.. post:: Jun 13, 2018
   :tags: parmec, tests, torsion, joints
   :author: Tomek

Parmec spherical joint
======================

Torsion spring has now been added to PARMEC, allowing to model angular hinges with rotational limits and spherical joints.
:ref:`TORSION_SPRING command <parmec-command-TORSION_SPRING>` is used to define an angle--torque relationship for three
angles of rotation about user specified local coordinate axes (x--roll, y--pitch, z--yaw). The command includes a cone
constraint which allows to model spherical joints in roll-pitch, roll-yaw, and pitch-yaw planes. Example application application
of this functionality is included as `tests/spherical_joint.py <https://github.com/tkoziara/parmec/blob/master/tests/spherical_joint.py>`_.
A `ParaView <https://www.paraview.org/>`_ animation generated by this test is included below. (...)

.. youtube:: https://www.youtube.com/watch?v=9JA1WQqGkR4
   :width: 640
   :height: 360