Simulation Tools
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Free
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A small collection of converters for quantities that come up regularly in simulation work. Each category has a quick reference table that updates to whichever units are currently selected.
LS-DYNA uses radians internally for most angular quantities in the model, including joint definitions, initial velocity directions and load curve angles. Engineering input is typically in degrees. NATO mils (6400 per full circle) appear in ballistics and impact angle test reports. Gradians (400 per full circle) are used in some European survey and artillery references.
Stress units span many orders of magnitude across LS-DYNA systems. Pa in SI, MPa in the common crash systems, GPa in mm/ms/kg, and Mbar in the explosives systems. Useful for cross-checking material card parameters when switching between systems.
Note that 1 mm/ms = 1 m/s exactly, which is why the two most common LS-DYNA crash systems (tonne/mm/s and g/mm/ms) give the same velocity factor. Impact velocities in ballistics are typically expressed in m/s, while LS-DYNA input for the mm/ms system uses the same numerical value.
Required for Johnson-Cook temperature softening and thermal material models. LS-DYNA expects temperature in whatever unit matches the rest of the system, most commonly Kelvin. Room temperature is approximately 293 K and steel melts around 1800 K.
In the tonne/mm/s system energy is in N·mm, which equals 1 mJ. In the g/mm/ms system energy is also in N·mm. In SI it is in Joules. The kN·mm unit is equal to 1 J and appears in the kg/mm/ms system.
Density values differ by large powers of 10 across systems. Steel at 7830 kg/m³ becomes 7.83×10⁻³ t/mm³ in the tonne/mm/s system and 7.83×10⁻⁶ kg/mm³ in SI-length mixed systems. Getting this wrong by a factor is a common source of incorrect simulation mass.
Straightforward, but included because model geometry is often defined in one unit while material cards use another. The most common mismatch is CAD geometry in mm imported into a model that expects m.