Kinematic coupling constraint

Problems xkcbeam.inp and xkcbem3.inp impose beam constraints using kinematic coupling constraints and are the same as the equivalent MPC problem. Problem xkcrevo.inp tests the finite-rotation revolute behavior of the kinematic coupling when only two rotational degrees of freedom are constrained. Problem xkcuniv.inp tests the finite-rotation universal behavior of the kinematic coupling when only one rotational degree of freedom is constrained.

The geometry for problems xkccirc.inp and xkccirc2.inp is shown in Figure 1.

Figure 1. Geometry for xkccirc.inp and xkccirc2.inp.

In this test the center node is the kinematic coupling reference node, and the perimeter nodes are the coupling nodes. To verify the options for specifying local coordinate systems at these coupling nodes, the constraint shown is created using four separate kinematic coupling definitions that share the center reference node. Each of these coupling definitions defines the local coordinate system using a different orientation system: cylindrical, rectangular, spherical, and a system defined in user subroutine ORIENT. In all cases the resulting local constraint basis directions coincide with the local directions of a cylindrical coordinate system whose axis is normal to the plane containing the nodes and passes through the reference node. Problem xkccirc.inp also includes nodal transformations at some nodes; this will have no effect on the constraints.

In the case of xkccirc.inp the kinematic coupling constrains all but the radial degree of freedom at the constrained nodes. Linear springs to ground (SPRING1) are attached to all constrained nodes and act in the x-direction. The reference node is then rotated $2\pi$ about z during a static step.

In the case of xkccirc2.inp the kinematic coupling constrains the circumferential degree of freedom only. Linear springs to ground (SPRING1) are attached to all constrained nodes and act in the x- and z-directions. The reference node is then rotated $2\pi$ about x during a static step.

Problem xkcsort.inp consists of a model composed of an axial arrangement of 20 shell elements. These elements are tied together using combinations of kinematic coupling constraints as well as MPCs. The constraints are defined such that kinematic coupling reference nodes appear after constraint definitions that eliminate degrees of freedom on these nodes; thus, sorting is required. The structure is clamped on one end and a concentrated axial load is applied to the other end.