لخّصلي

This issue is of paramount importance in the analysis and design of realistic multibody mechanical systems undergoing spatial motion.These forces are then incorporated into a standard formulation of the system's governing equations of motion as generalized external forces.When the spherical clearance joint is modeled as dry contact; i.e., when there is no lubricant between the mechanical elements which constitute the joint, a body-to-body (typically metal-tometal) contact takes place.In this situation, the squeeze film action, due to the relative approaching motion between the mechanical joint elements, is considered utilizing the lubrication theory associated with the spherical bearings.

This issue is of paramount importance
in the analysis and design of realistic multibody mechanical systems undergoing spatial motion.
When the spherical clearance joint is modeled as dry contact; i.e., when there is no lubricant
between the mechanical elements which constitute the joint, a body-to-body (typically metal-tometal) contact takes place. The joint reaction forces in this case are evaluated through a
Hertzian-based contact law. A hysteretic damping factor is included in the dry contact force
model to account for the energy dissipation during the contact process. The presence of a fluid
lubricant avoids the direct metal-to-metal contact. In this situation, the squeeze film action, due
to the relative approaching motion between the mechanical joint elements, is considered
utilizing the lubrication theory associated with the spherical bearings. In both cases, the intrajoint reaction forces are evaluated as functions of the geometrical, kinematical and physical
characteristics of the spherical joint. These forces are then incorporated into a standard
formulation of the system’s governing equations of motion as generalized external forces. A
spatial four bar mechanism that includes a spherical clearance joint is considered here as
example. The computational simulations are carried out with and without the fluid lubricant,
and the results are compared with those obtained when the system is modeled with perfect joints
only.