Clearance Joint Theory
The Clearance Joint allows two points that are connected to a pair of attachments or rigid domains to move within a specified clearance distance. The components connected through clearance joint are free to rotate relative to each other about all three axes and free to translate relative to each other within the specified clearance limit.
The following is an addition to the Ball Joint Theory and Hinge Joint Theory, some of which is also applicable for the clearance joint.
Clearance Joint Formulation
In 3D, the formulation of the clearance joint is similar to a ball joint, except for the translational constraints. Analogously, in 2D, the clearance joint formulation is similar to a hinge joint. Instead of translational constraints, a penalty-based formulation is used to enforce that the distance between specified points on both selected components is within the clearance distance.
The penalty force is computed as:
where Fj is the joint force magnitude, and pj is the penalty factor input having a default value of 0.1*diag*Eequ. In this expression, Eequ is an effective Young’s modulus, and diag is the geometric diagonal of the bounding box of the geometry.
The gap variable is the difference between the clearance (c) and the distance between the connection points (d).
The distance between connection points (d) is calculated as:
Here Xsrc and Xdst are the undeformed locations of the two connection points, and usrc and udst are the corresponding displacements.