Linear friction tester design and validation

Abstract

Due to the complexity of friction phenomena, empirical analysis is the best way to predict the friction coefficient. To accomplish this, laboratory test rigs are needed. Although a rotary dynamic friction test bed was available to the authors, it had its limitations, such as low speed, inducement of lateral force, and the limitation of testing samples with different shapes. This paper will explain the process of designing and manufacturing a novel test setup for measuring friction and wear of the tire. The newly designed test rig can apply dynamic loading during the tests, and it can automatically measure the wear rate and temperature between cycles. In addition, it can be used for measuring the wear rate of rubber samples sliding on different types of surfaces. Therefore, experiments can be run under more controlled conditions. The designed linear friction tester can slide flat and round rubber samples approximately three meters across a large flat surface. The frictional force of rubber samples can be measured for various normal loads, velocities, and surface conditions. The new setup can automatically control the applied normal load on the sample using proportional–integral–derivative controller control. The important difference between this novel design and the existing testers used by other researchers is implementing the ball screw technology and the servo motor with high accuracy encoder to achieve highly accurate test results. In this design, the new mechanism for the ball screw is designed to increase the speed limit and eliminating vibrations while keeping the precision. In addition, in this design, the sample's mass can be measured automatically after each test cycle, thus providing a measure of the rate of wear of the rubber. In this study, the data collected by the linear friction tester is validated by comparing the data to the data collected by the dynamic friction tester (a validated rotary friction tester that exists in CenTiRe Lab). The data collected by the new setup was later used to benchmark the Persson analytical friction model.