Spatial rigid-multibody systems with lubricated spherical clearance joints: modeling and simulation

Abstract

The dynamic modeling and simulation of spatial rigid-multi-body systems with lubricated spherical joints is the main purpose of the present work. 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. From the general results it is observed that the system's performance with lubricant effect presents fewer peaks in the kinematic and dynamic outputs, when compared with those from the dry contact joint model.

A parametric study on the dynamic response of planar multibody systems with multiple clearance joints

“…The serious consequences of the clearance joints on the behavior of the multibody systems have motivated various theoretical and experimental investigations over the last three decades [15][16][17][18][19][20][21][22][23]. Furthermore, mechanical systems with clearance joints can have a predictable nonlinear dynamic response [24][25][26].…”

Numerical and experimental investigation on multibody systems with revolute clearance joints

“…Over the last few decades, a number of researchers have proposed various methodologies for modeling mechanisms with clearance joints [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. However, most of these studies only deal with numerical models.…”

Multi-objective Optimization of Mechanisms with Clearances in Revolute Joints

“…During the period of contact, the indentation depth, relative penetration veloctiy and non-linear force are readily available and are related to the contact force. Flores et al [5] conducted extensive study using experimental and computer models to predict the dynamic response of a mechanical system with dry and lubricated revolute joints. In their study, the subjective measurements determined to be of influential to the performance of a mechanical system are clearance size, crank angular velocity and number of joints modeled as clearance joints.…”