16.2.1 Density

Products: ABAQUS/Standard  ABAQUS/Explicit  ABAQUS/CAE  



A material's mass density:

  • must be defined in ABAQUS/Standard for eigenfrequency and transient dynamic analysis, transient heat transfer analysis, adiabatic stress analysis, and acoustic analysis;

  • must be defined in ABAQUS/Standard for gravity, centrifugal, and rotary acceleration loading;

  • must be defined in ABAQUS/Explicit for all materials except hydrostatic fluids;

  • can be specified as a function of temperature and predefined variables; and

  • can be distributed from nonstructural features (such as paint on sheet metal panels in a car) to the underlying elements using a nonstructural mass definition.

Defining density

Density can be defined as a function of temperature and field variables; however, for all elements except acoustic, heat transfer, coupled temperature-displacement, and coupled thermal-electrical elements the density is a function of the initial values of temperature and field variables and changes in volume only. It will not be updated if temperatures and field variables change during the analysis.

For acoustic, heat transfer, coupled temperature-displacement, and coupled thermal-electrical elements the density will be continually updated to the value corresponding to the current temperature and field variables.

Input File Usage:           Use either of the following options:


Property module: material editor: GeneralDensity

You can toggle on Use temperature-dependent data to define the density as a function of temperature and/or select the Number of field variables to define the density as a function of field variables.


Since ABAQUS has no built-in dimensions, you must ensure that the density is given in consistent units. The use of consistent units, and density in particular, is discussed in Conventions, Section 1.2.2. If American or English units are used, you must be particularly careful that the density used is in units of , where mass is defined in units of .


The density behavior described in this section is used to specify mass density for all elements, except hydrostatic fluid elements and rigid elements. Mass density for hydrostatic fluid elements is defined as a fluid density (see Hydrostatic fluid models, Section 20.4.1), and mass density for rigid elements is specified as part of the rigid body definition (see Rigid elements, Section 24.3.1).

In ABAQUS/Explicit a nonzero mass density must be defined for all elements (except hydrostatic fluid elements) that are not part of a rigid body.

In ABAQUS/Standard density must be defined for heat transfer elements and acoustic elements; mass density can be defined for stress/displacement elements, coupled temperature-displacement elements, and elements including pore pressure. For elements that include pore pressure as a degree of freedom, the density of the dry material should be given for the porous medium in a coupled pore fluid flow/stress analysis.

If you have a complex density for an acoustic medium, you should enter its real part here and convert the imaginary part into a volumetric drag, as discussed in Acoustic medium, Section 20.3.1.

The mass contribution from features that have negligible structural stiffness can be added to the model by smearing the mass over an element set that is typically adjacent to the nonstructural feature. The nonstructural mass can be specified in the form of a total mass value, a mass per unit volume, a mass per unit area, or a mass per unit length (see Nonstructural mass definition, Section 2.6.1). A nonstructural mass definition contributes additional mass to the specified element set and does not alter the underlying material density.