Anisothermal variables management#

Anisothermal variables#

The Anisothermal variables command represents the main contribution of this new 8.4 version.

In the proposed methodology, the material model is first calibrated on isothermal experiments using the previous Sim-Opt commands. In this context, an optimal set of coefficients is thus obtained for each temperature.

The first aim of the Anisothermal variables command is to provide tools allowing to verify the evolution of those coefficients on the whole range of temperature. Global functions, that allow to monitor the evolution with temperature of critical material properties (eg. \(R_{O2}\) yield stress) that may be expressed as a particular function of the material model coefficients can be used.

The second aim of the Anisothermal variables command is to simplify the anisothermal models identification method. The idea consists of creating anisothermal variables based on the current simulation variables, and then fitting those new variables to the experiments defined for different temperatures. For instance, if the user has launched five optimizations to fit eight simulations to eight experiments defined at five distinct temperatures, the user can use the Anisothermal variables command to transform the current simulation variables into temperature dependent simulation variables. Such an approach needs the creation of a template file including the temperature depend-ant simulation variables that will appear in the Variables dialog. The user can then launch one optimization on the temperature depend-ant simulation variables to fit at the same time the experiments defined at five distinct temperatures. One can consider that this optimization amounts to fit the temperature depend-ant simulation variables to the best values of the current simulation variables stored in the histories (typically one history per temperature value). The Update sim command allows finally to create, at any temperature chosen by the user, new simulations based on the temperature depend-ant simulation variables.

Such a proceedings may be decomposed into four steps :

  • fit the set of optimization variables for each temperature value the solution of which is stored in an history item ;

  • create anisothermal variable items from the coefficients optimized for each temperature value :

    • evolution of the coefficients versus temperature may be plotted ;

    • global functions definition from several anisothermal variables (for instance 0.2% yield stress) that allows to evaluate the model built from tabulated temperature values ;

    • for each anisothermal variable, definition of an analytical function the coefficients of which may be optimized versus the tabulated temperature values ;

  • automatically add new items that contain the anisothermal behavior :

    • automatic creation of the template file corresponding to the chosen material file ;

    • automatic creation of new optimization parameters that are the coefficients of the functions attached to the anisothermal variables ;

    • creation of isothermal simulation items that use the anisothermal material file ;

  • execution of a whole optimization that implies the optimization parameters containing the anisothermal behavior.

Anisothermal variables management dialog#

The dialog is represented hereafter. The dialog can be decomposed into four parts. The first frame includes the anisothermal variables and their definition based on experimental data, the second concerns the parametric functions used to work out the anisothermal variables, the third contains the global functions, built from several anisothermal variables, while the last includes the current command buttons.

An anisothermal variable is created in the database from its corresponding variable when its definition versus the parameter values is done, its representative function is associated, and when the Update var command is clicked.

../_images/aniso_l.svg

\(\bullet\) At the top of this dialog, the first frame contains on the left a selection box that lists the anisothermal variables on which the sub-commands on the right can be activated, as described in the next pages. Note that the selection box is by default filled with all the variables.

Def var command#

This command allows to define the values of the anisothermal variable selected versus the parameter (temperature) values. By hitting the Def var command, the user opens a dialog shown in the next figure.

../_images/aniso_defvar.svg

By default, variable and parameter values are stored into a table constituted by five rows, the first two being activated. Addition of new definition lines is still possible by means of the Add row button. Note that an added row is activated by default (see the checkbox at the beginning of each line). The Sort button allows to sort the lines according to the parameter column. If the user clicks on the Go button despite of a not sorted parameter column, an error message is printed. The Set column button may be used to set a whole column to a constant value, as shown in the next figure.

../_images/aniso_defvar_setcol.svg

The Go button updates the definition of the selected anisothermal variable with the informations included in the dialog, while the Cancel button closes the parametric definition dialog without further modification to the definition of the selected anisothermal variable.

Mod var command#

This command allows to modify the definition of the anisothermal variable selected. If the user tries to modify an anisothermal variable not previously defined, an error message is printed. Note that this command opens the parametric definition dialog corresponding to the selected anisothermal variable.

Example#

The dialog shown in the next figure illustrates the definition of such an anisothermal variable.

../_images/aniso_defvar_ex.svg

Fill from hist command#

The aim of the Fill from hist command is to define at the same time all the variables selected in the Variables selection box, by using the best values of the current simulation variables stored in the histories (typically one history per temperature value). When the user clicks on this command, a warning message is printed to recall that the use of the Fill from hist dialog will modify the parametric variables already defined. By hitting the Fill from hist command, the user opens a dialog shown in the next figure.

../_images/aniso_fillfromhist.svg
The combo boxes of the left column allows to select an history among the whole history items list. The user is then supposed to associate the selected history item to a parameter value in the right column. Note that all the variables implied by the selected history item will be associated to the parameter value, while the others (listed in the anisothermal variables selection box but not included in the selected history item) will be associated to the parameter value too, but with their own value reduced to null. The Go button updates the definition of all the anisothermal variables with the informations included in the dialog. Addition of new definition lines is still possible by means of the Add row button. The Sort button allows to sort the lines according to the parameter column. If the user clicks on the Go button despite of a not sorted parameter column, an error message is printed. The Cancel button closes the Fill from hist dialog without further modification to the definition of the anisothermal variables.
\(\bullet\) The second frame allows to define a -or to use a predefined- function to fit the evolution of the selected anisothermal variable with temperature. At the top of the second frame, a combo box may be used to select a function among a list stored in the functions_data_base file. When the user selects a function, its expression appears in the textfield.

Plot func command#

This command allows to plot the function selected in the functions_data_base file. Note that only the functions of the functions_data_base file can be plotted by hitting the Plot func command. If the combo box displays the no function or the user's function option, an error message is printed if the user clicks on the Plot func command.

The dialog shown in the next figure illustrates the plot of a function stored in the functions_data_base file.

../_images/aniso_plotfunc.svg

The textfield may be used to build user’s function not obviously based on functions included in the functions_data_base file.

Go command#

This command assigns to the (previously defined) anisothermal variable selected the function the expression of which is written in the textfield.

More command#

This command allows to define or modify the current and min/max values of the parameters of the parametric function assigned to the selected anisothermal variable. By hitting the More command, the user opens the More : function definition dialog shown in the next figure.

../_images/aniso_more.svg

This dialog is based on a table that lists the parameters of the parametric function assigned to the selected anisothermal variable, with their current and min/max values, and a checkbox to activate or deactivate their optimization. The Precision textfield corresponds to the number of points the parametric function curve will be constituted of. Note that the parametric function curve will besides include all the parameter values contained in the definition of the selected anisothermal variable. The Go button updates the definition of the parametric function of the selected anisothermal variable with the informations included in the dialog. The Set weights button opens the Set points weight dialog described in a previous section (see Optimizations/Set weights). The Cancel button closes the More : function definition dialog without further modification to the definition of the parametric function of the selected anisothermal variables.

Optimize command#

This command launches the Zopt module on the checked parameters to fit the parametric function with the anisothermal variable experimental data. When the optimization terminates because of convergence, a window is opened showing the best values found by the optimizer, as shown in the next figure.

../_images/aniso_opt_res.svg

The Go button must be clicked if the user does want to update the checked parameters values in the definition of the parametric function with the optimized values. Otherwise, the checked parameters values are left unchanged.

Edit opt command#

This command opens the Zopt input file automatically generated by the application from the informations defined in the dialog. The various convergence parameters allowed by the optimization method selected should be changed directly in the input file under the ***convergence section. Default values are provided that may be adequate in the majority of cases, so this operation is seldom needed. The Optimization chapter of the Zmat manual describes the parameters available to finely tune the optimization algorithm. Note that modifications of the automatically generated input file will be taken into account if the user hits the Save command.

Plot cost command#

This command plots the evolution of the cost function associated with comparisons between the parametric function and the anisothermal variable experimental data during optimization iterations. The command can be activated to check the convergence while the optimizer is currently running (see Optimizations/Plot cost )
\(\bullet\) On the left of the third frame, a selection box lists the global functions, built from several anisothermal variables, on which the sub-commands on the right can be activated, as described in the next pages.

Add command#

This command may be used to add a new global function. By hitting this command, the user opens the Add/Mod a multi parametric variables function dialog shown in the next figure.

../_images/aniso_add.svg

The Name textfield allows to define the name of the global function. Note that no default name is given at creation. The edition textfield is used to write the expression of the global function. The Min and Max textfields define the min/max X values of the global function curve. Note that the Min and Max textfields are respectively filled by default with the min/max values of the parameter in the definition of the anisothermal variables implied in the global function. The Precision textfield corresponds to the number of points the global function curve will be constituted of. Note that the global function curve will besides include all the parameter values contained in the definition of the anisothermal variables implied in its definition. The Go button updates the definition of the global function with the informations included in the dialog, while the Cancel button closes the dialog without further modification to the definition of the global function.

Example#

The next figure illustrates the definition of such a global function.

../_images/aniso_add_ex.svg

Mod command#

This command edits the global function selected. The Add/Mod a multi parametric variables function dialog is opened allowing to change the definition of the selected global function (see Anisothermal variables/Add.

Cop command#

This command creates a new global function in the Global function selection box, by copying the informations contained in the selected global function. The new global function can then be edited by means of the Mod command.

Del command#

This command deletes from the database the global functions selected in the Global function selection box.
\(\bullet\) The fourth frame contains the following sub-commands.

Plot command#

This command plots at the same time in the graphics area the curves representing the anisothermal variables (with or without defined parametric function) selected in the Anisothermal variable selection box, and the ones corresponding to the global functions selected in the Global function selection box.

Gnuplot file command#

This command creates the gnuplot file corresponding to the curve associated to the anisothermal variables (with or without defined parametric function) selected in the Anisothermal variable selection box, or to the global functions selected in the Global function selection box. Note that an error message is printed if the user clicks on the Gnuplot file command while several items are selected. The created gnuplot file, named aniso.gnuplot, is located in the current directory.

Clear command#

This command clears at the same time the selections in the Anisothermal variable selection box and in the Global function selection box.

Update var command#

This command updates the variable database by adding as new variables all the coefficients of the parametric functions attached to the anisothermal variables defined in the Anisothermal variables dialog. By hitting the Update var command, the Variables Creation mode dialog (for instance) will display the next time it will be opened the aniso-thermal parameters in the Variables selection box, as shown as example in the next figure.

../_images/aniso_update.svg

Update sim command#

This command may be used to create new simulation items. By hitting this command, the user opens the Update simulations dialog shown in the next figure.

../_images/aniso_update_sim.svg

This dialog contains at the top a Simulation items selection tree that lists all the simulation items created by means of the Simulation dialog. In the middle of the dialog, the temperature textfield allows to define a temperature value for which the user wants to create a new simulation item copied from the one selected in the upper Simulation items selection tree. The just created simulation item is then displayed in the Simulation items selection tree at the bottom of the dialog. Note that this second Simulation items selection tree lists only the simulation items created by means of this dialog, located in the ANISO directory itself located in the current directory. The Go button creates the new simulation item from the one selected in the upper Simulation items selection tree, conjugated with the value written in the temperature textfield, and updates the database. The Del button deletes from the database the simulation items selected in the second Simulation items selection tree. The Refresh button updates the two Simulation items selection trees with the informations contained in the Simulation dialog, while the Cancel button closes the Update simulations dialog without further modification to the database.

Cancel command#

This command closes the Anisothermal variables dialog without further modification to the database.