/DT1/BRICK/Keyword3/Iflag
Engine Keyword Alternative time step calculation method for /TETRA4 using /PROP/SOLID I_{tetra4}=1000 solid elements.
It results in a lower but more accurate time step than the default calculation method. The result will be more robust and stable. Otherwise, this option is identical to /DT/BRICK/Keyword3/Iflag.
Format
/DT1/BRICK/Keyword3/Iflag
$\text{\Delta}{T}_{sca}$ $\text{\Delta}{T}_{\mathrm{min}}$
If using /DT1/BRICK/CST/1, insert the next line
ASP_min VDEF_min
Definitions
Field  Contents  SI Unit Example 

Keyword3  Time step control
type. 1
If Keyword3 is not specified, that is, /DT1/BRICK, then the default STOP option is used. 

$\text{\Delta}{T}_{sca}$  Scale factor on
critical time step. Default = 0.9 

$\text{\Delta}{T}_{\mathrm{min}}$  Minimum time step.  
Iflag  Number of additional
(optional) cards. Only used for
/DT/BRICK/CST/1.


ASP_min  Minimum Aspect ratio
(Tet collapse); Solid elements for which aspect ratio ≤
ASP_min will be switched to small strain
formulation to keep constant time step. 5
Default = 0 

VDEF_min  Minimum Volume ratio
(V/Vo); Solid element for which Volume change ≤
VDEF_min will be switched to small strain
formulation to keep constant time step. 5
Default = 0 
Comments
 The time step control will be
activated when the time step of the element controlling the time step of the
simulation becomes less than:
$\frac{\text{\Delta}{T}_{\mathrm{min}}}{\text{\Delta}{T}_{sca}}$
 /DT1/BRICK/Keyword3 can be used with /DT/NODA/Keyword3. It will also result in a more robust calculation of the time step, and a more stable computation.
 This time step calculation is actually the same as default one, except for /TETRA4 using I_{tetra4}=1000.
 /DT1/BRICK/CST is only active when I_{smstr}=2 or 12 is defined in /PROP/SOLID. It is compatible with /TETRA4 with I_{tetra4}=1000, /TETRA10, and /BRICK solid elements with I_{solid}=1, 2, 14, 17, or 24.
 When using /DT1/BRICK/CST/1, elements will be switched to small strain formulation when one of the two minimum values for ASP_min or VDEF_min have been reached. ASP_min uses the same tet collapse calculation as HyperMesh element quality check. Elements failing the ASP_min criteria will be switched to the small strain formulation at the beginning or during a simulation. VDEF_min can be used to switch highly deformed or compressed elements to the small strain formulation during the simulation thus avoiding negative volume issues that can arise.