
2. SURFACE INTERACTION "interaction name", ASSOCIATED WITH ONE OR MORE CONTACT PAIRS WITH SURFACES HAVING UNDERLYING ELEMENTS WITH ELECTRICAL, TEMPERATURE, AND DISPLACEMENT DEGREES OF FREEDOM, DOES NOT HAVE ANY ELECTRICAL INTERACTION DEFINED. NO ELECTRICAL INTERACTION WILL OCCUR.
I used to SI units and applied a pressure of 5 MPa at the top of upper spacer.
Can anyone help me?
I have attached the input file here
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You can try:
1. Increase IA (Step-Other-General solution control-edit step-specify-Time increment-more- change IA to the maximum value 30)
2. Refine the mesh in the contact regions to reduce the percentage of elements flipping in and out of contact.
3. Using mass scaling in Dynamic/Explicit to control the stable time increment.
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Hello to all.
I don't know if anybody here uses Abaqus, but I'll post a question here.
I've tried to compute simple geotechnical problem in it by using Mohr - Coulomb criterion as a constitutive model, and I came up to a problem.
When I assign properties to continuum as a "Homogeneous", Abaqus gives me a message that I cannot use MC in plane stress conditions. Ok, I understand that, but when I change to plane strain conditions, Abaqus starts to give me a messages that I haven't assigned nodes to section.
Does anybody know, or at least has an idea how to solve that?
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First, Mohr-Cuolomb constitutive law can be used for plain strain and it works, but as a failure Criteria you can not use it alone, you need to define the material as elastic material first
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Smeared cracking in concrete.
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I am modelling an extended end plate steel connection with ABAQUS. Here is my question; what should be the interaction type with end plate and and column? Surface to surface or node to surface? Also what should be the sliding formula, small sliding or finite sliding?
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Please provide more details, screenshots would be of great help here.
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I performed a simple 3d analysis of a beam (5x5x50) with steel properties (E=206e3 and v=0.33). As I decreased the element size, the results drastically changed. The changes are recorded in the excel sheet.
Why is the stress increasing exponentially?
Which region should we label 'safe or acceptable'?
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Using 3D elements is non consistent with concentrated load. This generates a singularity because stress tends to infinty. Using finite element in that specific will give a stress that rises to infinity as element size becomes smaller and smaller... this is what you observe.
The solution is to distribute your load on the entire face or, if you want it concentrated, define a small area to distribute your load that become surfacic then (on a small surface). There will be no more singularity and convergence will then be observed.
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I am using axisymmetric modeling to simulate indentation and the indentor is an analytic rigid body while the workpiece is a 2D deformable body. I am using ABAQUS 6.12 version and did displacement controlled test. Both indentor and work piece are modeled as axi symmetric. When I do the indentation, I get an unwanted reaction force along the perpendicular direction to the loading axis (RF1) which is high compared with the reaction force along the loading axis. I imposed encastre boundary condition for the bottom of the work piece and Y axis symmetric boundry condition for the workpiece axis as well as to the indentor. Could you please help me whether there are other things to be satisfied to get rid of that RF1 component?
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Hi, that reaction force is the consequence of the symmetry conditions imposed along the axis of symmetry, in some way it represents the internal forces "on the other half of the part" in order to keep it together. If you performed and overall 3D model you would see that RF1 stays equals to zero.
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CPD model in abaqus does not consider pinching effect.
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Dear Nima
If I am not mistaken, it is quite difficult to model the pinching effect of concrete in cyclic loading using Abaqus unless you are developing your own user stress-strain relationship for unloading behavior. I suggest that you may try to use another FE model which is designed more specifically for reinforced concrete structures such as ATENA Cervenka or TNO Diana where they are providing different type of uniaxial compression and tension behavior of concrete. In TNO Diana, once again If I am not mistaken, you can use Maekawa model for cyclic loading, me myself are conducting a study using ATENA Cervenka and I believe that in ATENA you can set a small value of Unloading Factor to get a more or less suitable pinching behavior. Hope it helps.
Does anyone have experience with porous structures modelling in Abaqus?
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I´d like to simulate stress-strain behaviour of titanium porous structures prepared by powder metallurgy.
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If I were you, I scan sample with CT or micro-ct and reconstructed it. But I think you want to work firstly, virtual model with ramdomly porous. In this case, I think you need a person can code some scripts. For instance, one can write code for deleting abaqus elements randomly from input file and reorganize it. Or code can randomly produce geometry files with random sized and orientation porous fields. Next year, I will try to write some codes similar aims. However, if you have small titanium porous sample, you can scan it micro-ct and reconstruct them (I can also help you), and you can use it for analysis, or you can use scaffold field element that shows similar behavior macro indentation.
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I am modelling BMG using abaqus and i have a problem of introducing shear band formation to the model.
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I add a link here that shows how we implemented and used SB models into CPFEM / MARC
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Analyzing wave propagation in plate by using the dynamic analysis.
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I would like to do something similar. Did you discover how to do this?
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What is the element that I should use it to find fracture intensity factor?
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I'm quoting Abaqus "Analysis User's Guide" here:
"[Contour integrals] can be used only with two-dimensional quadrilateral elements or three-dimensional brick elements when used with the conventional finite element method"
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Drilling process simulation
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what about your modelling of left of material? What type of material? Do you need element removal options? You can use many ways under abaqus..
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I also need to define the zig-zagged path of the heat source, which must have constant temperature.
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Indeed temperature is an important step to predict the residual stresses. Regarding the temperature, you can either use FEA method as suggested before, or use anlytical solution. I strongly advise you the analytical way, you will learn more about the physics and it is elegant. The moving heat source from the paper of Jaeger is a good start.
Now, in order to understand the source of residual stress, you need to understand the induced thermal stresses by the temperature gradient. The framework developed by Timoshenko and Goodier is outstanding, but advance mathematical understanding of the Green functions is required.
Then, you can look at the material behavior under these stresses, namely residual stresses, using a relaxation procedure. 
If you are interested in analytical modeling, I could provide you some open source codes from matlab that I used to achieve these steps.
Regards,
Omar 
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Can anybody tell me how i can open .inp files in Abaqus/CAE? I tried to open dcb_vcct_fatigue_3d.inp (Abaqus Example Problems Manual 1.4.7.) I found something about "abaqus fetch command". However i always get an error message (SyntaxError: invalid syntax), after i write "abaqus fetch job=dcb_vcct_fatigue_3d.inp" to the command line.
Does anybody know how to use fetch command or how can i open this example input files?
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Hi Eren,
Not sure if you already solved your problem. I am an Ansys user and new to Abaqus. I tried to import an input file to CAE to create a model and this method below seem to work. 
Right click "Models" - the parent of everything in model tree, then select import in the sub-menu. It should open a window, choose the filetype as "Abaqus input file, .inp". The window should now display all the input files in the working directory. Select your input file, this should import the model. 
You may then run by creating a new job and submitting the job. Hope this is helpful. 
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I am doing transient thermal analysis of rapid prototyping and I am having a problem with script writing, which is used for the continuous element activation process. I want the process to be continued for several stages. Can anyone with expertise in this field some advice?
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Dear Swayam Bikash Did you get any progress in the above mentioned problem ??
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When working with hyperelasatic materials in any FEA software, we need to select FE models such as Ogden, Van der Waals, Yeoh, Mooney-Rivlin, etc. And I also assume that you know that hyperelastic materials can handle 600-700% strains when stretched. FE Models are required to match the experimental results with minimum errors. In my case, the Yeoh 3rd degree model fits reasonably well.
I am trying to identify that the YEOH (3rd Degree) FE model falls in to which category of strain percentage. What I mean is that the 3rd Degree Yeoh Model is acceptable in which strain ranges?
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The simple truth is that the hyperelastic behaviour of different materials are not exactly the same. Hence the practice is to find which material model (Yeoh, Ogden etc.) best fits your experimental data. I assume you have done a uniaxial test. Make sure that your test data covers the range of strain that your material will be subjected to in your simulations and use the material model that best fits your data. We have found the Yeoh model is a good fit for rubber compounds for up to 1000%.
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I would like to ask the users of FEM/ FEA about the topics that they believe are missing and if not missing, topics that are not discussed in great detail. Also the topics on which FEM/ FEA users would like to see books or research on?
Are the users of FEA packages happy to get help from 'Help' integrated in the software or would like a summarized version of that help so they can find what they need instead of clicking links upon links just to find out a simple definition?
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Thanks Nicolas. I will look into that.
Any other topics?
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In Abaqus, you have the option to import your assemblies made in Creo (formerly Pro/E) as one single part or as an assembly. The difference is that, when imported as a single part, no interactions are required because Abaqus treats it as a single part no matter how complex the geometry is.
But when imported as an assembly, individual parts are imported which can be assembled later on. But with this kind of import, interactions are required. However my contacts (interactions) would be defined as 'TIE" which means it is a fixed part.
My question is that for a same assembly, should my results differ from each other in different import methods? If so, then which is an ideal way to do your analysis considering importing in part mode, it is very easy to run the analysis with minimum errors?
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Hi
The two methods you described for importing a model would generally obtain different meshes when you mesh your structure, which might affect the results slightly.
Hope this helped
Best regards
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In Abaqus when we want to define a concentrated force (CF) at a certain point but it is coupled with other surfaces/ nodes so the force is transfered to those surfaces or nodes.
Once you made a reference point (RP) and then under interactions module, you define kinematic coupling. In coupling option, when the surface is selected, the analysis solves without any problems. When edges are selected, again it solves. But when the nodes are selected, the error pops up 'too many attempts made for this increment'. Why?
Any ideas or suggestions?
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The problem happens all the time in the cases where you have surface contact/couplings. This is a common error happening most of the times dealing with surface tied couplings. I suggest most of the times to use nodal/edge connections to avoid the errors with mostly no considerable loss of accuracy. As you asked why, and it is a bit imaginable there are less conditions and equations to satisfy in the case of edge constraints than surface, and the analysis converges in way less steps and attempts.
However if you insist on using surface to surface interactions, I suggest you use simpler models, as it is very hard to satisfy no-slip conditions for to surfaces with a concentrate load applied at the boundaries. I believe it will never converge in the case of having highly deformable materials in excessive loading.
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In Abaqus there is something called 'Global CSys' and then the user is allowed to make several others according to the model and requirements to define forces and other things. However, whenever you solve an analysis, the default result shown in Visualization Module is according to the Global CSys even though your BCs and Materials and other things defined using the new or custom csys. We need to change the csys from Results > Options.
Is this correct? Or there is no need to change the CSys from results > options. The results vary very slightly but it's a bit confusing.
Any advise or comment?
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Following
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I'm modelling the interaction between plough tool and soil.
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Hi,
You can see ABAQUS analysis user's manuel in analysis procedures/6.8 coupled pore/fluid flow and stress analysis. If you have somme difficult see example on the topic.
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Abaqus, Ansys and Patran/ Nastran
I have used a lot of software during my degree and professional work and I know it depends on what you are trying to solve determines the advantages of a particular software. Hence, this question is not about which software is better.
I am trying to solve a very simple composite problem. I have a circular plate subjected to 70 bar of pressure. The plate is made of E-Glass and Epoxy through hand layup process. 50 plies of 0.5mm are used to make up the thickness of about 25mm. The plate is bolted (25 bolts equally divided).
Model: shell
Boundary Conditions: Pressure applied on the face, bolts = encastre.
Mesh: Tet/ sweep fine mesh
Why am I getting different results in Ansys Multiphysics 14.0, Abaqus 6.12 and Patran/ Nastran 2012? Am I doing something wrong?
For example: Max. Disp. in Abaqus 6.12 = 1200mm where as Max. Disp. in Patran/ Nastran 2012 = 3400mm
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I suggest to solve first a problem with analytical solution, a circular plate --with axisymmetric loading, for example-- or a beam. Once you have obtained this results you could proceed with your problem.
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I wasn't aware about distributed and parallel computing and advantages they had, but now I have been informed. Hence, I would like to build a new cluster to perform heavy mathematical calculations in Matlab and Abaqus. I have never clustered before and that's why I need assistance to setup.
Current workstation I own:
Dell Precision T5400
2 x Intel Xeon 2.5 GHz
16 GB RAM (2GB x 8)
1 x Western Digital 1TB HDD 7200 rpm
1 x nVidia Quadro FX4600 768MB GPU
1 x 870W PSU
OS: Windows 7 Ultimate 64-bit
2nd WS: I can buy another WS similar configuration to the one I own
I am not bothered about OS, I am willing to cluster with either Windows or Linux. However, my software are compatible with windows 64-bit only.
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I have positive experiences with Amazon Web Services (AWS) EC2.
I have also identified sabalcore.com as potentially good (or maybe even better), but as AWS worked immediately I did not discover it.
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I try to model couple thermal electric phenomena using two electrodes placed on the skin. All the settings of the Abaqus program seem to be fine. I check the job, which works well and I submit that. After submission I got the comment: Too many attempts made for this increment. I did some corrections and manipulations with the value of increment size in STEP; however, I cannot possibly get the optimum.
My questions are: Do you know what should be the settings in my case? Maybe I missed some parameters earlier, before getting to STEP.
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Have you tried increasing the number of iterations per step from the default 5? Some times this can help, as a few extra iteration could be the difference between converging or aborting the analysis.
Select the tool bar for "step" and from the top menu select Other>General Solution Controls>Manager. For a step other than "initial" select Edit,
then on the Time Incrementation tab select the first More Option, then change IA to 100 (or some other number larger than the default 5).
Source:
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Working with axis symmetric model in Abaqus. I have a sandwiched structure which consists of rubber and metal plates stacked on each other. In 2D I have a single edge which is shared both by the metallic section and the elastomeric section. Defining the material properties is a nightmare.
How will I define the cross section of sandwich structure in 2D Axis-symmetric analysis?
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In this case, my suggestion is to build two parts and assemble them together using position constrains. Then the interaction between them can be defined by contact or tie, depending the problem you want to solve.
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Can you describe your composite ? the epoxy is a coating applied on the concreate ? In this case your interaction can be realize by a constraint as a tied or by surface interaction
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I have programmed a UEL subroutine for a 3D cohesive element and I have a problem.
When I do the testing using a 3D single element, the subroutine converges if and only if I put initial boundary conditions on all nodes.
For example, imagine the bottom surface is fixed and the upper surface is prescribed a displacement to perform a tensile test. Then, it is necessary to impose the lateral displacements in order to obtain convergence. If this latter constraint is not applied, the subroutine does not work (wrong displacement values obtained, error message). It seems that stiffness matrix becomes ill conditioned in the absence of sufficient boundary conditions. Yet, I observe that the cohesive elements already available in Abaqus cause no problem. For these elements, the convergence is always obtained even if the lateral displacements are not applied.
Why does this work well with Abaqus elements, but not with a user element in UEL? I verified my subroutine and I think that I have strictly implemented the classical formulation for cohesive element.
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Apply the axial and lateral constraints at only the bottom surface of the tensile test model. If it does'nt work, check the element formulation in your subroutine.
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I am trying to match Abaqus FE results with experimental results. I have a quad lap specimen, rubber block measures 25.4 x 25.4 x 6 mm. For this test, assume there is only 1 rubber block rather than 4. From experimental results, 300% of shear strain equals 3 which means at original thickness, shear strain equals 1.
Keeping that in mind, I modeled 2D plane stress, 2D plane strain and 3D specimens and run the analysis with plane stress, plane strain and 3D stress elements respectively. The shear strain I am getting is 1.5 at 300% shear strain. I have also noticed that when using 100% of shear strain, I get around 0.88 shear strain, which means the deviation is 12%, however as I increase to larger strains, the deviation increases dramatically.
Rubber model being used: YEOH 3rd Order
Test data used: Uniaxial and Volumetric Compression
Can anyone help me in modeling shear strain of rubber like materials?
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I was recently simulating shear test of a stainless steel sample using abaqus. I had two versions of the model, one for the explicit solver and one for the implicit solver. Unfortunately, the two models gave quite different results after large deformations. Even the strain components were different. This was a surprise since the strain field in simple shear is determined by the geometry. After comparing the strains with the analytical solution, I was finally able to establish that the strains calculated using the explicit solver were wrong. But I never could find out why. Switching between the solvers is quite simple, therefore I think that probably there was nothing wrong with explicit model. It is more likely that the differences were caused by the different formulations used by the solvers.
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I have developed a phase field model in Comsol and I want to import the result to ABAQUS, and perform stress analysis using UMAT.
Helpful tips from my colleaques that use ABAQUS is needed.
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UEXTERNALDB subroutine has some flags that you need to use for the initial and final increment of time. When the flag is equal to zero (initial time), you define the OPEN statement (use the Unit = 15). When the flag is equal two (final time), you define the close statement. Thus, you opened the file with the information.
After this, you need to take this information and associate it with a STATEV and, then, you can use it inside the UMAT. To define the STATEV, you use the SDVINI subroutine. Inside the SDVINI, you need to define an integer/parameter, which is a parameter (len, for example) with the number of columns of the information that will be read (5 for example for 5 variable read. Therefore len=5), and a real variable, which will have the name for the information read (inf, for example. Therefore, inf(len) ). After this, you define the READ statement to read the information (use the same unit used for the OPEN statement).
The last step is to associate the information with the STATEV as
STATEV(1) = inf(1)...
STATEV(5) = inf(5)
Thus, you can use the STATEVS defined as you want.
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Is there any way to model a viscoelastic material in Abaqus using the results from tensile and relaxation tests of dog-bone shaped samples of adhesives?
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viscoelastic behaviour can be introduced from an experimental measurement "creep test data" or "relaxation test data". You can do it in the property module under viscoelastic behaviour. From a tensile test data I am not sure than you can used it directly in the software.
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I am modeling a truss structure, in which elements have different temperatures. I don't want to use thermal analysis, because there are no heat flows or thermal changes. The analysis is static and the effect of temperature is just initial strain.
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Mr. Nickpour,
I think this should be possible without doing a thermal analysis. Specify the temperature for each truss member as a "predefined condition" in the "step" category for your "initial" step. Choose "temperature" and select all elements in each truss one by one and set the temperature in them.
In material properties input your the coefficient of contraction and the reference temperature. Your reference temperature should that of the condition from which all trusses have changed, thus it is the initial temperature in calculating thermal strains for all members.
Now you should be able to simply run a general static or any other type of structural analysis with ABAQUS. The thermal strains will be calculated and implemented by ABAQUS in your analysis.
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I'm trying to carry out a seismic analysis for 2D frame, I tried to define a new step with new boundary conditions "release the U1", which is the direction of the input "X" direction, and deactivate the initial boundary conditions in this new step, but the drift is not logical.
Can anyone help me - what is the best way to improve my simulation?
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By Seismic Analysis, you mean Time History Analysis using a seismic record?
If this is what your looking for, you can do this by proceeding as follows (I assume your frame was correctly modeled):
1) place boundary conditions, as usual, with exception for the horizontal direction. Let it be freed or place a spring to simulate soil stiffness. If you consider that there is no differential displacement between column bases (classic scenario), use a constraint>coupling to make them "keep formation" during analysis. Use one of the column bases as control point;
EDIT: Don't forget to add mass and gravity loading!!
2) Assuming the classic scenario, apply an acceleration/velocity/displacement to the control point. The acceleration/velocity/displacement history (over time) is inputted through the Amplitude parameter (do not use Ramp!!). Consider tabular data and place your history in it.
3) Modify your step time to match you time history max time. Consider the min increment equal to the maximum interval in you time history data.
Ex: if you consider (not an earthquake record)
time | acceleration
0 .00 | 0.0
0.05 | 0.1
0.07 | 0.5
0.11 | 0.3
0.50 | 0.1
1.00 | 0.0
the step time is equal to 1 and max step is 0.07-0.05 = 0.02. This will prevent analysis to skip peaks.
4) Run job!
5) Get base shear from control point, if you want to assess base shear.
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I am a new Abaqus user. I tried to make a simple model of asperity flattening by imposing a downward displacement into an analytically rigid die compressing an Aluminum 3 asperity. I used Abaqus standard, pairwise contact with Hard normal behavior and friction less tangential behavior, and 2d symmetrical model.
I expect to have the maximum PEEQ and Mises stress on top layer ( based on hertz contact theory) but it is observed in under layer elements. Actually maximum PEEQ starts from contact area but gradually it goes down to the underlays. Also maximum Mises stress is a little bit lower than contact surface.
I tried surface- to-surface and node to surface discretization method, different contact constraint enforcement methods (Direct, Penalty, Augmented Lagrange), different elements (CPE4R, CPE3) also higher order elements with reduced integration points. but I still have the same problem. I have attached some pictures of initial model, Smises and PEEQ contours. Do you have any idea what's wrong?
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Actually , I believe it is a contact stress problem. See Hertz contact theory etc.. So its not wrong , its as how as it should be. Try a theoretical calculation of the critical depth and compare it with FEM.
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Some papers focus on the FEA of 2D cellular structures (in Abaqus). It seems that the yield surface can be obtained by applying biaxial loading to a specific 2D cellular structure (honeycomb). But how should the yield surface be plotted?
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To do this, you may try:
1) plotting the contour of elastic energy (if your material is elastic);
2) define your "yielding" point via individual stress-strain curve for given loading path.
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I am trying to implement the Yoshida-Uemori kinematic hardening model in Abaqus. Unfortunately, I cannot figure out how to handle the the non-isotropic hardening surface in the stress-integration. Does anybody know where I could find an algorithm for the integration of this model?
Ghaei and Green have written articles on the explicit and implicit integration of this model, but the papers are not very clear about the non-IH surface.
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See some of may papers
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In FEM, when shell elements are used, the stresses we obtain do not include peak stresses. But while calculating fatigue damage, we need to include peak stress too. How do we account for it?
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In solid elements, linearization is done across the thickness to get the membrane stress (avg stress, wch is a horizontal line), bending stress (linear), and peak stress (the left over in the curve). But shell elements give the stresses only at the mid surface . Stresses are assumed to be linear through the thickness. Thus the peak stresses are neglected when shell elements are used. But total stress = membrane stress + bending stress + peak stress + secondary stresses(due to thermal...).
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Could anybody compare shell element and solid element, with as many points as possible. Shell elements need low computational time. Is it that if we have high speed computer, it is better to go with solid elements? What are the other advantages of shell element?
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The main disadvantages of solid element in FEM with linear approximations for bending type problems is
LOCKING - phenomenon during bending -- the solid element will show the bending behavior much stiffer in comparison with analytical solution.
LOCKING is higher if the solid element looks like shell (thickness is smaller than two other sizes).
It can be resolved for solid element only by taking many elements for the thickness, therefore, leading to many FE's.
In order to eliminate the locking problems the Solid-Shell FE is introduced, in which
EAS or ANS methods to remove locking are implemented is presented even for FE with quadratic shape functions, because the locking phenomena can be found also for FE quadratic shape functions.
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Working with hyper-elastic materials in Abaqus/ CAE, I would like to convert the following:
Logarithmic (true) strain tensor (shear strain components of tensor)
TO
Engineering (nominal) strain tensor (shear strain components of tensor)
Does anybody have any freeware program, matlab code, formulas or a method that can be shared so I can achieve the task above?
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The log strain output is log(V), you can get V and compute the principal strains from the principal component of V (strain = V-I). You'll get a kind of engineering strains but expressed wrt the final configuration (Engineering strains are U-I and not V-I, i.e. in 1D you'll get the change of length over the final length not the initial one.
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The purpose of doing this work is to transfer the results of structural analysis of ABAQUS software to MATLAB software.
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This may help you. I haven't tested it yet.
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I want to create an UMAT for the analysis of damage and failure in FRC
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Hi! If you are new to writing subroutines for ABAQUS I recomend starting reading this ---> http://imechanica.org/files/Writing%20User%20Subroutines%20with%20ABAQUS.pdf
I found it to be very useful. At least, to begin reproducing the more simple UMATS that exemplified there and then moving on to more complex ones.
To write the codes I use VIsual Studio 2005 coupled with the Intel Visual Fortran Compiler 10.1. ABAQUS then runs the subroutine if you specify it in the "job" module.
Good luck!
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I have an .stl file that I want to analyse with Abaqus software. I know that I can import a stl file to Abaqus but I want to change its mesh size and kind. I then need to import it as a solid file.
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Did you tried to import it in some CAD software (Inventor, Catia) and then save it as a stp or igs file that you can import in abaqus and mesh the way you want ?
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I would like to receive some advice about creating a partition and then meshing a part in the proper way. I made a hexagonal 3D elastic solid with curved corners. I tried to use partition cell extrude cell/sweep edge in the the curved edge, but the solid it has not been partitioned yet. I attached the part image.
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If this is a 3D solid then it would be coloured. As it is it looks like a shell model. Check to make sure you have made a solid. If it is a solid then it should be a swept region and coloured solid yellow, or green to show it is a structured region. I would partition each of the radii from the centre point to the tangent point, and then partition the remaining region by drawing lines from each of the centres you have just created. You should have a hexagonal region left with sharp edges. which could be partitioned into triangular regions. Extrude all the lines created to partition the solid. These should be coloured green, but a better option maybe to leave it as swept regions
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I've been trying to get a multi-surface plasticity model running, without finally succeeding.
I am coding the algorithm Simo & Hughes give in "Computational Inelasticity" in Box 5.2a-c into an Abaqus-umat written in fortran. I apply it for perfect plasticity (at the moment), therefore it is simplified from the original.
Unfortunately, my code does not provide proper results even in a quite simple example (two surfaces only) that can be more or less followed.
Nevertheless, the algorithm does work if only one surface is active. These results are verified by a single-surface model. I assume therefore, that the algorithm is OK in principle, only the combinatorial terms are somehow not working properly. I have also rewritten the code in mathematica which yields the very same results - wrong ones in case of multiple active surfaces.
Questions to the community are:
- Is the algorithm given in Simo & Hughes working at all?
- Has someone experienced some troubles with this as well? Were there any minor/major/obvious/hidden misinterpretations or errors in understanding the procedure? Any hints what one can make wrong?
- Does anyone know of a similarly well-documented algorithm for multi-surface plasticity?
- Any other information that may be helpful?
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@Eligiusz and @ Matthew: Thanks for your answers! I didn't know about these things.
But I think you are talking about a different form of multi-surface plasticity. In "your" models, only one surface is active at a time but there may be the option that another "larger" surface becomes active at higher loading due to hardening of the material. And there is a smooth transition between the surfaces. Please correct me, if I did get that wrong.
Have a look on the paper @Stefan proposed, Figs. 3-6 show non-smooth corners which I meant with multi-surface plasticity models ( http://link.springer.com/article/10.1007%2Fs00107-006-0102-3 )
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I need to determine the element characteristic length L in Abaqus to identify the plastic displacement for ductile damage evolution. I know that characteristic length is roughly element diagonal dimensions but the problem is that my elements are around a typical cylindrical dog bone specimen. Is there any way to get the length using a specific tool or do I just need to approximate it with element dimensions?
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Hello,
Below are my suggestions:
1. Is there any specific reason for the using 3-D model ? . why not use Axis-symmetic 2-D model using shell elements
2. Rather than measuring any specific element(s) , why not create a node set and then history output its displacment.
Cheers,
Prasanna
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I am modeling a multi-layer bar. I have experimentally obtained storage/loss moduli data for individual layers,which I am giving as input in Abaqus. I want to get the viscoelastic behaviour of the whole bar as output.
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Gayathri,
ABAQUS will not provide the storage/loss modulus as output. You will need to calculate this output similar to how the DMA calculates the modulus. Depending on whether your test is in shear or uniaxial, you should use the reaction force (or moment/torque) output on your reaction surface along with the bulk deflection or deflection angle on the reaction surface to calculate the modulus based on the same equations the DMA uses.
I can try to be a bit more specific if you give some more information about your DMA and model test geometry and setup.
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I am trying to run the FEM simulations of an Si anode material used in a lithium ion battery. I am able to impose the equivalent thermal stress on the material. However, I wonder how to specify the charging rate (fast/slow insertion of lithium ions into Si) of the anode in the lithium ion battery while doing FEM simulations using ABAQUS?
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There is a vertical bar of height H, and we have varying temperature profile along the height, The curve is quite zig-zag. I have divided the curve into many parts and got the equation fitting each part. Then I have used the analytical field option to give the equation for each part. But as each equation is approximated, there is discontinuity at the point joining the two parts. (The temperature at that point should be the same, but as there are 2 different equations at that point, dr is discontinuity). Could anyone suggest how to solve this problem (other than writing a program)?
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You can use the coupled temperature-displacement step (pay attention for the type of elements), than define a fixed temperature as the boundary condition only at extremum points of your zig-zag temperature profile. Temperature will be almost linearly interpolated between defined points and in that way you will get full zig-zag temperature field. Because of coupling, temperatures became automatically the load for structural analysis. Sometimes a lot of memory is needed.
Analysis can be decoupled as well (second solution) into two steps:
1. Pure thermal analysis with the boundary conditions as described above.
2. Output from thermal analysis (full temperature field taken from existing odb file) applied as prescribed thermal boundary conditions for pure structural analysis.
In that way thermal step is calculated only once and used for multiple structural calculations. In your case it's probably better.
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I'm doing a simple linear elastic analysis of concrete beam.
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From the main menu go to either pre-processor or solution, then select define loads> Apply> Structural > inertia > gravity > global (to add the self weight of the overall structure) > then if your gravity (vertical) direction is in the +ve direction of Y-axis, then type in (ACCEL Y) box the value (+1). (+1) makes the gravity load down ward ( in the direction -Y)
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Can anyone help me to make the user subroutine UMATHT used in ABAQUS simulation for lithiation process in lithium ion battery (LIB)? I am working on anode part of LIB and need to run an FEM simulation. However, I am not aware of the programming part of this subroutine. I would really appreciate comments from people who know about it.
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It is thermo-mechanical analysis. Because, thermal strain can be taken as analogy to strain in structure after lithiation. Do you need more details ? I can send you some references.
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I have DMA data and I need a prony series coefficent in order to do viscoelastin modelling in ABAQUS.
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You can do this using Excel by defining the Prony series equation based on some initial constant trial values and using it to predict the modulus based on frequency or time (which ever you used in your DMA test). Sum the squared error between the experimental and trial Prony series calculations and minimize using the "Solver" function in Excel by allowing Solver to vary the parameters to achieve the closest agreement with experimental results.
I must caution you that fitting Prony series is very much dependent on your initial trial values and you could achieve multiple "fit"s for the same data. Thus some understanding of the meaning and physical interpretation of the parameters is needed in order input realistic initial values.
How can I make torsion on a tube in Abaqus?
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Torsion Load - Abaqus
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Create a reference point at the center of the tube and then constrain the cross section (surface) with the reference point. In loads, apart from the forces there are also moments. The moment along the tube axis will generate torque in the tube. Say if the tube axis is along Z-axis, then Mzz will cause the torque.