3. Operands#
3.1. Operand RESULTAT#
Refers to the result of the thermo-mechanical calculation for which the Bordet quantities are calculated. The RESULTAT data structure provided should have one and only one model and one and only one material field.
3.2. Operand TOUT/GROUP_MA#
♦/TOUT = “OUI”,
/GROUP_MA = group_ma, [l_group_ma]
Refers to the domain of the model on which the calculation of the Bordet quantities will be carried out. By default, it is performed on the entire model. Note that as the model involves the variation of plastic deformation, the group of elements on which the calculation is performed must contain at minima all the domain over which the plastic deformation evolved during loading, and that taking a larger domain will not change the result (but the duration of the calculation).
3.3. Operand INST/NUME_ORDRE#
♦/INST = instant, [R]
/NUME_ORDRE = order [I]
The calculation will be carried out for all the moments or order number up to the moment or order number designated by this operand.
The result will be a table containing the various calculation times, the constraint and the Bordet probability.
3.4. Operand PRECISION#
◊/PRECISION =1E-06 [DEFAUT]
prec, [R]
Allows you to define, in the case of the use of the keyword INST, a precision in the search for the last moment of calculating the Bordet quantities. If the precision is not set by the user, an accuracy of 1E-06 is applied.
If the time requested by the user does not correspond to any interval [instant-prec; instant+prec] saved in the result, the calculation stops in a fatal error.
3.5. Operand CRITERE#
◊/CRITERE = “ABSOLU” [DEFAUT]
“RELATIF”,
Allows you to define, when using the keywords INST and PRECISION, whether the precision is absolute or relative. By default, it is absolute.
3.6. Operand PROBA_NUCL#
◊ PROBA_NUCL = /” NON [DEFAUT]
/” OUI “
Indicates whether the user wants to take the term exponential into account in their calculation. This term, as specified above, is of negligible influence if \(\frac{{\sigma }_{\mathrm{ys}\mathrm{,0}}{\varepsilon }_{p\mathrm{,0}}}{{\sigma }_{\mathrm{ys}}(T,{\dot{\varepsilon }}_{p})}\gg {\varepsilon }_{p}\). If the user wishes to take this term into account, he must then enter an additional parameter, which is the equivalent reference plastic deformation. Otherwise, this setting is useless.
3.7. Operand PARAM#
♦ PARAM = _F (
♦ M = m, [R]
♦ SIGM_REFE = sigma_ref, [function]
♦ VOLU_REFE = r_sup, [R]
♦ SIG_CRIT = sigma_write, [R]
♦ SEUIL_REFE = lim_elas_ref, [R]
♦ SEUIL_CALC = lim_elas, [function, tablecloth]
♦ DEF_PLAS_REFE = lim_elas, [R]
),
Refers to all the material parameters necessary to calculate the quantities of the Bordet model. The first three have equivalents in the Beremin model (with values that may vary from model to model), the next four being specific to the Bordet model.
3.7.1. Keyword M#
♦ M = m, [R]
Refers to the exponent \(m\) of the Weibull law (sometimes called a form factor).
Attention: this quantity is not necessarily equal to its equivalent in the Beremin model.
3.7.2. Keyword SIGM_REFE#
♦ SIGM_REFE = sigma_ref, [function]
Refers to the reference constraint \({\sigma }_{u}(T)\) of the Weibull type law (sometimes called a scale factor). This is the constraint for which the cumulative probability of rupture of the potential cleavage sites is equal to 1.
This constraint depends on the temperature; a temperature function is expected here.
Attention: this quantity is not necessarily equal to its equivalent in the Beremin model.
3.7.3. Keyword VOLU_REFE#
♦ VOLU_REFE = V0 [R]
Refers to the elementary reference volume \({V}_{0}\) in the plastic zone.
Attention: this quantity is not necessarily equal to its equivalent in the Beremin model.
3.7.4. Keyword SIG_CRIT#
♦ SIG_CRIT = sigma_write, [R]
Refers to the critical stress \({\sigma }_{\mathrm{th}}\) below which the propagation of ferritic microcracks cannot be significant; if \({\sigma }_{1}<{\sigma }_{\mathrm{th}}\) at any point, then necessarily \({P}_{\mathrm{Bordet}}\text{=}0\).
3.7.5. Keyword SEUIL_REFE#
♦ SEUIL_REFE = lim_elas_ref, [R]
Refers to elastic limit \({\sigma }_{\mathrm{ys}\mathrm{,0}}\) at a reference temperature to be used in the model.
3.7.6. Keyword SEUIL_CALC#
♦ SEUIL_CALC = lim_elas, [function, tablecloth]
Refers to the elastic limit of material \({\sigma }_{\mathrm{ys}}(T,{\dot{\varepsilon }}_{p})\), which From a point of view depends on the temperature and the rate of plastic deformation.
If you don’t know the dependence on the plastic deformation rate, you can use a simple temperature function for SEUIL_CALC.
If we know the dependence on both the temperature and the plastic deformation rate, we can define a sheet; the parameter of the sheet must be the plastic deformation rate, and the variable for each function the temperature (cf. user document for DEFI_NAPPE)
Example:
SIGY1 = DEFI_FONCTION (NOM_PARA =” TEMP “,
VALE =( 0.,200.,100.,200.,),
PROL_DROITE =” CONSTANT “, PROL_GAUCHE =” CONSTANT”,);
SIGY2 = DEFI_FONCTION (NOM_PARA =” TEMP “,
VALE =( 0.,300.,100.,300.,),
PROL_DROITE =” CONSTANT “, PROL_GAUCHE =” CONSTANT”,);
SIGY = DEFI_NAPPE (NOM_PARA =” EPSI “,
PROL_DROITE =” CONSTANT “, PROL_GAUCHE =” CONSTANT”,
PARA =( 0.0005,0.001),
FONCTION =( SIGY1, SIGY2),);
CALC_BORDET (… SEUIL_CALC = SIGY, … );
3.7.7. Keyword DEF_PLAS_REFE#
♦ DEF_PLAS_REFE = lim_elas, [R]
This keyword is OBLIGATOIRE if PROBA_NUCL =” OUI “and INTERDIT if PROBA_NUCL =” NON”.
It refers to the equivalent plastic deformation of reference \({\varepsilon }_{p\mathrm{,0}}\) which only occurs in the term exponential.
3.8. Operand TEMP#
♦ TEMP = temperature, [function]
As specified in the preceding paragraphs, certain material parameters depend on temperature. TEMP refers to the temperature, considered uniform for the moment in the Bordet calculation zone. The user can enter a constant function, in which case the temperature is considered uniform in space and constant in time, or a function of time (parameter INST), in which case the temperature is considered uniform in space but evolves in time.
3.9. Operand COEF_MULT#
◊ COEF_MULT =1, [DEFAUT]
coefficient, [R]
The default value for this coefficient is 1.0.
The following table, in which the thickness is noted \(e\), indicates typical values of the \(C\) coefficient as a function of the type of symmetry:
simple symmetry: the plane of symmetry of the mesh passes through the plane of the defect and the defect is entirely meshed,
double symmetry: the plane of symmetry of the mesh also passes through the plane of the defect but only one half of the defect is meshed.
3D and 3D_SI |
AXIS **and** AXIS_SI ** |
D_ PLAN ** and D_ PLAN_SI |
C_ PLAN |
|
SIMPLE |
2 |
|
2nd |
2nd |
DOUBLE |
4 |
not applicable |
not applicable |
not applicable |
NON |
1 |
|
e |
e |
Table 3.9-1 : **Values of the symmetry-thickness multiplier ratio