EULER

Connection type EULER provides a rotational connection between two nodes where the total relative rotation between the nodes is parameterized by Euler angles. An Euler-angle parameterization of finite rotations is also called a 3–1–3 or precession-nutation-spin parameterization. Connection type EULER 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 EULER.

The EULER connection does not impose kinematic constraints. An EULER connection is a finite rotation connection where the local directions at node b are parameterized in terms of Euler angles relative to the local directions at node a. Local directions {e1b,e2b,e3b} are positioned relative to {e1a,e2a,e3a} by three successive finite rotations α, β, and γ as follows:

  1. Rotate by α radians about axis e3a;

  2. Rotate by β radians about the intermediate 1-axis, e1=cosαe1a+sinαe2a;

  3. Rotate by γ radians about axis e3b.

The Euler angles are determined by the local directions as

α=-tan-1(e1ae3be2ae3b)+iπ;
β=cos-1(e3ae3b)+jπ;
γ=tan-1(e3ae1be3ae2b)+kπ.

Here i, j, and k are integers that account for rotations with magnitudes greater than π. Initially, the intermediate rotation angle β is chosen in the interval 0βπ.

If the intermediate rotation is an even multiple of π, β=2mπ, where m=0,±1,±2,, the other two Euler angles become non-unique. In this case

α+γ=tan-1(e2ae1be1ae1b)+nπ.

Similarly, if the intermediate rotation is an odd multiple of π, β=(2m+1)π, where m= 0, ±1,±2,, the other two Euler angles become nonunique as well. In this case

α-γ=tan-1(e2ae1be1ae1b)+nπ.

In both of these cases a singularity results in the rotation parameterization when the e3a and e3b axes align. The EULER connection should be used in such a way that these axes do not align throughout the computation. For a singularity-free condition Abaqus will choose α and γ such that a smooth parameterization results for the above values of the intermediate angle β.

The available components of relative motion in the EULER connection are the changes in the Euler angles that position the local directions at node b relative to the local directions at node a. Therefore,

ur1=α-α0;    ur2=β-β0;    and    ur3=γ-γ0;

where α0, β0, and γ0 are the initial Euler angles. The connector constitutive rotations are

ur1mat=α-θ1ref;    ur2mat=β-θ2ref;    and    ur3mat=γ-θ3ref.

The kinetic moment in a EULER connection is determined from the three component relationships:

mEuler=m1e3a+m2(cosαe1a+sinαe2a)+m3e3b.

Summary

EULER
Basic, assembled, or complex: Basic
Kinematic constraints: None
Constraint moment output: None
Available components: ur1,ur2,ur3
Kinetic moment output: m1,m2,m3
Orientation at a: Required
Orientation at b: Optional
Connector stops: θ1minαθ1max,
  θ2minβθ2max,
  θ3minγθ3max
Constitutive reference angles: θ1ref,θ2ref,θ3ref
Predefined friction parameters: None
Contact force for predefined friction: None