# Mohr–Coulomb Abaqus Material
**URL:** https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194
**Category:** Feature Requests
**Created:** [May 19, 2022, 9:16am UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194 "2022-05-19T09:16:24Z")
**Posts on this page:** 15
**Page:** 2
### Author:  [@synt](https://prepomax.discourse.group/u/synt)
#### Post date: [February 23, 2024, 10:21am UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/21 "2024-02-23T10:21:03Z")
> [@ANYS](#):
>
> What is not working normally?
please follow the discussion, at least taken simple test individually.
> [@synt](#):
>
> The keyword card is readable but treated as elastic, required to investigate further.
> [@ANYS](#):
>
> Is yours an old sintax?
also, it’s not about syntax only, the old and new.
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### Author:  [@ANYS](https://prepomax.discourse.group/u/ANYS)
#### Post date: [February 23, 2024, 10:39am UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/22 "2024-02-23T10:39:01Z")
> [@synt](#):
>
> also, it’s not about syntax only, the old and new.
Sorry synt it’s sometimes hard to me to understanding. I’m following the discussion and I have some of the concepts still fresh. I’m interested because I didn’t enter into the hardening aspect of the model. I have done many individual tests. I simply don’t understand how could you expect the model to deliver plasticity if in the inp you show there seems to be no Hardening definition?
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### Author:  [@synt](https://prepomax.discourse.group/u/synt)
#### Post date: [February 23, 2024, 11:01am UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/23 "2024-02-23T11:01:57Z")
are you sure for Modified MC material model in latest version of CalculiX?
> [@ANYS](#):
>
> I have done many individual tests.
commonly a user material have different output parameter, like plastic strain or damage index. However, Modified MC models is not documented regarding this request.
> [@ANYS](#):
>
> I simply don’t understand how could you expect the model to deliver plasticity if in the inp you show there seems to be no Hardening definition?
it can lead to a bit confuse when mixed between Standard MC and Modified MC material models.
well the output of previous version (v2.15) given clear in stress and strain plasticity, but not available for PEEQ request.
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### Author:  [@ANYS](https://prepomax.discourse.group/u/ANYS)
#### Post date: [February 23, 2024, 11:53am UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/24 "2024-02-23T11:53:05Z")
No issues with plastic flow. If you have defined the Hardening correctly and you are looking at the right output most probably you have not reach the Yield surface yet.
I would take simple test individually with this parameters.
\*MATERIAL,NAME=MOHR-MB-30
\*ELASTIC
31000000000, 0.111
\*MOHR COULOMB
36.0,36.0
\*MOHR COULOMB HARDENING
3.0E6,0.0
3.1E6,0.01
3.2E6,0.02
3.3E6,0.03
3.4E6,0.04
3.5E6,0.05
3.6E6,0.06
\*SOLID SECTION,ELSET=Mohr,material=MOHR-MB-30
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### Author:  [@ANYS](https://prepomax.discourse.group/u/ANYS)
#### Post date: [February 23, 2024, 12:00pm UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/25 "2024-02-23T12:00:29Z")
I think I see what you both might be doing wrong. You are probably looking at Principal Stresses individually instead of elaborating the Cohesion value.
Try to apply formula to see if you should be yielding or not.
Refer to ccx manual 6.8.11 Mohr-Coulomb plasticity. in case of any doubt.
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### Author:  [@synt](https://prepomax.discourse.group/u/synt)
#### Post date: [February 23, 2024, 12:13pm UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/26 "2024-02-23T12:13:47Z")
again, you do mixed between Standard MC and Modified MC, here we are discussed for later ones.
> [@Damn](#):
>
> I have tried the model with the syntax for the modified Mohr-Coulomb material
my previous screenshot is only an example ones related to strain history (i…e worst principal), as shown by 8/31 in CGX
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### Author:  [@ANYS](https://prepomax.discourse.group/u/ANYS)
#### Post date: [February 23, 2024, 12:22pm UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/27 "2024-02-23T12:22:22Z")
> [@synt](#):
>
> here we are discussed for later on
I must have had too much coffee this morning.
> [@synt](#):
>
> my previous screenshot is only an example ones related to strain history (i…e worst principal), as shown by 8/31 in CGX
Yep, that’s why I thought posting the formula could be usefull.
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### Author:  [@Damn](https://prepomax.discourse.group/u/Damn)
#### Post date: [February 23, 2024, 12:23pm UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/28 "2024-02-23T12:23:29Z")
Good morning,
My masonry model should operate within the elastic range, with a maximum compression stress of -2.00 MPa [analytically calculated] and tensile stresses close to 0.00; that would be expected. The stress results with the traditional MC model fit within that range without any issues.
I have been gradually increasing the plasticity values to possibly exaggerated levels to force the monitoring of plastic deformations and verify the functionality of the Modified MC. However, since I haven’t observed any plastic deformation, I have questioned my model.
I have tried using the plasticity values you suggested, and unless I made an error, no type of plastic deformation is being monitored:
However, with the traditional MC material, I do get plastic deformations. Another point for discussion is whether they may be more or less coherent, but apparently, it may seem reasonable:
Using the syntax of the traditional MC material, I obtain results that, in my opinion, are more coherent. I would need to refine the mesh and analyze mesh convergence, but as an initial model, it could suffice, and unless you advise otherwise, I will continue using the traditional MC.
Thank you very much for your help and expertise.
Damián
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### Author:  [@synt](https://prepomax.discourse.group/u/synt)
#### Post date: [February 23, 2024, 12:37pm UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/29 "2024-02-23T12:37:11Z")
> [@Damn](#):
>
> However, with the traditional MC material, I do get plastic deformations. Another point for discussion is whether they may be more or less coherent, but apparently, it may seem reasonable:
that’s why i mention in early correction. Standard MC have no problem, but Modified MC has. The problem for Modified MC model is treated as elastic in latest CalculiX distribution (v2.21 and v2.20), this is not normally as i have frequently done in previous versions (v2.15).
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### Author:  [@synt](https://prepomax.discourse.group/u/synt)
#### Post date: [February 23, 2024, 12:40pm UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/30 "2024-02-23T12:40:59Z")
that’s okay, i’m having a bit confused also due to problem in solver itself of CalculiX latest distribution.
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### Author:  [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)
#### Post date: [February 23, 2024, 12:44pm UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/31 "2024-02-23T12:44:56Z")
Then, even though there’s a new MC model with its own keywords, it might be worth reporting on GitHub since the old model is still available and thus should work properly.
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### Author:  [@synt](https://prepomax.discourse.group/u/synt)
#### Post date: [February 23, 2024, 12:57pm UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/32 "2024-02-23T12:57:29Z")
right, normally it should be working expected as previous distribution, hopefully it can be fixed for next versions.
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### Author:  [@ANYS](https://prepomax.discourse.group/u/ANYS)
#### Post date: [February 23, 2024, 1:49pm UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/33 "2024-02-23T13:49:50Z")
I’m looking at this plasticity controversy but meanwhile I noticed there are some areas on your model that are disconnected and mess the convergence.
Not sure if that is an error when exporting.
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### Author:  [@Damn](https://prepomax.discourse.group/u/Damn)
#### Post date: [February 23, 2024, 10:33pm UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/34 "2024-02-23T22:33:57Z")
Perhaps that’s the reason why the plastic deformations aren’t symmetric, when in principle, some symmetry is expected. The initial idea is to use a HARD contact between the inner arch and the vault since they are not connected.
Ultimately, I’ve modeled it as a composite solid since I couldn’t achieve convergence; that’s likely the explanation. I greatly appreciate your input. I’ll review the model to see how I can address the issue.
Thank you very much for your help and expertise.
Damián
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### Author:  [@synt](https://prepomax.discourse.group/u/synt)
#### Post date: [March 22, 2026, 4:48am UTC](https://prepomax.discourse.group/t/mohr-coulomb-abaqus-material/194/35 "2026-03-22T04:48:20Z")
since it’s in feature request and the material already supported by CalculiX solver, i would like to be proposed available in menus. Maybe, a model plasticity names need to change to Nonlinear to be general, and several type i.e Plasticity, Mohr-Coulomb and Compression-Only, etc will provides there. Thank you
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