Difference between coplings and constrain equations
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When used in the ANSYS LS-DYNA explicit dynamics program, the CP command can be used only with translational DOFs (UX, UY, UZ), while the CE command can be used with both translational and rotational DOFs (UX, UY, UZ, ROTX, ROTY, ROTZ) when they are applicable.
Since the rotational DOFs (ROTX, ROTY, ROTZ) are not allowed for coupled nodes, the CP family of commands should not be used in an explicit analysis to model rigid body behavior that involves rotations. If CP is used in this manner, it could lead to nonphysical responses.
Also, be aware that a coupled set containing nodes that are not coincident or nodes that are not along the line of the coupled degree of freedom does not produce a moment constraint. This means that if the structure rotates, the set of coupled nodes will rotate. Only the applied forces and the reaction forces will satisfy the moment equilibrium in the model. For each node in the coupled set, the result of satisfying the moment will depend on the distance from the node to the center of the coupled set, and the direction of displacement will depend on the resulting moment. This may lead to a nonphysical response in some cases.
Since the rotational DOFs (ROTX, ROTY, ROTZ) are not allowed for coupled nodes, the CP family of commands should not be used in an explicit analysis to model rigid body behavior that involves rotations. If CP is used in this manner, it could lead to nonphysical responses.
Also, be aware that a coupled set containing nodes that are not coincident or nodes that are not along the line of the coupled degree of freedom does not produce a moment constraint. This means that if the structure rotates, the set of coupled nodes will rotate. Only the applied forces and the reaction forces will satisfy the moment equilibrium in the model. For each node in the coupled set, the result of satisfying the moment will depend on the distance from the node to the center of the coupled set, and the direction of displacement will depend on the resulting moment. This may lead to a nonphysical response in some cases.
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