2.3.3 Defining node-based surfaces

Products: ABAQUS/Standard  ABAQUS/Explicit  



A node-based “surface”:

  • can be used only as a “slave surface” in contact calculations;

  • can be used as a “slave” or “master surface” in a surface-based tie constraint;

  • is convenient in three-dimensional cases where ABAQUS cannot construct a unique physical surface on the elements, such as a pipe modeled with beam elements contacting the ocean floor or cables modeled with trusses contacting the ground after they break;

  • should be used with caution or not at all if accurate contact stresses are needed or if heat will be exchanged between the two surfaces;

  • can be assigned a nonzero thickness for use with the general contact algorithm in ABAQUS/Explicit;

  • should not be used to model a shell or membrane surface if the thickness and midsurface offset need to be considered in the problem;

  • must either contain nodes that are all part of the same rigid body or not contain any nodes that are part of a rigid body if the node-based surface is to be used in a penalty contact pair in ABAQUS/Explicit;

  • in ABAQUS/Standard does not provide heat conduction between surfaces in fully coupled temperature-displacement analysis or pore fluid flow between surfaces in coupled pore pressure–displacement analysis; and

  • does not include circumferential friction when used with axisymmetric elements with twist (CGAX, MGAX elements).

Alternatives to node-based surfaces are element-based surfaces (see Defining element-based surfaces, Section 2.3.2) and, in the case of rigid surfaces, analytical rigid surfaces (see Defining analytical rigid surfaces, Section 2.3.4). See Operating on surfaces, Section 2.3.5, for information on defining surfaces using Boolean combinations of existing surfaces.

Creating a node-based surface

You create a node-based surface by specifying the nodes or node sets that form the surface. You must assign a name to the node-based surface; this name will be used when defining contact interactions that involve the surface.

An optional associated area can be defined for each node. If no area is defined for a node and the surface is defined in a contact pair, the area specified as part of the contact property definition is used. If no area is specified as part of the contact property definition, a unit area is used.

In ABAQUS/Explicit the area used in contact pair calculations for a node in a node-based surface is always 1.0, regardless of the user-specified value. Therefore, the contact pressure output variable in ABAQUS/CAE should be interpreted as the contact force when a node-based surface is used for contact pairs in ABAQUS/Explicit.

In models that are defined in terms of an assembly of part instances, all surfaces must belong to a part, part instance, or the assembly. Additional rules are given in Defining an assembly, Section 2.9.1.

When the nodes of shell and membrane elements are used in a node-based surface, the thickness and midsurface offset of the shell or membrane at each node are not considered. However, a nonzero thickness can be assigned to node-based surfaces when used with the general contact algorithm in ABAQUS/Explicit (see Surface properties for general contact, Section 29.3.2, for more information).

Input File Usage:           
node number or node set, area