26.15.2 User-defined element library

Product: ABAQUS/Standard

References

Element types

Un n must be a positive integer () that will define the element type uniquely.

Active degrees of freedom

As defined in the user element definition.

Additional solution variables

You can define solution variables associated with nodes that are not connected to other elements. However, definition of constraints with Lagrange multipliers in user elements should be avoided because of potential equation solver problems.

Nodal coordinates required

None required for linear user elements.

As needed in user subroutine UEL for general user elements. The maximum number of coordinates per node is specified in the user element definition (see “Defining the maximum number of coordinates needed at any nodal point” in “User-defined elements,” Section 26.15.1). The first coordinate entries at each node should correspond to the standard ABAQUS convention (X, Y, Z or r, z for axisymmetric elements).

Element property definition

For a linear user element the properties are the stiffness and mass, defined via user-defined matrices or read from an ABAQUS/Standard results file. If necessary, you can specify Rayleigh damping values for linear user elements in the element property definition.

For a general user element defined via user subroutine UEL, you define the number of element properties in the user element definition and provide the numerical values in the element property definition. The definition of these properties depends on your coding in subroutine UEL.

Input File Usage:

*UEL PROPERTY

Element-based loading

None for linear user elements.

Un: Distributed load or flux whose magnitude is given via distributed load or distributed flux loading definitions (see “Distributed loads,” Section 27.4.3, or “Thermal loads,” Section 27.4.4) for a general user element. n must be a positive integer that is passed into user subroutine UEL to identify the particular load type.

UnNU: Distributed load or flux that is completely defined as equivalent nodal values inside user subroutine UEL for a general user element. n must be a positive integer: will be passed into subroutine UEL when such a load is active to identify the load type. The minus sign on n indicates that the load is of type NU.

Element output

For a linear user element there are no stress or strain components since the element only appears as a stiffness and mass.

For a general user element any stress, strain, or other solution-dependent variables within the element must be defined as solution-dependent state variables by your coding within subroutine UEL. They can be output using output variable SDV.

Currently element output to the output database is not supported for user-defined elements.

Node ordering on elements

As defined in the user element definition.

Un	n must be a positive integer () that will define the element type uniquely.