Analysis of the Dynamic Behavioral Performance of Mechanical Systems With Multi–Clearance Joints

2011 ◽  
Vol 7 (1) ◽  
Author(s):  
S.M. Megahed ◽  
A.F. Haroun
Keyword(s):  
Impact Force ◽  
Dynamic Performance ◽  
Mechanical Systems ◽  
Behavioral Performance ◽  
Clearance Joints ◽  
Revolute Joints ◽  
Clearance Joint ◽  
Computation Algorithm ◽  
Maximum Impact Force ◽  
Crank Mechanism

In this investigation, the effect of revolute joints’ clearance on the dynamic performance of mechanical systems is reported. A computation algorithm is developed with the aid of SolidWorks/CosmosMotion software package. A slider-crank mechanism with one and two clearance-joints is studied and analyzed when working in vertical and in horizontal planes. The simulation results point out that the presence of such clearance in the joints of the system understudy leads to high peaks in the characteristic curves of its kinematic and dynamic performance. For a multiclearance joints mechanism, the maximum impact force at its joints takes its highest value at the nearest joint to the input link. This study also shows that, when the mechanism works in horizontal plane, the rate of impacts at each clearance-joint increases and consequently the clearance-joints and actuators will deteriorate faster.

Analysis of the Dynamic Performance of Multibody Mechanical Systems With Multiple Lubricated Revolute Joints

2012 ◽  
Author(s):  
A. F. Haroun ◽  
S. M. Megahed
Keyword(s):  
Multibody Systems ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Dynamic Performance ◽  
Fluid Pressure ◽  
Mechanical Systems ◽  
Hertz Contact ◽  
Revolute Joints ◽  
Crank Mechanism ◽  
The Ideal

In this work a method is proposed for modeling and simulation of multibody mechanical systems with multiple lubricated revolute joints with the aid of CAD and dynamic simulators softwares. The hydrodynamic forces produced between joint components due to lubrication are obtained by integrating Reynolds’ equation that is used for evaluating the fluid pressure distribution in the journal–bearing joint. The resulted force equations are combined with Hertz contact model to make a complete model for lubricated revolute joints. This model is used with the aid of SolidWorks/CosmosMotion software package to simulate multibody systems with multiple lubricated revolute joints and a computational algorism is developed in the frame of multibody dynamics methodology. A slider–crank mechanism with two lubricated revolute joints is used as an application example to demonstrate the efficiency and versatility of the proposed method. The simulation results point out that the introduction of a lubricant at the joint clearance makes the performance of the mechanism so close to that of the ideal mechanism that does not suffer from the clearance problem, as well as improves the overall system performance.

Study of the Dynamic Performance of Mechanical Systems With Multi-Clearance Joints

2010 ◽  
Author(s):  
S. M. Megahed ◽  
A. F. Haroun
Keyword(s):  
Contact Force ◽  
Dynamic Performance ◽  
Mechanical Systems ◽  
Local Deformation ◽  
Elastic Behavior ◽  
Contact Period ◽  
Clearance Joints ◽  
Coulomb’S Friction ◽  
Energy Dissipated ◽  
Maximum Impact Force

Joints’ clearance in mechanical systems such as linkage mechanisms and robots is an inevitable matter due to wear of mating parts. The presence of such clearance is a main source of impact forces resulting local deformation, wear and tear of such joints and consequently degradation of system performance. In this investigation, the effect of revolute joints’ clearance on the dynamic performance of mechanical systems is reported. The contact force between the pin (journal) and the bearing of the joint is modeled using Coulomb’s friction law, and contact force approach. This approach takes into consideration the elastic behavior of the collided bodies and the energy dissipated due to collision during the contact period. A computation algorithm is developed with the aid of SolidWorks/CosmosMotion software package. A crank-slider mechanism with one and two clearance-joints working in horizontal or vertical planes is studied. The simulation results point out that the presence of such clearance in the joints of the system understudy leads to high peaks in the characteristic curves of its dynamic and kinematic performance. The amplitudes of these peaks become higher as the number of clearance-joints included in the mechanism increases. For a multi-clearance joints mechanism, the maximum impact force at its joints takes its highest value at the nearest joint to the input link. This study also shows that, when the mechanism works in horizontal plane, the rate of impacts at each clearance-joint increases and consequently the clearance-joints and actuators will deteriorate faster. This means that working of the real mechanisms in vertical plan is more advantageous and improves their performance.

Wear Analysis of Two Revolute Joints With Clearance in Multibody Systems

2016 ◽  
Vol 11 (1) ◽  
Author(s):  
Pei Li ◽  
Wei Chen ◽  
Desheng Li ◽  
Rufei Yu ◽  
Wenjing Zhang
Keyword(s):  
Dynamic Analysis ◽  
Multibody Systems ◽  
Mechanical Systems ◽  
Clearance Joints ◽  
Revolute Joints ◽  
Wear Analysis ◽  
Coupling Dynamics ◽  
System Life ◽  
Crank Mechanism

The wear of multiple joints with clearance is one of the main impacts on the life of mechanical systems while very limited study has been done on this subject. To be different with many existed researches focused on the dynamic analysis of multibody systems with multiple clearance joints, the wear of two revolute joints with clearance in multibody systems is analyzed in this paper by coupling dynamics with tribology. Based on a planar slider crank mechanism with two clearance joints, it is observed that the clearance sizes nonlinearly influence the wear depths of the two joints with clearance. Meanwhile, an appropriate relationship between the two joints' clearance sizes can significantly decrease the wear of the joints, which would greatly improve the system life. Both the independent and interactive influences of the two joints with clearances on the wear are investigated in this paper. The relation equations of the two clearances obtained in this work will significantly decrease the wear of the two clearance joints.

Modeling and Analysis of Spatial Flexible Mechanical Systems With a Spherical Clearance Joint Based on the LuGre Friction Model

2019 ◽  
Vol 15 (1) ◽  
Author(s):  
Xiao Tan ◽  
Guoping Chen ◽  
Hanbo Shao
Keyword(s):  
Mechanical Systems ◽  
Beam Element ◽  
Friction Model ◽  
Lugre Friction Model ◽  
Clearance Joint ◽  
Lugre Friction ◽  
Computational Methodology ◽  
Crank Mechanism ◽  
Flexible Components

Abstract A computational methodology for modeling spatial flexible mechanical systems with stick-slip friction in a spherical clearance joint is presented. A modified three-dimensional (3D) absolute nodal coordinate formulation based shear deformable beam element with two nodes is proposed and employed to discretize the flexible components. To avoid locking problems, we employed an enhanced continuum mechanics approach to evaluate the beam element elastic forces. The strain components εyz, εyy, and εzz are approximated using linear interpolation to improve the computational efficiency while the loss of accuracy is acceptable. The contact and friction forces in a spherical clearance joint were evaluated by the hybrid contact and LuGre friction models, respectively. Three numerical examples are presented and discussed. A simple pendulum was utilized to prove the correctness of the modified beam element. A classical slider–crank mechanism was employed to validate the computational methodology. A spatial rigid–flexible slider–crank mechanism with a spherical clearance joint was used to investigate the effect of link flexibility and joint clearance on the dynamic behavior of mechanical systems. Using the LuGre friction model, we reproduced the Stribeck effect as it is expected in real world settings. The components with appropriate stiffness play the role of suspension for spatial mechanical systems with imperfect joints. The vibrations of the flexible components play an active role of intensifying the collision in kinematic joint with clearance.

Dynamic Behavior of a Revolute Clearance Joint in Multibody Mechanical Systems

2003 ◽  
Author(s):  
P. Flores ◽  
H. M. Lankarani ◽  
J. Ambro´sio ◽  
J. C. P. Claro
Keyword(s):  
Mechanical Systems ◽  
Force Model ◽  
Continuous Contact ◽  
Revolute Clearance Joint ◽  
Regular Motion ◽  
Clearance Joint ◽  
Contact Force Model ◽  
The Coefficient Of Friction ◽  
The Impact ◽  
Crank Mechanism

This work describes the influence of the clearance size and the coefficient of friction on the dynamic response of a revolute clearance joint in multibody mechanical systems. When there is a clearance in a revolute joint, impacts between the journal and the bearing can occur, and consequently, local deformations take place. The impact is internal and the response of the system is performed using a continuous contact force model. The friction effect due to the contact between joint elements is also modeled. The clearance size and friction effects are analyzed separately. Through the use of Poincare´ maps both periodic and chaotic responses of the system are observed. The results predict the existence of the periodic or regular motion at certain clearance sizes and friction coefficients and chaotic or nonlinear in other cases. A detailed discussion of the results relative to a planar slider-crank mechanism with a revolute clearance joint is presented.

Modeling Lubricated Revolute Clearance Joints in Multibody Mechanical Systems

2003 ◽  
Author(s):  
P. Flores ◽  
H. M. Lankarani ◽  
J. Ambro´sio ◽  
J. C. P. Claro
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Equations Of Motion ◽  
Mechanical Systems ◽  
Hydrodynamic Forces ◽  
Dynamic Loads ◽  
Governing Equations ◽  
Clearance Joints ◽  
Revolute Joints ◽  
System A

This work is concerned with the modeling of lubricated revolute clearance joints in multibody mechanical systems. The existence of the clearance at revolute joints is inevitable in all mechanical systems, and most of them are designed to operate with a lubricant fluid. It is known that the use of lubricant at revolute joints is demonstrated to be an effective way to ensuring better performance of the mechanical systems. The long journal-bearing theory for dynamic loads is used to evaluate the resulting hydrodynamic forces of the pressure distribution in the lubricated revolute joints. These hydrodynamic forces are included into the governing equations of motion of the system. A numerical example is presented in order to demonstrate the efficiency and accuracy of the methodology and procedures adopted. The results are close to those obtained with ideal joints even when simulated in a high-speed mechanism.

Dynamics Modeling and Simulation of Deployable Mechanism with Double Clearance

2016 ◽  
Vol 693 ◽  
pp. 306-313 ◽  
Author(s):  
Hong Zhou Huang ◽  
Jun Lan Li ◽  
Yun Qiang Yang ◽  
Shao Ze Yan
Keyword(s):  
Modeling And Simulation ◽  
Significant Influence ◽  
Dynamic Performance ◽  
Joint Clearance ◽  
Dynamics Modeling ◽  
Clearance Joints ◽  
Clearance Joint ◽  
Deployable Mechanism ◽  
Joint Vibration ◽  
Multi Body

Space deployable mechanisms have been widely employed in aeronautic industry, and the dynamic performance of the space deployable mechanisms become increasingly important. In this paper, the model of space deployable mechanism with double clearances is established by the multi-body program ADAMS. The deployable mechanism with ideal joint, single clearance joint and double clearance joints are simulated to investigate the effects of double clearance on the dynamic performance of the deployable mechanism. The results reveal that the coupler of double joint clearance has significant influence on dynamic performance of deployable mechanism. The results of simulation could help to predict the joint vibration in space deployable mechanisms.

A Design Method for Reducing the Effects of Clearances at Revolute Joints

1985 ◽  
Vol 199 (2) ◽  
pp. 153-158 ◽  
Author(s):  
J K Shin ◽  
B M Kwak
Keyword(s):  
General Theory ◽  
Empirical Formula ◽  
Design Method ◽  
Mechanical Energy ◽  
Clearance Joints ◽  
Revolute Joints ◽  
Non Linear ◽  
Linear Spring ◽  
Crank Mechanism ◽  
Kinematic Properties

A method for designing a mechanism which is free of contact loss in clearance connections is developed. Only revolute joints are considered as possible clearance joints. Earles and Wu's empirical formula has been used for defining a perfect joint or contact loss free joint. A general theory for conditions of a perfect joint has been derived in terms of the mechanical energy and the kinematic properties of the joint. This general theory was applied to a slider crank mechanism and it was shown that designing a perfect joint is theoretically possible through balancing by a non-linear spring. Further it was shown that this technique gives a practical guide for balancing a mechanism with linear springs to reduce the possibility of contact loss in clearance joints.

The mechanics of a climbing fall with a belayer who can be lifted

2021 ◽  
pp. 175433712199261
Author(s):  
Ulrich Leuthäusser
Keyword(s):  
Exact Solution ◽  
Impact Force ◽  
Initial Position ◽  
Minimum Mass ◽  
Trade Off ◽  
Linear Elastic ◽  
Stopping Distance ◽  
Sport Climbing ◽  
Force Reduction ◽  
Maximum Impact Force

In sport climbing, a common method of belaying is to use a static rope brake attached to the belayer’s harness, but the belayer can move freely. This paper investigates the dynamics of a climbing fall with such a belayer. The dynamics are nontrivial because of the belayer’s constraint to be always at or above his initial position. An exact solution for a linear elastic rope is presented. Compared to a fix-point belay, one obtains a considerable force reduction on the belay-chain. However, there is a trade-off of a longer stopping distance of both climber and belayer. In order to calculate the stopping distance, friction between rope and the top carabiner has been taken into account. Closed-form formulas allow for calculating the maximum impact force, as well as the minimum mass of the belayer which is necessary to hold a fall from a certain height.

scholarly journals Dynamics of Multibody Systems With Spherical Clearance Joints

2005 ◽  
Author(s):  
P. Flores ◽  
J. Ambro´sio ◽  
J. C. P. Claro ◽  
H. M. Lankarani
Keyword(s):  
Contact Force ◽  
Multibody Systems ◽  
Contact Forces ◽  
Force Model ◽  
Clearance Joints ◽  
Continuous Contact ◽  
Clearance Joint ◽  
Contact Force Model ◽  
Dynamics Of Multibody Systems ◽  
The Impact

This work deals with a methodology to assess the influence of the spherical clearance joints in spatial multibody systems. The methodology is based on the Cartesian coordinates, being the dynamics of the joint elements modeled as impacting bodies and controlled by contact forces. The impacts and contacts are described by a continuous contact force model that accounts for geometric and mechanical characteristics of the contacting surfaces. The contact force is evaluated as function of the elastic pseudo-penetration between the impacting bodies, coupled with a nonlinear viscous-elastic factor representing the energy dissipation during the impact process. A spatial four bar mechanism is used as an illustrative example and some numerical results are presented, being the efficiency of the developed methodology discussed in the process of their presentation. The results obtained show that the inclusion of clearance joints in the modelization of spatial multibody systems significantly influences the prediction of components’ position and drastically increases the peaks in acceleration and reaction moments at the joints. Moreover, the system’s response clearly tends to be nonperiodic when a clearance joint is included in the simulation.

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