Bi modulus material modeling

1

Hello everyone

I am new to Calculix. Still learning it.

I want to model a Bi modulus material. Where the elastic modulus in tension and compression has considerable difference.

Are there any default material model or specific sources or examples, I can follow.

Any suggestion is much appreciated.

2

only way to search for Abaqus UMAT with this model and recompile exe (or ask somebody to do it)

3

The built-in material models can’t handle that, to the best of my knowledge.

So you will have to supply your own material model.

This requires you to;

  • build the necessary libraries and the CalculiX solver on your platform and
  • write a material model in Fortran or C.

These are not typical beginner projects. On the other hand, you will learn a lot by tackling them.

This post might help.

The scripts I use for building CalculiX with the Pastix solver on FreeBSD UNIX can be found here. They will need some changes to work on a typical Linux box. I haven’t built software on a microsoft platform since using Turbo C on MS-DOS, so I cannot offer assistance with that.
If you are on ms-windows, installing msys2 might be a good start.

4

Could merging two elements (Only tension + only copression) do the job.?

** Generated by Mecway 28
*NODE
1,0,0,0
2,0,0,0.02
3,0,-0.01,0
4,0.025,-0.01,0.02
5,0.025,0,0.02
6,0.025,-0.01,0
7,0.025,0,0
8,0,-0.01,0.02
*ELEMENT,TYPE=C3D8
1,3,8,4,6,1,2,5,7
2,3,8,4,6,1,2,5,7
*ELSET,ELSET=C1
1
*ELSET,ELSET=T1
2
*ELSET,ELSET=CONCRETE
1
2
*BOUNDARY
1,1,,0
1,2,,0
1,3,,0
3,3,,0
6,3,,0
7,2,,0
7,3,,0
*AMPLITUDE,NAME=Az_8_1
0,0
0.01,1.332267842713E-14
0.25,62.50001
0.49,1.332267842713E-14
0.51,-1.332267842713E-14
0.75,-62.50001
0.99,-1.332267842713E-14
1,0
*AMPLITUDE,NAME=Az_4_2
0,0
0.01,1.332267842713E-14
0.25,62.50001
0.49,1.332267842713E-14
0.51,-1.332267842713E-14
0.75,-62.50001
0.99,-1.332267842713E-14
1,0
*AMPLITUDE,NAME=Az_2_3
0,0
0.01,1.332267842713E-14
0.25,62.50001
0.49,1.332267842713E-14
0.51,-1.332267842713E-14
0.75,-62.50001
0.99,-1.332267842713E-14
1,0
*AMPLITUDE,NAME=Az_5_4
0,0
0.01,1.332267842713E-14
0.25,62.50001
0.49,1.332267842713E-14
0.51,-1.332267842713E-14
0.75,-62.50001
0.99,-1.332267842713E-14
1,0
*MATERIAL,NAME=COMPRESSION_ONLY
*USER MATERIAL,CONSTANTS=2
60000.E6, 100
*DENSITY
1800.

*SOLID SECTION,ELSET=C1,MATERIAL=COMPRESSION_ONLY

*MATERIAL,NAME=TENSION_ONLY
*USER MATERIAL,CONSTANTS=2
15000.E6, 100
*DENSITY
1800.

*SOLID SECTION,ELSET=T1,MATERIAL=TENSION_ONLY

*STEP,NLGEOM=YES,INC=110,AMPLITUDE=STEP
*STATIC,SOLVER=PARDISO
0.01,1,0,0.01
*CLOAD,AMPLITUDE=Az_8_1
8,3,1
*CLOAD,AMPLITUDE=Az_4_2
4,3,1
*CLOAD,AMPLITUDE=Az_2_3
2,3,1
*CLOAD,AMPLITUDE=Az_5_4
5,3,1
*NODE FILE,GLOBAL=YES
U,RF
*EL FILE
S,NOE
*END STEP
5

What about making a new material model based on a combination of the tension-only and compression only models?

A simple combination could be to just average the output of both models. I’m just not sure if that is mathematically and physically correct; My knowledge of solid mechanics is insufficient here.

I do think it is somehat important. A lot of composite materials I’m familiar with have different behavior in tension and compression. And I’m not just talking fiber reinforced composites but also e.g. adhesives with mineral fillers, epoxy “concrete” and polymeric foams.