Effect of Clearance and Friction in Revolute Imperfect Joints on Dynamic Behaviors of a Slider-Crank Mechanism with Two Sliders

To increase the productivity of machining process, a two slider crank mechanism is proposed in this paper. In general, friction and clearance always present in any mechanical system. Hence, the e ects of friction and clearance on a dynamic system are so critical. This paper aims to investigate their e ects on the dynamic response of a slider-crank mechanism with two sliders and imperfect joints. Firstly, the mechanism is created in Solidworks and then it is simulated via nite element method in ANSYS. The dynamic simulation is conducted to evaluate the mentioned e ects. The results revealed that the e ect degree of clearance on the dynamic behaviors of the proposed mechanisms is significantly higher than that of friction. Also, the results indicated that the velocities, acceleration, and contact force graph are almost same at different friction coe cient. However, compared with ideal joint case, they had a maximum value and an unstable oscillation. This problem is due to journal collide into bearing induced the maximum values of contact force.


Introduction
There are signicant factors that cause a low mechanical accuracy for a mechanical system.First, a clearance in a revolute joint is not evitable due to manufacturing and assembly tolerances, etc.The clearance causes undesired vibration and abrasion of the joint and increase the clearance.Second, the friction leads to an abrasion and a deformation of the joint.Moreover, the clearance size causes a contact-impact force in the revolute joint, which leads to a low accuracy in the mechanical system.The impact force also causes an abrasion joint and increases the clearance.Moreover, the dierent driving speed inuences on the dynamic behaviors.great interest in on resolving challenging problems for dynamic responses of a mechanical system.For example, some focused on the contact force models [1], their results compared with the experimental data at the dierent clearance and driving speed.Besides, the exible components and two clearance joints also were considered [2] where the wear prediction and optimization of maximum allowable wear occurred at the same number of rotation cycles for two clearance joints, simultaneously.Moreover, the eect of multiple clearance joints on dynamic of planar multibody mechanical system were analyzed and presented [3], in which three were motion phases of journal as: free motion, contact motion and impact motion, comparison between ideal joint and one clearance joint, two clearances, three clearances joint.In order to restrict clearance joint eects, a compliant mechanism or exible mechanism was revealed based Taguchi method [4].However, the dierent material characteristic between journal and bearing causes friction force lead to joint wear and then induced damage for mechanical systems as reported [5] which where r B , r j are the radii of bearing and journal, respectively.

c 1 VOLUME: 2 |
2017 Journal of Advanced Engineering and Computation (JAEC) ISSUE: 1 | 2018 | March Recently, a lot of researchers have been a inuences of restitution coecient and material characteristic cannot be ignored.Inuences of clearance size and friction on the planar slidercrank mechanism with a clearance joint were considered by Bai and Zhao [6].In addition, PSO algorithm was used to optimize the dynamics of a slider-crank mechanism with a clearance joint by Varedi [7].The mixed lubrication model in revolute clearance joint was used to reduce friction by Zhao [8, 9].During operation of the machining process, the productivity for machining the surface of a workpiece is one of the most important performance index.Almost previous studies have focused on designing and analyzing for one slider crank mechanism.However, for enhancing the manufacturing eciency, there is a real requirements for a multiple-slider crank mechanism.Actually, the existing machining machines have worked based one cut tool that leads to low performances.Instead of using one slider crank mechanism, a two slider crank mechanism is proposed in this paper in order to increase number of cut tools and productivity for the planning machine.The novelty of the present paper is to propose a innovative design for new slider crank mechanism with two sliders.Regarding a high effective motion of turning, milling, and drilling machines for machining process of removing undesired materials, a slider-crank mechanism with two sliders is proposed to practitioner, engineer, academics, and industry.The objectives of this paper are to design and evaluate eects of clearance and friction on the dynamic of slider-crank mechanism with two sliders.Dynamic simulations are analyzed by using the nite element analysis in ANSYS.

2. 2 .
Revolute clearance joint model In general, two bodies are linked by joint, which is called journal bearing.The infect joint always has clearance.The imperfect joint as depicted in Fig. 3, the radial clearance is determined as follows:

Fig. 12 -
Fig. 12-15 are the contact force in revolute imperfect joints and translaion joint.they proved this force is suddenly increased and vibrated with the maximum value compared with the ideal joint case.This problem was reported in reference [1, 3, 5].
investigated the eects of clearances and friction on the dynamic responses of a slider-crank mechanism with two sliders.The model included a crank, two connecting rods, two sliders was designed using Solidworks.In the meanwhile, seven revolute clearance joints, two translational joints, the ction coecients and driving speed were set up by ANSYS.The simulation results can be concluded that the friction has slightly aected while the clearance has signicantly aected on the dynamics characteristics.Because the accelerations of two sliders were vibrated with the high peaks from when the journal collided into bearing at radius clearance is 0.25 mm and compared with ideal joints.The problem induced contact force with high peaks and oscillation unstable, which is close to reference[1,3,5].In future work, the dynamic responses of the mechanism will be controlled to make a better stable system, the mathematic model of the mechanical systems will compare with experiment and simulation result.The main contribution of this study is to propose a design and analyze for a two slider crank mechanism with regard to eect of friction and clearance.In addition, the results of this study are basic guide for designing and analyzing the dynamics, and from those results, we can monitoring how a change in velocity and acceleration of the system.