Study of the Rolling Friction Coefficient between Dissimilar Materials through the Motion of a Conical Pendulum.

Stelian Alaci,Ilie Muscă,Ștefan-Gheorghe Pentiuc

doi:10.3390/ma13215032

Stelian Alaci, Ilie Muscă + Show 1 more

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https://doi.org/10.3390/ma13215032

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Abstract

The rolling friction phenomenon is encountered in a wide range of applications and when two different materials are involved, quantitative characterization is necessary. The parameter to be determined is the coefficient of rolling friction, for whose estimation a methodology is proposed, based on the damped oscillation of a conical pendulum. The pure rolling contact between a sphere and a plane is obtained when a steel ball is the bob of the pendulum, which rolls on an inclined plate made from a second material from the contacting pair. The mathematical model of the motion of a conical pendulum constructed from a revolution body supported on an inclined plane in the presence of the rolling friction is developed. The dynamic equations of the rigid body with fixed point are applied and the differential equation of motion of the pendulum is obtained together with the expressions of the reaction forces in the contact point. For different pairs of materials, tests are performed on a laboratory device. The damped oscillatory motion of the conical pendulum is video-captured for the estimation of the angular amplitude variation. A program for image processing is developed for measuring the values of angular elongations from the analysis of each frame of the video and, finally, the coefficient of rolling friction is obtained. For all the materials tested, a linear decrease in angular amplitude is detected and the slope of angular amplitude can be considered as a characteristic parameter related to the coefficient of rolling friction between the two materials.

Highlights

The elements of any mobile mechanical structure requiring the accomplishment of a definite function must have well expressed motions
For pure rolling motion, selected moving system consists in a conical pendulum afriction quantitative influencing thethe magnitude of the rolling friction torque
The coefficient of rolling friction is an important parameter influencing the tribological behavior of mechanical systems

Summary

Introduction

The elements of any mobile mechanical structure requiring the accomplishment of a definite function must have well expressed motions. In the zones of interaction between two elements, according to the action and reaction principle, a system of forces and torques will occur Their magnitude and orientation are critically influenced by the shape of the contacting surfaces and by the physical properties of the bodies. Adding the condition of smooth surfaces to the hypothesis of rigid bodies, the most general situation is characterized by the theoretical point contact, which is a nonconforming contact. Such contacts are known as higher pairs [1,2] and frequently met in engineering applications. The possible motions are as follows: sliding along a straight line from the tangent plane and the rotations about the normal (spinning motion), and about a line

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