TBFT, Oper, ID, Option1, Option2, Option3, Option4, Option5, Option6, Option7
Performs material curve-fitting operations.
Use material curve fitting to evaluate your experimental data and correlate it to the program's built-in nonlinear material models. You apply coefficients to your curve data, determine a fit with existing model, and write the data according to the table configurations outlined in the TB command. Curve fitting is available for nonlinear models associated with the material behaviors listed below:
For hyperelastic material behavior, see "TBFT Specifications for Hyperelastic Models".
For creep material behavior, see "TBFT Specifications for Creep Models".
For viscoelastic material behavior, see "TBFT Specifications for Viscoelastic Models".
For Chaboche plasticity material behavior, see "TBFT Specifications for Chaboche Kinematic Hardening Plasticity Models".
TBFT, Oper, ID, Option1, Option2, Option3, Option4, Option5, Option6, Option7
OperThe specific curve-fitting operation:
Define a constitutive model.
Delete a constitutive model.
Write data related to a constitutive model to the database (same as TB command).
Initialize coefficients of a constitutive model for nonlinear curve-fitting procedure.
Deletes coefficients at current reference temperature. Applicable only for temperature dependent coefficients.
Solve for coefficients.
Fix (hold constant) the coefficient
you specify in Option4.
Add experimental data.
Delete experimental data.
List all data associated with
the material model represented by the material ID number.
IDThe material reference number (same as MAT argument used in the TB command).
Valid entry is any number greater than zero (default = 1) but less
than 100,000.
Option1For curve-fit function operations (Oper = FADD, FDEL, FSET, SET, CDEL, SOLVE or FIX) this field specifies
the category (HYPER).
For adding or deleting your experiment
(Oper = EADD or EDEL), this field specifies the experimental data type. Valid options: UNIA, BIAX, SHEA, SSHE,and VOLU
(default = UNIA).
Option2For curve-fit function operations (Oper = FADD, FDEL, FSET, SET, CDEL, SOLVE, or FIX), this field specifies
constitutive model type. The valid entries are listed in Table 221: Hyperelastic Options below.
When you need to
specify a file name from which to get experimental data (Oper = EADD), place that string here. Valid entry is
any file name string. You can enter the entire path\filename.extension string and leave the next two fields (Option3 and Option4) blank, or you can specify
the name here, the extension in the next field, and the path following.
Option3For Oper = FADD, FDEL,
FSET, CDEL, SET, SOLVE or FIX, some of the cases specified in Option2 will require that the polynomial order be specified.
The applicable values for the order specification are listed in Table 221: Hyperelastic Options.
If a file name for experimental
data is being specified in Option2 (Oper = EADD), this field will contain the file extension.
Option4When you are working on a specific coefficient (Oper = FIX), this field specifies the index of that
coefficient. Valid entries vary from 1 to n, where n is the total number of coefficients
(default = 1).
For Oper = SET,
see Table 220: Set Operations, below.
If a file name for experimental data is being specified in Option2 (Oper = EADD), this
field will contain the directory/path specification.
If Oper = SOLVE, this value specifies
the curve-fitting procedure. Valid entries are 0 for unnormalized
least squares curve-fitting procedure, and 1 for normalized least
squares curve-fitting procedure.
Option5When you are working on a specific coefficient (Oper = FIX), this field specifies the index of that
coefficient. Valid entries vary from 1 to N, where N is the total
number of coefficients (default = 1)
For Oper = SET, see Table 220: Set Operations, below.
Table 220: Set Operations
| Purpose | Option4 | Option5 |
|---|---|---|
| Set the value of the coefficient. | Index of coefficient | Value of that coefficient |
| Set temperature dependency ON/OFF* | tdep | 1 for ON and 0 for OFF |
| Set reference temperature | tref | Temperature value |
* - Temperature data should be supplied in the same units as the TREF command.
If Oper = SOLVE, use this field to
specify the number of iterations to be used in the calculation of
the coefficients. Valid entry is any positive integer (default = 1000)
Option6If Oper = SOLVE, specifies
the allowed tolerance in residual change to stop an iteration. Valid
entry is 0.0 to 1.0 (default = 0.0).
Option7If Oper = SOLVE, specifies
the allowed tolerance in coefficient change to stop an iteration.
Valid entry is 0 to 1 (default = 0).
Table 221: Hyperelastic Options
| Option1 | Option2 | Option3 |
|---|---|---|
| HYPER | MOON | 2, 3, 5, 9 |
| HYPER | POLY | 1 to N |
| HYPER | OGDEN | 1 to N |
| HYPER | YEOH | 1 to N |
| HYPER | BOYC | NA |
| HYPER | GENT | NA |
| HYPER | NEO | NA |
| HYPER | BLAT | NA |
| HYPER | FOAM | 1 to N |
Following table summarizes the format for hyperelastic operations via the TBFT command:
| Oper | ID | Option1 | Option2 | Option3 | Option4 | Option5 | Option6 | Option7 |
|---|---|---|---|---|---|---|---|---|
| FADD | ID | HYPER | Option | Order | ||||
| FDEL | ID | HYPER | Option | Order | ||||
| FSET | ID | HYPER | Option | Order | ||||
| SET | ID | HYPER | Option | Order | Index | Value | ||
| SOLVE | ID | HYPER | Option | Order | Norm Flag | Num Iter | RTOL | CTOL |
| FIX | ID | HYPER | Option | Order | Index | Fix / Unfix Flag | ||
| EADD | ID | Exp Type | File | Extension | Directory | |||
| EDEL | ID | Exp Type / Index |
TBFT, Oper, ID, Option1, Option2, Option3, . . .
, Option7
OperThe specific curve-fitting operation:
Define a case/constitutive model for viscoelasticity (prony).
Define a constitutive model.
Delete a constitutive model.
Write data related to a constitutive model to the database (same as TB command).
Initialize coefficients of a constitutive model for nonlinear curve-fitting procedure.
Deletes coefficients at current reference temperature. Applicable only for temperature dependent coefficients.
Solve for coefficients.
Fix (hold constant) the coefficient
you specify in Option4.
Add experimental data.
Delete experimental data.
List all data associated with
the material model represented by the material ID number.
IDThe material reference number (same as MAT argument used in the TB command).
Valid entry is any number greater than zero (default = 1) but less
than 100,000.
Option1This option is set to VISCO for adding coefficients
(Oper = FADD). The FADD operation is used
to specify the shear order, the bulk order or the shift option.
This option (Oper = CASE) is set
to NEW or FINI. The FADD commands are always enclosed by TBFT,FCASE, ID, NEW and TBFT,FCASE,
ID, FINI. See Material Curve Fitting in the Structural Analysis Guide for more information.
For other curve-fit function operations (Oper = FDEL, FSET, SET, CDEL, SOLVE or FIX) this field is set to CASE.
For adding or deleting your experiment (Oper = EADD or EDEL), this field specifies
the experiment type. Valid options: SDEC (Shear Modulus vs. Time) or BDEC (Bulk Modulus vs. Time).
Option2For defining your viscoelastic case (Oper = FCASE), you specify PVHE.
For curve-fit
function operations (Oper = FDEL, FSET,
SET, CDEL, SOLVE, or FIX), this field specifies the case name.
To create a new case (Oper = FADD),
the valid options are listed in Table 223: Viscoelastic Options below.
When you need to specify a file name from which to get experimental
data (Oper = EADD), place that string here.
Valid entry is any file name string. You can enter the entire path\filename.extension string and leave the next two
fields (Option3 and Option4) blank, or you can specify the name here, the extension in the next
field, and the path following.
Option3For Oper = FCASE, this
field specifies the case name.
For Oper = FADD, this field specifies the order
If a file name for experimental data is being specified in Option2 (Oper = EADD), this
field will contain the file extension.
Option4When you are working on a specific coefficient (Oper = FIX), this field specifies the index of that
coefficient. Valid entries vary from 1 to n, where n is the total number of coefficients
(default = 1).
For Oper = SET,
see Table 222: Set Operations, below.
You can also specify TREF to indicate the reference temperature.
If a file name for experimental data is being specified in Option2 (Oper = EADD), this
field will contain the directory/path specification.
If Oper = SOLVE, this value specifies
the curve-fitting procedure. Valid entries are 0 for unnormalized
least squares curve-fitting procedure, and 1 for normalized least
squares curve-fitting procedure.
Option5For Oper = SET, see Table 222: Set Operations, below.
Table 222: Set Operations
| Purpose | Option4 | Option5 |
|---|---|---|
| Set the value of the coefficient | Index of coefficient | Value of coefficient |
| Set temperature dependency ON/OFF | tdep | 1 for ON and 0 for OFF |
| Set reference temperature | tref | Temperature value |
| Set current component to solve for | comp | pshea, pbulk, or pvhe |
If Oper = SOLVE, use this field to
specify the number of iterations to be used in the calculation of
the coefficients. Valid entry is any positive integer (default = 1000).
If you are specifying a coefficient to be held constant (Oper = FIX), a 1 FIXES the specified coefficient, and
a 0 allows it to vary (turns fixing OFF).
Option6If Oper = SOLVE, specifies
the allowed tolerance in residual change to stop an iteration. Valid
entry is 0.0 to 1.0 (default = 0.0).
Option7If Oper = SOLVE, specifies
the allowed tolerance in coefficient change to stop an iteration.
Valid entry is 0 to 1 (default = 0).
Table 223: Viscoelastic Options
| Category | Name | Option |
|---|---|---|
| VISCO | PSHEAR | 1 to N |
| VISCO | PBULK | 1 to N |
| VISCO | SHIFT | TN, WLF, NONE |
Following table summarizes the format for viscoelastic operations via the TBFT command:
| Oper | ID | Option1 | Option2 | Option3 | Option4 | Option5 | Option6 | Option7 |
|---|---|---|---|---|---|---|---|---|
| FCASE | ID | NEW | PVHE | Case Name | ||||
| FCASE | ID | FINI | ||||||
| FADD | ID | VISCO | Option | Order | ||||
| FDEL | ID | CASE | Case Name | NA | ||||
| FSET | ID | CASE | Case Name | NA | ||||
| SET | ID | CASE | Case Name | NA | Index | Value | ||
| SOLVE | ID | CASE | Case Name | NA | Norm Flag | Num Iter | RTOL | CTOL |
| FIX | ID | CASE | Case Name | NA | Index | Fix / Unfix Flag | ||
| EADD | ID | Exp Type | File | Extension | Directory | |||
| EDEL | ID | Exp Type / Index |
TBFT, Oper, ID, Option1, Option2, Option3, . . .
, Option7
OperThe specific curve-fitting operation:
Define a case/constitutive model for plasticity.
Define a constitutive model.
Delete a constitutive model.
Write data related to a constitutive model to the database (same as TB command).
Initialize coefficients of a constitutive model for nonlinear curve-fitting procedure.
Deletes coefficients at current reference temperature. Applicable only for temperature-dependent coefficients.
Solve for coefficients.
Fix (hold constant) the coefficient
you specify in Option4.
Add experimental data.
Delete experimental data.
List all data associated with
the material model represented by the material ID number.
IDThe material reference number (same as MAT argument used in the TB command).
Valid entry is any number greater than zero (default = 1) but less
than 100,000.
Option1For Oper = FCASE, set to
either NEW or FINI. The command TBFT,FCASE,ID,NEW initializes a new curve-fitting case. (The TBFT,FADD commands described next are always issued between TBFT,FCASE,ID,NEW and TBFT,FCASE,ID,FINI commands.)
After issuing TBFT,FCASE,ID,FINI, the Chaboche model is created and is ready to be used to perform
other curve-fitting operations. For more information, see Material Curve Fitting in the Material Reference.
For Oper = FADD, set to PLAS to add
options/parameters for the new case being created (via TBFT,FCASE,ID,NEW, which must be issued before the TBFT,FADD command).
This operation specifies the order of the Chaboche kinematic model.
For other curve-fitting function operations (Oper = FDEL, FSET, SET, CDEL, SOLVE or FIX), set to CASE.
For adding or deleting your experiment (Oper = EADD or EDEL), this option
specifies the experiment type. The only valid option is UNIA (plastic
strain vs. true stress).
Option2For Oper = FCASE (defining
your Chaboche case), set to CPLA.
For Oper = FDEL, FSET, SET, CDEL, SOLVE, or FIX (curve-fitting function operations),
this value specifies the case name being operated on.
For Oper = FADD (specifying options
for the plasticity model), valid options are:
CHAB -- Chaboche kinematic hardening (required for any defined curve-fitting case) BISO -- Bilinear isotropic hardening (optional) MISO -- Multilinear isotropic hardening (optional) VOCE -- Nonlinear isotropic hardening, Voce model (optional) The TBFT,FADD command can be issued twice, once to specify the order of the Chaboche model, and again to specify the isotropic hardening option. (Only one of the options BISO, MISO or VOCE can be used in a single curve-fitting case, and none of those options are required.)
For Oper = EADD (specifying a file
name from which to get experimental data), place that string here.
A valid entry is any file name string. You can either:
Enter the entire path\filename.extension string and leave the next two fields (Option3 and Option4) blank, or
Specify the name here, the extension in the next field, and the path in the following field.
Option3For Oper = FCASE, this
field specifies the case name.
For Oper = FADD, this field specifies either:
The order of the Chaboche kinematic hardening model
(Option2 = CHAB), or
The number of terms in the MISO model (Option2 = MISO).
If a file name for experimental data is being specified in Option2 (Oper = EADD), this
field contains the file extension.
Option4When fixing a specific coefficient to a desired value
(Oper = FIX), this field specifies the
index of that coefficient. Valid entries vary from 1 to n, where n is the total
number of coefficients (default = 1).
For Oper = SET, see Table 222: Set Operations.
You can also specify TREF to indicate the reference temperature, or COMP for a partial/complete solution (only for bulk, only for shear, or all coefficients).
If a file name for experimental data is being specified in Option2 (Oper = EADD), this
field contains the directory/path specification.
If Oper = SOLVE, this value specifies
the normalized/non-normalized option. This option is not available
for Chaboche curve fitting.
Option5For Oper = SET, refer to
the following table.
Table 224: Set Operations
| Purpose | Option4 | Option5 |
|---|---|---|
| Set the value of the coefficient | Index of coefficient | Value of coefficient |
| Set temperature dependency ON/OFF | tdep | 1 for ON and 0 for OFF |
| Set reference temperature | tref | Temperature value |
If Oper = SOLVE, use this field to
specify the number of iterations to be used in the calculation of
the coefficients. Valid entry is any positive integer (default = 1000).
If you are specifying a coefficient to be held constant (Oper = FIX): 1 fixes the specified coefficient, 0 allows
it to vary (disables fixing).
Option6If Oper = SOLVE, specifies
the allowed tolerance in residual change to stop an iteration. Valid
entry is 0.0 to 1.0 (default = 0.0).
Option7If Oper = SOLVE, specifies
the allowed tolerance in coefficient change to stop an iteration.
Valid entry is 0 to 1 (default = 0).
The following table summarizes the format for Chaboche curve-fitting operations via the TBFT command:
Following table summarizes the format for viscoelastic operations via the TBFT command:
| Oper | ID | Option1 | Option2 | Option3 | Option4 | Option5 | Option6 | Option7 |
|---|---|---|---|---|---|---|---|---|
| FCASE | ID | NEW | CPLA | Case Name | ||||
| FCASE | ID | FINI | ||||||
| FADD | ID | PLAS | Option | Order | ||||
| FDEL | ID | CASE | Case Name | NA | ||||
| FSET | ID | CASE | Case Name | NA | ||||
| SET | ID | CASE | Case Name | NA | Index | Value | ||
| SOLVE | ID | CASE | Case Name | NA | Not used | Num Iter | RTOL | CTOL |
| FIX | ID | CASE | Case Name | NA | Index | Fix / Unfix Flag | ||
| EADD | ID | Exp Type | File | Extension | Directory | |||
| EDEL | ID | Exp Type / Index |
TBFT, Oper, ID, Option1, Option2, Option3, . . .
, Option7
OperThe specific curve-fitting operation:
Define a constitutive model.
Delete a constitutive model.
Write data related to a constitutive model to the database (same as TB command).
Initialize coefficients of a constitutive model for nonlinear curve-fitting procedure.
Deletes coefficients at current reference temperature. Applicable only for temperature dependent coefficients.
Solve for coefficients.
Fix (hold constant) the coefficient
you specify in Option4.
Add experimental data.
Delete experimental data.
List all data associated with
the material model represented by the material ID number.
IDThe material reference number (same as MAT argument used in the TB command).
Valid entry is any number greater than zero (default = 1) but less
than 100,000.
Option1For curve-fit function operations (Oper = FADD, FDEL, FSET, SET, CDEL, SOLVE or FIX) this field specifies
the category (CREEP).
For adding or deleting your experiment
(Oper = EADD or EDEL), this field specifies the experimental data type (CREEP).
Option2For curve-fit function operations (Oper = FADD, FDEL, FSET, SET, CDEL, SOLVE, or FIX), this field specifies
constitutive model type. The valid entries are listed in Table 226: Creep Options below.
When you need to specify
a file name from which to get experimental data (Oper = EADD), place that string here. Valid entry is any file name string.
You can enter the entire path\filename.extension string and leave the next two fields (Option3 and Option4) blank, or you can specify
the name here, the extension in the next field, and the path following.
Option3If a file name for experimental data is being specified
in Option2 (Oper = EADD), this field will contain the file extension.
Option4When you are working on a specific coefficient (Oper = FIX), this field , specifies the index of that
coefficient. Valid entries vary from 1 to n, where n is the total number of coefficients
(default = 1).
For Oper =
SET, see Table 225: Set Operations, below.
If a file name for experimental data is being specified in Option2 (Oper = EADD), this
field will contain the directory/path specification.
If Oper = SOLVE, this value specifies
the curve-fitting procedure. Valid entries are 0 for unnormalized
least squares curve-fitting procedure, and 1 for normalized least
squares curve-fitting procedure.
Option5If Oper = SOLVE, use this
field to specify the number of iterations to be used in the calculation
of the coefficients. Valid entry is any positive integer (default
= 1000)
If you specify a coefficient to be held constant
(Oper = FIX), enter a 1 to FIX the coefficient,
and a 0 to allow it to vary (turn fixing OFF).
For Oper = SET, see Table 225: Set Operations, below.
Table 225: Set Operations
| Purpose | Option4 | Option5 |
|---|---|---|
| Set the value of the coefficient | Index of coefficient | Value of coefficient |
| Set temperature dependency ON/OFF* | tdep | 1 for ON and 0 for OFF |
| Set reference temperature | tref | Temperature value |
* - When tdep is OFF, the Arrhenius term (e.g. C4) in the strain hardening creep equation is calculated. Because TBTEMP is not included in the curve-fitting regimen, the experimental data (in absolute temperature) must be supplied using the /TEMP command.
* - When tdep is set ON, the Arrhenius term is set to 0 and the constants are separately computed for each temperature. The curve-fitting regimen uses TBTEMP. You must provide the experimental data using the same units as the TREF command.
Option6If Oper = SOLVE, specifies
the allowed tolerance in residual change to stop an iteration. Valid
entry is 0.0 to 1.0 (default = 0.0).
Option7If Oper = SOLVE, specifies
the allowed tolerance in coefficient change to stop an iteration.
Valid entry is 0 to 1 (default = 0).
Table 226: Creep Options
| Category | Name | Option |
|---|---|---|
| CREEP | SHAR | NA |
| CREEP | THAR | NA |
| CREEP | GEXP | NA |
| CREEP | GGRA | NA |
| CREEP | GBLA | NA |
| CREEP | MTHA | NA |
| CREEP | MSHA | NA |
| CREEP | GGAR | NA |
| CREEP | EXPO | NA |
| CREEP | NORT | NA |
| CREEP | PSTH | NA |
| CREEP | PSRP | NA |
| CREEP | GTHA | NA |
Following table summarizes the format for creep operations via the TBFT command:
| Oper | ID | Option1 | Option2 | Option3 | Option4 | Option5 | Option6 | Option7 |
|---|---|---|---|---|---|---|---|---|
| FADD | ID | CREEP | Option | NA | ||||
| FDEL | ID | CREEP | Option | NA | ||||
| FSET | ID | CREEP | Option | NA | ||||
| SET | ID | CREEP | Option | NA | Index | Value | ||
| SOLVE | ID | CREEP | Option | NA | Norm Flag | Num Iter | RTOL | CTOL |
| FIX | ID | CREEP | Option | NA | Index | Fix / Unfix Flag | ||
| EADD | ID | Exp Type | File | Extension | Directory | |||
| EDEL | ID | Exp Type / Index |
The TBFT command provides tools for comparing experimental material data to the program-provided calculated data for various nonlinear material options. Based on curve-fitting comparisons and error norms, choose the model to use during the solution phase of the analysis according to the best fit. All of the capabilities of the TBFT command are accessible interactively via the standard material GUI. See Material Curve Fitting in the Structural Analysis Guide for more information.
Display material model data associated with both the TB command and the TBFT,FSET command via TBLIST,ALL,ALL.
Material model data associated with the most recent TB or TBFT,FSET command overwrites previous data.
Display material model data associated with both the TB command and the TBFT,FSET command via TBLIST,ALL,ALL.
The capability to fix coefficients (Option4 = FIX) applies only to nonlinear curve fits (as listed in Table 7.3: Hyperelastic Curve-Fitting Model Types.
The uniaxial, biaxial, and shear experimental data use engineering stress. The volumetric data uses true stress. See the Material Reference for details about experimental data for creep and viscoelasticity.