Civil Engineering Reference
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offers a variety of contact elements that can be used when contact between
two bodies cannot be simulated with the surface-based contact approach.
These elements include the following:
(1) Gap contact elements, which can be used for mechanical and thermal
contact between two nodes. For example, these elements can be used
to model the contact between a piping system and its supports. They
can also be used to model an inextensible cable that supports only tensile
loads.
(2) Tube-to-tube contact elements, which can be used to model contact
between two pipes or tubes in conjunction with slide lines.
(3) Slide line contact elements, which can be used to model finite-sliding
contact between two axisymmetric structures that may undergo asym-
metric deformations in conjunction with slide lines. Slide line elements
can, for example, be used to model threaded connectors.
(4) Rigid surface contact elements can be used to model contact between an
analytical rigid surface and an axisymmetric deformable body that may
undergo asymmetric deformations. For example, rigid surface contact
elements might be used to model the contact between a rubber seal
and a much stiffer structure.
5.2.2.5 Frictional Behavior
When surfaces are in contact, they usually transmit shear as well as normal
forces across their interface. There is generally a relationship between these
two force components. The relationship, known as the friction between the
contacting bodies, is usually expressed in terms of the stresses at the interface
of the bodies. The friction models available in ABAQUS [1.29] can include
the classical isotropic Coulomb friction model, which in its general form
allows the friction coefficient to be defined in terms of slip rate, contact pres-
sure, average surface temperature at the contact point, and field variables; see
Figure 5.14
.
Coulomb friction model provides the option for modelers to
define a static friction coefficient and a kinetic friction coefficient with a
smooth transition zone defined by an exponential curve. Coulomb friction
model also allows the introduction of a shear stress limit, which is the max-
imum value of shear stress that can be carried by the interface before the sur-
faces begin to slide. ABAQUS assumes by default that the interaction
between contacting bodies is frictionless. Modelers can include a friction
model in a contact property definition for both surface-based contact and
element-based contact. The basic concept of the Coulomb friction model
is to relate the maximum allowable frictional (shear) stress across an interface
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