Engine Keyword Alternative time step calculation method for /TETRA4 using /PROP/SOLID Itetra4=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.



Δ T sca Δ T min

If using /DT1/BRICK/CST/1, insert the next line

ASP_min VDEF_min


Field Contents SI Unit Example
Keyword3 Time step control type. 1
Elements are switched to small strain formulation to maintain the constant time step, Δ T min . Only valid for certain values of Ismstr as defined in element properties. 4
The element which is controlling the time step is removed so that the constant time step, Δ T min , can be maintained.
The run will stop if the time step reaches Δ T min and a restart file will be written.

If Keyword3 is not specified, that is, /DT1/BRICK, then the default STOP option is used.

Δ T sca Scale factor on critical time step.

Default = 0.9

Δ T min Minimum time step.  
Iflag Number of additional (optional) cards. Only required for /DT1/BRICK/CST/Iflag.
= 0 or blank
Only one card for Δ T sca and Δ T min is read.
= 1
An additional card for ASP_min and VDEF_min are read.
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



  1. The time step control will be activated when the time step of the element controlling the time step of the simulation becomes less than:

    Δ T min Δ T s c a MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSaaaeaacq qHuoarcaWGubWaaSbaaSqaaiGac2gacaGGPbGaaiOBaaqabaaakeaa cqqHuoarcaWGubWaaSbaaSqaaiaadohacaWGJbGaamyyaaqabaaaaa aa@407F@

  2. /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.
  3. This time step calculation is actually the same as default one, except for /TETRA4 using Itetra4=1000.
  4. /DT1/BRICK/CST is only active when Ismstr=2 or 12 is defined in /PROP/SOLID. It is compatible with /TETRA4 with Itetra4=1000, /TETRA10, and /BRICK solid elements with Isolid=1, 2, 14, 17, or 24.
  5. 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.