The stability of the numerical algorithm depends on the size of the time step used for time integration . For brick elements, Radioss uses the following equation to calculate the size of the time step:(1)
h k l c ( α + α 2 + 1 )
This is the same form as the Courant condition for damped materials. The characteristic length of a particular element is computed using:(2)
l = E l e m e n t V o l u m e L a r g e s t S i d e S u r f a c e

For a 6-sided brick, this length is equal to the smallest distance between two opposite faces.

The terms inside the parentheses in the denominator are specific values for the damping of the material:
  • α = 2 v ρ c l
  • ν effective kinematic viscosity
  • c = 1 p ρ ρ for fluid materials
  • c = K ρ + 4 3 μ ρ = λ + 2 μ ρ for a solid elastic material
  • K MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbwvMCKf MBHbqefqvATv2CG4uz3bIuV1wyUbqedmvETj2BSbqefm0B1jxALjhi ov2DaebbnrfifHhDYfgasaacH8srps0lbbf9q8WrFfeuY=Hhbbf9v8 qqaqFr0xc9pk0xbba9q8WqFfea0=yr0RYxir=Jbba9q8aq0=yq=He9 q8qqQ8frFve9Fve9Ff0dmeaacaGacmGadaWaaiqacaabaiaafaaake aacaWGlbaaaa@39A7@ is the bulk modulus
  • λ , μ are Lame moduli

The scaling factor k=0.90 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4Aaiabg2 da9iaaicdacaGGUaGaaGyoaiaaicdaaaa@3AD5@ , is used to prevent strange results that may occur when the time step is equal to the Courant condition. This value can be altered by the user.