UNIVERSAL

Connection type UNIVERSAL provides a connection between two nodes where the rotations are fixed about one local direction and free about two others. Connection type UNIVERSAL provides the rotational part of a UJOINT connection. Connection type UNIVERSAL cannot be used in two-dimensional or axisymmetric analysis.

Related Topics
Connector elements
Connector element library
In Other Guides
*CONNECTOR BEHAVIOR
*CONNECTOR SECTION

ProductsAbaqus/StandardAbaqus/ExplicitAbaqus/CAE

Description

Figure 1. Connection type UNIVERSAL.

A UNIVERSAL connection constrains the rotation about the shaft directions at two nodes. The shaft directions at nodes a and b are e2a and e2b, respectively. A UNIVERSAL connection requires that local direction e1a be perpendicular to e3b. This single constraint is written

e1ae3b=0 .

This constraint is equivalent to constraining the second Cardan angle to be zero in a Cardan angle parameterization of the local directions at node b relative to those at node a. If the initial orientation directions at node b do not satisfy the above constraint condition, the universal constraint will hold the second Cardan angle fixed at its initial value.

The constraint moment imposed by the UNIVERSAL connection is

m¯=m2(cosαe2a+sinαe3a).

A UNIVERSAL connection allows two free rotational components of relative motion between two nodes. The first and third Cardan angles that position local directions at node b relative to those at node a are

α=-tan-1(e2ae3be3ae3b)    and    γ=-tan-1(e1ae2be1ae1b).

The two available components of relative motion for the UNIVERSAL connection, ur1 and ur3, are the changes in the two unconstrained Cardan angles when the second Cardan angle is fixed. Therefore,

ur1=α-α0    and    ur3=γ-γ0,

where α0 and γ0 are the initial Cardan angles. The connector constitutive rotations are

ur1mat=α-θ1ref    and    ur3mat=γ-θ3ref.

The kinetic moment in the UNIVERSAL connection is

muniversal=m1e1a+m3e3b.

Friction

When used by itself, there is no predefined Coulomb-like friction in the UNIVERSAL connection. However, when the UNIVERSAL connection is used in combination with the JOIN connection type, the predefined friction is the same as the UJOINT connection.

Summary

UNIVERSAL
Basic, assembled, or complex: Basic
Kinematic constraints: e1ae3b=0
Constraint moment output: m2
Available components: ur1,ur3
Kinetic moment output: m1,m3
Orientation at a: Required
Orientation at b: Optional
Connector stops: θ1minαθ1max,
  θ3minγθ3max
Constitutive reference angles: θ1ref,θ3ref
Predefined friction parameters: None
Contact force for predefined friction: None