Tension and compresion

Hello everyone. Please forgive me because I’m just learning and this forum is full of great news. I don’t speak English and I use Google Translator, so please forgive the translation. Is it possible to model the analysis in ppm so that there is a different yield stress for tension and a different yield stress for compression? If possible, how to do it? Thank you for all the answers and help. You are cool

Do you want to model concrete or something like that ? The capabilities of CalculiX in this regard are quite limited but maybe you could use a Drucker-Prager model, for example. It’s not normally available but it’s provided as an example of a umat.f subroutine in the CalculiX User’s Manual. You can also check the discussions about the MFront library on the CalculiX forum.

Maybe, it can be started by material law with the simplest ones named Compression_Only in CalculiX. Then extended to plasticity with Modified-MC (UMat) or Drucker Prager Cap (Mfront) material laws. All of these material type have tension cut-off or limited.

Thanks for all the replies and help. The problem is that I don’t know calculix. I thought maybe some of you had already done something like this and could share an example.

as a started, an example of reinforced concrete model by compression_only material can be found in CalculiX documentation or mirror links here.

Hello, I am sending you the file in which I used “COMPRESSION_ONLY” (this is a wall arch), can you check if everything is OK?
LUK1.pmx (4.5 MB)

You have:

600, 0.1

Looks good if Young’s modulus is 600 MPa in this case.

Looking a model of stone arch structures, i’m not really sure if it can be simplified and treated as homogen material at whole part. Shear and slip between block being ignored, for masonry type wall it can not be.

Elastic modulus value being used seems too low and far from normally of stone itself, tension have negligible values. Some specific software can be used as comparison, but it could be okay for the purpose of preliminary analysis to review.

Below approximation of material like concrete and some experimental results from references,

2023-09-24 04_40_13-SMath Solver - concreteprop.sm_

Regarding support at the left and right side, it could be better using soil active lateral pressure instead of fixed displacement.

Hello. Thank you for all your replies. I would like to use the Druker-Prager model for this brick arch. I found some tips on the Internet on how to do this in calculix, but it’s all unclear to me. Maybe you could help. Thank you in advance and best regards.

Drucker-Prager material can be defined with umat.f subroutine. In fact, the usage of umat subroutine is explained in the documentation using this material model as an example so check the CalculiX User’s Manual (chapter 8.5.1).

when specific to material model, it may ask in CalculiX forum. There are many users reported successful modeling concrete like material, including advanced one’s damage type (cracking).

i did not find Fortran files of umat_drucker_prager.f from official source code distribution, is this placed out there? I’m interesting to do comparison with Drucker-Prager material from MFront and one i get from Abaqus user.

According to the documentation, you may have to modify the files yourself:

For instance, assume you want to write a material user routine for a DruckerPrager material model. Let us call this routine umat drucker prager.f. To write the routine, you can use the umat user.f routine as a template.

Hello. Thanks for these tips and advice, but I don’t think I can handle it. I don’t know the basics of these programs and I think I need to give it a try. Pity. Thanks for everything

You could try using MFront (more details to be found on the CalculiX forum). Or maybe the Mohr-Coulomb model (implemented in the newest release of CalculiX) could be applicable in your case.

it’s quite simple and similar to another specific material definition, only needed to provide MFront DLL from CalculiX forums placed at the same directory of solver.

i’m using these material also, it fairly fast to converged in calculation times.

hi, i read several paper. Cracking is mainly due to separation of stone bricks and mortar filler, not to the limit of nonlinearity material itself. In this case, contact or cohesive zone model is required.

i took simple test of model as above, top soil filler, side wall and pavement layer need to be include in modeling to capture betters of confinement.

Good evening. If you’ll allow me, I find this topic very interesting, and I’d like to contribute. I believe that the choice of material model depends on what you want to visualize. In the case of a brick or stone factory, the goal is to monitor tensile stresses that lead to crack formation and check if working stresses are within acceptable limits.

Correct me if I’m wrong, but it may not be necessary to model complex material plasticity behavior for this purpose. You can establish a limit in the results so that you obtain a comparative graphical model of stresses in the structure relative to the material’s allowable values, both in tension and compression. This way, you can analyze the areas where the material undergoes plastic deformation, in this case due to excessive tension or compression.

I’m sharing a model of a project I worked on at university, and I appreciate your feedback in case I’m mistaken (which is quite likely). Nonetheless, I would love to be able to work with the Drucker-Prager model and accurately model concrete, but that’s beyond my current capabilities. Thank you very much for your assistance.

Best regards, Damián.
230609 Boveda.zip (3.5 MB)

Could you please share the model? Please

thanks for sharing. is there any basic report about material properties being used? also, result comparison if available.

unfurnately, my PrePoMax files seem to have problem due to switching operation in linear contact and tied type. it changes the units from N-mm to N-m also. i need to repair before

please ignore my previous screenshot of deflection result, something wrong or incomplete at master and slave surface definition by auto-detect feature.

Below, after correction, link attachment of input files also. There’s having three type of block and mortar joint interaction for observing.