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Viscoelastic Material Data in Abaqus

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ang.grim
Posts: 11
Topic starter
(@ang.grim)
Active Member
Joined: 13 years ago

Dear all,

Recently I have got a masters thesis about PTFE and in the appendix, Abaqus/Standard Code is given.

I am trying to put this data into abaqus/cae in order to see the material behavior with this data set. However, I could not put the data into correct places.

I can put Shear Test data in viscoelastic material. When I just put this data and submit the work, I get this error:

-

Error in job uehuzt034o: *VISCOELASTICITY REQUIRES THE USE OF EITHER *ELASTIC, *HYPERELASTIC OR *HYPERFOAM

Error in job uehuzt034o: 1 elements have been defined with zero hour glass stiffness. You may use *hourglass stiffness or change the element type. The elements have been identified in element set ErrElemZeroHourGlassStiffness.

Error in job uehuzt034o: 1 elements are missing elastic property reference. The elements have been identified in element set ErrElemMissingElasticPropRef.

Error in job uehuzt034o: Analysis Input File Processor exited with an error.

Job uehuzt034o aborted due to errors.

-

In this data, what is Long-term normalized shear compliance or modulus?

I am pasting the code below. I would like to create a material from this data.

*NODE

*INCLUDE, INPUT=sleeve_n.inp

**

**

*ELEMENT, TYPE=C3D8R

*INCLUDE, INPUT=sleeve_e.inp

**

**

*NSET, NSET=SLEEVE_NSET, GENERATE

1, 90918, 1

*ELSET, ELSET=SLEEVE_ELSET, GENERATE

1, 78662, 1

**

**

*NSET, NSET=BOUNDARY_X

21,

*NSET, NSET=BOUNDARY_Y

*INCLUDE, INPUT=sleeve_y.inp

*NSET, NSET=BOUNDARY_Z

*INCLUDE, INPUT=sleeve_z.inp

**

*NSET, NSET=RIB_NSET

1306, 10041, 9923, 9805, 9687, 9569, 9451, 9333, 9215, 9097, 424, 5012, 4894, 289, 16310,

16311,

16312, 16313, 16294, 16295, 16296, 16277, 16278, 16259, 16260, 16261, 16242, 16243, 16244,

16245, 16226, 16227,

16228, 16209, 1663, 21042, 21101, 21160, 21219, 21278, 21337, 21396, 21455, 21514, 21573,

22238, 22239, 22240,

2236

**

*ELSET, ELSET=RIB_ELSET

17990, 17871, 17752, 17633, 17514, 17395, 17276,

17157, 17038, 16919, 2740, 1788, 836,

42957, 42757, 42767,

42777, 42787, 42587, 42597, 42607, 42407, 42417,

42427, 42437, 42237, 42037, 42047, 42057,

42067, 41867, 41877,

41887, 41687, 54332, 54863, 55394, 55925, 56456,

56987, 57518, 58049, 58580, 59111, 66179,

66180, 66181, 66182,

**

**

*SOLID SECTION, ELSET=SLEEVE_ELSET, MATERIAL=PTFE_ELASTIC

1.,

**

**

*MATERIAL, NAME=PTFE_ELASTIC

*ELASTIC, MODULI=LONG TERM

4.82e+08, .45

*DENSITY

2160.

*VISCOELASTIC, TIME=RELAXATION TEST DATA

*SHEAR TEST DATA, SHRINF=0.409979

1., 0.001067

0.980599, 0.001386

0.971032, 0.00167

0.924608, 0.003118

0.897826, 0.004528

0.863317, 0.007284

0.838317, 0.010575

0.814023, 0.015071

0.790447, 0.020691

0.752652, 0.035201

0.723731, 0.063331

0.695908, 0.097242

42

0.669162, 0.14519

0.643445, 0.2402

0.618711, 0.39368

0.600791, 0.5405

0.583392, 0.77026

0.56649, 1.1501

0.550086, 1.4931

0.534145, 1.9934

0.523779, 2.9214

0.513622, 3.8282

0.50365, 5.1588

0.489062, 6.7602

0.479576, 8.4552

0.47489, 10.

0.461135, 11.609

0.456647, 15.071

0.452193, 17.991

0.447785, 19.566

0.443412, 25.879

0.439086, 32.978

0.430571, 39.003

0.426372, 42.022

0.4181, 55.067

0.414016, 70.828

0.409979, 87.765

**

**

*BOUNDARY

SLEEVE_NSET, 1, 1

SLEEVE_NSET, 2, 2

SLEEVE_NSET, 3, 3

**

**

*INITIAL CONDITIONS, TYPE=STRESS

*INCLUDE, INPUT=initialstress.inp

**

**

** -----------------------------------------------------

*STEP, NAME=DISPLACEMENTS

*STATIC

.01,.01,,

**

**

*OUTPUT, FIELD

*ELEMENT OUTPUT

S

**

*OUTPUT, HISTORY

*ELEMENT OUTPUT, ELSET=RIB_ELSET

MISES

**

**

*END STEP

** -----------------------------------------------------

*STEP, NAME=RELAX1

*VISCO

.05, 1, ,

**

**

*OUTPUT, FIELD

*ELEMENT OUTPUT

S

**

*OUTPUT, HISTORY

*ELEMENT OUTPUT, ELSET=RIB_ELSET

MISES

**

**

*EL PRINT, ELSET=RIB_ELSET, SUMMARY=NO, TOTALS=NO

MISES

**

**

*END STEP

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8 Replies
ang.grim
Posts: 11
Topic starter
(@ang.grim)
Active Member
Joined: 13 years ago

I just put the elastic data (Moduli and Poissons Ratio), now it works.

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8 Replies
ang.grim
Posts: 11
Topic starter
(@ang.grim)
Active Member
Joined: 13 years ago

The problem is, when I extract stress vs strain data, I am having a linear behavior. Is that normal?

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Jorgen
Posts: 3964
(@jorgen)
Member
Joined: 3 years ago

You can get a linear response if the characteristic time of the applied strain is smaller or larger than what is covered in the linear viscoelastic Prony series. It is important to use a wide enough range of relaxation times in the Prony series to cover the conditions that are of interest.

-Jorgen

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ang.grim
Posts: 11
Topic starter
(@ang.grim)
Active Member
Joined: 13 years ago

How can I change the characteristic time of the applied strain and have a wide enough range of relaxation time?

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ang.grim
Posts: 11
Topic starter
(@ang.grim)
Active Member
Joined: 13 years ago

[QUOTE=Jorgen,5217]You can get a linear response if the characteristic time of the applied strain is smaller or larger than what is covered in the linear viscoelastic Prony series. It is important to use a wide enough range of relaxation times in the Prony series to cover the conditions that are of interest.

-Jorgen[/QUOTE]

In my analysis, I used Frequency: Formula

g1*real and all others are 0.

If i change it to Prony, what should I enter there?

Reply
Jorgen
Posts: 3964
(@jorgen)
Member
Joined: 3 years ago

It appears that your simulation is using a max time of 1 sec. What range of frequencies do you have data for?

The Prony series input format is useful is your have stress-relaxation data available.

-Jorgen

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