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Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. Includes tables. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 104-107).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1959. / Typescript. Abstracted in Dissertation abstracts, v. 20 (1959) no. 5, p. 1721-1722. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 122-123).

Thesis (M.S.)--University of Wisconsin--Madison, 1960. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 220-229).

Coefficient of friction is considered to be a system property. Unlike physical properties of a material, coefficient of friction is dependent on an entire system. Surface roughness, wear rate, temperature and velocity are some of the factors that influence the COF in a brake system. Due to these factors, current testing strategies fail to make an accurate prediction about the performance of a brake system in smaller scale. This paper explores how a small-scale tester correlates to a full scale dynamometer test when proper scaling strategies are utilized. Series of tests are carried out on non-asbestos organic, semi metallic and low steel using the Bruker’s Universal Mechanical Tester (UMT) TriboLab. Results are then compared to the Greening full-scale dual ended brake dynamometer (Horiba) using AK master standard procedure. Area based Scaling laws are applied as the approach to scale down the conditions of the full- scale dyno test for UMT test. As friction is a system property, dynamometer and UMT tests showed different results. However, performance (COF) for these tests between UMT and Dyno has the same general trend. Therefore, with more repetition on different friction material, it is possible to make more relevant and accurate predictions of performance.

The dependence of the static coefficient of friction on the time of stationary contact has been determined using stick-slip vibration to provide a periodic time of stationary contact between two metallic bodies. To describe this time dependence a theory based on the creep by diffusion for metals in contact has been developed. This approach is similar to the adhesion theory presented by many authors as representative of junction strength in friction. Eleven friction-couples were studied; ten couples being very pure metals run against an annealed steel disk. The eleventh couple consisted of a hardened steel slider against the annealed steel disk. The results indicated that, fundamentally, very little difference in static friction values was apparent between the friction-couples. Because of the difficulty in obtaining material properties it was not possible to compare the experimental results with purely theoretical predictions. However, within reasonable experimental accuracy, the shape of the friction-time curves agreed with those predicted by theory. By varying the system parameters it was found that, in general, the static coefficient of friction was load and area independent but seemed to be very dependent on surface finish and the micro—structure of the friction-couples. Notable exceptions to this rule were indium and silver which showed excessive creep under load thus directly affecting the static coefficients of friction. It is important to stress that quantitative results for the friction-growth curves are not applicable since the system parameters affect the results greatly. However, a qualitative idea of the fundamental problems that exist allows a reasonable prediction of friction values to be made. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The present report summarizes the results of an experimental study of static friction. Stick-slip type vibration was produced in a pin on disk friction system in order to determine the effect of various parameters on the static friction force. In the first part of the study it was found that two distinct types of sliding behaviour could be produced by controlling the preparation of the surfaces prior to sliding. If the surfaces were freshly polished and kept relatively free of organic contaminants then the sliding behaviour was characterized by high friction coefficients and extensive surface damage. Under lubricated conditions however, stick-slip vibration was possible at low driven surface velocities. These results show the importance of surface history with regard to friction phenomena and aid in the interpretation of subsequent experimental results. By measuring the electrical resistance of the slider-disk interface it was possible to monitor changes in the area of contact during stick-slip. It was observed that there was metallic contact throughout the complete cycle although the amount of metallic contact varied. The stick portion of the cycle was found to be a region of increasing metallic contact. The amount of metallic contact area at slip was a function of the rate at which the tangential force was applied. During slip, the area in metallic contact decreased rapidly and there was some evidence that the normal load on the slider was partially supported by a lubricant film in this part of the cycle. The amount of contact during slip was determined by the relative velocity during slip. By monitoring the resistance of the interface during a "delayed" stick cycle it was possible to show that the area in contact did not increase with time under a stationary loading condition. Instead the area of contact at slip and also the static friction force were found to be dependent on the rate of application of the tangential force. These findings contradict earlier work on time-dependent creep models for static friction and provide additional evidence in support of the visco-elastic model proposed by Johannes [27]. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Motion control systems are usually designed to track trajectories and/or regulate about a desired point. Most of the other objectives, like minimizing the tracking time or minimizing the energy expended, are secondary which quantify the above described objectives. The control problem in hard disk drives is tracking and seeking the desired tracks. Recent increase in the storage capacity demands higher accuracy of the read/write head. Dual stage actuators as compared to conventional single actuator increases the accuracy of the read/write head in hard disk drives. A scaled up version of the dual stage actuator is considered as the test bed for this thesis. Friction is present in all electromechanical systems. This thesis deals with modelling of the dual stage actuator test bed. A linear model predicts the behavior of the fine stage. Friction is significant in the coarse stage. Considerable time has been spent to model the coarse stage as a friction based model. Initially, static friction models were considered to model the friction. Dynamic models, which describe friction better when crossing zero velocity were considered. By analyzing several experimental data it was concluded that the friction was dependent on position and velocity as compared to conventional friction models which are dependent on the direction of motion. Static and Coulomb friction were modelled as functions of velocity and position. This model was able to predict the behavior of the coarse stage satisfactorily for various initial conditions. A friction compensation scheme based on the modelled friction is used to linearize the system based on feedback linearization techniques.

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Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1910. / The entire thesis text is included in file. Typescript. Illustrated by authors. Title from title screen of thesis/dissertation PDF file (viewed January 15, 2009) Oliver W. Holmes determined to be Oliver Wendell Holmes from "Forty-First Annual Catalogue. School of Mines and Metallurgy, University of Missouri."