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Constitutive Modelling - Science topic
Explore the latest questions and answers in Constitutive Modelling, and find Constitutive Modelling experts.
Questions related to Constitutive Modelling
There are many constitutive models to describe the mechanical behavior of a material . Concrete is a composite material.
Of course not. Any first semester student of continuum mechanics learns the tools to prove that it is not even Galilean invariant. Yet, I have found myself stuck in an absurd 7-year-long debate with a person who insists that grad (rho*v) is an objective tensor. Normally, I would leave this person to his own willful ignorance--however, he is a professor who, without bothering to carry out the Euclidean transformation, has managed through rhetoric alone to convince others, including at least one journal editor, that this is the case. I guess I just wonder if anyone else finds this as depressing as I do?
Dear Researchers and Faculty,
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VUMAT subroutine which describes cyclic constitutive model of steel bars which tell us the ultimate strain bars using FORTRAN language for ABAQUS user defined material.
Hello all,
I am learning to write an ABAQUS VUMAT subroutine for Deshpande Evans (DE)/ Preston-Tonks-Wallace Material (PTW)constitutive model. I didn't write a subroutine before. I would appreciate any guidance toward the development of a subroutine. If anyone can share a VUMAT subroutine for DE/PTW model it would be of great help!
Thank you!
Best Regards,
Arif
Where can I find the stress-strain relation in terms of Young's modulus, Poission's ratio, and components of contravariant metric tensor?
Hello,
I am using the JH-2 model, which is a VUMAT constitutive model embedded in the Abaqus/explicit program. I would like to directly check how this VUMAT file is written, and if possible, I would like to modify it. Could you please tell me where I can find this VUMAT file?
Thank you.
How to formulate a constitutive model for the elastic-plastic behavior of thermoset polymer at elevated temeperature? Are there any reaonable method (have physical meaning) which are widely accepted?
Dear all,
I am currently dealing with a problem of spurious oscillations in wave propagation in elastoplastic bodies.
The problem in question is a 1D column subjected to a 10Hz sine wave acceleration input motion at the bottom of the mesh. Abaqus/Standard is used for the dynamic analysis.
Generally, the stress strain behavior looks fine, the same with displacements and velocities. The oscillations are most pronouncedly experienced in the calculated accelerations. They appear in time when the element/Gauss point is subjected to a sharp change in stiffness, e.g. from elastic branch into plastic one when no smooth hyperbolic relationship is used. The oscillations are of much higher frequency than the input motion [say around 100Hz].
I am wondering where these oscillations come from. I have tried to include numerical damping in the HHT direct time integration scheme however this did not influence the observed oscillations. I am wondering if further “play” with alpha, beta, gamma parameters in the HHT method could result in damping out the oscillation I experience. So far I have only used set of parameters as suggested in Abaqus Manual for “application=moderate dissipation” option.
I have also tried the effects of time and space discretization, non of the two was effective [for space discretization going for much finer solution than the minimum of 10 nodes per wave length as typically advised]. The problem remains and is insensitive to mesh or time step refinement. The only way of removing the oscillations is applying the Rayleigh damping, however this seems to be artificial way of removing the problem since the constitutive model is elastoplastic and deemed to be capable of accounting for material damping.
Generally, Abaqus manual says “The principal advantage of these operators is that they are unconditionally stable for linear systems; there is no mathematical limit on the size of the time increment that can be used to integrate a linear system” so I understand that maybe this scheme is not stable or inaccurate for the nonlinear dynamic problems or a family of nonlinear dynamic problems. Would some another commonly used direct time integration scheme, such as lets say Bathe be more accurate here?
Anyone has experienced maybe a similar problem? Where is it I can look for the reason of the oscillations?
Thanks in advance for any help and advice on that.
I want to input a user defined model in Plaxis. I know that a .dll file has to be created in order to do so. However I need help in creating the .dll file.
BACKGROUNDS: As we all known, the capture of the failure and post-failure in simulation of timber structures is very important. Timber structures deveops fast up to now, simulation methods have been play ing critical roles in understanding the failure mechanics and structural behavior. With the success of simulation, i.e. getting reasonable simulation results, one can proceed the subsequent works, such as design, assessment, and strengthening, etc.
FIELDS : CLT, GLT, Ttaditional timber structures, wood-based structures, furniture structures, etc.
especially some elements needed fined simulation to reflect the whole failure process.
PROPOSE: every one can actively say anything here, from ideas to some discussions, dont just limited to the answer of my questin.
Hi everyone:
I'm confused that if the CPFEM can be used to design materials. As for most studies, the experiments are done before the simulation because some parameters of the constitutive model or hardening model are needed to be calibrated. Now, I'm trying to use the parameters from others' papers to design materials, can this be done? Looking forward to your answers.Thanks a lot.
I tried to model a machine foundation from an available literature. I applied all the properties, constitutive model, boundary conditions and modelling procedure as per the given literature but I didn't get the proper displacement as given in the literature. Rather I got hardly one tenth to one fifteenth of it. Has anyone the same problem.? Can anyone help me with this.?
According to my actual needs, I modified the "plastic_dislotwin.f90" in the SRC folder of damask_ However, after running, I found that the program runs the unmodified constitutive model by default. How can I add my own constitutive model to this software? What program content do I need to modify? I didn't find a detailed introduction on the Internet. If anyone knows about this, I hope to get your guidance
I am trying to reproduce a TX test on a sand by using a FE 1-element, axisymmetric geometry ABAQUS model, assigned to a SANISAND material. For this purpose, I am using a umat subroutine that is made available at soilmodels.com (https://soilmodels.com/download/plaxis-umat-sanisand/)
In my ABAQUS model, I have set a material with 36 state variables and 19 parameters, as suggested by the developers of the subroutine. The only additional feature of the material is the density, set = 1 (ton/m^3). The adopted element type is axisymmetric stress, hybrid formulation (CAX4H). A confinement load of 100 (kPa) is applied to the two boundaries of the soil element along a "confinement" and a "shear" static steps of analysis. During the "shear" step, I applied a vertical (axial) displacement of the upper boundary of the sample, producing a deviatoric stress.
I properly linked the subroutine to the job in the "General" option of the job menu.
When I run the job, an error occurs before the analysis is run reporting "Abaqus/Standard Analysis exited with an error - Please see the message file for possible error messages if the file exists."
Hi everyone,
A constitutive model taking the effect of grain size, dislocation interaction (thermal glide and climb mechanism), second phase strengthening, and temperature are good to study materials' mechanical properties and creep behaviors at different temperatures. There are many such models considering one or more factors proposed. The paper (https://link.springer.com/content/pdf/10.1007/s11661-017-4011-3.pdf) is a very great study. Could anyone help me with how to introduce and implement this crystal plasticity model for polycrystal structure in one kind of simulation software?
Specific constitutive model for soils, (Simpson is the key name). I will be very grateful for any help.
Dear Colleagues,
We are working on new non-linear constitutive model for metals. I have implemented it in ABAQUS in frame of UMAT procedure for 3D elements. It works fine. The problem is that we would like to use also shell elements for analysis of thin walled structures. I don't know what should be included in UMAT in case of shell elements (elements S4, S3). I assume that plane components like in case of plain stress case, but what else? I would be glad for precise information regarding that matter and maybe some exemplary UMAT procedure for shell elements (simpler constitutive model the better). The simplest constitutive model is isotropic linear Hooke's relationship - how the UMAT for shells looks like than?
Dear all,
I would like to know if anyone can help me on how to Calculate Phan-Thien-Tanner (PTT) constitutive model parameters from rheology experimental data. I need those parameter for an ANSYS polyflow simulation of die swell. I have experimental viscosity curve for PLA at 200C.
Thanks
Is there any command to extract plastic strain values (Volmetric and Deviatoric) in FLAC 2D for Mohr-Coulomb constitutive model.
Hello everybody,
I was wondering to ask you to share with me the works that used AI/machine learning for determining the parameters of a constitutive model. Thanks.
regards,
Faezeh
I use the contour integral method in ABAQUS to calculate the J-integral of CT specimen(2D). The constitutive model is Ramberg-Osgood model, which is the deformation plasticity in ABAQUS. When the Nlgoem is Off, the J-integral is correct. However, the mesh deformation in the crack tip region is very large. When the Nlgoem is On, the analysis will terminate because of too many attempts made for this increment.
I will be appreciate that if you can help me to solve this problem.
PS:
The CT model, the the mesh deformation in the crack tip region, and the results of J-integral are shown below.
I use the contour integral method in ABAQUS to calculate the J-integral of CT specimen(2D). The material is elastic-plastic, and the constitutive model is established by using incremental plasticity. Considering geometric nonlinearity, Nlgoem is On in the Step Module.The results indicate that the J-integral is relatied to the path, and some J-integral values are negative.
I don't know how to solve this problem. I will be appreciate that if you can help me.
PS:
The CT model, the shape of blunted crack, and the results of J-integtal are shown below.
Including the so-called kinematic hardening in phenomenological material models allows capturing the accumulation of plastic deformation in materials subjected to cyclic loadings. It determines that the size of the "elastic domain" in the deviatoric stress space remains constant and that upon plastic yielding, the domain is simply translated.
In largely deformed materials in tension, the kinematic hardening may result in a translation of the elastic domain to levels where the initial compression yield-limit becomes now a tensile stress value. This implies that upon unloading a plastically-deformed material (returning to zero loads), it may experience plastic deformation as well. My question is, is that physically possible? If yes, how can it be explained?
The figure provided is the force/width vs strain measured for a piece of fabric in uniaxial stress configuration (the thickness is unimportant but you can assume what you like e.g. 1mm).
The sample is stretched up to max 0.1 strain with constant rate (0.1/s) and then released at the same rate of deformation until the load frame cross-head is at the original location (associated with initial length of the sample). It will then get reloaded repeatedly to maximum 50 cycles. The data is shown at specific cycles (not all). As the sample is deformed its behavior changes.
1- I am looking for suitable constitutive models that may or may not be the right choice for the following data in the attached picture.
2- I am also looking to find if there are any material subroutines available in FE codes that are compatible with this response and/or an specific constitutive model.
I have done some literature search but I have not get to a desirable result as I am new to this field. Introducing any paper or document on this topic can help me to start my studies from an optimum point and save time.
Please share any Example, Tutorial or any article related to CDPM. For a 3D Pushover analysis.
Thanking in anticipation!
Greetings to everyone,
Our team is currently working on the development of a VUMAT code in Abaqus for composite modelling using the Puck's failure theory as damage initiation criteria. Currently we manage to develop 6 different algorithms (4 on literature and 2 of our own) to find the fracture angle of any state of stress in an accurrate and efficient manner.
My question is related to the post damage behavior. Let's assume that a material point reach the Puck's failure initiation condition for an angle of -58° in matrix compression. It is clear that the material can resist further load in matrix tension and we need to degrade the stiffness matrix and so on. However, for this post damage stresses the fracture angle needs to be set to -58° or do we need to still look for the fracture angle? It is also known that the most critical angle depends on the state of stress and if we set constant from that point on are we understimating the damage?
If you need further instructions or the question is not clear enough please let me know. I'll be glad to share more details in case they are required.
Thanks in advance for your aid and support
I would like to use CDM (continuum damage mechanics) for modeling damage in my constitutive model and I need to incorporate a variable (or its effects) into my mechanical damage that doesn't evolve or change by time but changes by other factors (such as irradiation dose or etc..). Does anyone know of a paper which had been used the similar approach? I would really appreciate it if you can provide the link for me because I couldn't find any so far.
Regards,
Faezeh
I am new to AUTODYN and have used a little bit of ANSYS workbench. I have been looking at implementing a visco-hyperelastic constitutive model in AUTODYN. However, I could not find any way to do this. None the user subroutines that ANSYS/AUTODYN allows us to incorporate does contain a feature of implementing a user-defined hyperelastic or visco-hyperelastic material model.
Our objective is to model the high strain rate response of polyurea using AUTODYN.
If someone can throw some light on this topic, it would be helpful for my research.
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Has anyone used Norsand constitutive model in FLAC2D for Embankments? I would like to discuss.
Hey,
Please share your work on UMAT and resources (except popular imechanica tutorial).
Thanks.
Hello, all.
I was wondering if there are any attempts of creating artificial soil, so that can be used as a benchmark for different custom tests and constitutive models. Especially interested if cohesive soils can be created (I imagine that cohesionless soils are fairly easy to create ).
Thanks.
Dear all,
I am trying to model soil-monopile interaction (3D) in ABAQUS/Standard in order to perform subsequently a cyclic and dynamic analysis.
For the soil I am using the SANISAND umat constitutive model and for the parameters I am using those given by Dafalias and Manzari (2004) for Toyoura sand.
For the soil-monopile contact I am using the surface to surface contact pair formulation with small sliding that is found in ABAQUS/Standard.
In ABAQUS I am performing first of all a geostatic step in which the monopile and the (soil-monopile) contact pair are desactivated by using the the “*Model change , Remove” for the monopile and the “*Model change Type = CONTACT PAIR, remove” for the interaction.
Simultaneously , in the same step I am activating a soil part (having the same geometry as the monopile) having the same SANISAND material properties as the whole soil domain to replace the monopile.
A predefined initial geostatic stress field and an inital uniform void ratio field (= Parameter 19) are applied to the soil. The weight of the soil is also applied in this step in order to have equilibrium with the initial predefined stresses.
The geostatic step finishes succesfully in a short time and at the end of this step I am obtaining relatively a very small displacements thus verifying its succesful implimentation.
The next step (Step 2), is a static general step in which the weight of the monopile is applied. In this step, the monopile and the soil-monopile interaction are reactivated using “*Model change, add” for the monopile and “*Model change, Type = CONTACT PAIR, add” for the interaction. Also, the soil part which has been added previously in the geostatic step to replace the monopile is removed in this step by using the “*Model change, remove”.
Unfortunatly, STEP 2 is giving me errors upon the second increment.
The error is an Overconstraint checks. meaning that there are multiple constraint that are applied directly or chained constraints that are applied indirectly at various nodes of the soil.
By asking ABAQUS to print the constraints in the message file, I was able to identify that these overconstraints are from one side due to the tie of the soil nodes with the removed soil nodes, and from the other side due to the tie of the soil nodes with those of the monopile.
It should be noted that the soil part that has been added in geostatic step and then removed in the static step is removed by using the Model change, remove.
I tried to check very well the different interactions, to verify that the problem is not a modelling problem. I am sure that is not like that.
It should be noted that the analysis run successfuly shen using the Mohr-Coulomb constitutive model founf in ABAQUS.
Does anyone have any idea, or have encountered the same problem when dealing with the SANISAND umat ?
Any idea how the SANISAND umat is dealing with the model remove or add ? {because in ABAQUS documentation it is stated that elements with a user-defined material type can be removed and reactivated}
Can the problem be at the level of the input parameters for the SANISAND model ?
or Maybe at the level of the type of interaction ?
Thank you all in advance
Best regards,
Philip
Dear researchers
I hope that you are having good and healthy days
I am modeling a direct shear test using FLAC3D V6, the model actually works properly when it assigned to the elastic model, however, the same model does not reach the equilibrium if it switched into Mohr-Coulomb model to model pure sand (without cohesion c=0)
Have anyone of you guys faced the same problem?
Best,
Omar
I am unsuccessfully trying to introduce residual stresses in a hyperelastic anisotropic material characterized by the well-known HGO constitutive model via predefined fields. Any other idea?
Thank you in advance.
I have a question for those who have experience with ABAQUS/UMAT or ANSYS/USERMAT.
Let say that you have a material model to be implemented and tested. I have some questions for you to check what are your needs:
- Do you believe that the implementation and testing of a material model is an open issue?
- How much is desired to avoid FORTRAN programming?
- What are your issues when implementing your model? What are your needs?
- How valuable would it be for you to have a simple Mathematica FEM, which would enable relatively simple implementation? Not for professional use, with millions of finite elements, only for few hundreds for the development purposes.
- What is your opinion on this topic?
If willing, please share your experience.
Tnx in advance, B.
Hello,
I am trying to simulate a beam test (2D) according to EN14651 (according to the attached figure). In the middle of the beam, a 4mm downward displacement is applied in order to simulate the test with displacement control. However, I have errors when inserting the MC2010 tension constitutive model, where there is a rise to the peak of tension, and after that the softnening occurs. Other models, such as the EHE (also attached) work without problems. The size of the increment, maximums and minimums have already been left very small, and I've also tried it using the arc length method (Static Riks). The constitutive model only gives 4 points of tension and deformation, so thinking that it would solve the problem, I interpolated more points, and played 12 in total. Unsuccessful too. Nothing works and the error is always the same: it is not converging (see attached figures). Can someone help me? Please?
An image of the ABAQUS/CAE model is attached, where a rigid upturned bucket is embedded in a deform-able soil base. I am able to successfully execute a geostatic step by defining initial stress conditions, but only if the soil material is defined as elastic only. When I add Mohr-coulomb plasticity with the parameters listed below for dense sand, the job aborts with error “time increment too large.” The job does not reach a solution when I use the enhanced geostatic procedure (automatic incrementation) with default settings, either.
Please help me identify which part of the model needs to be adjusted:
Is the mohr-coulomb plasticity causing problems with the parameters I have chosen?
or
Does the mesh need to be adjusted to have smoother transitions between mesh densities? Are different element sizes causing problems?
or
Should I adjust the settings for automatic incrementation and maximum displacement tolerance?
Any advice or helpful documentation is greatly appreciated.
Input file is attached
Dense sand parameters:
Density = 835 kg/m3
Es = 60 MN/m
v = 0.3
Friction angle = 39 degrees
Dilation angle = 9 degrees
Cohesion yield stress = 0.10 KN/m2
Abs Plastic Strain = 0
I am looking for Hall-Petch Coefficient for alpha-beta titanium alloy to use in my model. Other I am also looking for relative contribution of alpha and beta volume to strengthening of alpha-beta titanium alloy.
dε/dt = Asinh[B(σ-σ0)(1-H)**m0]
dH/dt =( h/σ) (1-H/H0)dε/dt
This is a constitutive model describing creep behavior ,A,B,σ0,h,H0 are all material constants.
That's what this paper is about
I need references on research that uses the drone to study biodiversity.
Some example in studys the marine biodiversity, modelling biodiversity in micro scale or biodiversity in particular habitat
I simulated one tunnel in the soil medium, I going to study on the ground surface settelment due to excavation tunnels
Which Constitutive model of the soils (SC-GC) is better? and why?
1. Mohr coulumb (MC)
2. Soft soil
3. Softening strain (SS)
4. Hardening soil (HS)
5.Hardening soil small-stiffness (HS-SS)
6. CY-Soil
7.CH-Soil
8. Druker-prager
9. cam-clay
As for my case, my analysis problem is fall under Plane Stress/Strain but i need to utilized the DOF's of shell element ( 5 or 6 DOFs) on plane stress problem. Is it possible to use Shell instead of Plane Element without effecting the outcome. As i tried to solve one problem from both elements, but they are not giving the same results.
I am trying to implement a continuum damage mechanics based constitutive model in Abaqus using the user-defined subroutine UMAT. In that context, I am having hard time finding any available example UMAT subroutine which is modeling only damage elastic material (no plasticity).
In my model I am assuming isotropic scalar damage and single scale modeling (no multiscaling feature) framework. Once I get the updated damage for an increment or iteration, I update DDSDDE. The code works fine until peak stress, i.e. until softening happens. I am using viscous stabilization to complete the simulation. However, the overall strain vs. stress plot shows brittle pattern of failure due to localization (for all simulation having more than one element).
A snippet of my UMAT code is given below showing damage update and DDSDDE update.
I have 2 thoughts on modeling damage elastic material in Abaqus using UMAT:
- From my experience I have seen Abaqus examples related to snapping for structural geometry, but not snapping in damage elastic material. On the other hand, when I am using Riks method or Arclength method in Abaqus no localization happens. All the elements in my geometrical model fails and the strain vs. stress behavior is no longer brittle. Here is the dilemma, we are losing the physical insight to get energy consistent result. Is there any available technique for the commercial software Abaqus to handle material localization, especially when used with user subroutine UMAT ?
- The second possibility is that I am doing something wrong in my code? Do I need to get some other expression for consistent tangent stiffness matrix or DDSDDE update after damage accumulation?
Hi! Does anyone have the constitutive models of FLAC 2D Version 7 which were uploaded on the UDM Library?
Thank you.
Is it possible to deactivate the effect of water so that FLAC adds the amount of steady state PWP to the effective stresses in all zones such that all the stresses in the soil constitutive model are considered as the total stresses hereinafter?
Hi
I downloaded the code of UBCsand constitutive model from Itasca site.(note pad and 005.dll).
How do I load this code into flac software?
I have uniaxial lab results from a granite specimen which I am trying to replicate in Plaxis 2D using the soil test module. The graph looks good until the peak, then after that in Plaxis the line becomes a straight line at the peak strength, whereas in the lab the strength drops after failure.
(I am using Hoek-Brown constitutive model)
Hello Researchers!
Currently i simulated slope in dynamic analysis with steady flow seepage, the properties of the slope is soft and the earthquake is so terrifying. My groundwater table model is follow the geometry of the slope.
I have a problem with my model, as your prejudice, my model always get bad geometry in the middle of the calculation. I have read in example FLAC (earthquake in wharf model), but it is not fit with my model since the groundwater condition isn't flat.
So, do you know how to write code to rezone in dynamic analysis with steady seepage? Attached is the image of my model and my rezone code (but it still doesn't work).
Thank you
i am currently working on my thesis entitled on the numerical simulation of field vane shear test using finite element.The reason is the lab test are not accurate and digital especially the Triaxil test for simulation with different constitutive model of the soil.
Hi,
I'm self-developing explicit 3-D FEM code using GPGPU for my research regarding Penetration of projectile into rock. In the code, I'm incorporating JH-2(Johnson holmquist) constitutive model.
The question is how can I efficiently calculate effective plastic strain rate in the context of Explicit FEM like LS-DYNA and Abacus Explicit?( I don't know what kind of algorithm is implemented in the commercial software because it is black box to me.)
For this, I reviewed several literature but I cannot find the detailed description regarding how to calculate the effective plastic strain rate. For example, I found the flowchart of implementation of JH2 from Table 1 in
But the table only says "calculate effective plastic strain rate".
I did my verification simulation based on
and successfully passed the Case A. But I failed in the Case B in which evaluation of plastic strain rate is the key.
Any help would be sincerely appreciated.
Thank you in advance.
Best regards,
Daisuke Fukuda
Which model estimates behavior of soils accurately among HS, HS - cap and hybrid hyperbolic?.
Is it possible to employ the said soil model so as to investigate the seismically-induced excess pore water pressure. Note that liquefaction is not considered herein.
Hello Scholars!
I'm currently trying to model a viscoelastic material using LS Dyna and as part of it, I would like to constitutively model its behaviour using a model as shown in the attached figure.
I want to know how to represent that using a Prony Series. Any pointers to detailed tutorials/lectures are highly appreciated.
For a while our research group has been using a constitutive model, namely, Drucker-Prager/Cap implemented in Abaqus. It is a plasticity model with multiple yield surfaces. One of these surfaces is implemented with no hardening (perfect plasticity). But we have observed that for some granular materials, this behavior is not physically representative. For example, a compacted alumina specimen has hardening under uniaxial compression:
Thus, we would like to know if there are some numerical or physical meaning for the implementation of a yield surface (Drucker-Prager) with no hardening?
I am looking for some references or general comments that I can use for granular material, incorporating geologic conditions (i.e alluvium material, colluvium,or igneous, metamorphic and sedimentary lithology).
Additionally, I would like to ask for you opinion in earthdam construction what measures I need to take to avoid an excessive particle breakage under compaction and hydraulic load.
Regards
Johnatan
Hey There.
Assuming that the Mohr-Coulomb shear failure envelope as an elastic-perfectly plastic soil constitutive model is employed in FLAC3D. Referring to the dynamic section of the aforesaid software manual, the liquefaction analysis is able to be conducted throughout the Martin et al. equation. It is crystal patent that the dynamic pore-water pressure is totally different from the MC model to the other one. My question is how to interpret the changes in the total mean pressures such that the effective mean pressure in the liquefaction model is more or less the same as the one, derived from the MC soil model?
Regards,
Navid
The Mohr-Coulomb model gives a bi-linear plot of stress-strain curve. The softening behaviour, which is a highlight of cemented soils is not captured. Which is the model capable of capturing the above behaviour?
Up to now, many constitutive models were proposed for semi-solid deformation. However, some aspects of the deformation mechanisms are confusing. For example, what is the main breakdown mechanism of the solid skeleton (at relatively high solid fractions)? is it the fracture of the solid bonds or the local dilatancy (as stated experimentally with the in-situ X-ray tomography)? The former one is related to the thixotropic models (e.g. the micromechanical model proposed by Favier and Atkinson), while the latter is related to the granular models. This problem is important to analyse the deformation pattern of semi-solid materials such as the formation of segregation bands, shear banding and plastic deformation of part of solid grains.
Hi, everyone. I have a question about constitutive equation used in abaqus.
I just finish 2D a linear elastic FEA solver using Matlab. The interesting thing is that if i tried the plane stress model then my result is the same as abaqus' while if I tried the plane strain, results cannot match. I have checked the constitutive model over and over again but got nothing wrong. So can anybody have any idea what trick does abaqus use in plain strain problem? (I also used anasys to run the same model and its results can match abaqus' result).
Hi everyone.
I am coding a USDM in plx considering a linear softening.
I need to activate the non local strain available in dEps (13:20) variable. (Brinkgreve 1994)
I tried with the opt-file data.opt.rsa with the following containt:
$$NonLocal
1
$$NonLocalDL
1
$$End
and, despite that, the variable dEps (13:20) given by PLX is equal zero (no matter the internal length).
Does anyone used this non local strain? Did you have the same problem?
Thanks in advance
Problem solved. The solution is in the attached jpg.
Each line must have a carriage return (CR) and a line feed (LF) to be recognized by PLX kernel.
I want to use EPS geofoam as dynamic energy absorbent structures around piles. I want to know the most effective constitutive model and hysteresis damping parameter for it.
Dear colleagues,
I'm trying to run a model of ground improvement using rigid inclusions. To do that I have 3 different materials to model: rigid inclusions, compressible soil and a load transfer platform (LTP) of granular material in between this two materials and the foundation.
I used a rad cylinder to create the geometry and 3 constitutive models to simulate the behavior (elastic model for the inclusions, cam clay for the compressible soil and CYSoil for the LTP).
The main problem occurs when I intall the LTP layer and I apply equilibrium under self weight, cause some gridpoints (not all of them) start derforming a lot (I add a figure that shows this behavior).
The weird thing is that the deformed GP are located inside and sometimes around the cylindrical shape. If I applied Mohr Coulomb in the LTP then I don't observe this behavior...
I changed the radcylinder by radtunnel cause I thought that maybe the cylindrical shape of the mesh and the interpolation could affect the deformation of the GPs but anyway I observe the same behavior.
I'm running out of ideas so I ask you if you know what would be the problem...
Thank you a lot
Right now I'm simulating a concrete damage model with ABAQUS/Explicit, a CDP constitutive model with compressive and tensile damage is used in the model. When conducting the Quasi static analysis in A/E, I found that most part of the concrete had become tensile damaged during the beginning steps. Is it OK if this happens? or if I've made some mistake?
Capturing of crack pattern in RC under nonlinear temperature profiles.
When I try to run stress-strain analysis of excavation in limestone rock which is described with soil hardening constitutive model the soil body seems to collapse. Same model with a Hoek-Brown constitutive model runs alright. I try to aproximate the deformation line of the shotcrete (rock support) and I think that with soil hardening model I would get better results.
And also some papers about the relationship between the macro parameters and the meso parameters, I mean the macroscopic and microscopic damage constitutive model during hydraulic fracturing. Thank you so much.
To reduce the fem model, I use the concept of symmetry and the applied constitutive model is the Mohr - Coulomb model (non - linear). According to "Concepts and applications of finite element analysis, Cook, et.al." can generate unwanted solutions. I need to justify that the model is approximate and can be considered correct despite the aforementioned.
Help please....
Note: I am aware that it is possible with C++, but I want to know whether it is possible with FISH or not.
I have a Consolidation Curve , ( e-log p ) curve , How could i get the parameters of cam-clay model
Gamma ...specific volume of the normal compression line at unit pressure
Thanks for your advice.
Regards
The best model depends on the deformation and the loading type, the question is which hyperelastic model is best to describe the behavior of these materials.
Hi all.
I am trying to code Dafalias and Manzari model in multiaxial space with mathcad. I could not complete it successfully, I wonder if somebody who knows the model well could help me with that.
Thanks in advance,
Dear Researchers,
What is the best strain energy function for the heart tissue?
Thanks,
Saeed
I need these values for modelling of Hostun Sand in Abaqus Software
I saw several papers about cohesive elements and all of them usually implement the traction separation law such as PPR-based TSL, in UEL instead of UMAT.
Is there any specific reason why people treat the cohesive element as a user element, not just treat them as a constitutive model and implement it in UMAT?
Is there any info that we need from Abaqus that is available in UEL but not in UMAT, such that it forces us to use UEL?
The reason I am asking is because when we implement it as UEL, for post processing, UEL does not show any elements in the GUI. not nice for presentation purpose in which you want to see which cohesive already fully cracked or not.
Currently, I am working on unsaturated soil mechanics applied to slope stability, I read about ICFEP (general code for geotechnical analysis with a wide range of capabilities) developed by Potts & Zdravkovic and their team.
Is anyone working with ICFEP?, I am looking for experiences using this program.
In Concrete Damaged Plasticity property in ABAQUS, we input 5 properties like Viscosity, Dilation Angle, Eccentricity, K and fb/fc. There are 2 more optional parameters - tension recovery and compression recovery.
Could someone help on the background to these values. How should we change these values for different models?
Dear all,
I am new to Abaqus, and would ask you two questions in Abaqus modeling, related to soil materials. For example a model is used to simulate the pile static testing, a two soil layer model is created by partitioning one part into two partitions in Abaqus version 6.14-2:
Firstly, the interface between the two partition will be an interface for the two soil formations, will this interface need to apply contact interaction or constraint?
Secondly, after I have applied the initial geostatic stress (gravity stress) and got initial equilibrium. there are two more standard steps in this model, loading step and unloading step. In CREATE STEP popup window, should I choose 'Static, General', or 'Geostatic'? Because I heard that all static steps in soil related model should use the 'Geostatic' step, not a 'Static, General' step.
Thank you very much,
David
I want to model a 2D FGM cylinder(Abaqus Explicit). I want to model the density, young's modulus and poission's ratio as a function of the coordinates(x,y) by VUSDFLD. I define a field in VUSDFLD as follows:
DO J = 1, nblock
X=coordMp(J,1)
Y=coordMp(J,2)
R = ((X**2)+(Y**2))**0.50
field(J,1)= R
END DO
After calculating the radius of each material points, Abaqus will obtain young's modulus and poission's ratio in each material points by interpolation in the table No.1.
For density abaqus acts in a different way. For all of the material points abaqus uses only the first row of the table No.2 (2.7e-9). How do I overcome this problem?
Please help me,
Thanks.
Im totally new to UMATs and i try to write a subroutine to degrade the Youngs Modulus in accordance to VDI 2014 for an isotropic fiber-reinforced plastic. Therefore i want to reduce the Youngs Modulus depending on a degradation-function which depends on the actual v.Mises-stress.
However i combined some code examples i have found and the code runs but it doesnt converge. I guess the problem is the updating of the Youngs Modulus, but i dont know how to fix it. So if anybody has a tip i'd be very thankful.
Hi all,
i'm coding a umat for hyper-viscoelastic behaviour and i wonder what formula use for the exact deformation gradient tensor F since dfgdr0 and dfgrd1 passed into the umat (according to Abaqus user subroutine reference manual 1.1.40) are a modified deformation gradients at the begining and the end of time increment respectively?
thanks in advance
I'm modeling CFT using ABAQUS ,and I need data for Concrete damaged plasticity and Drucker-prager
I am using the subroutine for polycrystal plasticity but I am not able to obtain right deformation texture. if anybody has already used it for the said purpose, would be delighted to seek guidance in this regard.
Dear Sir,
I am Working on project in which i need to write a matlab code to determine johnson cook parameters from Stress strain graph. Please Suggest me the methods or references I can go throgh and figure out the correct procedures. The Code which I have Written I am not Getting Correct values of the Parameters (A, B, C, n, m ).
Regards
Krati Singh
I am trying to model granular material during compaction using an extended Drucker-Prager cap model and density change is an important parameter to validate my model! I would appreciate your value response!
Kind regards!
I would like to use this constitutive model in FLAC 7.0, but this model has been formulated in FLAC 8.0. Is there any possibility?
Actually when I use this UDM (Ubcsand) in my modeling, Flac does not obtain correct amount of properties, and all properties take 0.0 value!!
Dear researches,
With FLAC 3D using mohr-coulomb constitutive model, I want to model a block of soil under earthquake loading. The soil is dense sand with these properties: Vs=300 m/s, p=2000 kg/m3, v=0.4. According to Gmax=pVs2 , we have Gmax=180 Mpa and using E=2G(1+v), we have E=504 MPa. Compare with ranges recommended in literature for young's modulus of dense sand (see the attachment), this is a very high value.
As we know, in dynamic analysis shear modulus decreases by cyclic strain amplitude increasing. My question is about initial static equilibrium. Should I use the same Gmax in initial static equilibrium? Then such a high value for young's modulus of dense sand is feasible?
I'm putting together a reading list for a course, and I'm having trouble finding a good, concise analytical overview (neither a puff piece, nor a hatchet job) on the Bolivarian constitutional model. I want to pair it with the classic Gargarella article on the three types of historical Latin American constitutions (conservative, liberal, and majoritarian/radical). I think the Bolivarian model fits in that third category (majoritarian/radical), but I'd like an article that discusses a constitution more recent than the 1800s. Thanks!
Hello
I want to model the FG Material in VUMAT. For this I need x and y components of each material point. But Abaqus gives me only one x and y per each nblock. While each nblock is composed of multiple material point.
Please help me.
Thanks,
Reza Pourshab
How to determine the recoverable deformation at the surface by the layered theory using the unloading modulus as the elastic modulus. The question is for finding the pavement rut depth prediction.
Reference: Pavement Analysis and Design by Yang H Huang (Second Edition Page 332)
Thanks in advance
Hello everyone,
I am interested in modelling silo discharge of sand by using FEM. Should I use hyper elasticity based constitutive model or hypo elasticity based ? I think, It is a valid assumption that elastic deformations during discharge are infinitesimal , therefore, hypo elasticity based constitutive model can be used. What is your opinion in this context ?
I already have the documentation of the version 904aR, but I need more information about the theory of this constitutive model. Please!
I need to know what is the suitable constitutive model for reinforced concrete in shear walls with openings in the FEM Program ABAQUS.
The shear walls are with different openings configuration and subjected to axial and lateral forces.
I need to implement vertical and horizontal (confinement) steel reinforcement.
Hi, I am reading some materials about volumetric compression testing on rubber materials. Who can explain that in volumetric compression test, why the slope of the engineering strain-stress curve equals to THREE times of bulk modulus?
- P/A0=3*K(ΔV/V0)? where, K is bulk modulus.
Thank you in advance!
I want to implement an elastic plastic creep constitutive model in a numerical code, but i'm clueless. Could you tell me what code I could work on ? And do you have some examples you could send me ?
