The objective of this work was to develop a new method for establishing the coefficient of friction for the machining conditions found on the rake face of a cutting tool. Critical aspects include the high pressures and high temperatures in the cutting zone. Using the base of an existing High-load High Temperature tribometer an adaptation referred to as a double-sided pin was implemented. The objectives were two-fold to improve the repeatability of the measurements and reduce the setup time by simplifying the alignment problems experienced on the previously used system. The concept of the new setup is to press a double-end spherical pin made of the tool material between two flat surfaces made of workpiece material and rotating it using a string connected to a slider module. The normal load applied, the friction force needed to rotate the pin together with the temperature provided by a welder are then gathered and with the measurements of the imprints the coefficient of friction under specific loads can be established. This work also studied the impact on the tests of pin radius and roughness of the pin surface in order to stablish the measurement limitations and conditions for a successful test. Roughness of the pin had a significant impact on coefficient of friction results. Pins with roughness values around Ra = 0.5 demonstrated half the values of coefficient of friction than pins with Ra = 0.05. This was due the wear and the penetration of the pin into the workpiece sample material. The increase in pin dimensions facilitated testing on softer materials like AISI 1045. It was found to avoid seizure conditions but could not achieve pressures typical of machining difficult to cut materials like Ti-6Al-4V. The increase in pin size also helped in developing an understanding of how to measure the temperature at the contact zone between the pin and disk. Final testing showed a system repeatability of 8% was achieved with setup time reduced by approximately five times. / Thesis / Master of Science in Mechanical Engineering (MSME)

AN ABSTRACT OF THE THESIS OF Jacob Boone, for the Master of Science degree in Mechanical Engineering, presented on 10/28/2010, at Southern Illinois University Carbondale. TITLE: DESIGN, CONSTRUCTION, AND EVALUTAION OF UNIVERSAL FRICTION TESTER MAJOR PROFESSOR: Dr. Peter Filip Many different types of friction testers are currently available for testing specific frictional applications. Of these machines very few have versatility, and of the ones that do, the amount of versatility is limited. Since friction is a property specific to each system, all operating parameters need to match the specific application as closely as possible in order to obtain accurate data. This requires many research facilities to have several specific friction testers in order to provide the necessary testing capabilities. The goal of this project was to design a Universal Friction Tester (UFT) with enough versatility to reproduce most types of sliding friction situations. This was accomplished by providing a wide range of testing capabilities through the use of interchangeable system components. Results show that the UFT provides quality data over its entire operating range. It was shown that normal pressure, sliding speed, temperature and system stiffness all have drastic effects on frictional performance. By using a borosilicate glass disc, the friction surface was viewed in-situ during testing. This allowed insights into true surface temperature and contact area. In conclusion, the UFT can successfully take the place of several friction testers and thus provide many friction research capabilities while requiring fewer resources. The wide range of testing capabilities will allow the UFT to be used as a research tool for many types of advanced friction studies. Some of these may include true surface temperatures, true contact area, influence of conditions on stick-slip phenomenon, and thermo-elastic instabilities.

Målet med detta examensarbete var att utforma ett koncept för friktionsmätning i trycksatt ångmiljö mellan materialparen trä/metall och metall/metall. Krav på konstruktionen var att hastigheten skulle kunna regleras mellan 0-100 meter per sekund under sex bars övertryck i 100 % luftfuktighet vid temperatur upptill 180 grader Celsius till uppdragsgivaren Mittuniversitetet i Sundsvall. Arbetets utförande redovisas i denna rapport, målet är att utforma ett koncept, utforma en 3D modell av konceptet, utföra hållfasthetsberäkning som stöder att konceptet kan utstå specificerad belastning och undersöka om formförändringar av trycksatts anordning har en inverkan på de spänningar som uppstår. För att uppnå målet att utforma ett koncept användes en designprocess innehållande funktionsanalys, idégenerering enligt brainstorming och konceptutvärdering med beslutsmatris som resulterade i ett koncept för friktionsmätning där vissa komponenter definierades med krav och dimensionering av drivlina utfördes med programmet Gates Design flex Pro. Som metod för att konstruera en 3D-modell användes programmet Solidworks, för att undersöka konceptets hållfasthet utfördes dimensionering till en början med beräkningsprogrammet Matlab där materialet EN 1.4571 användes, därefter utfördes simuleringar med Solidworks för att undersöka egenfrekvenser hos utvalda komponenter av konstruktionen och hållfasthetsberäkningar. Hållfasthetsberäkningarna och undersökning av inverkan av formförändringar av inre hörn utfördes i Solidworks där tryck och temperatur tillsattes på tryckkärlets insida. Resultatet var att konceptet inte riskerar att hamna i egenfrekvens, konceptet kan i teorin producera hastigheten 101,64 meter per sekund. Maximal spänning enligt beräkningar i Matlab var 40,02 MPa, motsvarande värde vid simulering i Solidworks var 38,16 MPa. Vid undersökning av formförändring av inre hörn hos trycksatt anordning blev resultatet att en radie på 25 millimeter vid de inre hörnen hos tryckkärl gav en spänningsreducering på 29,5% och en minskning av utböjning med 12.5%. Projektet har lyckats med att uppfylla sina mål och kan i teorin producera den hastighet som efterfrågades, utstå de förhållanden som efterfrågas och utföra friktionstest med både materialen metall och trä.

Denna rapport omfattar utveckling av en rigg för att testa slitage av däck. Detta sker genom omkonstruktion av existerande pinne-på-skivatribometer rigg som man finner hos Kungliga Tekniska Högskolan. Pinne-på-skivatribometer även känd som tribometer, används för att undersöka hur olika material interagerar med varandra genom glidning, rullning eller kombination av dessa två. Mikropartiklarna som skapas vid slitage av däck och de effekter det har på sin omgivning är förfarande i bred utsträckning okända. Partiklarna från däckslitage uppskattas bidra till minst hälften av de mikroplaster som hamnar i vår omgivning. För att utöka kunskaperna om detta så testar man hur däck slits under olika driftförhållanden. Att testa i full skala med riktiga fordon på testbana är dyrt och ger inte samma kontroll över parametrar som i en testrigg som befinner sig i en kontrollerad miljö. En konstruktion som uppfyller uppdragsgivarens krav och önskemål har skapats i form av en CAD modell. Konstruktionen är en modifikation av pinne-på-skivatribometer testriggen och använder sig i stor utsträckning av komponenter från radiostyrda bilar samt andra vanliga standardkomponenter. Ett viktigt krav som uppfylldes var att kunna ändra vinkel på däcket, så att man också kan testa kantkontakten. / This report covers the development of a rig for testing tire wear. This is done by redesigning the existing pin-on-disc tribometer rig that can be found at the Royal Institute of Technology. Pin-on-disc tribometer also known as a tribometer, is used to investigate how different materials interact with each other through sliding, rolling, or a combination of the two. The microparticles that are created during tire wear and the effects they have on their surroundings are largely unknown. The particles from tire wear are estimated to contribute to at least half of the microplastics that end up in our environment. To expand knowledge about this, they test how tires wear under different operating conditions. Full-scale testing with real vehicles on a test track is expensive and does not provide the same control over parameters as in a test rig that is in a controlled environment. A construction that meets the client's requirements and wishes has been created in the form of a CAD model. The design is a modification of the pin-on-disc tribometer test rig and makes extensive use of components from radio-controlled cars as well as other common standard components. An important requirement that was met was being able to change the angle of the tire so that you can also test the edge contact.

The use of threaded fasteners can be found throughout the manufacturing industry due to their simplicity. When tightening a threaded fastener, the goal is to reach a desired clamping force. However, the clamping force is not directly measurable in production environments and the tightening torque is instead used to estimate the clamping force. This master thesis covers the development and verification of the control system for a tribometer for simulating the underhead friction of a threaded fastener during the tightening process. The control loop for the tribometer is implemented as a cascaded PI controller, using both speed and current as feedback. Tuning of the controller is performed through numerical optimization with Powell’s method. The experiments are set up to verify the performance of the system as well as test the validity of the measurements that are generated by the tribometer. The results show that the tribometer is capable of simulating tightenings of threaded fasteners. The coefficient of friction was measured for three different coatings: zinc flake, zinc nickel, and zinc phosphate. The zinc flake coating had the smallest coefficient of friction while the zinc nickel coating had the highest. / Gängade fästelement används i större delen av tillverkningsindustrin. Åtdragningen av ett gängat fästelement är en enkel uppgift där svårigheten ligger i att uppnå samma klämkraft vid upprepade åtdragningar eftersom den inte kan mätas i en produktionsmiljö. Det här exjobbet täcker utvecklingen och verifikationen av reglersystemet för en tribometer som simulerar friktionen under skruvhuvudet vid en åtdragning. Reglersystemet är implementerat som två kaskadkopplade PI regulatorer med hastighet och ström som återkoppling. Inställningen av regulatorn utfördes via numerisk optimering med Powell’s metod. Experimenten som utfördes var designade för att verifiera systemets prestanda samt giltigheten i mätvärdena som genereras av tribometern. Resultaten visar på att tribometerns prestanda är tillräcklig för att simulera åtdragningar av gängade fästelement. Friktionskoefficienten mättes för tre typer av beläggningar: zinkflingor, zink-nickel och zinc-fosfat. Zinkflingsbeläggningen hade den lägsta friktionskoefficienten medans zink-nickelbeläggningen hade den högsta.

The friction between the under-head of a bolt and the mounting surface affects the necessary torque from a tightening tool. To study the friction behaviour during a highly dynamic tightening process, a Pin-on-Disc testrig has been developed. In this thesis the implications of adding model following control to already well tuned PID controllers of the pin and disc actuation have been compared and evaluated. The results show that adding model following control improves the set point tracking of both the pin and disc without considerably increasing the overshoot. It also shows the importance of having a good mathematical model of the system to be controlled, in order for the model following control to be effective and maintain the same robustness. / Friktionen som uppstår mellan undersidan av en bult och monteringsytan påverkar hur stort vridmoment som behövs under en åtdragningsprocess. För att kunna studera hur friktionen varierar under olika åtdragningsförhållanden har en pinne-skiva testrigg utvecklats. I det här examensarbetet undersöks och jämförs konsekvenserna av att lägga till modell baserad styrning till ett befintligt PID reglersystem, för både pinnen och disken. Resultatet visar att om man lägger till modell baserad styrning så förbättras spårningen av referensen. Detta utan att märkbart överskjuta referensen. Det påvisas även hur viktigt det är att ha en bra matematiskt modell av systemet som ska kontrolleras, för att den modell baserade styrningen ska vara effektiv och bibehålla samma robusthet.

A demanda crescente por veículos mais confortáveis e mais seguros apresenta desafios à indústria. Os freios são um dos mais importantes sistemas de segurança dos veículos e também são frequentemente objeto de reclamações de consumidores por motivo de ruído. Os materiais de atrito empregados nos sistemas de freio devem apresentar desempenho satisfatório sob diferentes condições de temperatura e umidade, possuindo resistência à corrosão, longa vida útil, baixo custo e produzindo baixos níveis de ruído. Com o objetivo de caracterizar diferentes materiais quanto ao coeficiente de atrito e à produção de ruído, foram realizados ensaios de frenagem em diferentes condições utilizando um tribômetro. Esse equipamento possui sistemas de medição e controle capazes de registrar os coeficientes de atrito a cada frenagem simulada. O tribômetro também foi instrumentado com uma célula de carga capaz de medir variações da força de atrito. Os ensaios foram realizados em diferentes condições de temperatura e de intervalos de tempo entre as frenagens, alternando etapas quentes e frias. Durante o assentamento dos materiais, foram verificados diferentes comportamentos do coeficiente de atrito. Os materiais ensaiados apresentaram sensibilidade às variações de temperatura e de intervalos de tempo entre frenagens. Foi observada correlação entre as variações da força de atrito e o coeficiente de atrito. Também foram evidenciados os efeitos da velocidade de deslizamento sobre o espectro de frequências de variação da força de atrito. / The growing demand for more comfortable and safer vehicles comes up with new challenges to the industry. The brakes are one of the most important vehicle safety systems and are also often the subject of customer complaints about noise. The brake friction materials need to perform properly under different conditions of temperature and humidity, presenting resistance to corrosion, long life, low cost and producing low noise levels. In order to characterize the friction coefficient and noise generation of different friction materials, different conditions were tested using a tribometer. This equipment has measurement and control systems capable of record each brake stop friction coefficient. The tribometer was also instrumented with a load cell capable of measuring friction force variations. The tests were performed at different temperatures and time intervals between brake applications, alternating hot and cold stages. During the materials running-in, different behaviors of the friction coefficients were found. The friction materials tested showed sensitivity to temperature variations and time intervals between brake applications. There was a correlation between friction force variations and coefficient of friction. There were also effects of the slip speed on the frequency spectrum of the frictional force variations.

In sheet metal forming (SMF), the major failure reason is galling. Galling is a process of different wear stages that leads to destruction of both the forming tool and the sheet metal working piece and is, because of that, of big economic importance for the SMF industries. Therefore, investigations and researches about how tool steels microstructure affect the tool steels galling resistance is of high priority. In the present work, different carbide properties were studied to find out how their properties affected the tool materials galling resistance. The investigated carbide properties were: Shape and size of the carbides   Carbide volume fraction Carbide distribution in the microstructure The investigation included three tools, all made of the PM tool steel S390, that were heattreated differently in order to achieve different carbide properties but still maintain the same hardness. The tools were galling tested in a slider-on-flat-surface (SOFS) tribometer to determine their galling resistances. In a scanning surface electron microscope (SEM) the tools galling marks were analyzed to find explanations for the SOFS tribometer results and the connection to the tools different carbide properties.  The investigations most galling resistant tool was the tool that had the microstructure with largest carbides which were distributed at grain boundaries and the second highest carbide volume fraction among the investigated tools.

A demanda crescente por veículos mais confortáveis e mais seguros apresenta desafios à indústria. Os freios são um dos mais importantes sistemas de segurança dos veículos e também são frequentemente objeto de reclamações de consumidores por motivo de ruído. Os materiais de atrito empregados nos sistemas de freio devem apresentar desempenho satisfatório sob diferentes condições de temperatura e umidade, possuindo resistência à corrosão, longa vida útil, baixo custo e produzindo baixos níveis de ruído. Com o objetivo de caracterizar diferentes materiais quanto ao coeficiente de atrito e à produção de ruído, foram realizados ensaios de frenagem em diferentes condições utilizando um tribômetro. Esse equipamento possui sistemas de medição e controle capazes de registrar os coeficientes de atrito a cada frenagem simulada. O tribômetro também foi instrumentado com uma célula de carga capaz de medir variações da força de atrito. Os ensaios foram realizados em diferentes condições de temperatura e de intervalos de tempo entre as frenagens, alternando etapas quentes e frias. Durante o assentamento dos materiais, foram verificados diferentes comportamentos do coeficiente de atrito. Os materiais ensaiados apresentaram sensibilidade às variações de temperatura e de intervalos de tempo entre frenagens. Foi observada correlação entre as variações da força de atrito e o coeficiente de atrito. Também foram evidenciados os efeitos da velocidade de deslizamento sobre o espectro de frequências de variação da força de atrito. / The growing demand for more comfortable and safer vehicles comes up with new challenges to the industry. The brakes are one of the most important vehicle safety systems and are also often the subject of customer complaints about noise. The brake friction materials need to perform properly under different conditions of temperature and humidity, presenting resistance to corrosion, long life, low cost and producing low noise levels. In order to characterize the friction coefficient and noise generation of different friction materials, different conditions were tested using a tribometer. This equipment has measurement and control systems capable of record each brake stop friction coefficient. The tribometer was also instrumented with a load cell capable of measuring friction force variations. The tests were performed at different temperatures and time intervals between brake applications, alternating hot and cold stages. During the materials running-in, different behaviors of the friction coefficients were found. The friction materials tested showed sensitivity to temperature variations and time intervals between brake applications. There was a correlation between friction force variations and coefficient of friction. There were also effects of the slip speed on the frequency spectrum of the frictional force variations.

A presente tese descreve as etapas de desenvolvimento de um equipamento (tribômetro) e metodologia de ensaio para caracterização do efeito isolado da temperatura sobre o atrito medido em materiais de fricção utilizados em freios veiculares. O projeto deste equipamento foi baseado nas funcionalidades e limitações encontradas nas principais máquinas e procedimentos de ensaio para freios automotivos. São apresentados e discutidos detalhes do projeto mecânico e de automação do tribômetro, bem como são levantadas suas incertezas de medição instrumentais e precisão. Além disso, é proposta uma nova metodologia de ensaio para caracterização do efeito isolado da temperatura sobre os resultados de atrito obtidos durante os testes. O projeto mecânico atual do tribômetro contempla recursos que contribuem para facilitar a operacionalidade do equipamento e, consequentemente, reduzir o tempo envolvido na etapa de preparação dos testes. São exemplos destes recursos um mecanismo de fuso e manivela, o qual é empregado para a regulagem do raio de deslizamento, e um dispositivo para troca rápida da amostra a partir do ajuste de um único parafuso. O atual projeto de automação do tribômetro é composto por circuitos de controle da carga, rotação, torque e temperatura, os quais operam em malha fechada. A incerteza instrumental do sistema de medição de atrito do tribômetro é igual a ±2,9% do valor nominal medido, considerando a faixa típica de aplicação da máquina. Em termos de precisão, verificou-se experimentalmente que o equipamento projetado apresenta uma repetitividade de ±0,013. O projeto de automação também contemplou a ligação do tribômetro a um aquecedor indutivo. O uso da referida tecnologia em conjunto com a metodologia de ensaio proposta na presente tese mostraram-se capazes de caracterizar de forma acelerada e independente o efeito da temperatura sobre o coeficiente de atrito obtido a partir de ensaios de frenagem executados no tribômetro. Complementa o estudo ainda o desenvolvimento de uma técnica para pós-processamento dos dados relativos aos ensaios executados no tribômetro segundo a metodologia proposta. A referida técnica mostrou-se uma maneira eficiente e relativamente simples de avaliar os efeitos simultâneos da carga e da temperatura sobre o atrito. / The current thesis describes the development of equipment (tribometer) and testing procedure for characterizing the isolated effect of temperature on friction measurements obtained from vehicular friction materials. The design of this equipment was based on the features and limitations found in the main machinery and testing procedures for brakes. Details about the mechanical design and automation of the tribometer are presented as well as its instrumental measurement uncertainties and precision. Besides, a new testing procedure is proposed in order to characterize the isolated effect of temperature on friction results obtained in the tests. The current mechanical design of the tribometer comprises some features that contribute to make the equipment operation ease and thus reduce its setup time. A crank and screw mechanism, which is used for adjusting the sliding radius, and a device for rapid exchange of the samples by means of a single screw are both examples of those features. The current automation design of the tribometer consists of circuits for controlling load, speed, torque and temperature, which operate in closed loop mode. The instrumental measurement uncertainty from the friction measuring system is ±2,9% of the nominal friction measurement, considering the typical operating range of the machine. Experimental tests performed on the tribometer showed that the repeatability (precision) of the friction measurements is ±0,013. The automation design also included the connection between the tribometer and an induction heater. The use of this technology together with the proposed testing procedure proved to be a suitable tool for characterizing the isolated effect of temperature on friction during braking tests performed on the tribometer. This work is also complemented by the development of a technique for post-processing the data related to the tests carried out in accordance with the proposed testing procedure for the tribometer. This technique proved to be an efficient and clear way to assess the simultaneous effects of load and temperature on friction measurements.