*UNIT SYSTEM

Define a unit system for an Abaqus model for translation to other solvers.

This option is used to define the units system used in the Abaqus model for the purpose of translating to other formats. It is used for importing external fields, for co-simulation, and to create a Simpack Flexible Body Interface (FBI) file.

This information has no effect on the Abaqus simulation; you must ensure that a consistent set of units is used.

The units of a mechanical system can be defined by specifying one of the basic triples: length-mass-time or length-force-time. These two methods are mutually exclusive. If you specify length-mass-time, the force unit is defined implicitly. If you specify length-force-time, the mass unit is defined implicitly.

This page discusses:

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Defining a Unit System for Translating Data with Other Solvers

Products Abaqus/Standard Abaqus/Explicit

Type Model data

LevelModel

Optional parameters

SYSTEM

Set SYSTEM=SI if the model uses the International System of units.

Set SYSTEM=MKS if the model uses meter-kilogram-second units.

Set SYSTEM=CGS if the model using centimeter-gram-second units.

Set SYSTEM=FPS if the model uses foot-pound-second units.

The MKS, CGS, and FPS unit systems apply to mechanical simulations only and do not define other quantities such as temperature.

Optional data lines to define units for the physical dimensions if the SYSTEM parameter is omitted

First line

  1. Physical dimension name LENGTH, MASS, FORCE, TIME, TEMPERATURE, ELECTRIC CURRENT, AMOUNT SUBSTANCE, or LUMINOSITY.

  2. Unit symbol to derive the conversion factor. The unit symbol defines the conversion factor between the Abaqus model and the SI system. If this field is left blank, the following SI units are assumed: length (m), mass (kg) or force (N), time (s), temperature (K), electric current (A), amount substance (mole), and luminosity (candela).

    The following unit symbols are available: length (m, cm, mm, km, in, ft, yd, and mi); mass (kg, g, t, lb, klb, oz, slug, slinch, and uton); force (N, lbf, kgf, ozf, dyne, kN, klbf, tf, and pdl); time (s, ms, h, min, and d); and force (N, lbf, kgf, ozf, dyne, kN, klbf, tf, and pdl); temperature (K, C, and F), electric current (A, mA, microA, nA, and pA), amount of substance (mole), and luminosity (candela).

    For a description of unit names, unit symbols, and the associated conversion factor, see Defining a Unit System for Translating Data with Other Solvers.

  3. The "To SI" conversion factor. For units not defined in the list of unit symbols, specify the conversion factor from the Abaqus model to the SI system. In this case the second field should be left blank. If this field is left blank, a conversion factor of 1.0 is used.

Repeat this data line as often as necessary to define units for the physical dimensions.

If the data line for a physical dimension is omitted, the default SI unit is assumed. Any rotations are in radians. Data lines for the mass and force physical dimensions are mutually exclusive. If neither mass nor force is specified, the SI unit of mass is assumed, and the force unit is derived. When converting temperatures, you must define the absolute zero value by defining physical constants. If both the unit symbol and the “To SI” factors are specified on the data line, then resulting conversion factor will be the product from both entries.