On the measurement of friction coefficient utilizing the ring compression test

The main objective of this research was to investigate whether generalized friction calibration curves, as recommended in the literature for use with ring compression tests, are applicable to all types of materials and test conditions. Specifically, the effects of material properties, strain-rate sensitivity, and “barreling” on the behavior of friction calibration curves were investigated. To this end, a series of ring compression tests were conducted in order to determine the magnitude of the friction coefficient, μ, as well as the corresponding calibration curves for two types of modeling materials, white and black Plasticine. The experiments were first conducted using the Physical Modeling Technique (PMT) and then simulated via an elastic–plastic finite element code (ABAQUS). In contrast to the results available in the literature, where the same friction calibration curves are recommended for all types of materials and test conditions, the results of this investigation showed that friction calibration curves are indeed affected by the material properties and test conditions and every material possesses its own distinctive friction calibration curve.     

Surface roughness and material strength of tribo-pairs in ring compression tests

The quantification of friction by means of simple models such as Amonton-Coulomb’s and the law of constant friction is questionable because the influence of surface roughness and material strength, among other factors, is not considered.This paper provides a comprehensive analysis on the influence of surface roughness and material strength in friction and proposes a new operator based on a sigmoid function to incorporate the combined influence of both phenomena in a modified version of the Amonton-Coulomb’s law.The presentation is supported by thoroughly researched quantitative data obtained from experimentation and finite element modelling of the ring compression test.     

虚拟仪器在触点分断电弧性能测试系统中的应用

本文采用虚拟仪器技术,研制了一套触点分断电弧性能测试系统,该系统基于触点材料试验机、工业控制计算机和高速数据采集卡,用于研究分断电流、电极分断速度、触头材料等参数对电弧性能的影响。系统操作简便,自动化程度高,测量准确度高。     

Simulation of wear and contact pressure distribution at the pad-to-rotor interface in a disc brake using general purpose finite element analysis software

Passenger car disc brakes are safety-critical components whose performance depends strongly on contact conditions at the pad-to-rotor interface. The interface can be classified as a conformal dry sliding contact. During braking both brake pad and rotor surfaces are worn, affecting the useful life of the brake as well as its behavior. This paper discusses how wear of the pad-to-rotor interface can be predicted using general purpose finite element analysis software. A three-dimensional finite element model of the brake pad and the rotor is developed to calculate the pressure distribution in the pad-to-rotor contact. A wear simulation procedure based on a generalized form of Archard's wear law and explicit Euler integration is used to simulate the wear of the brake pad under steady-state drag conditions.