# /DT/THERM

Engine Keyword Stability time step for thermal analysis.

## Format

/DT/THERM

# The next line is optional

$\text{\Delta}{T}_{sca}$

## Definition

Field | Contents | SI Unit Example |
---|---|---|

$\text{\Delta}{T}_{sca}$ | Optional scale factor
for element thermal time step. Default = 0.9 |

## Comments

- The thermal time step is computed for stability of thermal analysis. It is much larger than the mechanical time step; and therefore, computational time cost is lower.
- The thermal time step is based on thermal properties.
- The choice between the two available
methods depends on the type of simulation.
Element Thermal Step (default):

The stability condition is:

$$\text{\Delta}t=\underset{\mathit{elements}}{\mathrm{min}}\left(\frac{{l}_{c}{}^{2}}{2\alpha}\right)$$Where,- ${l}_{c}$
- Characteristic length of elements
- $\alpha $
- Thermal diffusitivity

This option is available for solids and shells.

Nodal Thermal Time Step:

The nodal time step is smaller than the element time step and it is used when thermal exchange with tools in contact with sheet is considered to insure precision and stability of results. This option is activated when the option /DT/NODA/Keyword3/Iflag is set or when interfaces are defined.

$$\text{\Delta}t=\underset{\mathit{nodes}}{\mathrm{min}}\left(\frac{2{m}_{\mathit{node}}c}{{K}_{\mathit{node}}}\right)$$Where,- ${m}_{\mathit{node}}c$
- Nodal heat capacity
- ${K}_{node}$
- Equivalent nodal conductivity

- This option is used only for pure thermal analysis. All nodes are automatically constrained when /DT/THERM is used. After the run is complete, constraints are released for all nodes to the state at the beginning of the run. If using LAW80, thermal expansion is ignored.