Output Rotation of Deformable body – Lesson 6

How to output the rotations of a deformable body consisting of solid elements in Ansys LS-DYNA® nonlinear dynamics structural simulation software?

Typical solid elements do not have nodal rotational degrees of freedom, therefore, there are no nodal rotations to output. The following approaches can be followed to output the rotations of a deformable body.

1) An approach to output the rotation of a region of a solid part is to define a small rigid patch using *CONSTRAINED_NODAL_RIGID_BODY. Then, the rotations of the nodal rigid body will be available in the RBDOUT file.

2) A second approach is to use the functions AX2(n1,n2), AY2(n1,n2), AZ2(n1,n2) of *DEFINE_CURVE_FUNCTION. These require that a local coordinate system is attached to node n1 and another one to n2. The local coordinate system should be defined with *DEFINE_COORDINATE_NODES and FLAG=1. Also, node n2 should not be omitted from the function arguments. The *DEFINE_CURVE_FUNCTION value with respect to the time is written to the output file CURVOUT, which is triggered by *DATABASE_CURVOUT.

3) A third approach is to add a new node and constrain it to a node set of the solid elements using *CONSTRAINED_INTERPOLATION. The rotations at this dependent node are written in NODOUT. However, to activate the rotation slots in NODOUT, you also need to add at least one shell or beam element in the model. This approach will not affect the stiffness of the deformable part.