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Appendix 4: Switch
In geotechnics, one is often constrained to deactivate progressively some finite elements, so that a hollow proceeding is simulated and to activate other finite elements, modeling the progressive appearance of a support or a stratum construction.
In metal forming processes such as continuous casting or additive manufacturing, thermal boundaries (CONRA element) or material modeled by solid elements can appear.
The present appendix proposes a solution for these types of problems.
The switch process is activated by the variable ISWI=1 on the 3rd line of the execution data (ex.dat). It essentially concerns the sub-program ELEMB. The concerned elements are already present in the lag files but the switch file determines their activation. If they are inactive, the stresses, internal variables and the stiffness matrix are potentially put to zero (NSAVES variable defines it). Otherwise they are computed and saved as usually.
The various stages: hollow, building wall tunnel, cooling by water spray, new metal deposit etc must be distinguished. They are called phases hereafter.
The elements which are active during the whole computation do not have to be specified.
Data to be given in the file .SWI
| First line (5I5) | |
|---|---|
| NGR(I5) | Number of activation or deactivation phases (maximum value is currently 10000, changed by G. Gilles on May 2015. It’s possible to change this value!) |
| IFORM (I5) | When this number is equal to 0 or 1, the elements to be activated are written in the format 14I5. When it is equal to 2, the elements to be activated are written in the format 8I10. This is useful when the number of nodes exceeds 10 000. |
| iOFF_elem(I5) | Maximum number of deactivated elements at any given IGR |
| iON_elem(I5) | Maximum number of activated elements at any given IGR |
| iTFORM(I5) | When this number is equal to 1, the format for the definition of activation and deactivation moments is G15.0 (instead of G10.0) |
Group of 1+NPICS(IGR) lines repeated NGR times
| Line 1 - (2I5) | |
|---|---|
| NPICS(IGR) | ≤ 20 (maximal value in the code) |
| NSAVES(IGR) | Normally, when an item is deactivated, stresses and state variables of this element are canceled. Sometimes, however, it is interesting to remember either the stresses or the state variables, or both. The NSAVES variable allows managing this problem, according to its value the following data is stored: = 0 stresses and state variables are set to 0 = 1 computed stresses are stored and state computed variables are set to zero = 2 computed state variables are stored and computed stresses are set to zero = 3 computed stresses and state variables are stored |
| Line 2 to NPICS(IGR) - (2G10.0) or (2G15.0) if iTFORM=1 | |
| PICAR (IPIC,1,IGR) IPIC=1,NPICS | Activation moment - it can be equal to 0, in this case, the elements are active since the beginning of the analysis |
| PICAR (IPIC,2,IGR) IPIC=1,NPICS | Deactivation moment - it can be greater than the duration of the analysis, in this case, when they are active, the elements stay present until the end of the analysis |
