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/DT/GLOB |
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/DT/GLOB |
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/DT/GLOB |
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/DT/GLOB |
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/DT/GLOB - Global Time Step
Description
Global time step estimation, enables setting the time step to a higher value than the usual elementary or nodal time step.
/DT/GLOB or /DT/GLOB/Iflag
Tol_GTS Ncycles
Data |
Description |
|---|---|
Iflag |
Number of additional (optional) cards = 0 or blank: only one card for =1: Tol_GTS and Ncycles are read from input. (Comment 2) |
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Scale factor on time stop Default = 0.9 |
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Minimum time step |
Tol_GTS |
Tolerance for GTS convergence Default = 10-3 |
Ncycles |
Frequency (number of cycles) for global time step estimation Default = 20 |
| 1. | If /DT/GLOB is used with /DT/NODA, the simulation begins with nodal time step and global time step follows. If /DT/GLOB is used alone or with /DT, the starting time step is element type step followed by global time step. |
| 2. | If Iflag =1, the tolerance for GTS convergence, Tol_GTS and the frequency Ncycles for global time step must be entered. If Iflag =0 or is omitted, default values of 10-3 for Tol_GTS and 20 for Ncycles are used. |
| 3. | The Global Time Step option is available for the following features: |
| • | Solid elements: /TETRA4, /TETRA10, hexa with the flags below |
| • | /PROP/SOLID: Isolid = 1 (Belytschko), 14 (HA8), 17 (H8C), 24 (HEPH) and 16 (20-noded) |
| • | Shell elements: Ishell = 1 (Belytschko-Tsay), 12 (Batoz), and 24 (HEPH) |
| • | Truss element |
| • | Beam element |
| • | Contact interfaces: TYPE7, TYPE24 (without edge-to-edge option), and TYPE2 with spotflag 25 |
| 4. | In most cases, default values are sufficient to ensure a stable run, however in cases where the global stiffness varies frequently due to oscillating contact conditions, it is recommended to increase the convergence tolerance, Tol_GTS = 0.05 and reduce the scale factor on time step,  = 0.8. |
and 
is read. 
