Global Time Step

The global time step (GTS) method can be used to calculate the time step of a model based on the natural frequency of the model.

For some models the global time step method results in a higher time step when compared to calculating the time step based on each element or node. An iterative algorithm is used to calculate the global time step which is more expensive than calculating the element or nodal time step. Therefore, the global time step calculation is done every 20 cycles by default.
  • /DT/GLOB/Iflag
  • Δ T sca

If Iflag=1, insert the next line

Tol_GTS Ncycles

Δ T sca
Scale factor for the element time step
Convergence tolerance for the iterative algorithm
Number cycles between the calculation of the global time step

The global time method is useful in models without a large change in stiffness such as drop test simulations.

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 and 27